|Previous page||Table of Contents||Next page|
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 eighth Annual Report to the Finance Committee and the Bursars' Committee and covers the period from 1 August 1999 to 31 July 2000.
2 The Granta Backbone Network (GBN) consists of ducts and cabling in over 25 km of trenches interlinking over 80 separate sites stretching from New Addenbrooke's to Girton College, and was installed in 1992 to provide for the communications infrastructure needs of the University and the Colleges for the next 25 years or more. The GBN carries many kinds of traffic including that from 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 were, and are still being, provided with connections at the expense of individual institutions.
3 Professor R. M. Needham continued as Chairman and the other members were Dr R. Hanka, Dr J. R. Seagrave, Dr R. D. H. Walker, and Mrs J. M. Womack. 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 M. J. Dowling from the Estate Management and Building Service (EMBS).
4 The circuit re-routings on account of the new Unilever Centre at the Department of Chemistry remained in place throughout the year, but after much investigation agreement was reached on a new route into the building from a chamber in Union Road, for installation in between the different phases of the planned Chemistry Building refurbishment. After the new ducts and cables are in place, it will be possible to carry out a detailed investigation of the problems which were discovered with the ducts at Downing College when the re-routings were carried out.
5 At West Cambridge, there was agreement that each of the four or so individual development sites should have a separate GBN node; the first is to be in the new Computer Laboratory, to serve both it and two adjacent buildings, including one for Microsoft. Later in the year, diversions were agreed and installed for the existing routes over the site, which needed to be moved so that the access road could be widened.
6 Replacement ducts and cables were installed at St Edmund's College outside the footprint of a new building across the existing GBN route. Unfortunately a wrong cable was cut because they had been incorrectly labelled during the initial GBN installation, and this caused a loss of connectivity to New Hall, St Edmund's College, and Trinity Hall (Wychfield) for two hours. A chamber at New Hall was strengthened for the construction of a new car park and, after more accidental damage, it was agreed to replace all the existing footway frames and covers at the University Farm by stronger driveway ones, as and when necessary. Plans for landscaping around the new ducts at the Department of Earth Sciences (Madingley Rise) were approved.
7 Considerable concern was caused by two 'near-miss' incidents, at the University Library and on the Downing Site, in each of which contractors carrying out other work unwittingly came close to severing GBN ducts and power cables. Investigation revealed that, although the correct procedures had been followed when the work was planned, there had been a subsequent failure within EMBS to provide the contractors with the relevant information; and steps were taken to ensure that this did not happen again.
8 The new Mathematics building at Clarkson Road was provided with separate GBN connections for the CUDN, security, and a private link to Mill Lane. The GBN mininode for St John's College at 1 Madingley Road was completed and planning took place to connect a Darwin College hostel in Newnham Road.
9 Homerton College is to be connected to the EastNet regional network via the GBN. Ducts from a chamber at the railway to a building on the site had been installed as part of their recent building project, but they have failed an integrity check and remedial measures are under consideration. EMBS engineering services plan to move into the vacant buildings at Laundry Farm and arrangements are being made to connect them by installing new ducts across the farm land to join the existing GBN ducts at Rifle Range Road.
10 Most GBN routes in the initial installation have three ducts, one of which is primarily for the voice telephone network, and contain a specially made fibre-optic 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 from the New Museums Site to 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 at July 2000 (with allocations at July 1999 in brackets). The allocations shown in the table represent the following proportions of the total fibre length available in the network (with the 1999 proportions in brackets): 62.5 µm 77% (74%); 50 µm 18% (17%); singlemode 35% (24%).
|Type of use||Type of fibre||No. of fibres||Total length (km)|
|University Data Network||62.5 µm||154||(146)||194||(182)|
|Telephone network Security||50µm||6||(6)||15||(15)|
|Private fibres||62.5 µm||87||(82)||109||(107)|
12 Some of the main uses to which the GBN is being put at present are:
The GBN is used both to interconnect the eight area routers and the central switches and to link the area routers to local area networks in just about every University institution and College. Since the withdrawal of the last asynchronous and X.25 connections in October 1999, the CUDN has almost exclusively ethernet connections. Between July 1999 and July 2000, the number of fast lines (100 Mbps or more) increased from 22 to 48 while that of the slow ones (10 Mbps or less) fell from 119 to 94. Much effort was put into increasing CUDN resilience and making it easier to track down faults by simplifying the structure of the backbone, replacing some older equipment, and providing at least two paths to each area router.
Apart from the fibres which provide the main connections for Jesus and Robinson Colleges, most use in connection with the telephone network involves fairly short runs of multi-pair copper cables in GBN ducts to distribute individual telephone circuits from network nodes to nearby sites.
The GBN is used to transport a variety of information to the Security Control Room on the New Museums Site via both fibre and copper connections, including 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.
Institutions use these to link networks on two or more physically separate sites. During the year, new private fibre links were provided for institutions including King's and St John's Colleges, Mathematics, Engineering, and the University Offices.
13 The Computing Service continued to carry out all GBN operations. Fibre allocations and general administration were the province of Dr C. A. Robinson, a half-time Computer Associate, while the other Network Division staff either carried out themselves the necessary technical installation and maintenance work or supervised the use of outside contractors.
14 The passive nature of the ducts and fibres means that the running costs of the GBN are comparatively modest. They are met from rental charges (depending on the total length of fibre in each connection) which also provide for the capital cost of installing additional fibres as required. The standard rental rate applies in most cases but there is a cheaper research rate for short-term projects; both have remained unchanged since 1995. The Computing Service (in respect of the CUDN) is by far the largest single contributor to this source of income.
15 Although expenditure on repairs and additional fibre installation was lower this year, the need to buy a new network management system (shared with the CUDN) and move the existing GBN data to it caused total spending to exceed income by £1,693, which was easily met from the accumulated surplus from previous years. With no exceptional items of expenditure being expected in 2000-01, the Committee left the 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, but to require the GBNMC to recover the interest charges by means of an additional surcharge for University institutions with either CUDN or private GBN connections.
17 These financial arrangements used to bring extra money into the University from outside, but given the present practically universal provision of network connectivity, imposing and collecting the University surcharge now only produces unproductive complexity by shuffling money around to little or no useful purpose. In July, a paper asking that the loan be made interest-free was approved by the Council, on the advice of its Finance Committee, and the University surcharge has been abolished with effect from 1 August 2000.
|October 2000||R. M. Needham, Chairman|
|Previous page||Table of Contents||Next page|
Cambridge University Reporter Special, 19 January 2001
Copyright © 2011 The Chancellor, Masters and Scholars of the University of Cambridge.