Ethernet has pretty much taken over the LAN market. As
recently as the 1980s and the early 1990s,
Ethernet faced many challenges from other LAN technologies,
including token ring, FDDI and ATM.
Some of these other technologies succeeded at captur
CSMA/CD: Ethernet's Multiple Access
Nodes in an Ethernet LAN are interconnected by a broadcast
channel, so that when an adapter transmits
a frame, all the adapters on the LAN receive the frame. As we
discussed in section 5.3, Ethernet uses a
An Unreliable Connectionless Service
All of the Ethernet technologies provide connectionless service
to the network layer. That is to say,
when adapter A wants to send a datagram to adapter B,
adapter A encapsulates the datagram in an
Ethernet frame and s
Today Ethernet comes in many shapes and forms. An Ethernet
LAN can have a "bus topology" or a "star
topology." An Ethernet LAN can run over coaxial cable,
twisted-pair copper wire, or fiber optics.
Furthermore, Ethernet can transmit data a
The most common Ethernet technologies today are 10Base2,
which uses thin coaxial cable in a bus
topology and has a transmission rate of 10 Mbps; 10BaseT,
which uses twisted-pair cooper wire in a star
topology and has a transmission r
10BaseT and100BaseT Ethernet
10BaseT and100BaseT Ethernet together, as they are similar
technologies. The most
important difference between them is that 10BaseT transmits
at 10 Mbps and 100BaseT Ethernet
transmits at 100 Mbps. 100BaseT is also commonly ca
Bridges versus Routers
As we learned in Chapter 4, routers are store-and-forward packet switches that
forward packets using IP addresses.
Although a bridge is also a store-and-forward packet switch, it is fundamentally
different from a router in that it
In contrast to hubs, which are physical-level devices, bridges
operate on Ethernet frames and thus are layer-2 devices.
In fact, bridges are full-fledged packet switches that forward
and filter frames using the LAN destination addresses.
When a fr
The simplest way to interconnect LANs is to use a hub. A hub
is a simple device that takes an input (i.e., a frame's
bits) an retransmits the input on the hub's outgoing ports.
Hubs are essentially repeaters, operating on bits. They are
Gigabit Ethernet is an extension to the highly successful 10
Mbps and 100 Mbps Ethernet standards.
Offering a raw data rate of 1000 Mbps, Gigabit Ethernet
maintains full compatibility with the huge
installed base of Ethernet equipment. Th