Information Technology Reference
In-Depth Information
Link type
1000 Base
- T
Cat 5
" - CX
" - SX
" - SX
" - LX
" - LX
" - LX
" - SLX
Coax
850/62.5
850/50
1300/62.5
1300/50
1300/SMF*
1550/SMF*
100 m
200 m
300 m
Distance
400 m
500 m
5 km
10 km
*
FIGURE 12.5
Gigabit Ethernet cabling distances.
SMF = Single-mode fiber. All multimode fiber is shown with wavelength/core diam.
Layout Topology.
The first step is to determine a topological layout for the gigabit net-
work. Whether you are using Gigabit Ethernet or ATM technology, this will be an
important guide to the facilities you must provide. We will cover the process for Gigabit
Ethernet, because it is in much wider use and the process for ATM is essentially the same.
As you know, Gigabit Ethernet can be used for either work area or backbone
connections. Chances are that you currently have an installation that uses Fast
Ethernet (100 Mbps) switches with 10/100 Mbps network interface cards (NICs) in
workstations and servers. Typically, these devices are cabled according to TIA-568-
C cabling standards, and operate at either 10BaseT or 100BaseTX. Let's say you
want to migrate your network to gigabit, and intend to continue using the Fast
Ethernet NICs to the workstations, but you want to add gigabit NICs to the servers.
This is very viable migration strategy.
Initially, you can add gigabit switches in the backbone of the network to con-
nect the servers (Fig. 12.6) and use your existing Fast Ethernet switches to support
the desktop. This will eliminate most of the bottlenecks from your network topol-
ogy, while allowing you to preserve your existing infrastructure. This allows a giga-
bit-connected server to service as many as 10 of your 100 Mbps workstations at the
same time. If you are still using some 10 Mbps workstations, a gigabit backbone
would allow a throughput gain of almost a factor of 100 into the server. New
servers and workstations may be equipped with 10/100/1000 Mbps NICs, and like-
wise, 10/100/1000 Mbps Ethernet switches can be added at the network core.
An additional bonus from using Gigabit Ethernet technology is that it is engi-
neered to provide throughput of around 90%. This is quite a bit above the normal uti-
lization limit of 30% to 40% on 10 Mbps Ethernet (although it is possible to adjust
some of the network parameters to achieve more than double this for discrete links).
