Information Technology Reference
In-Depth Information
prietary operating modes called SLX, ELX, and ZX that extend the fiber distances
to 10, 70, and 80 km, respectively. These longer-distance Gigabit Ethernet connec-
tions mean that many networking applications can use the commonly associated IP
networking within a metro area.
Copper 10GBaseT and CX Wiring
Who would have thought 20 years ago that we would seriously be talking about
transmitting 10 Gbps of data over fiber-optic cable, let alone over twisted-pair cop-
per? Yet, that is what we have achieved. As with any new technology, 10 Gig
Ethernet (or 10 GbE, as the IEEE often calls it) is primarily used for high-capacity
backbones in high-performance environments. For example, the so-called backbone
network that interconnects large computers or large Web server networks is an
application made for multi-gigabit connections. Although we have had multiplexed
gigabit trunks for some time, there is something really sweet about a single 10-Gig
connection, like the sound when a baseball player hits one out of the park.
As with 1 GbE, 10 GbE offers choices between multimode and single-mode
fiber, and between unshielded twisted pair and twinax copper. Officially, the physi-
cal interconnections for 10 GbE are called
10GBaseX
, where the X stands for one
or two letters that describe the cabling technology. The fiber options for 10GbaseX
include SX, LX4, and LR. Some of these run over multimode fiber (not very far),
and some run over single-mode fiber (up to 10 km, which is very respectable). As
with 1 GbE, multimode fiber's optical bandwidth greatly influences the 10 GbE
transmission distances. And in all cases, 50-micron fiber fares much better than
older 62.5-micron fiber. Single-mode fiber has an easier time of it, and can actually
let you reach up to 10 km.
The basic topology of 10GBase networks is essentially the same as its slower
cousins. Wiring can be run directly between two devices, or through an active-star
hub or switch. Fiber still gets you the greatest distance, but you may have to replace
older fiber types to achieve the distances you want.
Copper 10GBaseT, on the other hand, endeavors to hit the magic 100 m range
of TIA-568-C sstructured Cabling. Unfortunately, it is unlikely you can get
10GBaseT to work without a cable-plant upgrade, unless you were fortunate enough
to install an “enhanced” version of Category 6 cabling (equivalent to Augmented
Class E using the ISO/IEC 11801-European Standard that corresponds to TIA-568-
C), or have very good quality Cat 5e or Cat 6 and can accept shorter distances—pos-
sibly up to 55 m. Enhanced Class F (ISO/IEC 11801) and Category 7 cabling are
shielded systems that can support 10GBaseT fairly easily, which certainly throws
