UNIT II
Network switching
Switching is process to forward packets coming in from one port to a port leading
towards the destination. When data comes on a port it is called ingress, and when data
leaves a port or goes out it is called egress. A communication system may include
number of switches and nodes. At broad level, switching can be divided into two major
categories:
Connectionless: The data is forwarded on behalf of forwarding tables. No
previous handshaking is required and acknowledgements are optional.
Connection Oriented: Before switching data to be forwarded to destination, there
is a need to pre-establish circuit along the path between both endpoints. Data is
then forwarded on that circuit. After the transfer is completed, circuits can be
kept for future use or can be turned down immediately.
Circuit Switching
When two nodes communicate with each other over a dedicated communication path, it
is called circuit switching.There 'is a need of pre-specified route from which data will
travels and no other data is permitted.In circuit switching, to transfer the data, circuit
must be established so that the data transfer can take place.
Circuits can be permanent or temporary. Applications which use circuit switching may
have to go through three phases:
Establish a circuit
Transfer the data
Disconnect the circuit
, Circuit switching was designed for voice applications. Telephone is the best suitable
example of circuit switching. Before a user can make a call, a virtual path between caller
and callee is established over the network.
Message Switching
This technique was somewhere in middle of circuit switching and packet switching. In
message switching, the whole message is treated as a data unit and is switching /
transferred in its entirety.
A switch working on message switching, first receives the whole message and buffers
it until there are resources available to transfer it to the next hop. If the next hop is not
having enough resource to accommodate large size message, the message is stored
and switch waits.
Network switching
Switching is process to forward packets coming in from one port to a port leading
towards the destination. When data comes on a port it is called ingress, and when data
leaves a port or goes out it is called egress. A communication system may include
number of switches and nodes. At broad level, switching can be divided into two major
categories:
Connectionless: The data is forwarded on behalf of forwarding tables. No
previous handshaking is required and acknowledgements are optional.
Connection Oriented: Before switching data to be forwarded to destination, there
is a need to pre-establish circuit along the path between both endpoints. Data is
then forwarded on that circuit. After the transfer is completed, circuits can be
kept for future use or can be turned down immediately.
Circuit Switching
When two nodes communicate with each other over a dedicated communication path, it
is called circuit switching.There 'is a need of pre-specified route from which data will
travels and no other data is permitted.In circuit switching, to transfer the data, circuit
must be established so that the data transfer can take place.
Circuits can be permanent or temporary. Applications which use circuit switching may
have to go through three phases:
Establish a circuit
Transfer the data
Disconnect the circuit
, Circuit switching was designed for voice applications. Telephone is the best suitable
example of circuit switching. Before a user can make a call, a virtual path between caller
and callee is established over the network.
Message Switching
This technique was somewhere in middle of circuit switching and packet switching. In
message switching, the whole message is treated as a data unit and is switching /
transferred in its entirety.
A switch working on message switching, first receives the whole message and buffers
it until there are resources available to transfer it to the next hop. If the next hop is not
having enough resource to accommodate large size message, the message is stored
and switch waits.
