Gigabit and 10 Gigabit Cabling Technology - LAN Wiring - page 285

TABLE 12.2
Operating Specs for 1000BaseT

1000BaseT standard IEEE 802.3ab

Medium Copper UTP or ScTP

Number of pairs required 4 pairs

Pair usage Bidirectional

Operating speed 1000 Mbps

Distance limit 100 m

Propagation delay 548 ns

Delay skew 50 ns

sense, however, says that these links are a little nearer the marginal limits when
operated at this higher data rate, and corresponding higher operating frequencies.
We will cover this in more detail in the section “Wiring Standards to Support
Gigabit Speeds,” which follows.
The important thing to realize is that network speeds are moving at a rate that
defies Moore's law. 3 The jump to gigabit occurred much faster than many had
expected, and the jump to 10 Gbps is occurring very quickly as well. However, in
all fairness, advances in networking technology have not really occurred linearly, as
they are totally dependent on standards implementations, and as such, are not incre-
mental at all. This means that a 10% or 20% increase in a network operating speed
will never be implemented, because enterprise users deploy new networks in tan-
dem, unlike workstation and server technology.
It is quite possible to have one workstation that operates at a processor speed
of X and another that operates at a much improved processor speed of X 30%.

Yet a network that envisioned one connection at 100 Mbps and the next one at 130
Mbps would be deemed patently ridiculous.
Or would it? As it turns out, we describe a network more or less like this in
Chapter 13.
It uses wireless transmission as the medium, which is much more tolerant of
mixed speeds than a wired network would be. The technique that is used for wire-
less is to always send the header at the lowest (common denominator) data rate, and
then allow what follows to be speeded up, super-encoded, or encrypted. But such a
technique could not possibly be used with a wired network…or could it?

3 Moore's law states that computing speeds will double approximately every 18 months. It is generally
recognized that the jump from 100 Mbps to 1000 Mbps has occurred at approximately double this
rate (double would have been to 200 Mbps), in concert with the increase of bandwidth requirements
on the Internet. Moore's law is named for Gordon Moore, a founder of Intel Corporation, who first
proposed it.