Message Switching

Message Switching
 This is whereby the whole message may be routed by any convenient
route.
 No physical/dedicated path is established in advance between sender
and receiver
 Data is stored at a hop (which may be router) then forwarded one hop
later.
 Each block is received in its entity form, inspected for errors
 Data is not transmitted in real time.
 Blocking cannot occur
 Delays are very common
 Sender and receiver need not be compatible since sending will be done
by routers, which can change data format, bit rate and then revert it
back to original format on receiving or submit it in different form.
 Storing data solves congested networks since data can be stored in
queue and forwarded later when channel becomes free
 Priorities can be used to manage networks
 Very slow if the number of nodes is many since each node stores before
forwarding the data
 In message switching, whole message is routed in its entirety, one hop
at a time.
 Now implemented over packet or circuit switched data networks.
 Each message is treated as a separate entity.
 Each message contains addressing information, which is used by switch
for transfer to the next destination.
 Also called a store and forward network
 Used in e-mails and in telex forwarding
 There is often no real limit on the message / block size.
Advantages
• more devices can share network bandwidth
• reduced traffic congestion
• one message can be sent to many destinations through broadcast
addresses
Disadvantages
• often costly – must have large storage devices to hold potentially long
messages
• not compatible with most real time applications