A broadband network is one in which the signals are carried in discrete channels multiplexed on a coaxial cable. Broadband networks are primarily used for video, although they can also be used to provide voice and data services, especially in homes. In a broadband network multiple users share the same channel for data transmission, meaning that heavy simultaneous usage can lead to congestion. Good engineering can alleviate this, but broadband data networks are still more susceptible to bottlenecks than other network technologies.

UCSD has two separate broadband networks:

• Triton Cable network, the newer of the two, provides video services to the student residences on campus and to certain other campus buildings, including Thornton Hospital, RIMAC, Preuss School and the Price Center. It is a two-way hybrid fiber optic coaxial cable system, using fiber cables to carry the signals between the headend and clusters of buildings, and then co-axial cables to distribute signals within those clusters. The headend is located at Thornton Hospital. This is where all of the video is prepared for distribution, and also where the data channels are inserted.

  Triton Cable was originally used to provide data services for all of the undergraduate student residences on campus through the use of Cable Data Modems (CDMs). In 2002, five of the 16 networks in the residential complexes were upgraded and their CDM networks were replaced with switched ethernet. CDMs are still used for networking for the remaining residential complexes, and about 3,600 of the 6,600 students who live on campus use CDMs.

  The current CDMs were purchased from Cisco in 2001, and use the DOCSIS standard. This allows us to manage and monitor them much more closely than earlier CDMs, and we can restrict bandwidth to individual CDMs or even turn them off if the traffic patterns indicate that there is an inappropriate amount of usage. At present our traffic management statistics show that there are no congestion problems within the CDM network. This may be because we use a Packetshaper to carefully control the amount and type of traffic between the student residential network and the internet. Without this control the students would download so many music and video files that there would be bottlenecks in the CDM network and maybe even within the residential ethernet networks.

  ACT's main customer and partner in the Triton Cable network is the Housing and Dining Services Department (HDS).

• The Broadband Network, as the second broadband network at UCSD is called, is a coaxial network linking every academic and administrative building on the campus. It was installed in the mid 1980s, and was used as the campus's first data backbone, but all of the data traffic has long since been transferred to newer and faster networks.

  The Broadband Network's other purpose was to provide video channels for educational purposes and it is still used for this. The Media Center uses it to transmit video signals to classrooms, lecture theaters and other locations around the campus. In addition, one channel is used for carrying some traffic for Facilities Management's building management system, although PPS is phasing this out and replacing it with a VLAN on the ethernet network.

There are currently 42 video channels on Triton Cable, plus channels which are run by the students (SRTV and KSDT) and the colleges. Triton cable could carry another five or six channels before it needs to be upgraded. HDS determines when and what channels they want added to the lineup through a student committee vote. HDS is also very much interested in running a marketing channel on the Triton network.

There is no great interest yet in High Definition Television (HDTV) services, but this is something which could become more important in future years. Similarly, there have been no requests yet from HDS or the students for Video on Demand, but this may become a requirement in the future.

Switched ethernet networks are being installed in all new student residential complexes. Triton cable is used to provide data services in some of the older student residences, and as mentioned above there are presently no congestion problems with the Cable Data Modems. However, we will need to provide higher speed connections in the student residences in future years, and there may be a time when the Cable Data Modem technology can no longer meet our requirements. If we open up the Packetshaper, or if there is a requirement for faster downloads within UCSD’s own network, then the CDMs could become a bottleneck.

CDMs will continue to improve, but the planned DOCSIS 2 standard does not provide much of an improvement in downstream traffic capacity. We can re-engineer the downstream capabilities by putting fewer students on each channel, but the better long term solution will be to replace the CDMs with switched ethernet networks. Another benefit of ethernet in the student residences is that we can install wireless services there. Adding wireless to a CDM network is less straightforward, and leads to problems with authentication.

No new services have been added to the Broadband Network for many years, and use of the network is declining. It is now essentially a video network for the Media Center, who use it mainly in the classrooms. All of the classrooms now have ethernet connections and wireless coverage, so there are alternative ways of transmitting video to these locations. Video streaming on the data network may become an acceptable replacement for the broadband network.

As the Cable Data Modems are removed from Triton Cable, it will become a video-only network. Installing switched ethernet in the residences will be complicated because many of them are old and hard to recable, and they are also occupied throughout most of the year. (HDS runs a busy summer conference program.) There will be significant expense for HDS to install the switched ethernet and wireless, and we need to agree an installation schedule with them which will meet their funding requirements.

After Triton Cable becomes a video-only network, it may make sense to outsource some or all parts of its operation to Time Warner or another public company. This would allow us to concentrate our resources on the data and voice networks, and may be the most cost effective way of upgrading Triton Cable to support HDTV, Video on Demand and Digital Cable. Another option may be to have Housing take over the management of the video network.

What will be the role of the Broadband Network in future years? If video streaming on the switched ethernet network meets the Media Center's requirements then there may be no need for a dedicated video network in the academic and administrative buildings. At the other extreme, there may be a need for extensive video in these areas ( including entertainment programming), and we could meet this requirement by integrating the Broadband Network's cable system into Triton Cable. Every old Broadband drop would then get the full range of channels currently available on Triton Cable. There are major funding issues associated with this because the users in the buildings would need to pay for this programming, whether they used it or not, and use of the broadband is presently free.

• Meet with HDS, and come up with a joint plan for upgrading the remaining student residences from Cable Data Modems to switched ethernet

  We will also install wireless networks in the student residences. The upgrade will take several years, and will follow Housing’s funding requirements.

• Add video channels to Triton Cable as requested by HDS

• Research what upgrades to Triton Cable are necessary to provide HDTV and Video on Demand

• Test video streaming on the switched ethernet network, and meet with the Media Center to discuss using this as an alternative to the Broadband Network

Adding new channels and capabilities to the system will increase the costs for Housing. HDS typically needs a long notice for new costs, so cost increases have to be identified well in advance.

Although it is technically straightforward to put the Triton Cable programming on the broadband system, thereby making Triton Cable available in the academic and administrative areas, this would have a big financial impact on our customers. They would need to pay for video programming, including entertainment programs, but they presently get their instructional and business oriented video for free. It is unlikely that merging Triton Cable and the Broadband Network will be in the best interests of the campus.