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Chapter 1

Internetworking

Typically, the AUI has a built-in transceiver, and the connections are now
usually just RJ-45 connections.

The thing is, the AUI interface cannot support 100Mbps Ethernet because

of the high frequencies involved. So 100BaseT needed a new interface, and
the 802.3U specifications created one called the Media Independent Inter-
face (MII), which provides 100Mbps throughput. The MII uses a nibble,
defined as four bits. Gigabit Ethernet uses a Gigabit Media Independent
Interface (GMII) and is eight bits at a time.

802.3U (FastEthernet) is compatible with 802.3 Ethernet because they

share the same physical characteristics. FastEthernet and Ethernet use the
same maximum transmission unit (MTU), same Media Access Control
(MAC) mechanisms, and preserve the frame format that is used by 10BaseT
Ethernet. Basically, FastEthernet is just based on an extension to the IEEE
802.3 specification, except it offers a speed increase of 10 times that of
10BaseT.

Here are the expanded IEEE Ethernet 802.3 standards:

100BaseTX EIA/TIA Category 5, 6, or 7 UTP two-pair wiring. One
user per segment; up to 100 meters long. It uses an RJ-45 MII connector
with a physical star topology and a logical bus.

100BaseFX Uses fiber cabling 62.5/125-micron multimode fiber. Point-
to-point topology; up to 412 meters long. It uses an ST or SC connector,
which are duplex media-interface connectors.

1000BaseCX

Copper shielded twisted-pair that can only run up to

25 meters.

1000BaseT Category 5, four-pair UTP wiring up to 100 meters long.

1000BaseSX MMF using 62.5 and 50-micron core; uses a 780-
nano-meter laser and can go up to 260 meters.

1000BaseLX Single-mode fiber that uses a 9-micron core, 1300-
nano-meter laser and can go from 3km up to 10km.

100VG-AnyLAN is a twisted-pair technology that was the first 100Mbps LAN.

But since it was incompatible with Ethernet signaling techniques (it used a

demand priority access method), it wasn't very popular, and is now essen-

tially dead.

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