The use of wide area network fibre optic and SDH technology

THE USE OF WIDE AREA NETWORK FIBRE
OPTIC AND SDH TECHNOLOGY BY UK PLC
MARCH 2006
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Contents
Executive summary............................................................................ 3
Scope and approach .......................................................................... 4
References .......................................................................................... 5
Definitions and abbreviations ........................................................... 6
SDH and fibre infrastructure in the UK............................................. 9
End user services............................................................................. 16
Security and resilience .................................................................... 24
Conclusions and recommendations............................................... 28
Appendix A: Ofcom telecommunications report 2005 .................. 30
Appendix B: Service providers, carrier operators and
equipment providers ................................................. 49
Appendix C: BT 21st century network............................................ 54
Appendix D: Evolution of SDH ........................................................ 56
Appendix E: Element and network management .......................... 61
Appendix F: Regulatory position .................................................... 65
Bibliography...................................................................................... 67
History ............................................................................................... 67
2
Executive summary
This report examines the SDH and fibre optic infrastructure in the UK and considers its
importance in terms of supporting critical national infrastructure and its vulnerability to
electronic attack. SDH has become the preferred telecom transport technology to support
premium services in the UK since 1990. Since 1997 some routes have been enhanced
through combination with WDM which has substantially increased fibre transmission capacity
and reduced the ‘per bit’ transmission costs. More recent standards developments have led to
formal definitions for WDM technologies under the title ‘Optical Transport Network’. The
standards are under active development, particularly to make SDH more efficient in carrying
data services such as Ethernet and in providing better operational flexibility and improved
customer control.
SDH supports the public voice telephony service, the Internet, mobile network services and
corporate networks. Without SDH these services could not operate and therefore would be
unable to support the critical national infrastructure. The market situation of each of these
telecom services is examined as a way of indicating the size, and by implication the
importance, of each. Private circuits are used as a way of providing interconnection capacity
to other operators to enable them to build their own networks and to provide their own
services. In effect private circuits are an intermediate stage between the end user services
and the SDH network, although they are sold as a service to other network operators.
In its present form SDH offers a high degree of resilience against network failure and some
security against electronic attack, noting that the security is only as good as the associated
security policies and their implementation. There are potential opportunities for compromise if
an attacker were to gain access to the data communications network or to the management
system. Unauthorised access to network or element managers could lead to major service
disruption, but providing that security policies are carefully implemented the disruption could
be contained. Unauthorised access to the higher level management systems could allow
billing or service levels to be compromised.
In the UK, by far the most transmission capacity is provided by BT, though changing
regulation has ensured that other network operators now provide significant infrastructure,
particularly within and between major towns and cities. Because of its dominance in terms of
available infrastructure, special consideration is given to the BT network as well as general
consideration to other networks.
Given the open source nature of this report, a number of recommendations are made for
further study which would involve specific discussion with Telecoms Equipment, Service and
Network Providers.
3
Scope and approach
This report describes the use of ‘Wide Area Network Optic and SDH technology by UK PLC’
and will be used by NISCC in their role to protect the UK Critical National Infrastructure (CNI)
against an electronic attack. The report sets out the UK environment in terms of Services,
Providers, Technology and the Regulatory position using open source material identified and
listed in the reports reference section and bibliography. This report is also a reference for the
sister report on the use of ‘Submarine Cable technology in UK PLC’ to avoid duplication.
Operators who own SDH infrastructure also offer telecommunications services
(such as fixed voice or corporate data), but service providers do not always own
SDH and fibre infrastructure. Instead they lease transmission capacity from one
of the infrastructure (or ‘facilities’) providers through private circuits. Whilst
private circuits may be supplied on either a wholesale or retail basis, in fact they
provide a means to construct a network to deliver an end user service and
therefore lie between ‘infrastructure’ and ‘end user services’.
In order to assess the dependency of the CNI on this technology, the UK SDH and fibre optic
infrastructure are described and the nature of private circuits is examined. Next the overall UK
telecom market and each major end user service is assessed by analysing market
information. The major services identified are:
•
Fixed line voice
•
Mobile
•
Internet
•
Corporate data
Liberalisation and regulation in recent years have had a major impact on shaping the industry
and in ensuring competition and diversity in suppliers. The effect of regulation on each
service is therefore examined and the relationship of the service to the SDH and fibre
infrastructure is discussed. The dependency of each service on SDH and fibre infrastructure is
then summarised. For each service the relevant market leaders are identified and their
location and contact details are listed in an annex to the report.
Following this analysis the key features of SDH and fibre optic technology are examined and
the dominant technology issues identified as the first stage in an assessment of the security
and resilience.
Given the open source constraints of this high-level study, specific security issues are not
detailed however areas of potential concern are identified. These can be used in any follow-up
discussions with the providers, as it is only the providers who can validate and comment
authoritatively given the sensitivity surrounding potential vulnerabilities. Finally, conclusions
are presented and recommendations made on how this report could be taken forward.
NB. This report was produced from open source information and without direct contact with
any Telecom Equipment, Network or Service Providers.
4
References
For the purposes of this document, the following references apply:
1.
‘Communications Market 2005 – Telecommunications’, Ofcom Report:
http://www.ofcom.org.uk/research/cm/cm05/.
2. BT Products and Services:
http://www.bt.com/b4b/b4b_campaign.jsp?BV_SessionID=@@@@0545397933.1141318
432@@@@&BV_EngineID=ccccaddheflfkmhcflgcefkdffndfni.0&EditorialName=private_cir
cuits&UserSegment=SME&obsNoSee=Y&vStore=1302&obsPage=/b4b/b4b_sme_ps_hub
.jsp&obsNoSee=Y&vStore=1302&obsPag
3. BT Wavestream Connect service
http://www.btindirectchannels.com/index/products/products-portfolio-ict/products-portfolioict-wavestconnetnat.htm
4. BT 21st Century Network:
http://www.btplc.com/21CN/?com.bea.event.type=linkclick&oLName=link.searchresults&o
LDesc=KB_568
5. Cable and Wireless Network: http://www.cw.com/our_network/worldindex.html
6. ntl Network: http://www.ntl.com/mediacentre/thecompany/ntlnetwork/
7. Global Crossing Network: http://www.globalcrossing.com/xml/network/index.xml
8. Colt Network: http://www.colt.net/our_infrastructure
9. Surf telecom Network: http://www.surftelecoms.co.uk/network.html
10. UK Core Transmission Network for the New Millenium, I. Hawker, G. Hill and I. Taylor: BT
Technology Journal, July 2000, Vol 18 No.3, July 2000
11. Generic requirements for operations based on the Telecommunications Management
Network (TMN) architecture; Bellcore, Generic Requirements GR-2869-CORE, Issue 1,
October 1995
5
Definitions and abbreviations
Definitions
For the purposes of this document, the following terms and definitions apply:
Dominant technology issues
Those technology issues which are likely to have the
greatest impact on the security and resilience of the CNI
Private circuits or leased lines
A point to point private line used by an organisation to
provide a telecommunication connection between
remote sites
Dark fibre
The name given to optic fibre that is not yet used
2G mobile
Digital mobile network system with basic capability for
supporting data services such as SMS
3G mobile
Broadband digital mobile network system with advanced
capability for supporting data services such e-mail and
web browsing
DSL
Digital Subscriber Line system, a technology which
enables a copper telephone pair to deliver high speed
broadband data to customers
Cable modem
A customer unit that enables high speed broadband data
to be carried over a cable TV system channel. The
equivalent equipment at the CATV hub is called a Cable
Modem Termination System.
WiFi
The name commonly given to a set of standards that
define the requirements for transmitting data over a
wireless local area network.
WiMax
The name commonly given to a fixed wireless
metropolitan area network standard that is being
developed for metropolitan area applications.
Carrier Pre Selection
A service offered by BT and Kingston Communications
to customers which allows them to opt for certain defined
classes of call to be carried by an operator contracted in
advance, without having to dial a routing prefix or follow
any other special procedure
Bluephone
A handset product developed by BT that can route
phone calls over either a fixed or mobile network
6
Abbreviations
For the purposes of this document, the following abbreviations apply:
21CN
21st Century Network
3GPP
3rd Generation Partnership Project
ADM
Add Drop Multiplexer
ADSL
Asymmetric Digital Subscriber Line
Alt-Net
Alternative network supplier
ASTN
Automatic Switched Transport Network
ATM
Asynchronous Transport Mode
BLSR
Bidirectional Line Switched Ring
CNI
Critical National Infrastructure
CPS
Carrier Pre-Select
DCM
Dispersion Compensation Module
DMSU
Digital Main Switching Unit
DSL
Digital Subscriber Line
DSLAM
Digital Subscriber Line Access Module
EDFA
Erbium Doped Fibre Amplifier
EM
Element Manager
EMS
Element Manager System
FDM
Frequency Division Multiplex
GbE
Gigabit Ethernet
GDP
Gross Domestic Product
GFP
Generic Framing Protocol
GMPLS
Generalised MultiProtocol label Switching
GSM
Global System for Mobile communication
IP
Internet Protocol
ISDN
Integrated Services Digital Network
LAN
Local Area Network
LCAS
Line Capacity Adjustment Scheme
LLU
Local Loop Unbundling
MMS
Multimedia Message service
MPLS
Multi Protocol Label Switching
NACC
Network Administration Control Centre
NE
Network Element
NGS
Next Generation System
NMS
Network Management System
NOC
Network Operations Centre
OAM
Operations, Administration and Management
7
OSS
Operational Support System
OTN
Optical Transport Network
PCP
Primary Cross-connection Point
PDH
Plesiochronous Digital Hierarchy
PSTN
Public Switched Telephone Network
QoS
Quality of Service
RPR
Resilient Packet Ring
SDH
Synchronous Digital Hierarchy
SLA
Service Level Agreement
SME
Small and Medium Enterprises
SMS
Short Message Service
TDM
Time Division multiplex
VCAT
Virtual Concatenation
VoIP
Voice over Internet Protocol
VPN
Virtual Private Network
WAP
Wireless Application Protocol
WDM
Wavelength Division Multiplexing
DWDM
Dense Wavelength Division Multiplexing
8
SDH and fibre infrastructure in the UK
Industry structure
Fibre system deployments
SDH has been deployed in the UK since around 1990 and is now the predominant transport
method for carrying telecommunications signals over fibre. Prior to that time PDH had been
the main high capacity transport technology since 1980 and indeed was being installed until
the late 1990’s. As demand for capacity grew, the first optically switched and optically
amplified WDM systems in the UK were introduced by BT in 1997. These early WDM systems
were designed to be able to support both PDH and SDH signals. Since these early WDM
systems were introduced higher capacity systems better able to support internet and data
services have also been deployed.
The growth in capacity of digital systems is illustrated in Figure 1.
WDM
Optical technologies
EDFA … Raman
Single-mode fibre
Multi-mode fibre
160λ
80λ
1 Tb/s
32λ
16λ
8λ
Capacity
(log scale)
40Gb/s
10Gb/s 4λ
2.5Gb/s
Optical
networking?
565Mb/s
140Mb/s
34Mb/s
8Mb/s
2Mb/s
1980
1985
1990
1995
2000
Year
Plesiochronous digital hierarchy
Electrical transport
Synchronous digital hierarchy
Figure 1 Technology trends in fibre systems
This shows how multimode fibre gave way to single mode fibre, how PDH gave way to SDH
and how WDM technology was introduced. It should be noted that although the design
capacity of the highest capacity systems exceeds 1Tb/s, in practice the ‘lit’ and ‘revenue
earning’ capacities of these systems is much lower in practice. The design capacity is
therefore an indication of potential to grow, rather than an indication of traffic carried.
Currently the technology trend is not to seek increased capacity and range, but towards
making transport networks more adaptable to the needs of data networking. This trend is
discussed later.
9
Transport network providers
With 7.3 million miles of installed optical fibre, BT owns by far the biggest transport network
infrastructure in the UK and in effect provides network coverage across 100% of the country.
Access to the BT fibre network infrastructure is made available to other operators through
private circuit services [2] or, for higher capacities, through the Wavestream service [3]. BT
now claims to provide services to more than 600 fixed and mobile operators and service
providers across the UK.
Liberalisation and regulation has enabled a number of competing carrier network operators to
enter the field and several of these have installed their own infrastructure, also based on fibre,
SDH and WDM. Cable and Wireless claim to have the second largest UK fibre network [5]
with a presence in more than 100 UK cities. Following their acquisition of Bulldog they
announced plans in 2004 to expand into the local network through local loop unbundling
arrangements, with a presence in 400 exchanges.
Cable TV service providers’ ntl and Telewest also have extensive regional fibre networks (e.g.
[6]) that interconnect with their national networks and provide distribution via cable modem
feeders. The networks are used to provide carrier services (e.g. for corporate networks) as
well as broadband data and CATV. The ntl network contains 7,800 fibre km and they (also)
have claimed this to be the second largest fibre network in the UK. However much of this will
carry FDM channels for video and broadband distribution rather than SDH.
Global Crossing’s UK network [7] was scheduled for completion in Q2 2005. It has a Lucent
Technologies DWDM core providing a potential capacity at each of seven core nodes of 320
Gbit/s, and the capability to support 40 10-Gbit/s channels on any route. The Global Crossing
UK core interconnects with Global Crossing’s international optical transmission network,
allowing for global service delivery.
The COLT network [8] links 13 fully-integrated data centres in 11 major European cities,
providing very high reliability and security for corporate networks. The connected cities are:
Amsterdam , Barcelona , Berlin , Frankfurt , London, Madrid , Paris, Rome, Turin and Zurich
Surf Telecoms have a fibre network [9] extending over 1600 km in the South West peninsular
and into southern Wales. Products include dark optical fibre, carrier wholesale bandwidth,
communications sites, and regional leased lines (non-switched) for the corporate, business,
educational and utility sectors.
Details of leading network infrastructure providers are given in Appendix 2. Each network
infrastructure operator buys from the major equipment providers, which results in a range of
equipment designs, technologies and architectures. However the interfaces are standardised
so that equipment from different suppliers will interwork.
10
The BT fibre optic network
The BT PDH network
The first commercial fibre systems were installed in BT’s UK network in 1980. These carried
low bit rate PDH services over multimode fibre. PDH systems with faster 565Mb/s rates were
introduced around 1985 and these continued to be installed into the late 1990’s.
From 1985 BT also invested in extensive single mode fibre cabling, typically using 96-fibre
cables from around 1990. Once the cables were installed BT saw it as economic to continue
deploying low cost PDH systems, even though higher capacity SDH systems were available
by 1990. Because of the widespread use of 565Mb/s PDH the fibre cables progressively filled
with these low system capacities. Many of these PDH systems are still in use, mainly
supporting the PSTN and occupying many of the cable fibres, although they are now likely to
be phased out as BT introduces its 21st Century Network. Apart from cost, another reason it
has taken time to replace them is that they have also carried some premium leased line
services (Kilostream or Megastream) and changing over to SDH requires customer notification
which is manually intensive and therefore expensive.
The BT SDH network architecture
Overlapping with the PDH deployments, BT’s first SDH systems were introduced around
1990, principally to serve the premium 2 Mb/s leased line market. The network architecture
was arranged in 4 tiers as illustrated in Figure 2 [10]:
Wideband
Access:
50,000 Sites
40% of Cost
Access
Tier 2:
500 Nodes
20% of Cost
Tier 1:
50 Nodes
10% of Cost
Tier 3
Small Towns
& Suburbs
Tier 3:
2000 Nodes
30% of Cost
Outer
Core
Tier 2
Large Towns
Tier 1
Cities
Tier 0: International Backhaul
Frontier Stn
Frontier Stn
Figure 2 The BT SDH network. Source: BT Technol. Jnl., July 2000
11
Tier 0 is a network providing very high capacity connections between the sub-sea frontier
stations and the international switching centres in London. Generally these are very high
capacity SDH/WDM point to point systems, with connections to the major international
gateways in London and Madley. They may take the form of point to point systems with fast
1+1 protection or automatically protected rings.
Tier 1 is a high capacity, intercity network connecting about 170 core nodes. The Tier 1
network mostly uses point to point connections and is fully meshed so that capacity can be
readily allocated on demand. Large cross-connect switches at the nodes provide the flexibility
to configure circuit connections and a range of other features to support network operations.
A very high level of network protection is provided based mainly on 1+1 automatic protection
which provides milliseconds switch-over to a diverse route in the event of failure. Diversity
usually dictates a link on a different cable route, but in some cases it may be a different cable
on the same route, or a different fibre pair in the same cable. Possibly in some cases where
capacity is in short supply 1+N protection may be provided (i.e. where 1 protection circuit
protects N working circuits). Open sources do not provide this level of detail.
Regional networks in Tier 2 connect approximately 1000 towns on to SDH rings. Add-drop
multiplexers on the rings allow traffic to be conveniently added or dropped as well as providing
other network operations features. Rural and city SDH rings in Tier 3 connect well over 1000
local exchanges. These largely provide infill with city and urban areas and extend the reach of
SDH into the outer core. Tier 2 and Tier 3 SDH networks usually employ rings for resilience (if
one part of the ring fails the traffic can be rerouted via the complementary section of the ring).
In addition to these tiers there is also a ‘super tier’ between tiers 1 and 2, providing
interconnection between several tier 2 rings. SDH systems also connect to more than 1000
large customer sites at 155 Mb/s and above and to other operators.
BT is thought to have 9 Network Operations Centres (NOC) at regional locations such as
Manchester and Cambridge and an overall Network Management Centre at Oswestry for
operations personnel. Each is supported by a Network Administration Computer Centre
(NACC), which contains the associated computer equipment. All facilities are duplicated at a
remote location for disaster protection, although distances between NOC and back up facilities
are not known.
12
Meeting growth in the BT transport network
The resulting network was very flexible but was not easily scalable and proved expensive as
demand for capacity increased in the late 1990’s. By 12/2000 the network had been expanded
to give increased tier 1 coverage with links to the global backbone. Expansion of the SDH
network has no doubt occurred since this time, but details are not known.
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Figure 3 Tier 1 and principle tier 2
Figure 4 Broadband 10Gb/s overlay
network by 12/2000
Sources: BT internal presentation and BT Technol. Jnl., July 2000
A new flexible and scalable network infrastructure was introduced from 1998 with a
significantly lower cost 10 Gb/s broadband overlay network. Broadband traffic that was
previously carried on the earlier SDH network was migrated across to the overlay, releasing
capacity to support the growth of narrowband traffic on the earlier network. This broadband
network had 80 nodes and 35 rings by 6/2000. The map shows the main rings only.
The broadband overlay was able to efficiently handle churn of 155Mb/s services, but the
10Gb/s channels were insufficient to handle churn at 2.5Gb/s, as needed by IP services. By
this time WDM technology offering 16 wavelengths per fibre became available and was
introduced on some routes where fibres were in short supply. From 2000, as the Internet
traffic grew even the broadband 10Gb/s network became inefficient in carrying this traffic and
an ‘IP over WDM’ network (named ‘Colossus’) was introduced by BT.
13
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Figure 5
BT WDM networks 12/2000
Source: BT internal presentation
Private circuits
Fibre infrastructure providers (also known as ‘facilities providers’) generally offer a range of
private circuit services to operators of service networks (or service providers). Private circuits
provide fixed, high-performance connections between two locations and enable others to build
their own higher level service networks without installing their own transmission infrastructure.
The circuits are permanently available and are supported by Service-Level Agreements (SLA).
Private circuits are used in a variety of different network applications and are able to carry
voice, mobile, data and Internet traffic. Their capacities range from around 2.4kb/s to 622
Mb/s. Private services offering capacities of 2Mb/s or below are usually delivered to customer
premises via copper pairs (which can also handle up to 8Mb/s). Services of 8Mb/s and higher
are delivered by fibre.
Because they are a premium service they are usually provided over a resilient (automatically
protected) system and they are often fed via an SDH add-drop multiplexer (ADM). They may
be supplied either as a retail product to a company to enable them to build their own, usually
small-scale, private network, or they may be provided as a wholesale product to another
public network operator.
Traditionally leased lines have been provided using ‘circuit’ techniques, but packet based
(virtual) private circuits and also wavelength multiplexed circuits are also now available.
14
Examples of circuit based private circuit services include:
•
BT’s Kilostream/Kilostream N which offer services from 2.4 kb/s to 1024 kb/s and which
are used mainly for connecting phone systems and smaller LAN’s.
•
BT’s Megastream which offers connections from 1.5, 2, 34, 45, 140, 155 and 622 Mb/s
bandwidths and which is mainly used for voice and data backbone networks. Megastream
Longlines offers the ability to aggregate multiple individual circuits routed from multiple
customer sites onto a single 155Mb/s bearer. Lower speed Megastream circuits up to
8Mb/s can be delivered via copper or fibre.
•
BT’s International Private Circuits.
•
ntl’s Point to Point Leased Lines.
•
Global Crossing provides private circuit services in the range 2 to 34 Mbit/s.
Examples of packet based private circuits include:
•
BT Ethernet Private Services are point to point or point to multipoint connection oriented
data services. They provide transparent, symmetrical, uncontended bandwidth from
200kb/s to 100Mb/s, with customer interfaces at speeds up to and 1000baseT
•
ntl’s Internet Leased Lines (which offer connections ranging from 2Mb/s to 45Mb/s with 1
to 1 contention).
Wavelength services are a very high capacity form of private circuit. Examples of wavelength
services include:
•
BT Wavestream which provides a fibre point to point service using dense WDM and
providing bandwidths up to 80Gb/s. Wavestream services are aimed at interconnections
for large data centres for real time information back up, information storage and disaster
recovery. The service is also used for network consolidation following company mergers.
•
Dark fibre is also available from some suppliers such as Surf Telecoms.
15
End user services
Identification of major services
Optical fibre technologies provide reliable, high capacity, network connections which the
telecommunications industry currently relies on heavily to provide a wide range of services to
end users. A comprehensive review of these services is provided by the Ofcom report
‘Communications Market 2005 – Telecommunications’ (see Appendix A). This is perhaps the
most comprehensive view of the UK telecoms market that is openly available and an analysis
identified fixed line telephony, mobile telephony and data, the Internet and corporate data as
the major telecommunications service categories. Without fibre and SDH, these services
would not operate. Critical national infrastructures depend on all of these services and
therefore on the fibre and SDH infrastructure.
As it is beyond the scope of this report to examine all service dependencies on SDH the
following approach is adopted. First an overall view is taken of the telecoms market to assess
its size, and then each individual service is considered in turn. For each service a view is
given of its market status and key players, and the impact of regulation on the service is
discussed. Finally the relationship of the service to SDH is examined. The resilience and
security of each service depends in part on the SDH network and this is considered in the
following section so that conclusions can be drawn. In this section no distinction is drawn
between SDH and WDM regarding dependencies. The reason for this is that SDH can only
operate over optical fibre cables while the primary function of WDM is to increase the capacity
that a single fibre can carry. WDM is therefore particularly applicable on those routes where
traffic capacities are highest.
Size of the UK Telecoms market
In their market report of 2005 (Appendix A) Ofcom reported that the size of the telecom market
had progressively increased since 2000 and that the value in 2004 was £44.6 bn of which
£36.1 bn was retail and £8.6 bn was wholesale. The value added by telecom markets to GDP
in 2004 was estimated as £26.7 bn, or 2.8% of GDP.
Although BT was by far the largest operator in the UK in 2004, its overall market share had
fallen to 41% (lower than most other European incumbent operators) while mobile network
operators held a combined share of 34%.
In 2004 revenues from mobile voice and data exceeded the revenues from fixed voice and
access for the first time. Internet and broadband, followed by corporate data services were
also identified as major revenue earners, though at rather lower levels than fixed voice and
mobile. Ofcom also estimated that businesses accounted for almost a half of all end user
spending on the main telecom services in 2004, amounting to over £14 bn.
16
Fixed line voice services
Call volumes and exchange lines
Call volumes over the fixed voice network has been declining slightly in recent years, as too
has the number of exchange lines [1]. This is partly due to mobile call substitution, partly to
broadband substituting both ISDN connections and second lines for Internet access and partly
due to other forms of substitution such as e-mail or SMS messaging.
Fixed line voice operators
By far the largest fixed line voice network is owned by BT. Consequently many alternative
voice network providers depend on the BT infrastructure for their services. In a strategic
review which commenced in April 2004, Ofcom considered that competition was not effective
in all areas needed to provide voice network services. Following the review and consultation,
BT has launched a new company called Openreach to deliver installation and maintenance
services on behalf of alternative telephone and Internet service providers. Openreach, which
includes almost all of the BT field engineers, is required to provide a service to all service
providers on an equal basis and at the same price. Its products will include Local Loop
Unbundling, Wholesale Line Rental and Backhaul products.
Ntl, Telewest and some others have their own infrastructure on a much smaller scale. But the
majority of voice network providers lease capacity from BT. This study has not identified the
relative sizes of the other service providers but they include major companies such as
Telecom Plus, Onetel, Eurexel and Toucan.
Fixed and mobile
Although fixed voice call volumes have been falling and mobile calls growing, there seems no
likelihood in the near future that mobile will replace the fixed line market. The number of
households with mobile phone only is 9% and that with fixed line only is 10%, with the majority
of households owning both fixed and mobile. This indicates that mobile complements fixed,
rather than substituting it, although there may be a small element of substitution.
VoIP
VoIP technology allows users to make voice calls over data networks and particularly the
Internet. Calls can be made directly between users over the Internet, or between the Internet
and the PSTN, within the PSTN or within corporate networks. Voice over IP is perhaps a
greater threat to the conventional circuit switched PSTN than mobile and many operators are
starting to use VOIP technology within their networks. BT for example is now well advanced
in its plans to replace the PSTN with its 21st Century Network (See Appendix C) which will
carry voice using the VoIP protocols.
17
Some large UK corporates are moving to a VoIP platform: all large businesses have high
bandwidth IP connections so the benefit for them is free calls between corporate sites. The
Skype service is also proving very popular for both business and residential users who have
broadband, particularly because of free or cheap international calling, and also because of its
ease of use. Skype claims to have downloaded 250m copies of its free software. Vonage
have also launched a VoIP service in the UK. Following this, BT launched its own VoIP
service to broadband customers and also an SME service.
The impact of regulation on fixed voice
Regulation has had a significant impact on the fixed voice market by creating conditions that
facilitate carrier pre-selection (CPS) voice services, including the provision of a wholesale line
rental product from BT. Increased competition has led to innovative tariff changes such as
increased line rental in exchange for lower average call prices, or simply a flat rate charge per
month. With consumers also being willing to switch to a cheaper provider there has been a
reduction in total revenues for the fixed voice network. Although CPS services have taken an
increasing share of the market in recent years (see Appendix A), BT remains the dominant
provider, particularly for SME’s.
Recent regulatory action has led to the creation of BT Openreach as a separate company.
This will help to ensure fairer competition between BT provided voice services and competing
services that depend on the BT network infrastructure (see section 5.2.2).
Dependency of fixed voice on SDH
In the UK a high proportion of the PSTN traffic is thought to be carried over legacy PDH
systems (which also depend on the fibre infrastructure) with a smaller proportion carried over
SDH channels. Alternative network operators such as ntl and Telewest are thought to use
SDH for their voice networks. Some other operators (e.g. Telecom Plus) lease capacity from
other infrastructure providers and so are likely to also depend on SDH. The extent and detail
of these arrangements is not known. As BT plan to replace their circuit switched PSTN with
VOIP by 2008 (see Appendix 3) it seems likely that the PDH equipment will be replaced by a
SDH/OTN (Appendix D).
Mobile services
Three generations of mobile
Mobile services are now entering their ‘third generation’. First generation mobile was voice
only and was based on analogue techniques. This has been replaced by second generation
(2G) networks which are based on digital encoding and which also allow basic multimedia
services such as SMS messaging to be carried. 2G networks are widely used and most
networks now cover 99% of the population [1].
However the small bandwidth available in 2G networks has been insufficient for higher quality
multimedia services and so in recent years mobile companies have been investing in 3G
technology which will enable networks to carry broadband signals (typically 384 kb/s rising to
2 Mb/s) to and from a mobile device. In 2004 and 2005 the 5 principle mobile operating
18
companies (Appendix 2) introduced 3G networks as a complement to their 2G networks
(rather than as a replacement) with seamless handover when passing from one network to
another. Population coverage of the new networks in early 2005 ranged from 30% to 70%
(and this is no doubt growing), compared to 99% which is typical for 2G networks.
The services that are unique to 3G are video calling and video streaming. The broadband
transmission rates that are now available should also make existing services more appealing.
However in order to take full advantage of the 3G networks, a new range of mobile devices
and services has proved necessary. New devices are appearing but initial growth in take up
and usage of the services began slowly. (The reasons for this are discussed in Appendix A).
As 3G usage increases and higher speed data services are taken up the outlook is that the
fixed network interconnection capacity required by mobile services will increase in coming
years.
A more detailed view of the mobile market, based on the Ofcom report ‘The Communications
Market 2005 – Telecommunications’, is given in Appendix 1.
Mobile operators
The principle mobile network operators are:
•
•
•
•
•
Vodaphone
O2
Orange
T-Mobile
3UK
The impact of regulation on mobile
Unlike the fixed voice market there have been several main players in the mobile market with
a broadly similar market share and competition has been keen for several years. As a result
regulation has perhaps been lighter than for fixed voice. One area affected by regulation is
spectrum usage: radio spectrum is a scarce commodity and bids for spectrum come from
diverse groups, including from the military. The other area relates to interconnection charges:
earlier high prices for interconnecting from fixed to mobile and between mobile networks have
been reduced through regulation. Keen competition between the mobile operators has served
to ensure prices are held down.
Dependency of mobile on SDH
Mobile networks have a cellular radio part and also a fixed network part. The radio part
provides a network of base stations which can transmit and receive radio frequency signals to
and from mobile devices. The fixed part provides interconnections between the base stations
and the exchanges. It also provides the longer links needed between the different exchanges.
Both parts of the fixed transmission network are normally provided via private circuits. Lower
capacity private circuits to remote base stations are likely to be carried by bunched copper
pairs, using for example a low rate BT Megastream service or equivalent. Where base station
traffic is aggregated and higher capacity is needed aggregating services such as the BT
19
Megastream Longlines service, can also be used. For the higher capacity connections
between exchanges SDH links would be essential.
Every single mobile call in the UK must be carried across some part of the fixed network (in
some cases this may be over fixed SDH microwave links). The dependence of mobile on
fibre/SDH therefore is approaching 100%.
Internet
This section deals specifically with Internet services for consumers and SMEs. Corporate
large bandwidth Internet services are considered part of the Corporate Data services in
section 5.5.
Access methods
Access to Internet services can be via several methods. Narrowband access via the PSTN
has in effect been covered already in the section on voice networks. Access via leased lines
and ISDN are possible but they are at a low level and declining. The main method for Internet
access in the UK is now via broadband and a number of flavours are possible. Several types
of technology solution are used, including DSL over copper pairs, cable modems and fixed
wireless access. Broadband mobile wireless access was discussed in the previous section
and satellite access is generally available but is rarely used because of its high price.
Competition in broadband access can be either at the facilities (or infrastructure) level, or it
can be at the services level. Three main players provide infrastructure for broadband access:
BT through its copper pair network and ntl and Telewest through their cable TV networks. In
addition, some infrastructure is provided by via fixed wireless access and satellite. At the
services level consumers with access to ADSL are able to choose from more than 20
broadband ISP’s.
Growth of broadband
Broadband access has grown rapidly in recent years and has now become a mass market
consumer product, with more than 7.5m broadband connections in May 2005. Ofcom [1] has
reported that this growth has been driven by two major factors: BT’s widespread deployment
of DSL systems to make broadband available to 99.6% of the population by December 2005
and by falling prices, driven by competition. As the broadband service availability has
increased and the price differential between narrowband and broadband decreased,
customers who previously used dial up or unmetered access are migrating to broadband and
this is leading to increased revenues from broadband services.
Access speeds have also risen in the past two years. Previously 512 kb/s was the norm, but
now 1 Mb/s is commonplace and 2 Mb/s widely available as a premium service with 512 kb/s
as a discount option. This increase of speed seems set to continue and companies such as
Bulldog and UK Online now offer 4 Mb/s and 8 Mb/s services. As next generation technology
is introduced speeds of around 20 Mb/s should be possible.
20
Operators and market share
The main providers of broadband
infrastructure:
• BT
• Ntl
• Telewest
The main broadband service providers:
•
•
•
•
•
•
BT
Ntl
Telewest
Wanadoo
AOL
Tiscali
Further details of the providers are given in Appendix B.
Although the number of broadband customers served by BT virtually trebled in 2004, BT’s
proportion of subscribers fell slightly from 26% to 24%. Ntl and Telewest also saw reductions
in the proportion of subscribers. Wanadoo, AOL and Tiscali are the main competing service
providers and their market share increased over this period, as did that of other service
providers.
The impact of regulation on the Internet
The copper pair network is owned by BT and it delivered 67% of broadband connections by
the end of 2004. But regulatory actions have ensured that not all broadband services
delivered using copper pair and DSL technology are supplied by BT to the consumer. Resale
arrangements allow other entities to provide a ‘rebadged’ BT broadband service and sell
through their own channels, so creating competition at the retail level.
Local loop unbundling and shared access allow alternative network operators (alt-nets) to
make use of the BT copper lines but deliver broadband service using their own DSL
equipment. Collocation agreements allow the alt-net to site equipment on the BT premises
(e.g. Bulldog and UKOnline). Bitstream access allows an alt-net to use BT equipment (as in
resale) but to gain access to the data stream. This allows the alt-net to provide a greater
degree of service differentiation than simple resale.
At the core level it is thought that wholesale pricing applies to private circuits that can be used
for Internet connections and that interconnection charges between networks are regulated.
Dependency of Internet services on SDH
As with other services, Internet services have an access component and a core component.
The three main access methods (DSL, cable modem and fixed wireless access) depend in
different ways on SDH. First, DSL access depends on SDH for the backhaul connection
between local DSL equipment (sited at a local exchange and within a few km of the
customers) and the ISP (maybe 50 miles away). In this case the DSL signals are mapped into
ATM cells and then carried over private circuits using SDH links. Wireless access adopts a
similar architecture except the local distribution area is defined by the range and quality of
wireless coverage. Again SDH is used to carry the signals back to the ISP.
21
Cable modem architecture is slightly different as part of the backhaul connection (from the
‘optical node’ to the cable TV head end - up to 150 km from the customer) is carried over fibre
in an FDM multiplex. This is for compatibility with the TV service. From the ISP looking into
the Internet core, the signals are usually in an Ethernet format and again carried over an
SDH/fibre connection. Within the BT network the inner core part is carried over the ‘IP over
WDM’ Colossus network which uses SDH high speed interface standards so that the network
can be effectively managed (but which does not use SDH add-drop multiplexing, crossconnect technologies or low-order interfaces).
Corporate data
Corporate data services
Corporate data services are generally provided by network operators to deliver wide area
connectivity between business sites, connectivity to Internet points of presence or to extend
virtual private networks (VPN’s) to home workers. A large proportion of fixed telecoms
network operator revenue is derived from the supply of corporate data services.
Ethernet services are growing very rapidly and Web hosting too is expected to grow. Also,
with very high dependence on electronic data, businesses are turning to more resilient storage
area networks with their higher guarantees of reliable ‘mirror’ storage and instant switch-over
in the event of network failure. This trend has grown since the 9/11 terrorist activity.
The networks can be constructed from a mix of other operator services such as private
circuits, dial up lines or broadband Internet access. However as more people take up
broadband, other connection services such as ISDN, dial up and VPN access via private
circuits are likely to fall for both office to office and home to office connections.
WiFi hotspots
Business users also make significant use of public Internet access ‘hotspots’. These use WiFi
technology that allows users with laptops to gain access to the Internet whilst on the move.
This service grew significantly in 2004, with many broadband wireless access points being
provided at locations such as railway stations, airports and restaurants. Generally they are
designed for ‘portable’ access to broadband (where portable devices such as laptops can be
taken to a fixed location) rather than mobile where there are handover facilities between
adjacent cells.
The standards for WiFi are being actively developed to give higher speeds, better security and
quality of service and wider deployments. Another technology, WiMax is also being
developed to offer even wider bandwidths and offers the prospect of a wide range of
applications and possibly becoming a competitor to fixed line broadband access systems. A
mobile version of WiMax has already been standardised.
22
The impact of regulation on corporate data
Perhaps the main impact of regulation on corporate data networks is that it has created an
environment in which there are a number of alternative network operators able to provide
private circuits.
Dependence of corporate data services on SDH
Corporate networks depend heavily on private circuits carried over SDH for interconnections
between office sites, whether the service is based on a VPN or on conventional circuit
methods. Bunched copper pairs can be used for shorter links of a few km that carry up to 8
Mb/s. However, for higher bit rates or longer connections SDH is standard practice. When
VPN’s are extended to the home, dial up or broadband access is commonly used. If
broadband access is used then the dependencies on SDH are the same as for the Internet.
23
Security and resilience
Analysis of the key features of SDH and fibre optic technology suggests that the most likely
area for exploitation in terms of an electronic attack is through the management systems. The
opening up of the telecom market creates management system interconnect and
interoperability issues not only between providers but also between providers and clients for
the service, This is exacerbated from a security viewpoint because SDH was not originally
designed to allow secure working in this way as it was designed when the state owned Telco
was the norm.
Given the open source constraints of this high level study, specific security issues are not
detailed, however areas of potential concern are identified. These areas can be used in any
follow-up discussions with the providers, as it is only the providers who can validate and
comment authoritatively given the sensitivity surrounding potential vulnerabilities
The management of SDH networks is based on the Telecommunications Management
Network (TMN) standards (see Appendix E). However, actual implementations by different
manufacturers and operators can vary significantly. The detail of the security mechanisms
can also vary and in any case are kept confidential. This section therefore describes the types
of security mechanism that are available for use within TMN, including prevention of security
failure, detection and containment. Implementation of security policy is also considered.
Finally the areas of potential concern are discussed, including possible points of attack and
attack mechanisms.
SDH management systems
The TMN standards describe architecture from four different viewpoints, including functional,
physical, information and a logical layering. The standards split the network into a series of
layers, representing different types of management responsibility, starting with network
elements in the physical layer. Above this is an element management layer which deals with
all managed functions associated with a particular network element. A network manager
takes an abstracted view of a group of element managers so that network level functions such
as end to end connectivity and faults can be managed. Above this is a service management
layer which handles functions associated with customer services (such as access, billing and
QoS) and a business management layer which deals with policy and planning.
The various parts are linked together by a Data Communications Network (DCN). Often a
DCN will use private circuits for connectivity, although it is also possible that some form of
VPN may be used. Information is transmitted over the DCN when modifying the network or
service configuration, checking equipment status, investigating faults or downloading new
software releases etc. It therefore carries a great deal of sensitive information.
24
Security management
As part of the wider management framework, TMN provides the functionality to provide a
degree of security [11]. The extent to which this is implemented and the detail of how it is
implemented in particular manufacturer equipment and deployed systems are not openly
available. However the principles and type of protection described in the standards provides a
generic view of security methods.
In particular, the TMN standard addresses the requirements of a security policy and considers
security life cycle, including prevention, detection and containment and recovery. Prevention,
detection and containment and recovery functions are incorporated as appropriate at each of
the TMN layers.
Prevention
Prevention includes functions that restrict access to management systems and information. In
particular, for electronic vulnerability it includes functions that protect management operations
such as authentication, access control and data confidentiality. In addition security screening,
validating that a user or customer is trustworthy, provides a prevention measure. Screening
information is also likely to be held in a database.
Detection
Detection enables security breaches such as unauthorised access, corruption of data,
customer fraud and unauthorised actions to be specifically identified so that corrective actions
can be taken. Detection also includes the monitoring and analysis of alarm systems such as
those protecting power, heating and ventilation or the detection of intrusion. Usage patterns
can be monitored, for example by a particular customer, or traffic can be measured and
analysed to identify anomalies or to collect audit trail information.
Containment and recovery
Containment is the group of functions that limit damage to the network, such as isolating
viruses or revoking a customer’s privileges where activities are deemed to be unacceptable.
Recovery enables the restoration of service and network integrity by providing data back-up.
Containment and recovery actions may be initiated through an exception report arising from a
detection process. Revocation lists may also be held to prevent further access to those
known or suspected of being invalid due to security violations.
Security policy
Implementing a security policy requires the creation and dissemination of a substantial amount
of sensitive information. This may include encryption keys, access control rules, access
control certificates, directories, security event definitions and security audit logs. A security
administration system is therefore required to manage the processes which include creating,
disseminating and updating security data. This includes functions such as audit trail analysis,
disaster recovery planning and security alarm analysis.
25
Resilience
SDH is protected by a number of resilience mechanisms. Resilience includes both protection
and restoration mechanisms. Protection automatically and rapidly switches traffic over to a
reserved protection circuit in the event of a failure, while restoration involves searching for
available capacity and progressively switching traffic over following failure.
Premium circuits are usually protected, for example using ‘1+1’ protection which provides 1
spare circuit for every working circuit or with ring protection where the system is arranged in a
ring with both working and protection circuits. In the event of a ring failure the traffic is turned
around so that it follows the complementary section of the ring. In the BT network 1+1 is
widely used to protect the Tier 1 network while ring protection is commonly used in the Tier 2
and Tier 3 networks.
Resilience therefore depends on unused capacity in the network. Network operators must
therefore ‘trade-off’ the ability to easily and quickly restore failed circuits with the extra cost of
providing redundancy.
Areas of potential concern
Points of attack
Potential points of software attack in today’s network include those from within a management
centre , via the DCN or via the increasing number of interfaces between operators and service
providers. Regulation has led to an increased number of operators and their need for ‘end to
end’ service management increases the amount of management information that needs to be
exchanged between different operators and service providers over the established interfaces.
The number of interfaces and the amount of data passing over them is likely to increase as
greater control over network services is delegated to customers. Good security mechanisms
are available, but security depends on how tightly the security policies are managed. If the
security was compromised the potential for disruption would be substantial.
Risk of attack from within a management centre is minimised by careful vetting of staff, by
strong authorisation and authentication procedures, including frequent password changes,
and by the way responsibility for different parts of the network and different job functions are
partitioned.
In the future, these types of protection will need to be extended to customers as new services
give them a degree of control over the network configuration. In the early stages the
customers are likely to be large trusted organisations with good staffing practices but as
services develop this may filter down to smaller customers where practices may be more
variable.
Risk of attack via the DCN could be seen as more challenging as the DCN is distributed
across the whole network and points of weakness are more difficult to ascertain. Where
private circuits are used to provide connections the first level of protection is that they are not
publicly accessible and any access to physical equipment would require entry to an exchange
26
building, which are normally kept secure. If an intruder did gain access to an exchange
building that housed SDH equipment then a ‘CRAFT’ terminal associated with a network or
element manager would provide instant access to part of the SDH network. A CRAFT
terminal gives full control access to all features in that particular sub-network or element. In
this case access to the network manager would provide the greatest risk as it would give
access to many network elements.
It would be good practice for encrypted VPN’s to be used when providing remote access to
management system functions and network elements but whether these are currently
implemented would have to be validated with individual network and service providers.
Attack mechanisms
Ability to gain access to the DCN at the network manager level would allow service and
network configurations to be modified, for example changing the routing of 10Gb/s circuits
would immediately affect a wide range of services while suppressing alarms could conceal
later failures. A forced protection switching action could route traffic to a disconnected or
rerouted service. A combination of simultaneous changes could make problem identification
difficult.
Ability to gain access to an element manager would allow line system or cross-connect switch
parameters to be changed. Maladjustment of line amplifier parameters (e.g. the pump power)
could affect all wavelengths and therefore all services carried over a fibre system.
27
Conclusions and recommendations
The report describes the use of ‘Wide Area Network Optic and SDH technology by UK PLC’
by setting out the UK environment in terms of Services, Providers, Technology and the
Regulatory position using open source material. It was found that open source material on this
subject was readily available with one of the most useful sources being Ofcom. However, as
suspected, specific information on security surrounding SDH was less available but some was
found in telecom standards documentation. No supplier was directly approached during the
creation of this report.
Although SDH has become the preferred telecom transport technology to support premium
services in the UK since 1990, it is not an obsolescent technology. Since 1997 some routes
have been enhanced through combination with WDM which has substantially increased fibre
transmission capacity and reduced the ‘per bit’ transmission costs. More recent standards
developments have led to formal definitions for WDM technologies under the title ‘Optical
Transport Network’. The standards are under active development, particularly to make SDH
more efficient in carrying data services such as Ethernet and in providing better operational
flexibility and improved customer control.
The main service types which SDH supports from an analysis of the Ofcom data are:
•
•
•
•
Public voice telephony service;
Internet;
Mobile network services;
Corporate networks.
It is suggested that these four services support many of the critical national infrastructure
sectors, not only the telecoms sector. Without SDH these services could not operate and
therefore it is concluded that the UK critical national infrastructure is very much dependent on
SDH and Wide Area Network Optic technologies.
During the analysis it became clear that private circuits are used as a way of providing
interconnection capacity to other operators to enable them to build their own networks and to
provide their own services. In effect private circuits are an intermediate stage between the
end user services and the SDH network, although they are sold as a service to other network
operators. Therefore the critical national infrastructure is also dependent on private circuits.
In the UK, by far the most transmission capacity is provided by BT, though changing
regulation has ensured that other network operators now provide significant infrastructure,
particularly within and between major towns and cities. Because of its dominance in terms of
available infrastructure, it is concluded that special consideration should be given to the BT
network as well as general consideration to other networks.
28
SDH was designed and developed when the emphasis on electronic security was not such an
issue, because it was mainly deployed within a trusted environment such as the state owned
Telco. There are, however, security features which can provide some protection. Whether
these are sufficient in the new environment with interconnected multiple operators and a less
trusted environment have not been studied within this report.
However, SDH does offer a high degree of resilience against network failure and some
security against electronic attack, but with the caveat that the security is only as good as the
associated security policies and their implementation.
It is concluded that there are potential opportunities for compromise if an attacker were to gain
access to the data communications network or to the management system. Unauthorised
access to network or element managers could lead to major service disruption. But providing
that security policies are carefully implemented the disruption could be contained.
Unauthorised access to the higher level management systems could allow billing or service
levels to be compromised. This conclusion is not based on a vulnerability analysis of specific
service offerings but on the technology and management systems in general.
Due to the open source nature of this report, not all aspects could be studied. Therefore the
following recommendations are made for future investigation if thought necessary:
1. The current standard security features available within SDH and Wide Area Network Optic
technologies could be studied to see if they are complete and effective in the new
environment where you have interconnected multiple operators and clients;
2. Suppliers could be approached to understand how the security features of the technology
are deployed and how effective they are against an electronic attack;
3. The BT networks could be studied in more depth, given that they are the dominant
supplier and likely to lead the way on standards and potential improvements in security;
4. An analysis could be made of the effectiveness of the security in relation to each of the
major service offerings to see if one was less secure than another and therefore to judge
best practice;
5. Dependent on the results of the previous points, a good practice guide could be produced
outlining how best to secure SDH and Wide Area Network Optic technologies.
29
Appendix A: Ofcom telecommunications report 2005
This appendix examines the key markets as described in the Ofcom report ‘Communications
Market 2005 – Telecommunications’. The Ofcom report has taken perhaps the most
comprehensive recent and authoritative analysis of the various markets that is openly
available. It identifies key themes that take account of industry structure and competition
which provide a broad view of the telecommunications market up to 2005, with emphasis on
developments in 2004. It then looks at trends in telecommunications services from both
industry and user perspectives and the impact that competition has had on the services.
In this Appendix the charts, and messages from the charts, are the same as in the Ofcom
report. However the information has been reorganised on the basis of the four major services
provided so that the market information can be more clearly seen in the context of the CNI.
The first section discusses the overall size of the telecoms market and subsequent sections
examine the individual market sectors, including fixed voice, mobile, Internet and corporate
data.
Size of the telecoms market
Key players
Figure 6 gives a summary of the main telecoms market players
Figure 6 UK telecoms market players (NB Energis has been bought by C&W)
30
Turnover and value added
Ofcom estimated that the size of the UK telecoms sector in relevant turnover terms was
£44.6bn in 2004. This
Figure 7 Turnover of UK wholesale and retail telecom markets
The value added by the UK telecoms sector to GDP was measured as £25.5bn in 2003 and
estimated as £26.7bn in 2004, or 2.8% of GDP.
Figure 8 Value added by UK telecoms industry
BT was the biggest player in the industry by far, but its share of the market has fallen to 41%,
lower than that of most other incumbent operators in other countries. This reflects the degree
of competition in the UK and also the fact that BT does not have a mobile network business.
31
Figure 9 Share of telecom industry revenues
Another way of viewing the telecom market share is by examining the number of connections
(of all kinds) provided by each of the network operators. This also illustrates the degree of
competition in the market.
Share of market connections
Figure 10 Share of UK telecom connections
32
Service revenues
During 2004 the total revenues from mobile voice and data exceeded the revenues from fixed
calls and access for the first time. This applied to both residential and business customers.
Figure 11 UK telecoms industry retail revenues
Examination of the changes from 2003 to 2004 shows that mobile is the biggest single driver
for growth.
Ofcom also estimated that businesses accounted for almost a half of all end user spending on
the main telecom services in 2004, amounting to over £14bn.
Figure 12 Business spending on telecom services.
33
Fixed line voice
Call volumes
Overall Ofcom reports that fixed voice traffic declined slightly in 2004, partly due to mobile call
substitution, but also because of other forms of substitution. However, regulatory intervention
to facilitate carrier pre-selection (CPS) call services and, more recently, the provision of a
wholesale line rental product from BT, has assisted a number of recent entrants to achieve
strong growth in terms of both customers and revenues. This competition led to innovative
tariff changes such as increased line rental in exchange for lower average call prices, or
simply a flat rate charge per month.
Voice over IP, the technology that allows voice calls to be carried over the Internet is also
likely to be having an effect although at this stage Ofcom have not gathered data to analyse
this. VOIP is expected to become a preferred mechanism for voice calls in a future converged
environment. The Skype service in particular claims to be handling huge volumes of calls
worldwide and this is becoming popular for both business and residential calls.
Figure 13 Fixed and mobile voice traffic volumes
There was also a reduction in both call volumes and in the total PSTN exchange lines in the
same period. Ofcom attributs this partly to mobile substituting voice calls and partly to
broadband substituting both ISDN connections and second lines for Internet access. This
effect was noticeable particularly in ‘high end’ users.
34
Figure 14 Fixed telecom lines
Figure 15 Fixed telecom call volumes
Revenues
The result of the reductions in fixed lines and call volumes was a reduction in total revenues
for the fixed voice network. However a more important factor in the reduced revenues was the
effect of stiff price competition, the introduction of new tariff schemes and the willingness of
consumers to switch to a cheaper provider.
Figure 16 Average UK fixed telecoms call revenues
35
Figure 17 Fixed line voice telecoms revenues
Fixed line usage
In spite of some substitution of mobile the average use per residential fixed line has been fairly
constant in recent years.
Figure 18 Average use per residential fixed line
In addition to substitution by mobile, voice calls are sometime substituted by SMS messaging
or by e-mail. The following responses indicate this effect.
Figure 19 Reasons for replacing fixed voice with messaging
36
Figure 20 Reasons for replacing fixed voice with e-mail
Business use
Voice calls for business have been falling in recent years and it is likely that e-mail and other
forms of electronic communication (such as VOIP) have led to this change.
Figure 21 Average use per business fixed line
Carrier pre-select services (Indirect Access – IA) appear also to have taken increased market
share in businesses while BT’s market share has reduced. Ofcom reports that BT remains the
dominant supplier to SME’s, with 86% using BT services for some or all of their requirements.
Figure 22 Market share of business call volumes
37
Fixed and mobile
Although fixed voice call volumes have been falling and mobile calls growing, there seems no
likelihood in the near future that mobile will replace the fixed line market. The number of
household with mobile phone only is 9% and those with fixed line only is 10%, with the
majority of households with both fixed and mobile. This indicates that mobile complements
fixed, rather than substituting it, although there may be a small element of substitution.
Figure 23 Household penetration of fixed and mobile telephony
The levels of fixed line ownership are fairly similar across the UK.
Figure 24 Household penetration of fixed/mobile telephony among the nations
Around 20% of consumers said they use mobile as their main way of making calls and Ofcom
research showed that around 42% of all consumers used their mobile phone in preference to
a fixed line citing cost, convenience and availability as the main reasons.
Figure 25 Main method of making and receiving calls among UK adults
38
VOIP
VOIP technology allows users to make voice calls over data networks and particularly the
Internet. Calls can be made directly between users over the Internet, or between the Internet
and the PSTN, within the PSTN or within corporate networks. Voice over IP is perhaps a
greater threat to the conventional circuit switched PSTN thann mobile and seems likely to
force all voice network operating companies to rethink their pricing and investment strategies
and particularly BT, cable and mobile operators. BT is now well advanced in its network plans
to replace the PSTN with its 21st Century Network which will carry voice using the IP protocols.
VOIP has seen an increase in take up with some large UK corporates moving to a VOIP
platform. All large businesses have high bandwidth IP connections so the benefit for them is
free call between corporate sites. For residential users the benefits are less immediate as
both caller and called parties must have a broadband connection and both must download the
same software. Skype is proving very popular, particularly because of its ease of use, and
also because of free or cheap international calling. Skype claims to have downloaded 250m
copies of its free software. Vonage have also launched a VOIP service in the UK using an
adapter that sits between a customer’s normal telephone and their broadband connection.
Following this, BT launched its own VOIP service to broadband customers and also an SME
service called BT Business Broadband Voice. These developments are likely to have
significant impact in the future on voice calls.
Mobile
Call volumes
Call volumes for mobile were discussed in the Fixed Line Voice section.
Revenues
Mobile revenues are close to those generated by fixed calls (see also Figure xxx in fixed call
revenues section). There has been a trend to bundle services together within the monthly fee,
particularly SMS messaging with voice. When SMS revenues are also included the mobile
total exceeds fixed voice revenues. Overall mobile retail revenues were £12.3bn in 2004.
However data revenues other than SMS remain very low.
Figure 26 Mobile retail revenues
39
Most of the increased revenues are attributed to growth in customer numbers. However the
market is now reaching saturation and it seems likely that mobile operators will strive to
encourage use of new data services.
Regulatory controls on the prices mobile operators can charge for interconnection with other
networks have brought prices down and affected revenues.
Mobile usage
At the end of 2004 the five mobile network operators reported that there were 61.4m mobile
users in the UK, more than one per head of population. This may be accounted for in part by
users holding more than one type of device (for example a mobile phone and a ‘blackberry’ email device). It is also possible that not all of these users are active.
Figure 27 Mobile active customers
The 4 main mobile operators have retained a fairly equal share of the customer base, while
3UK have grown their customer base, and has become a significant player.
40
Figure 28 Active mobile customers by network operator
Revenues by the main operators remain in relative proportion to the size of the customer
base. Vodaphone does particularly well in part because it dominates the top end corporate
market.
Figure 29 Estimated retail revenues by network operator
SMS messaging has also grown in recent years although the growth appeared flat in 2004.
The chart below shows messages per customer, so the figures for 2004 may be slightly
suppressed because some users have more than one device. Ofcom research in 2004
showed that over 40% of consumers claimed to send a mobile text message instead of
making a fixed voice call, generally because it was perceived to be cheaper and more
convenient than making a call with their fixed phone.
41
Figure 30 Average SMS and MMS messages sent per active mobile customer
The use of WAP (for Internet access) and MMS (for picture transmission) services remains
low.
Business use
The penetration of mobiles among small businesses is low compared to that for residential
use, with less than 60% claiming to own a mobile phone. Small businesses place greater
importance on access to data.
Figure 31 Penetration of mobile telephony among SMEs
Internet
Access to Internet services can be via several methods. Narrowband access via the PSTN
has been discussed already in the section on voice networks. Access via leased lines and
ISDN are possible but is at a low level and declining. The main other method to be examined
is broadband access.
Broadband access has grown rapidly in recent years and has now become a mass market
consumer product, with more than 7.5m broadband connections in May 2005.
42
Figure 32 Broadband penetration in the UK
The reasons for this growth has been driven by two major factors: BT’s deployment of DSL
systems to make broadband available to 99.6% of the population by December 2005 and by
falling prices.
Figure 33 Average UK residential subscription prices from broadband
Consumers with access to ADSL are able to choose from more than 20 broadband ISP’s
(including BT, Tiscali, Wanadoo, Blueyonder (Telewest) and AOL). If they live in a cable area
they can also opt to take service from either Telewest or ntl.
Access speeds have also risen in the past two years. Previously 512kb/s was the norm, but
now 1Mb/s has become the norm with 2Mb/s generally available as a premium service and
512kb/s as a discount option. This increase of speed seems set to continue and companies
such as Bulldog and UK Online offer 4Mb/s and 8Mb/s. As next generation technology is
introduced speeds of around 20Mb/s should be possible.
The majority of these connections are supplied via BT’s copper pairs and DSL technology.
However not all are supplied entirely by BT. A high proportion is provided through ‘resale’
arrangements in which BT provides the equipment and maintains the network under a
wholesale arrangement, but the services are sold by the resale provider. A smaller proportion
are sold through local loop unbundling arrangements in which the alternative network provider
provides the DSL equipment and the local connection is diverted to this equipment, rather
than to the BT equipment.
43
Broadband is now widely available across the UK.
Figure 34 Broadband availability across the UK
As the broadband service availability has increased and the price differential between
narrowband and broadband decreased, customers who previously used dial up or unmetered
access are migrating to broadband. This is leading to increased revenues from broadband
services.
Figure 35 UK Internet connections
44
Figure 36 Internet and broadband provision service revenues
Broadband access competition can be either at the facilities or infrastructure level, or it can be
at the services level. Three main players provide infrastructure: BT, ntl and Telewest. In
addition, some infrastructure is also provided by via fixed wireless access, satellite and local
loop unbundling (LLU). With LLU alternative network operators are able to lease copper pairs
from BT and to install their equipment in the local exchanges. Limited deployment of cable
infrastructure and low take up of LLU meant that BT wholesale products provided 67% of
broadband connections at the end of 2004.
Figure 37 Broadband connections
Although the number of broadband customers served by BT virtually trebled in 2004, BT’s
proportion of subscribers fell slightly from 26% to 24%. Ntl and Telewest also saw reductions
in the proportion of subscribers. Wanadoo, AOL and Tiscali are the main competing service
providers and their market share increased over this period, as did that of other service
providers.
45
Figure 38 UK broadband service provision: share of subscribers
Ofcom reported that, by the end of 2004, 55% of UK homes had an Internet connection and
63% had a PC, though there was some variation across the UK with Wales being significantly
lower on Internet connections.
Figure 39 Internet and PC penetration in UK homes
In addition to home use, Ofcom reports that around a quarter of all UK adults use the Internet
at work and others use them at Internet cafes and libraries. A significant proportion claim they
have no need for an Internet connection and gave the following reasons.
Figure 40 Reasons for not having the Internet at home
46
Ofcom research indicated that broadband users say they spend more time on the Internet (18
hours) than narrowband users who claimed to spend around 8 hours. Also broadband users
are more likely to use more advanced features. In particular, broadband users download
more music and videos, use messaging services more and purchase more on line.
Figure 41 Online applications used by broadband and narrowband users.
Corporate data
A large proportion of fixed telecoms network operator revenue is derived from the supply of
corporate data services. Business data services are generally provided by network operators
to deliver wide area connectivity between business sites, or to extend virtual private networks
(VPNs) to home workers. Services can be integrated with more well-known services such as
leased line and dial up or broadband Internet access. Historical data was not available to
Ofcom and so a forecast was prepared instead.
The forecast indicates that leased lines are expected to give way to VPNs. As VPNs are
extended to home workers, the recently established widespread availability of broadband
services can also be seen as an important factor. Ethernet services are growing very rapidly
and Web hosting is also expected to grow.
Figure 42 Corporate data service revenues
47
Increasing numbers of SME’s are taking up broadband Internet access while the numbers of
ISDN lines and dial up connections are reducing.
Figure 43 SME Internet access by connection method
Business users also make significant use of public Internet access ‘hotspots’. These use WiFi
technology that allows users with laptops to gain access to the Internet whilst on the move.
This service grew significantly in 2004, with many broadband wireless access points being
provided at locations such as railway stations, airports and restaurants. Generally they are
designed for ‘portable’ access to broadband (where portable devices such as laptops can be
taken to a fixed location) rather than mobile where there are handover facilities between
adjacent cells.
Roaming agreements allow customers of one operator to make use of networks belonging to
another. Thus many more hotspots are advertised than there are physical locations.
Nonetheless there were around 8000 hotspots available across the UK by the end of 2004
with more than 20 operators offering service. However even this coverage is small compared
to mobile coverage.
The standards for WiFi are being actively developed to give higher speeds, better security and
quality of service and wider deployments. Another technology, WiMax is also being
developed to offer even wider bandwidths and offers the prospect of a wide range of
applications and possibly becoming a competitor to fixed line broadband access systems. A
mobile version of WiMax has already been standardised.
48
Appendix B: Service providers, carrier operators and
equipment providers
Details of mobile operators
Company
Contact
Location
Ownership
Size
Company
Contact
Location
Ownership
Size
Company
Contact
Location
Ownership
Size
Vodafone UK
Vodafone Group plc,
The Courtyard,
2-4 London Road,
Newbury,
Berkshire RG14 1JX
Tel: +44(0) 1635 33251
Newbury, UK
Vodafone Group plc
5000+
O2
O2 Ltd
Wellington Street
Slough
Berkshire SL1 1YP
Tel: +44(0)113 272 2000
Web: www.o2.com
Slough, UK
Telefonica, Spain
5000+
Orange UK
Orange plc,
The Chase
John Tate Road
Foxholes Business Park
Hertford SG13 7NN
Hertford, UK
France Telecom
5000+
49
Company
Contact
Location
Ownership
Size
Company
Contact
Location
Ownership
Size
T Mobile
T-Mobile - Head Office
Comet Way
Hatfield Business Park,
Hatfield, AL10 9BW
Tel: + not available
Hatfield, UK
Deutsche Telekom AG
5000+
3UK
3G UK Ltd
Star House
20 Grenfell Road
Maidenhead
SL6 1EH
Tel: 0870 7330333
Hatfield, UK
Hutchison 3G UK Limited
5000+
Details of carrier operators
Company
Contact
BT plc
BT Centre
81 Newgate Street
London EC1A 7AJ
Tel: 0207 356 5000
Location
Ownership
Size
London, UK
BT Group
50000+
Company
Contact
Cable and Wireless plc
Cable & Wireless plc.
124 Theobalds Road,
London, WC1X 8RX
Tel: 020 7315 4000
Location
Ownership
Size
London, UK
C&W
10000+
50
Company
Contact
ntl
ntl House
Bartley Wood Business Park
Bartley Way
Hook
Hampshire RG27 9UP
Tel: 01256 75 1045
Location
Ownership
Size
Hook, UK
ntl Group Ltd
2000+
Company
Contact
Telewest
Currently merging with ntl
Location
Ownership
Size
London, UK
ntl
1000+
Company
Contact
Global Crossing
Chineham Gate
Crockford Lane
Chineham Business Park
Basingstoke, Hants
U.K. RG24 8NA
Tel: 0 845 000 1000
Location
Ownership
Size
Basingstoke
Global Crossing, USA
5000+?
Company
COLT Telecom Group plc
Contact
Location
Ownership
Size
Beaufort House
15 St Botolph Street
London
EC3A 7QN
Tel: +44 (0)20 7390 3900
Fax: +44 (0) 20 7390 3901
[email protected]
London
Colt
5000+?
51
Company
Contact
Location
Ownership
Size
SURF Telecoms
Western Power Distribution
Venture Way
Priors Wood Industrial Estate
Taunton
Somerset
TA2 8DG
Telephone: 01823 348 710
Fax: 01823 348 688
London
Western Power Distribution
1000+?
Details of equipment suppliers
Company
Contact
Alcatel
Alcatel IP Networks
7a The Long Room
Coppermill Lock
Canal Side
Harefield UB9 6JA
Tel: 0870903 3600
Location
Ownership
Size
Paris, France
Alcatel
58000
Company
Contact
Lucent Technologies
Lucent Technologies
600 Mountain Ave.
Murray Hill, NJ 07974-0636
Tel: +1 908 582-3000
New Jersey, USA
Lucent
30000 +
Location
Ownership
Size
52
Company
Contact
Location
Ownership
Size
Fujitsu
Fujitsu Telecommunications Europe Ltd
Solihull Parkway
Birmingham Business Park
Birmingham
B37 7YU
Tel: +44 (0) 121 717 6000
Fax: +44 (0) 121 717 6161
www.fujitsu.com/uk/services/telecom
[email protected]
Birmingham
Fujitsu, Japan
100000 +
Details of fibre cable manufacturers
Company
Contact
Location
Ownership
Size
Pirelli (now Prysmian Cables & Systems)
Cannot find details in time available
Company
Contact
Function
Location
Ownership
Size
BICC
Cannot find details in time available
Company
Contact
Corning optical fibres
Second Avenue
Deeside Industrial Park
Deeside
Flintshire
CH5 2NX
Tel: 01244 281281
UK
n/a
1000 +
Location
Ownership
Size
53
Appendix C: BT 21st century network
The main network development activity currently underway in the UK is the BT 21st Century
Network (21CN). This is a radical and comprehensive replacement of BT’s 22 different
networks and some 2000 operational support systems. The networks include the PSTN (from
the core out to concentrator level), leased line, WDM, SDH, PDH, KiloStream, MegaStream,
data and other service networks. From the concentrator level out to the customer will remain
mainly analogue. The published target is to switch off these networks, including the circuit
switched PSTN by 2008. The challenge is to keep the services fully running while this takes
place. During the transition period extensive interworking between old and new networks and
between old and new OSS will be essential if service disruption is to be avoided. The
timescales are therefore short because operating two parallel networks will be very costly.
While other administrations have offered VoIP services or carried out partial replacement of
circuit switched technology with IP based technology, BT is the first to attempt to carry out a
comprehensive core/metropolitan network replacement. Estimated to cost £2 billion per
annum up to the end of the decade the objectives are ambitious. They are (i) to improve the
customer experience and provide them with a much increased level of choice and control, (ii)
to provide a single converged platform able to efficiently deliver new services and (iii) to
reduce operational costs by about £1 billion per year from 2008/9. The stated target is to
achieve a 40% reduction in whole life costs of the network. The initiative recognises the many
types of convergence taking place today, including hardware and software, voice and data,
fixed and mobile etc. and the aim is to provide a network platform able to support all types of
convergence.
Logical
Nodes
~80,000
PCPs
in the
Access
Network
Today
~100,000
Remote
Concs,
DLAMS
& Data
Muxes
~1000 +
Voice Switches
and Data Cross
Connects
~170 Core
Switches
(DMSU / NGS)
Data
Centre
International
Networks
Internet
Peering
End Customer
Logical
Nodes
Future
Begin
Fibre
to the
PCP
~30,000
MultiService
Access
Devices
~100
Metro
Routers
~10
Core
Routers
Aggregation
Service Edge
Core
Data
Centre
Figure 44 Migration of BT network to 21CN. Source: BT presentation by Paul Reynolds
54
21CN is built around a common core IP platform that has the capability to support both data
and real time services: it will offer capability to support the highest speeds and they plan an
unprecedented open and transparent approach. It will be controlled by an intelligence layer
that is mobile enabled and based on 3GPP concepts (c.f. mobile without the handover). OSS
is based on commercial off-the-shelf equipment in a hub architecture. It will use a work
manager approach that allows new services and applications to be built in an open way on a
common core in the hub. Policy control mechanisms will ensure security and privacy.
ATM and Frame Relay will be replaced by IP/VPN’s, the PSTN by VoIP and video services will
be added. Services will be converged to Ethernet /IP over fibre and DSL. It will be possible to
connect any device from anywhere, including a Bluephone service that allows a standard
mobile phone to connect either to an access point on a fixed network in the home or office or
to a GSM network in a seamless way.
55
Appendix D: Evolution of SDH
Synchronous Digital Hierarchy (SDH) and Synchronous Optical Network (SONET) are two
families of closely related standards that govern parameters for high speed transmission.
SDH, with a basic rate near 155 Mb/s, is used principally in Europe and Asia and commonly
handles tributary channels at multiples of 2Mb/s while SONET, with a basic rate near 52 Mb/s
is used principally in N America and was designed to handle 1.5 Mb/s granularity tributary
channels. 1.5 Mb/s signals can be mapped into SDH containers and 2 Mb/s signals can be
mapped into SONET. Higher speed signals map into the SDH bit rates of 155Mb/s and
above. SONET and SDH are both able to carry TDM and packet traffic.
All transport resources in an SDH system are allocated on a TDM channel basis. Any
aggregation of packet traffic is left to the client layer services network while the SDH network
focuses on its task of transporting signals reliably between end points. This keeps SDH
network design simple but it has the deficiency that it does not allow differentiation between
lucrative high-end services and best-effort low-end services: all data is treated equally.
Main elements of SDH systems
The main elements of SDH are optical line systems (consisting of optical transmitters,
regenerators and optical receivers), add-drop multiplexers and cross-connect switches.
First generation SDH consisted of the line systems and a single-stage
multiplexer/demultiplexer that aggregated various lower-rate inputs (e.g. 2Mb/s and n x 2
Mb/s) into a high-speed line signal (e.g. 155Mb/s). At an add/drop site, only those signals that
need to be accessed are dropped or inserted, with the remaining traffic continuing through the
network element without requiring special processing. The ADM’s could be configured either
as a linear system or, more commonly, as a resilient ring such as in a Bidirectional Line
Switched Ring (BLSR).
Second generation SDH introduced cross-connect elements, which enabled carriers to
perform TDM channel switching at the edge of the SDH network, allowing further automation
of service provision or service change processes. In addition, Ethernet interfaces were added
to enable simple and transparent mapping of Ethernet traffic to SDH/SONET circuits. These
enhancements and traffic multiplexing options have been advantageous while the network still
predominantly carries synchronous voice traffic, but has also to carry some data traffic.
Enhancements to SDH through the use of WDM and optical amplifiers have enabled SDH
systems to reach across much greater distances and with far higher capacities. Strictly
speaking, WDM and optical amplifiers are standardised under the name Optical Transport
Network (OTN), rather than SDH. Typically the WDM and amplifier components are
integrated into the same equipment as SDH for economic reasons. WDM equipment is
available that allows individual wavelengths to be added or dropped at a node in the same
way that SDH allows a 2 Mb/s or 155Mb/s channel to be added or dropped.
56
Next Generation SDH/SONET technologies
Since the late 1990’s standards bodies have defined and developed a new optical layer able
to support multiple protocols and recently a new transport hierarchy has been introduced,
known as the Optical Transport Hierarchy (OTH). This is in effect an extension of the SDH
standards for the Optical Transport Network (OTN).
OTN has been developed for core network applications and is analogous to the SDH
standards, but with enhancements. In particular OTH allows multiplexing to be extended into
the optical domain and uses a new frame structure known as a digital wrapper, which provides
transparent transport of SDH and other client payloads (such as Ethernet) across the optical
domain with full carrier class management functionality.
OTN provides consolidated data transport, allowing SDH, Ethernet and other packet formats
to be efficiently mapped into optical data units which can be routed across a network under
the control of MPLS switching (Multi Protocol Label Switching), rather than TDM switching.
The first equipment products based on OTN are now available from leading manufacturers
though the standardization process is not yet complete and interoperability testing is ongoing.
A key feature of data networks has been the ability of a service to request capacity from a
lower network layer when it is needed, packet by packet. When the capacity is not needed by
that service it is available to be used by other services and users. (For example the Media
Access Control layer in an Ethernet must handle these requests and resolve contention when
two users both want the same channel at the same time). No equivalent mechanism existed
in earlier SDH systems as the process of setting up a circuit connection in an SDH network up
to now has been carried out via a network manager and involves manual steps. Given the
increased volumes of data and the need to utilise capacity efficiently, data services need to be
able to request capacity from the underlying physical layer as and when it is needed.
Improvements to the basic SDH standards have therefore been recently developed in the
following ways.
1. A variety of formats and rates are used by data networks that up to now have been
awkward to map into SDH. A Generic Framing Procedure (‘digital wrapper’) has been
developed to allow a wide range of packet formats to be readily adapted to SDH
containers.
2. Multi Protocol Label Switching has being adapted for application to SDH networks in a
general form (called GMPLS). This allows improved end-to-end management and control
of a transport network through supporting the dynamic provisioning of resources.
3. In practice, SDH network planning leads to ‘stranded capacity’ where capacity on a link is
unused, but cannot be used by a new connection because available bit rates in adjacent
links don’t match. Virtual concatenation (VCAT) allows this stranded capacity to be
utilised. It also allows the transmission capacity to be more accurately matched to the
capacity needed by the data network.
57
4. Adjustment of the transmission capacity needs to be done dynamically to get best
efficiency from virtual concatenation. The Link Capacity Adjustment Scheme (LCAS)
provides the signalling protocol to allow this to happen allowing hitless in-service addition
and removal of STM containers to or from a virtual concatenation group.
5. Conventional SDH ring architectures provide (circa) 50 ms protection switching in network
failure scenarios but in most cases but the capacity to provide this protection is largely
wasted. Resilient Packet Ring (RPR) is a packet based transport technology that adopts
statistical multiplexing to better utilize all available bandwidth, including protection
bandwidth. The fibre ring is still able to provide 50 ms protection switching for high
network availability.
These techniques are described more fully below.
Generic Framing Procedure (GFP)
Ref: ITU-T Recommendation G.7041, ANSI T1.105
Generic Framing Protocol is designed to adapt a variety of character and packet oriented
payloads into SDH so they can be mapped into SDH containers. This will allow SDH to
readily carry data and storage protocols such as Ethernet, Fibre Channel and ESCON. GFP
has wide industry support and interoperability tests are under way.
Generalized Multiprotocol Label Switching (GMPLS)
Ref: Internet Engineering Task Force (IETF) draft-ietf-ccamp-gmpls-sonet-sdh-08.txt and
draft-ietf-ccamp-gmpls-architecture-07.txt.
GMPLS is a family of protocols under development by the IETF designed to extend MPLS to
encompass SDH channels, wavelengths and even whole fibres. The attraction of GMPLS is its
ability to improve end-to-end management and control of a transport network through
supporting the dynamic provisioning of resources.
NB MPLS is a framework specified by the IETF to enable efficient designation, routing,
forwarding, and switching of traffic flows through a network. It specifies mechanisms to
manage traffic flows of various granularities between different hardware, machines or
applications and provides a means to map IP addresses to simple, fixed-length labels used by
different packet-forwarding and packet-switching methods. MPLS interfaces to existing
routing protocols such as resource reservation protocol (RSVP) and open shortest path first
(OSPF). It supports the IP, ATM, and frame-relay Layer-2 protocols but remains independent
of them.
Virtual Concatenation
ITU-T Recommendation G.707 and G.783, ANSI T1.105
Virtual Concatenation (VCAT) aggregates fragmented virtual containers between two end
points to form a higher capacity virtual channel. The virtual containers do not have to be
contiguous within the SDH frame and do not even have to follow the same route to the
common destination.
58
In a traditional SDH connection, Gigabit Ethernet, mapped over SDH, would occupy an entire
STM-16 (2.5 Gb/s) channel, leaving 1.5 Gb/s unused. Similarly a 10 Mb/s Ethernet would be
carried in a 51 Mb/s VC-3, meaning 41 Mbps would be unused. VCAT allows channel
capacity to be built as needed from selected combinations of tributaries. These tributaries can
be logically combined, with the individual tributaries being routed independently across the
network.
VCAT can be viewed as an inverse multiplexing scheme in which a number of virtual
containers are bound together to form a virtual concatenated group. Thus a single GbE
service channel could be supported by say 8 separate VC4 channels in the SDH network. A
crucial property of VCAT is that it does not place any new requirements on the existing SDH
network since the containers that make up the group travel independently from the source
over the SDH network to their common destination. Hence it is sufficient to support VCAT
only in both termination points. This allows a smooth upgrade path, since VCAT equipment
needs only to be provided at the endpoints to establish the connection. The rest of the network
remains unchanged. Trail trace and parity checks are made on the group as a whole.
Link Capacity Adjustment Scheme
ITU-T G.7042/T1.105
LCAS provides the signalling control mechanism for the VCAT groups, giving the carrier
dynamic bandwidth and protection management. LCAS allows hitless in-service addition and
removal of STM containers to or from a virtual concatenation group. Capacity can be
dynamically adjusted to match the service need, restore failed circuits or adjust capacity
during failure.
For example a 1 GbE signal may only require 100 Mb/s of bandwidth on day 1, and so only
one VC-4 is needed across the SDH network. Later as the traffic grows additional VC-4s can
be connected up to the maximum bandwidth of the GbE interface. Commands to provide,
remove or change the service may come from the Network Manager or Automatic Switched
Transport Network (ASTN) control and may be triggered by customer demand, protection or
restoration plans. The scheme allows temporary removal of failed VC members, allows
automatic decrease of capacity during network failures and automatic increase after recovery.
This feature can be used to plan a service that can tolerate a defined minimum bandwidth
during failure conditions, but under normal conditions has a higher bandwidth allocation.
Additionally, the LCAS protocol provides load sharing protection by dynamically removing
failed members from the group when there are faults. This temporarily reduces the bandwidth
of the end-to-end service, but the applications that use the channel are usually capable of
adapting to such varying bandwidths. This functionality allows a provider to significantly
improve the resilience offered to end users by provisioning diversely routed SDH paths that
belong to the same group. The combination of VCAT and LCAS is a very powerful addition to
the SDH standard as it solves the bandwidth granularity problem and harnesses stranded
capacity without requiring huge changes to existing equipment.
59
Resilient Packet Rings
IEEE specification 802.17
Resilient Packet Ring (RPR) is a transport technology that has been available for several
years and is now being deployed to support IP based multimedia services.
Conventional SDH ring architectures provide 50 ms protection switching in network failure
scenarios but in most cases but the capacity to provide this protection is largely wasted. Also,
because SDH is channelized, no statistical multiplexing gain can be achieved between
channels, leading to network inefficiencies because unused bandwidth on one channel cannot
be utilized by another.
Resilient Packet Ring (RPR) is a packet based transport technology that adopts statistical
multiplexing to better utilize all available bandwidth, including protection bandwidth. The fibre
ring is still able to provide 50 ms protection switching for high network availability. RPR also
provides several levels of Quality of Service (QoS) guarantees, including QoS sufficient to
support any type of TDM service transported over packets.
60
Appendix E: Element and network management
ITU-T Recommendation M.3010, Principles for a Telecommunication Management Network.
Management and control features of SDH
SDH networks are made up of a set of network elements. Basic elements include
•
•
•
•
Point to point systems (including interface cards, multiplexers, protection switching
mechanisms, transponders, optical amplifiers and regenerators etc.)
Add-drop multiplexers
Cross-connect switches
Ring systems
Each element is managed by an element manager which holds a complete data
representation of the components in the element, including what is in the element, how it is
configured, and status etc.). Normally there will be a craft terminal associated with the
element which provides facilities for configuring and interrogating each component within the
element. A LAN operates within the element to provide data communications within the
element.
Each element manager in a network is connected to a network manager via a Data
Communications Network (DCN). The network manager is able to look across abstracted
data from all element managers within its domain to manage end to end processes such as
provisioning and maintenance and to ascertain root causes of faults. The network manager in
turn is linked to a Network Operations Unit (NOU) which allows personnel to intervene in
network operations.
Behind the NOU there are generally a series of Operational Support Systems (OSS) that
provide the tools for operational functions such as plan and build, assign and configure service
and maintain and restore. These also include other essential data such as information about
the cables and fibres in the network. Usually the operational support systems and network
manager (at least in early systems) have been provided by the network operator.
61
The following diagram illustrates the typical management architecture and identifies the main
elements:
Operational support systems
(all technologies)
Plan & build
Assign & configure
service
Maintain & restore
Network inventory
Datacomms
network
Standard
interfaces
Element
manager
Element
manager
Element
manager
Software to map
TMN to OSS
Network elements & managers
are technology specific
Figure 45
SDH management architecture
Element managers
Element managers provide local software resources to manage all aspects of an individual
element such as a line system, add-drop multiplexer or cross-connect switch. They contain a
detailed data representation of all aspects of the element, including what cards and versions
are in the element, how the components are connected and what their status is. Usually they
are associated with a local workstation that is used for commissioning purposes and may be
used later by maintenance personnel.
The functions of the element manager are:
•
•
•
•
•
•
Event & alarm management
Configuration management
Communications facilities
Performance management
Access & security
Local control and testing facilities
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The element managers are normally provided by the equipment manufacturer and links
between elements and element managers are made via an equipment LAN, according to the
design of the particular manufacturer. The types of information carried between an element
manager and the equipment is illustrated in the following diagram:
WS
retrieve
inventory
wavelength summary, channel power
alarm information
attributes
logical view, equipment view
performance
events
set
EM
switch state
thresholds
configuration
NE Id
inhibit alarm reporting
enable/disable APSD
notifications
NE
alarms
protection switching events
threshold crossing alerts
Figure 46 Information carried between element manager and element
The element manager can also be accessed from a remote workstation at a network
management centre, where changes to equipment configuration can be made, the status of
the element monitored or administrative data collected. The network management centre
personnel can generally interrogate or change parameters associated with many network
elements from the workstation, but the element manager itself is defined as managing only a
single element.
Network managers
Network managers provide software resources to manage network level entities and contain
network level information, such as the path taken by a particular circuit and information
abstracted from element managers. They oversee a number of element managers and allow
functions such as management of end to end connections or root cause analyses of faults to
be carried out.
The links between element managers and network managers and workstations are made
through a data communications network (DCN). Multiplex section overheads in the SDH
frame provide a connection for the DCN and supports OA&M functions. Control bytes in the
section overheads also make provision for a range of automatic protection mechanisms in
both point to point and ring configurations. Protection can act at channel (155Mb/s), multiplex
section (n x 155 Mb/s) or system level (line rate). A switchover time of 50ms is commonly
quoted for SDH protection mechanisms, but this refers to specific network test conditions and
in practice the figure can vary.
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Data communications network
The DCN can be carried either over a separate network, such as leased lines, or can be
carried over capacity provided in the SDH frame. Three types of management channels can
be carried over the SDH frame, as illustrated below.
NMS (Network Management System)
EMS (Element Management System)
EMS
Node
Node
EMS
Node
Regen
EMS
Node
EMS
Control plane channels
Orderwire
provides 64kb/s telephony
Telemetry provides communications
between node & line site for remote
management of line equipment
Fault management channel
provides high priority comms
between nodes, for initiating
network restoration following
network failure. Passes
transparently through line
sites
General network management
provides high capacity, medium
priority channel between NMS &
EMS, for managing nodes and
downloading software
Figure 47 DCN channels carried within the SDH frame.
An ‘order wire’ provides a 64kb/s telephony channel and telemetry services between node and
line sites for remote management of line equipment. This is able to monitor environmental
factors such as temperature or physical alarms. A fault management channel provides high
priority communications between nodes and is used to initiate network restoration following a
failure. This channel passes transparently through the line sites. A general network
management channel provides a high capacity, medium priority channel between NMS &
EMS, and is used for managing nodes and downloading software upgrades. These channels
can all be carried in the system overheads and, if carried in this way are only accessible to the
operator.
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Appendix F: Regulatory position
Background
In 1984 the Government embarked on a policy to introduce competition into UK
telecommunications. BT was privatised and Oftel was set up to ensure fair competition and
pricing. The policy has progressively resulted in new alternative network providers (‘alt-nets’)
entering the market such as Cable and Wireless (including Energis), Colt and Surf telecom.
This also opened the way for cable TV providers (ntl and Telewest) to provide telecom
services over their fibre networks.
During the 1990s the European Union assumed an increasing role in telecoms, working
towards a single European telecoms market. In 2000 it issued 5 new directives and one
regulation to cover converging telecoms, radiocoms and broadcasting markets. The
European objectives are to promote competition in the industry, stimulate the internal market
and ensure the interests of citizens/consumers are served.
Current legislation
To comply with this the UK regulatory system was radically reformed in 2003 and a new
regulator, Ofcom, was set up with responsibility for telecoms, radiocoms and broadcasting.
Regulation moved away from a licensed based system to one in which there is a general
entitlement to operate providing certain rules are met. Special rules apply to providers who
hold 'Significant Market Power' and for 'Universal Service Obligations' to be met.
The breadth of the regulation is very broad and not all parts can be applied to the special field
of fibre optic and SDH infrastructure. However the Access Directive deals with relationships
between operators and undertakings regarding access to network facilities and to
interconnection between networks. The content of the Authorisation Directive is to implement
an internal market in electronic communications networks and services through the
harmonisation and simplification of authorisation rules. The Processing Personal Data
directive addresses in particular the right to privacy and the processing of personal data. It is
designed to ensure the free movement of such data and of telecommunications equipment
and services in the Community.
Impact on the carriers
A key effect of regulation on the fibre optic and SDH markets has been through price controls
on ‘Significant Market Players’ and the provision of wholesale and retail services. These have
helped to ensure fair competition and to establish multiple providers of operator services. This
has been further helped through the framework directive which has ensured the establishment
of consultation processes on new regulatory proposals and of an appeals procedure. There
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has also been a major impact on the way BT is organised and managed to ensure
transparency and equal access. This has been evident in the recent formation of Openreach
which will provide an installation and maintenance service to all service providers on an equal
basis and at the same price. Its products will include Local Loop Unbundling, Wholesale Line
Rental and Backhaul products.
Future regulatory scenarios
Regulation is currently under review in the UK and in Europe and guidance will no doubt
change. A possible output of this report could be to identify areas where specific provisions
should be made in future regulation to ensure security of network related information and
communications networks in the future.
Currently the Universal Service Directive deals with basic public services and circumstances
in which the needs of some end users are not satisfactorily met by the market. However
regulation is constantly under review and it is possible that other topics could be the subject of
Universal Service provisions in the future, including for example the provision of broadband
and mobile services.
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Bibliography
SONET SDH, A sourcebook of Synchronous Networking, Edited by Curtis A. Siller, Jr. and
Mansoor Shafi, IEEE Press
Optical Networks, A Practical Perspective, Rajiv Ramaswami and Kumar N. Sivarajan,
Morgan Kauffman
History
Version
V1.0
Date
March 2006
Description
First issue for client approval
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