Understanding the network.pdf - Back to Home

protocol. Figure 6.3 illustrates the application of
FDDI-to-Ethernet encapsulation bridges to interconnect three
Ethernet LANs.
Figure 6.3. FDDI-to-Ethernet encapsulation
bridge.
Translation bridges also come in a low bandwidth WAN variety
known as a half-bridge. Half-bridges use an HDLC or PPP
synchronous serial link to connect to same type Layer 2 LAN
segments.
• Source route bridges—These bridges (in most cases) are used
to join network segments that are based on the same Layer 2
protocol, however, they rely on the packet's source to provide
the path the packet will take through the Layer 2 network.
Source route bridges then use this information to forward the
packet from segment to segment.
Although different types of bridges exist, there is one condition that is
common to all bridges. Bridges, like all other nodes connected to a
shared wire, operate under the protocol transmission rules governing
the networks they connect. For example, an Ethernet bridge must
wait until the wire is clear before it can forward packets to its
destination, and token-based bridges can only transmit data when
they have the token. This dependency on network availability,
coupled with the processing required for bridges to forward traffic
between network bridges, is why bridges can impact network
performance.