The network bridge is device that divides the network into segments. Each segment represents the separate collision domain, so the are number of the collisions on network is reduced. Also, because each is collision domain has its own separate bandwidth, the bridge also improves overall network performance.
The
bridge works at Data link layer (Layer 2) of OSI model, just like the switch
does. It’s inspects incoming traffic & decide whether to the forward its or
filter it. Each incoming Ethernet frame inspected the destination MAC address.
If bridge determines that destination host is on the another segment of
network, it forwards frame to that segments.
Consider
the following networks are:
In
example above we have the network of four computers. The networks are divided
into segments by the bridge. Each segment is separate collision domain with the
own bandwidth. Let say that the Host A wants to the communicate with the Host C.
Host A will be send the frame with Host C’s destination MAC address to bridge.
The bridge will be inspecting frame and forward it to segment of network Host C
is on.
Network
bridges offered substantial improvements over network hubs, but that are not widely
used anymore in the modern LANs – switches are the commonly used instead. Here
is why:
·
Most the bridges have only 2 or 4 ports. The switch can have tens
or even hundreds of the ports
·
bridges are the software based, while switches are the hardware-based
and use chips (ASICs) when making forwarding decisions, which makes them much
faster than the bridges
·
the switches can have multiples spanning-tree instances, bridges
can have the only one
·
the switches can have multiple broadcast domains (one per VLAN)
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