11 Feb
1999
11 Feb
'99
12:26 p.m.
About gigabit ethernet:
Let me push the question a bit more....
-How do they squeeze that much data down the line? Fiber-optics cabling
only? Data multiplexing?
1 Gbps on fiber isn't that much harder than OC12 (622 Mbps). Of course,
it's easy for me to say that, but one of my friends who works for HP's
optoelectronics division designing the laser diodes and transceiver modules
might disagree. But from the point of view of a maker of NIC cards or hubs,
the magic is all encapsulated in a nice little plastic package.
For twisted pair, they use four pairs at 250 Mbps each, half duplex. For
comparison, 100-base-TX uses a single CAT 5 pair at 100 Mbps for transmit,
and a second pair for receive, so they can optionally support full duplex.
And 100-base-T4 uses four CAT 3 pairs at 25 Mpbs, half duplex.
-How do they discriminate the beginning of one packet
from the end of
another when running at such high speeds?
Basically the same way they do it at lower speeds; by looking for coding
violations.