Cambridge University Reporter


Report of the Granta Backbone Network Management Committee for 2003-04

Introduction

1. Since 1992, the remit of the Granta Backbone Network Management Committee (GBNMC) has been to oversee, on behalf of the University and the Colleges, the operation, maintenance, and development of the physical network of ducts and cables. The GBNMC reports annually to the Finance Committee and the Bursars' Committee. This is the twelfth report and covers the period from 1 August 2003 to 31 July 2004.

Granta Backbone Network

2. The Granta Backbone Network (GBN), which stretches from Girton College to New Addenbrooke's, consists of ducts and cabling in more than 32 km of trenches connecting over 90 separate sites. The GBN's design brief was to be capable of meeting the communications infrastructure needs of the University and the Colleges for at least 25 years; the network as installed has done so easily for the last twelve years and seems set fair to continue. While most GBN traffic is for data communications, it also carries telephony, video transmissions, pictures from security cameras, and signals from remote alarms and performance monitors. The basic network of 58 sites was financed corporately on a formula basis (University 60%, Colleges 40%), but additional connections were and are still being provided at the request and expense of individual University institutions or Colleges.

Membership

3. Professor A. Hopper continued as Chairman and Dr J. R. Seagrave and Dr R. D. H. Walker continued as members. Mr S. W. Hedley and Mrs J. M. Womack resigned at the start of the year and were replaced by Mr J. K. Milner and Mr A. M. Reid, respectively. Dr B. A. Westwood resigned as secretary at the start of the year and was replaced by Mr C. J. Cheney. Dr M. D. Sayers from the Computing Service and Mr M. J. Dowling from the Estate Management and Building Service were in attendance. Apart from one face-to-face meeting in February 2004, the Committee's business was routine and was satisfactorily conducted by electronic mail.

Extensions, building work, and other incidents affecting the GBN

4. At the New Addenbrooke's Site, the duct route to the new CR-UK building from the existing ducts serving the Clinical School was agreed. It is anticipated that the new route will be ready for cabling in the third quarter of 2005.

5. At Homerton, ducts to the new Education building were installed along the new access road. The route will be cabled when the new building is completed in the fourth quarter of 2004.

6. At Fenner's, no disturbance to the GBN occurred when the Cricket School was built adjacent to the duct route. The ducts around the new Hughes Hall building were anticipated to be ready for recabling over the 2004 Long Vacation. The GBN ducts were extended to Gonville and Caius hostels in the adjacent Mortimer Road.

7. Building work at the Magdalene College hostel is in progress. The GBN cabinet and cables have been temporarily removed whilst this is being done.

8. The three ducts running along Downing Street that seemed be damaged were excavated and no damage was found. Ducts in Downing College were excavated and repaired; there was no apparent damage to the cables.

9. Estate Management anticipate installing ducts in the public highway around the buildings occupied by Education at 17 and 19 Brookside in September 2004 to allow this route to be recabled before sale of the buildings is complete.

10. The GBN mini-node for the West Cambridge Residences was expected to be installed in September 2004.

11. New Hall's building contractors were expected to have an alternative duct route available for cabling in August 2004 to resolve conflict with a new building.

12. The final section of ducts on the Sidgwick Site for the route diversion on account of the new buildings for the University and Gonville and Caius was completed and cabled. Asbestos dust contamination in underground walkways on the site caused an alternative route through the basement of the Economics building to be installed.

13. The GBN was extended to the Agronomy Centre in Huntingdon Road and to a Darwin Hostel in Newnham Road.

14. When installing a new cable to relieve congestion between Clare Hall and the Cavendish Laboratory, the new cable became stuck during a 400-metre pull across a farm field south of the Cavendish. This was resolved by excavating a hole in the middle of the field, breaking into the duct, installing the cable with two pulls and then reinstating. However, because it was anticipated that the problem might recur in a future installation, a second new cable was installed at the same time to give sufficient capacity for many years to come.

15. Work is in progress to overlay the GBN route onto the map of Cambridge produced by the University Press so that it can be made available on the World Wide Web, with the permission of the Press. This will allow Departments and Colleges to see if any of their proposed building works or other activities will conflict with the GBN.

Network allocations

16. Most GBN routes have three ducts, of which one is primarily for the voice telephone network. The standard GBN fibre-optic cable is specially made and contains 48 fibres in all, of which 8 are 50 μm multimode, 16 are 62.5 μm multimode and the remaining 24 are single mode, although cables with other combinations of fibre capacities have also been installed in parts of the GBN to meet particular requirements. Because of the recent growth in single-mode use, new cables are now tending to contain single-mode fibres only. There are also five 'direct' cables from the New Museums Site to the Cavendish Laboratory, to Chemistry, to Engineering and to New Addenbrooke's (each with sixteen 62.5 μm fibres) and one of sixteen 50 μm fibres from the New Museums Site to the Sidgwick Site.

17. The GBNMC does not itself provide end-user services but rather allocates individual fibres in GBN cables for the University Data Network, for the University Telephone network, for security uses and for private links between physically separated sites of individual institutions and space in the GBN ducts for local wiring for the voice network. The following table summarizes fibre allocations at July 2004 (with the corresponding July 2003 statistics in brackets):
Type of useType of fibreNo of fibresTotal length(km)
University Data Network62.5 μm141(141)170(170)
 50 μm18(18)16(16)
 single-mode58(58)153(152)
University Telephone Networksingle-mode6(0)29(0)
Security62.5 μm5(5)7(7)
 single-mode25(23)75(63)
Private fibres62.5 μm99(106)118(122)
 50 μm8(6)10(9)
 single-mode63(53)217(166)
Total 423(410)795(704)

The allocations shown in the table represent the following proportions of the total fibre length available in the network (with the 2002-03 proportions in brackets): 62.5 μm 30% (75%); 50 μm 7% (12%); single mode 45% (59%).

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

(a) CUDN

The gigabit ethernet (1000 Mbps, being upgraded to 10 Gbps) backbone infrastructure that interconnects the eight area routers and central switches and the ethernet connections from the area routers to the local area networks in just about every University institution and College both rely on using the GBN. At the end of July 2004, the total numbers and bandwidths of ethernet connections were 35 at 10 Mbps or less, 80 at 100 Mbps and 43 at 1000 Mbps (July 2003: 46, 76, and 35 respectively).

(b) University Telephone Network

Trials of the use of voice multiplexors with GBN fibre were undertaken by the JTMC and proved successful. As a result, the JTMC has ordered a significant number of GBN fibre circuits for which a substantial amount of additional cable is being installed. There is also widespread use of fairly short runs of multi-pair copper cables in GBN ducts to distribute individual telephone circuits from network nodes to nearby sites.

(c) Security

A mixture of fibre and copper connections transmits information to the Security Control Room on the New Museums Site, including pictures from remote security cameras, signals from remote intruder entry and security loop alarms and monitoring information for building services equipment such as boilers and air-conditioning plant.

(d) Private fibres

Links between physically separate sites are rented by individual institutions for various purposes. During the year, new private fibre links were installed for MISD, Corpus Christi, the University Farm, and the Computer Laboratory.

Staffing and finance

19. The Network Division of the University Computing Service continued to carry out all GBN operations on behalf of the GBNMC. Fibre allocations and general administration were handled by Dr C. A. Robinson who calls on the Network Installation team for either carrying out the technical installation and maintenance work or supervising external contractors. Civil engineering works for the GBN, carried out for the University, are supervised by EMBS, liaising as appropriate with Dr Robinson.

20. The GBN rental charges, which are pro rata to the total length of fibre in each connection, are intended to cover the running costs of the network, including the capital cost of installing additional fibres as required. For some years past all rentals have been at the standard rental rate, with none at the previously cheaper rate for short term research or similar projects. The Computing Service (in respect of the CUDN) is by far the largest single contributor to the rental income.

21. While maintaining the existing network is comparatively cheap because of the passive nature of the ducts and cables, there is usually a moderate amount of expenditure each year on repairing damage due to unknown causes. The costs of route diversions on account of new building work can be quite large but are normally recoverable under the provisions of the wayleaves. The most variable factor affecting recurrent expenditure is the installation of additional cables in heavily used parts of the network, which tends to be much more expensive than other maintenance but usually only becomes necessary every few years.

22. In 2002-03, income exceeded expenditure by £22,483 and the accumulated balance rose to £66,622. In February 2004, the Committee decided that the rental rates should be reduced to £6.00 per 100 metres or part thereof from the start of the 2004-05 University financial year as the accumulated balance was still growing. In 2003-04, income exceeded expenditure by £7,024, but this excludes 25% matching SRIF funding that was taken from the accumulated balance which, as a result, fell to £64,732. The accumulated balance can be expected to fall further over the next few years as a result of expenditure not being matched by the (reduced) rental income.

A. HOPPER ChairmanOctober 2004