CTNET - The New Age

Horizontal Rule [Sept 97]

C.Y. Kwok

The three year-long network upgrade project is now entering its final stage. Despite many problems have been encountered in the past, its progress is still under control and it is expected to be completed by mid-1998, as originally planned.

What Have Been Done?

The project is divided into three phases. The first phase of the network upgrade was to carry out a pilot network upgrade with two departments, namely the Department of Physics & Materials Science (AP) and the Computing Services Centre (CSC). In this pilot, a central Fiber Distributed Data Interface (FDDI) switch was introduced as the new network backbone (collapsed backbone), interconnecting the old FDDI ring and the Local Area Networks (LANs) of the two departments. The latter were connected to the FDDI switch via FDDI-Ethernet LAN switching hubs. The switches were linked together using fibre optic cables and computer connections in the two departments were completely rewired with unshielded twisted pair (UTP) cables. The objective of the pilot was to experiment with LAN switching, and to find out problems which might arise during a large-scale installation of fibre optic and UTP cables. At that point of time, dedicated bandwidth was considered too expensive. Hence, the pilot was based on group switching which is a group of computers sharing a switched port of 10Mbps (megabits per second). The pilot network upgrade enabled each computer to enjoy a higher network bandwidth of around 1-2 Mbps on average, tenfold that before the pilot.

From this pilot, the following experiences were learned:

The second phase of the network upgrade was focused on building an advanced fibre cable plant and at the same time experimenting with the new ATM technology. With strong support from the President, the CSC was able to acquire spaces and build 50 wiring closets. The fibre cable plant was also installed early this year, which consists of over 80 12-core multimode fibre optic cables, each with one end terminating in the CSC Computer Room while the other end terminating at either a wiring closet or a duct room close by.

At The Moment

In July, the third (or last) phase of the network upgrade has already started. This phase covers the following three major parts:

The upgraded network will have a tree-like topology which can be simplified and depicted as follows:


                                   ATM backbone
                                        |
                                        |            <-Fibre (>=150Mbps)
                                        |
        +-------------------------------+-------------------------------+
        |                               |                               |
        |                               |                               |
        |....                           |....                           |
       Edge                            Edge                            Edge
      Device                          Device                          Device
        |                               |                               |
        |                               |                               |
   +----+----+                     +----+----+                     +----+----+
   |         |                     |         |                     |         |   
   |         |                     |         |                     |         | <-UTP (10/100Mbps)
   |....     |                     |....     |                     |....     |
  PC         PC                   PC         PC                   PC         PC		
		

The upgraded network will be one of the most advanced campus networks amongst local universities and it will be capable of supporting multimedia applications such as videoconferencing, video on demand, etc. Users on CTNET will be able to enjoy a much higher bandwidth and improved network performance. By applying the built-in virtual networking support of ATM, all networked computers belonging to the same department will be logically grouped together regardless of their physical locations. This will overcome the existing problems of some users being affected by the network traffic of their neighbouring departments and the errors brought about by other departments. Problems arising from move, addition and change of computer connections on the network will also be eliminated.

A Never Ending Process...

The major advantages of ATM are its scalability and its support of quality of service. However, while new standards of ATM are still under development, new networking technologies (Gigabit Ethernet in particular) are also emerging and they tend to compete heavily with ATM. Consequently, CTNET needs to be upgraded from time to time in order to incorporate such new standards and technologies so as to cater for higher bandwidth requirements and to support new network applications. As the CSC is committed to providing quality services to our users, network upgrade will indeed be a never ending process.


[Issue No. 12]


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Computing Services Centre
City University of Hong Kong
ccnetcom@cityu.edu.hk

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