Bridges
and repeaters are both important devices in the field of telecommunications and
computer networking. In this article we discuss about these two and differences
between them.
- The repeaters are deployed at the physical layer whereas one can
find bridges at the MAC layer.
- Thus, we called repeaters as the physical layer
device.
- Similarly, bridge is known as the MAC layer device.
- Bridge is
responsible for storing as well forwarding the data packets in an Ethernet.
- Firstly, it examines the header of the data frame, selects few of them and then forwards
them to the destination address mentioned in the frame.
- Bridge uses the CSMA/CD for accessing a segment whenever the data frame has to be forwarded to it.
- Another
characteristic of a bridge is that its operation is transparent.
- This means
that the hosts in the network do not know that the bridge is also present in
the network.
- Bridges learn themselves; they do not have to be configured again
and again.
- They can be simply plugged in to the network.
- Installing a bridge
causes formation of LAN segments by breaking a LAN.
- Packets are filtered with
the help of bridges.
- The frames that belong to one LAN segment are not sent to
the other segments.
- This implies separate collision domains are formed.
The
bridge maintains a bridge table consisting of the following entries:
- LAN
address of the node
- Bridge
interface
- Time
stamp
- Stale
table entries
- Bridges
themselves learn that which interface can be used for reaching which host.
- After
receiving a frame, it looks for the location of the sending node and records
it.
- It keeps the collision domains isolated from one another thus, giving the
maximum throughput.
- It is capable of connecting a number of nodes and offer
limitless geographical coverage.
- Even different types of Ethernet can be
connected through it.
- Even the repeaters are plug and play devices but they
do not provide any traffic isolation.
- Repeaters are used for the purpose of
regenerating the incoming signals as they get attenuated with time and
distance.
- If physical media such as the wifi, Ethernet etc. is being used,
the signals can travel only for a limited distance and after that their quality
starts degrading.
- The work of the repeaters is to increase the extent of the
distance over which the signals can travel till they reach their destination.
- Repeaters also provide strength to the signals so that their integrity can be
maintained.
- Active hubs are an example of the repeaters and they are often
known as the multi-port repeaters.
- Passive hubs do not serve as repeaters.
- Another
example of the repeaters are the access points in a wifi network.
- But it is
only in repeater mode that they function as repeaters.
- Regenerating signals
using repeaters is a way of overcoming the attenuation which occurs because of
the cable loss or the electromagnetic field divergence.
- For long distances, a
series of repeaters is often used.
- Also, the unwanted noise that gets added up
with the signal is removed by the repeaters.
- The repeaters can only perceive
and restore the digital signals.
- This is not possible with the analog signals.
- Signal
can be amplified with the help of amplifiers but they have a disadvantage which
is that on using the amplifiers, the noise is amplified as well.
- Digital
signals are more prone to dissipation when compared to analog signals since
they are completely dependent up on the presence of the voltages.
- This is why
they have to be repeated again and again using repeaters.
