Designing an Effective IT Backbone
- By Stephen Fredette
- February 1st, 2001
A college or university has an incredibly diverse set of requirements for voice, data and video services. A university infrastructure must deliver high-speed Quality of Service (QoS) for the digital library, number-crunching capability for the researchers, ubiquitous LAN access for the students and relational database access for finance and administration.
Upgrading the infrastructure to a unified high-speed system architecture is both expensive and time-consuming. But academic institutions must take on this challenge if they are to continue to attract top-performing faculty and students, garner research dollars and contribute fully to their communities. Here are some of the key planning issues involved in this type of project.
Selection of the platform or protocol - the active electronics that transmit signals through the cables - will have a major effect on the ability of the telecommunications system to support voice, data and video.
Ethernet, which uses Internet protocol (IP), is the best platform for data transmission, and is widely used for network connections on college campuses. It is cost-effective, runs across category 5E cabling and supports many users. However, Ethernet is not the optimal platform for voice and video transmission. Asynchronous transfer mode (ATM) is the ideal platform to support voice, data and video transmission. This protocol is designed to deliver time-sensitive data, such as a video signal, without any delay caused by network traffic.
For this reason, ATM is an attractive choice for the current and future voice and video needs of academia. However, ATM hardware is expensive; it is not practical to abandon a recently purchased Ethernet system and replace it with ATM. A cost-effective compromise is to deploy the Ethernet/IP protocol within each building and inter-network the campuses with an ATM backbone.
With the protocol for signal transmission in place, it is the passive telecommunications infrastructure - the cable distribution plants, conduit and cable itself - that actually transmits the signals from one point to another in the network. There are a number of decisions, including selection of fiber optic and copper cable, cabling topology and conduit, which affect the network’s capabilities, reliability, flexibility and cost.
Be sure that the system is designed using a combination of multimode and single mode fiber optic cable - multimode for the Ethernet platform and single mode for sending video signals and data across a longer distance and at higher speeds, such as in high-speed (1 gigabit) Ethernet, ATM and Sonet applications.
The design of a network’s cabling topology - the arrangement of distribution frames and cable - is a critical issue. The installation of cable easily can cost millions of dollars and should be capable of providing effective service for 30 to 40 years. In concept, a single main distribution frame at the center of a star is the simplest cabling topology; however, it is not always the most functional. The design must be based on the particular geography of the campus. Effective strategic planning is essential to designing a cabling topology that will remain functional through the long term.
Getting From Here to There
Most academic institutions elect to route cable using a combination of buried conduit, aerial runs and wireless technology. Cost, aesthetics and reliability are factors in the decision. There is an enormous cost to trenching and burying steel pipe, pouring concrete fill and installing manholes, yet these activities constitute an effective method of protecting cable. Innerduct, a corrugated plastic tube used by many long-distance telephone carriers, and schedule 80 PVC pipe are cheaper alternatives. Either can be covered with soil without concrete fill. Direct-buried cable, which uses no conduit, is the cheapest alternative, but it could easily be broken by indiscriminate digging during a future construction project.
Aerial cable runs are less expensive and easier to install, but overhead wires are at risk during storms, and telephone poles are unsightly. A practical approach, if aesthetics are less important and the costs of trenching are too high, is to employ aerial runs, such as to a maintenance building in an outlying area or one that is surrounded by parking lots.
Recent improvements in wireless WAN technology that enable faster (11 megabits/second) transmission have made this a practical way to supplement, but not replace, wired connections.
Buried cable? Steel vs. plastic? Aerial runs? Wireless? Ultimately, these decisions depend on a careful balance of the budget with site-specific logistics and the value of the data. Some of the risk may be mitigated by design of a cabling topology that uses diverse or redundant pathways. In any case, it is always recommended to prepare for future expansion by laying empty conduit.
The Unit Cost Contract
To complete a project of this scope within a reasonable time frame requires that implementation proceed while design is in progress. The unit cost contract is an effective way to hire a contractor(s) after design of one building is completed, while still getting some degree of pricing protection. In this method, the contractor bases his or her bid on each element of the project - a unit cost for a foot of cable, a connector, etc. - based on the designer’s projections from the first set of drawings.
The consultant must review any changes to the drawings suggested by the contractor, approve the changes and resubmit revised drawings. Construction supervision also is essential to the success of the project; without it, through the course of the project, a contractor may proceed with unauthorized design changes or substitution of equipment and materials.
Close-Out: The Crucial Final Step
Once testing is completed and all involved parties breathe a sigh of relief that ‘it works,’ the temptation is to cut the ribbon and label the project complete. However, it is important first to ensure that a careful project close-out is performed. It is absolutely essential for future operations, troubleshooting and system expansions to prepare and maintain the following documents: a site map of the cable layout and schematic wiring diagrams, and a database of all labeled wiring points, floor plans with outlets labeled and test results on disk.
Developing an IT infrastructure that supports the needs of a diverse higher-education community truly is a marriage of art and science. Like any successful marriage, it requires time, planning, commitment, flexibility and, above all, a shared vision of the future.