- Route used in Message switching
- The transmitted message will use the best route at the moment that the messages is sent
- Example:
- The (best) route
taken by
message
at some moment in time:
- The (best) route
taken by
message
at another moment in time:
- The (best) route
taken by
message
at some moment in time:
- Message:
- Message =
a unit of
data that is
sent by
a computer application (program)
(to another computer application)
- Message =
a unit of
data that is
sent by
a computer application (program)
(to another computer application)
-
Network limitations:
- Most communication network
impose a
maximum size on
transmissions
over the network !!!
- This limitation is imposed due to maximum buffer size used
- Transmission of
of a message over
most
computer networks:
- A message is often transmitted in multiple packets
Illustrated:
Note:
- A sequence number is
included to allow the
receiver to
re-assembler the
messages
(More on this topic later)
- Most communication network
impose a
maximum size on
transmissions
over the network !!!
- Packet:
- Packet = a unit of data that is transmitted on a communication network
- Routes used in Packet switching
- The message is
fragmented into
packets
- Each transmitted packet will use the best route at the moment that the packet is sent
- The message is
fragmented into
packets
-
Properties of message/packet switching:
- Different messages/packets can
take different routes
towards the
destination
- Notable result::
- Messages/packets transmitted later can arrive earlier than some message/packet that was transmitted earlier !!!!
because some earlier messages/packets were delayed due to congestion
Example: how a later message can overtake an earlier message
- Different messages/packets can
take different routes
towards the
destination
- Datagram:
- Datagram = a unit of data transmission on a network
- Datagram switching:
- Datagram switching = the routing decision is made on a per datagram basis
- So a datagram can be:
- A message or
- A packet
- Note:
-
Message switching is
no longer used
in today's network
- All communication networks
today impose some
maximum packet size
- So all networks are are thus packet switched networks
-
Message switching is
no longer used
in today's network