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Report of the Granta Backbone Network Management Committee for 1998-99

Introduction

1 The Granta Backbone Network Management Committee (GBNMC) was established in 1992, to oversee the operation, maintenance, and development of the physical network of ducts and cables on behalf of the University and the Colleges. This is the seventh Annual Report to the Finance Committee and the Bursars' Committee and covers the period from 1 August 1998 to 31 July 1999.

Granta Backbone Network

2 The Granta Backbone Network (GBN), which consists of ducts and cabling in more than 25 km of trenches interlinking over 80 separate sites stretching from New Addenbrooke's to Girton College, was installed in 1992 to provide for the communications infrastructure needs of the University and the Colleges for the next 25 years. The GBN carries many kinds of traffic including that from the data communications networks, the telephone network, video transmissions, security cameras, and remote alarm monitoring. The basic network (58 sites) was financed jointly on a formula basis (University 60%, Colleges 40%) while additional sites have been provided with connections at the expense of individual institutions.

Membership

3 Professor Sir Alan Cook, who completed his time on the Committee in December 1998, first became involved with the GBN in 1988 as Chairman of the Joint Working Party, which was established first to assess the need for the GBN and suggest ways of funding it, and later to oversee its establishment; when the Management Committee took over in 1992 he continued in the same role. Sir Alan contributed very greatly to the successful progress of the GBN through many vicissitudes along its path and his experience will be much missed.

4 Professor R. M. Needham took over as Chairman, Dr R. Hanka was newly appointed, and Dr J. R. Seagrave, Dr R. D. H. Walker, and Mrs J. M. Womack continued to serve. Meetings were regularly attended by Dr M. D. Sayers, Dr B. A. Westwood, and Mr C. J. Cheney from the Computing Service, and by Mr D. Reader from the Estate Management and Building Service.

Maintaining the existing network

5 Major temporary and permanent reroutings of GBN cables have been required because of two new buildings. At the BP Institute at Madingley Rise, the existing GBN cables were pulled back to a new GBN chamber built over existing ducts running though the University Farm, and re-installed through new ducts to a new GBN cabinet location. In order to minimize the disruption to network services to Girton College and other locations only fed by this route, staff carried out the reroutings over two weekends out of Full Term.

6 The site of the new Unilever Centre at the Department of Chemistry not only conflicts with the GBN route between Chemistry and the Local Examination Syndicate, but is also very close to the only GBN route to locations to the south of it, including New Addenbrooke's. After considering all the alternatives, seven circuits were rerouted using a new copper cable installed between Downing College and Hughes Hall and two cables were pulled back from the GBN cabinet in Chemistry though the basement of the building to a chamber in Union Road. The installation of the copper cable revealed a problem with the ducts at Downing College which may date back several years; because the route is so critical at the moment, detailed investigation has been deferred until the installation of cables on a new route into Chemistry has been completed.

7 Earlier in the year, the installation of additional 62.5 μm fibres on ten heavily-used routes in the City centre was completed, restoring the ability to provide links as required between any pair of GBN sites. The mechanism for providing utilities with information about GBN routes in areas where they plan to carry out work continued to prevent any major damage being caused to the GBN.

8 In May, a discrepancy between the GBN records and the actual situation in the cable cabinet led to an active fibre being mistakenly spliced to provide a new circuit; this cut the CUDN connection to Robinson College at a time which unfortunately involved its remaining out of service for the whole of a Bank Holiday weekend. A number of changes in procedure have been introduced to ensure that in future, similar discrepancies will be detected in advance; additional safeguards will result from the already scheduled transfer of the GBN information to a new and more structured cable management system.

New connections

9 Much of the ductwork needed at Homerton College is now present, while the completion of the connection forms part of the bid to the HEFCE for funds to establish the EastNet regional network. The installation of a GBN mininode for Pembroke College at 10 Selwyn Gardens was completed and another is in progress for St John's College at 1 Madingley Road. Planning continued for future connections at Clarkson Road and West Cambridge.

Network allocations

10 GBN routes in the initial installation generally have at least three ducts, one primarily for the voice telephone network. The fibre-optic capacity on most routes consists of a specially made cable with a total of 48 fibres of three types: 50 μm multimode (8 fibres), 62.5 μm multimode (16 fibres), and singlemode (24 fibres); a few busy routes have either a second similar cable or one with twenty-four 62.5 μm fibres. There are also direct cables with sixteen 62.5 μm fibres each between the New Museums Site and the Cavendish Laboratory, Chemistry, Engineering, and New Addenbrooke's, and a sixteen 50 μm fibre direct cable from the New Museums Site to the Sidgwick Site.

11 The GBNMC does not provide its own end-user services, but allocates space in GBN ducts and fibres in GBN cables for University-wide service providers such as the Computing Service (data network) and the Joint Telecommunications Management Committee (telephone network), for security uses and to meet the needs of individual institutions for private links between physically separated sites. The following table summarizes fibre allocations made up to July 1999 (with allocations up to July 1998 in brackets). The allocations shown in the table represent the following proportions of the total fibre length available in the network (with the 1998 proportions in brackets): 62.5 μm 74% (67%); 50 μm 17% (17%); singlemode 24% (23%).

12 Some of the main uses to which the GBN is being put at present are:

(a) Cambridge University Data Network

The main data network service provides ethernet connections to end users in practically every University and College institution, using GBN fibres to link local area networks at individual sites and buildings to a backbone of routers which are themselves interconnected using the GBN. During the year, the last of the older and non Year 2000 compliant routers in this backbone were replaced, with the result that all CUDN client sites can now have 100 Mbit/s connections, while Virtual Private Networks are now available in suitable cases.

(b) University Telephone Network

Although fibres are used to provide the main connections for Jesus and Robinson Colleges, most use of GBN ducts in connection with the telephone network involves fairly short runs of multi-pair copper cables to distribute individual telephone circuits from network nodes to nearby sites.

(c) Security

The GBN is used to bring to the Security Control Room on the New Museums Site, via both fibre and copper connections, pictures from cameras installed on remote sites, signals from remote intruder entry and security loop alarms and monitoring information for building services equipment such as boilers and air-conditioning plants.

(d) Private fibres

Institutions often use these to link networks on two or more physically separate sites. During the year, new private fibre links were provided for institutions including Corpus Christi, King's, Pembroke, and Robinson Colleges, the Engineering Department, and Modern and Medieval Languages.

Staffing and finance

13 Dr C. A. Robinson, a half-time Computer Associate on the staff of the Computing Service, continued to have the main responsibity for fibre allocations and other aspects of GBN administration, while the Network Division of the Service carried out all the technical work involved in installing and maintaining GBN fibre links, using either its own staff or outside contractors supervised by Service staff.

14 The running costs of the GBN are comparatively modest because of the passive nature of the ducts and fibres, and are met from the basic fibre rental charges (i.e. net of the University surcharge); these charges also provide for the capital cost of installing additional fibres as required. While the standard rental rate applies in most cases, there is a cheaper research rate for short- term projects; both have remained unchanged since 1995. Charges are made according to the total length of fibre in each connection, with the result that the Computing Service (in respect of the CUDN) is by far the largest single contributor.

15 This year again saw a higher than normal level of expenditure, due to the completion of the programme of installing additional fibre cables on congested routes. The net result for 1998-99 was that expenditure exceeded income by £1,431, reducing the accumulated surplus of £10,084 from previous years to £8,897. On the assumption that expenditure in 1999-2000 is likely to return to more normal levels, the Committee left the basic rental rates unchanged.

16 When the GBN was installed, the University financed its share of the capital cost by means of an internal loan; in early 1996, the Council reviewed the operation of this loan and decided to write off its capital value in yearly instalments while requiring the GBNMC to recover the interest charges by means of an additional surcharge for University institutions using the GBN. The introduction of the surcharge substantially increased private fibre rental costs for University users, although the GBN rates are still generally lower than those of other cable providers, especially for short distances.

17 As a result of falling interest rates in the second half of the year, surcharge income exceeded expenditure by £11,293 and so, although unchanged rates for 1999-2000 had been announced earlier, the Committee decided to reduce the surcharge by rather more than 20% before the bills were sent out. The Council is to review the operation of the surcharge in 2000 and, since most potential customers are now unaware of the background and find the surcharge confusing and off-putting, the Committee is currently minded to recommend its abolition.

October 1999      R. M. Needham, Chairman

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Cambridge University Reporter Special, 17 January 2000
Copyright © 2000 The Chancellor, Masters and Scholars of the University of Cambridge.