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• They can be used with voice telephones.

• They can be used to accommodate visitors or demo machines.

• The cost of the materials is typically only 5%–10% of the total cost.

• Your best guess doubled is often a good estimate.

• It’s much cheaper to do it once rather than adding wires later.

If you’re in the process of wiring your entire building, you might consider installing a few outlets in the hallways, conference rooms, lunch rooms, and bathrooms. Networking is becoming pervasive.

Wiring standards

Modern buildings often require a large and complex wiring infrastructure to support all of the various activities that take place inside. Walking into the average telecommunications closet is usually a shocking experience for the weak of stomach, as identically colored, unlabeled wires often cover the walls.

In an effort to increase traceability and standardize building wiring, the TIA/EIA-606 Administration Standard for the telecommunication infrastructure of commercial buildings was released in February, 1993. EIA-606 specifies requirements and guidelines for the identification and documentation of telecommunications infrastructure.

Items covered by EIA-606 include:

• Termination hardware

• Cables

• Cable pathways

• Equipment spaces

• Infrastructure color coding

• Symbols for standard components

In particular, it specifies standard colors to be used for wiring. The occult details are revealed in Table 15.4.

Table 15.4 EIA-606 color chart

a. According to the Pantone Matching System®

b. PBXes, hosts, LANs, muxes, etc.

Pantone now sells software to map between the Pantone systems for ink-on-paper, textile dyes, and colored plastic. Hey, you could color-coordinate the wiring, the uniforms of the installers, and the wiring documentation! On second thought...

15.11 NETWORK DESIGN ISSUES

This section addresses the logical and physical design of the network. It’s targeted at medium-sized installations. The ideas presented here will scale up to a few hundred hosts but are overkill for three machines and inadequate for thousands. We also assume that you have an adequate budget and are starting from scratch, which is probably only partially true.

Most of network design consists of the specification of:

• The types of media that will be used

• The topology and routing of cables

• The use of repeaters, bridges, and routers

Another key issue in network design is congestion control. For example, NFS taxes the network quite heavily, and so file serving on a backbone cable is undesirable.

The issues presented in the following sections are typical of those that must be considered in any network design.

Network architecture vs. building architecture

The network architecture is usually more flexible than the building architecture, but the two must coexist. If you are lucky enough to be able to specify the network before the building is constructed, be lavish. For most of us, both the building and a facilities management department already exist and are somewhat rigid.

In existing buildings, the network must use the building architecture, not fight it. Modern buildings often contain utility raceways for data and telephone cables in addition to high-voltage electrical wiring and water or gas pipes. They often use drop ceilings, a boon to network installers. Many campuses and organizations have underground utility tunnels that facilitate network installation.

The integrity of fire walls8

must be maintained; if you route a cable through a fire wall, the hole must be snug and filled in with a noncombustible substance. Respect return air plenums in your choice of cable. If you are caught violating fire codes, you may be fined and will be required to fix the problems you have created, even if that means tearing down the entire network and rebuilding it correctly.

Your network’s logical design must fit into the physical constraints of the buildings it serves. As you specify the network, keep