Previous page
Table of Contents
|
Previous page
|
Table of Contents
|
Next page
|
1. The Granta Backbone Network Management Committee (GBNMC) was established in 1992 with a remit to oversee the operation, maintenance, and development of the physical network of ducts and cables on behalf of the University and the Colleges and to report annually to the Finance Committee and the Bursars' Committee. This is the tenth annual report and covers the period from 1 August 2001 to 31 July 2002.
2. The Granta Backbone Network (GBN) consists of over 25 km of trenches which stretch from Girton College to New Addenbrooke's and contain ducts and cabling interlinking over 80 separate sites. At the time of the initial installation in 1992, the intention was that it should provide a communications infrastructure capable of meeting the needs of the University and the Colleges for at least 25 years. Although most GBN use is for data communications, it also carries traffic for the telephone network, video transmissions, security cameras, and remote alarm monitoring. Although the basic network (58 sites) was financed jointly on a formula basis (University 60%, Colleges 40%), connections to the other sites have been provided over the years as requested by, and at the expense of, individual University institutions or Colleges.
3. During the year, the membership continued to be Professor R. M. Needham (Chairman), Dr R. Hanka, Dr J. R. Seagrave, Dr R. D. H. Walker, and Mrs J. M. Womack, with Dr M. D. Sayers, Dr B. A. Westwood, and Mr C. J. Cheney from the Computing Service and Mr M. J. Dowling from the Estate Management and Building Service in attendance. In practice, following a decision taken in July 2001, as much business as possible was conducted by electronic mail.
4. At the Sidgwick Site and Harvey Court, where both the University and Gonville and Caius were about to build, a new duct and cable route was eventually agreed with the City Council. Completion of the first phase of ducts, from Economics to Harvey Court, cable installation and the transfer of active circuits were all finished in good time for a July start to work on the new English building. (While the consulting engineers had been given the GBN duct specification, the ducts actually installed by the contractor had a slightly larger diameter, but fortunately matching glands caulking could be obtained.) Although there is slightly less urgency about the second phase, involving ducts through Harvey Court and across West Road, because building there is not expected to start there for some time, planning consent has already been obtained where there are trees which need to be removed.
5. The 1999-2000 report mentioned the discovery, during the preliminaries for installing a new route into Chemistry, of possible damage to ducts and cables at Downing College. Following the completion last year of the new route to Chemistry, all the services running through the relevant duct and cable section were diverted to allow detailed investigation to take place, although its start has been deferred until Autumn 2002 so as to cause less damage to a hedge planted since the ducts were installed. At the University Farm, near the BP Institute, a frame and covers thought to have been damaged by contractors were replaced while at Churchill both ntl and the College were told to remove cables which had been installed without permission in the GBN ducts.
6. Much time was again spent planning diversions around new buildings; in this context the ubiquity of the GBN is a mixed blessing. The longest single cable run in the GBN (over two kilometres from the University Press to New Addenbrooke's) passes directly under the site of the proposed new Cancer Research Centre on the old Downing College playing fields; to avoid the cost and inconvenience of complete replacement, temporary in-line splice boxes will be used until a GBN node can be installed in the Centre's building. The latest plans for a new building at the Botanic Garden and for the new cricket school at Fenners, with its adjacent residential development for Hughes Hall, both run very close to existing GBN routes and information is awaited from EMBS about whether diversions will be required.
7. University and College building works are not the only potential hazards, and staff are often to be seen marking out with white paint exactly where the GBN ducts run in the vicinity of proposed works by the City Council or utility companies. This year, cases where this has been necessary include the replacement of lamp posts in Queens' and Newnham Roads, the erection of large marquees on Parker's Piece, and the major roadworks in Sidney Street.
8. During the year, GBN mininodes were installed at a Darwin College hostel in Newnham Road and at the Temporary Catering Facility on the West Cambridge Site. To alleviate a shortage of fibres on busy routes, additional 48 or 24 fibre cables were installed in the centre on the routes New Museums Site - Corpus Christi - St Catharine's - King's and St Catharine's - Mill Lane North - Mill Lane South, and at West Cambridge between Astronomy and the Whittle Laboratory and between the Whittle and the William Gates Building.
9. Most GBN routes in the initial installation have three ducts, one of which is primarily for the voice telephone network and two for fibre-optic cables. The standard, specially made, 48-fibre GBN fibre-optic cable has 8 50 µm multimode fibres, 16 62.5 µm multimode fibres, and 24 singlemode fibres, although this is supplemented by the use of versions with 24 62.5 µm and 24 singlemode fibres or just 24 62.5 µm fibres where appropriate to meet particular requirements. There are also direct cables with 16 62.5 µm fibres each from the New Museums Site to the Cavendish Laboratory, Chemistry, Engineering, and New Addenbrooke's and a 16 50 µm fibre direct cable from the New Museums Site to the Sidgwick Site.
10. The GBNMC does not itself provide 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), 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 2002 (with allocations at July 2001 in brackets):
| Type of Use | Type of Fibre | No of Fibres | Total Length (km) | ||
| University Data Network | 62.5 µm | 153 | (164) | 182 | (200) |
| 50 µm | 20 | (16) | 17 | (16) | |
| singlemode | 52 | (38) | 145 | (126) | |
| Security | 62.5 µm | 5 | (5) | 7 | (7) |
| singlemode | 23 | (21) | 63 | (51) | |
| Telephone network | 50 µm | (6) | (15) | ||
| Private fibres | 62.5 µm | 99 | (93) | 116 | (115) |
| 50 µm | 6 | (6) | 9 | (8) | |
| singlemode | 41 | (39) | 139 | (124) | |
| Total | 399 | (388) | 676 | (662) | |
The allocations shown in the table represent the following proportions of the total fibre length available in the network (with the 2001 proportions in brackets): 62.5 µm 76% (80%); 50 µm 13% (18%); singlemode 58% (50%).
11. Some of the main uses to which the GBN is being put at present are:
The GBN is used both for the gigabit (1000 Mbps) backbone infrastructure which interconnects the eight area routers and central switches and for the ethernet links between the area routers and the local area networks in just about every University institution and College. New gigabit Cisco router equipment was installed in the backbone network during June and August 2002. By the end of July, total ethernet connections to user institutions consisted of 55 at 10 Mbps or less (compared to 73 in July 2001), 72 at 100 Mbps, and 26 at 1000 Mbps (compared to a combined 2001 total of 76).
Connections to the Security Control Room on the New Museums Site use both fibre and copper cables and transmit information which includes pictures from remote cameras, signals from remote intruder entry and security loop alarms, and monitoring information for building services equipment such as boilers and air-conditioning plant.
Although GBN fibres are no longer used to provide trunk voice connections, fairly short runs of multi-pair copper cables in GBN ducts are heavily used to distribute individual telephone circuits from network nodes to nearby sites.
Institutions use these to link networks on two or more physically separate sites for a variety of purposes. During the year, institutions with new private fibre links included Architecture, Darwin College, Engineering Laboratory, the Old Schools (Management Information Services Division), and St Catharine's College.
12. As in the past, the Network Division of the Computing Service continued to carry out all GBN operations on behalf of the management Committee. All fibre allocations and general administration were handled by Dr C. A. Robinson (a part-time Computer Associate) while the Network Installation team either carried out the necessary technical installation and maintenance work themselves or supervised the use of outside contractors.
13. The GBN rental charges depend on the total length of fibre in each connection and are intended to cover the running costs of the network, including the capital cost of installing additional fibres as required. Rental rates have remained unchanged since 1995, although for some years now all rentals have been at the standard rental rate and none at the cheaper research rate for short term projects. The Computing Service (in respect of the CUDN) is by far the largest single contributor to the rental income.
14. Because of the passive nature of the ducts and cables, maintaining existing connections is comparatively cheap, but the expense of installing additional fibres on busy routes fluctuates quite widely, depending on the actual requirements in each particular year.
15. In 2000-01, when most work on the GBN ducts and cables was carried out for and funded by various building projects, a considerable amount of GBN cable was used from stock and its cost recovered, and this contributed to an overall surplus of £21,500. In 2001-02, it was necessary to install more additional network capacity on busy routes (see above) than in the past or, as far as one can tell, for several years to come. To do this, new drums of cable had to be purchased (of which about two-thirds is still in stock) and considerable expenditure was incurred on pulling in and splicing the additional runs.
16. The cost of this additional network infrastructure resulted in an overall deficit of £22,167 on the year's operations. (Offsetting this, although neither appears in the formal accounts, there is cable in stock worth about £14,000 and a further £4,000 spent this year will be recovered once the work at the Sidgwick Site and Harvey Court is complete.) Because of the operational deficit, the accumulated balance fell from £66,306 to £44,139.
17. The Committee has considered all the circumstances, and concludes there is no reason to expect a similar scale of deficit in 2002-03. It has agreed, therefore, that while a close eye should be kept on future expenditure, the GBN rental rates can safely be left unchanged for the time being.
October 2002
R. M. NEEDHAM, Chairman
|
Previous page
|
Table of Contents
|
Next page
|
Cambridge University Reporter, Monday 20 January 2003
Copyright © 2003 The Chancellor, Masters and Scholars
of the University of Cambridge.