This preview shows page 1. Sign up to view the full content.
Unformatted text preview: m
the source to the destination either by store-and-forward method or broadcast
As shown in Figure 17.17, in the store-and-forward method, the message is
transmitted from the source node to an intermediate node. The intermediate node
stores the complete message temporarily, inspects it for errors, and transmits the
message to the next node based on an available free channel and its routing
information. The actual path taken by the message to its destination is dynamic as
the path is established as it travels along. When the message reaches a node, the
channel on which it came is released for use by another message. In Figure 17.16,
if a message is to be transmitted from station A to station B, it may take either path
1-2-3-4 or 1-5-4 depending on the availability of a free output path at that
As shown in Figure 17.18, in the broadcast method, the message is broadcast over
a common medium known as broadcast channel. All the stations check the
destination address of each message as they pass by and accept only those
addressed to them. The routing delays inherent in store-and-forward method are
eliminated in this method. However, this method requires that all stations must be
connected to the broadcast channel.
1. In message switching, no physical connection is required between the source
and the destination as required in case of circuit switching. 2. As channels are used only when, messages are transmitted, this method uses
the channels very effectively.
1. As the message length is unlimited, each switching node must have sufficient
storage to buffer messages. In many cases, this storage space may be underutilized.
2. In message switching, a message is delayed at each node for the time required
to receive the message plus a queuing delay waiting for an opportunity to
retransmit the message to the next node.
3. The method is too slow for interactive/real-time applications. Hence, it is used
when message delays are not critica...
View Full Document
- Spring '14