Page 80 - DCAP207_NETWORKS_DCAP406_COMPUTER_NETWORKS

Unit 5: Networking Devices

5.6.3 Message Switching Notes

In message switching, there is no need for a connection to be established all the way from source
to destination. Figure 5.15 shows communication between Tx (sending or transmitting device)
and Rx (receiving device) via a number of links as Tx to Tx , Tx to Tx , Tx2 to Tx , Tx to Rx.
1 1 2 3 3
Figure 5.15: A Connection between Two Systems Tx and Rx through 3 Links

Tx Tx1 Tx2 Tx3 Rx

The switching nodes like Tx1, Tx2 and so on receive the message, store it and forward the
message to the adjacent message switching node after creating a connection with the adjacent
message switch. Message switching is also known as store-and-forward switching since the
messages are stored at intermediate nodes en route to their destinations. The difference between
packet switching and message switching may be understood by the size of packets. In case of the
packet switching, the size of packet is very short compared to the size of message in message
switching. The short size packet takes less time to reach the destination and therefore reassembling
of out of order packets does not require a dedicated connection. Thus the packet switching
allows packets belonging to other messages to be sent in between other packets. Packet switching
uses pipelining to make a continuous flow of packets from source to destination devices via
intermediate switching nodes. Therefore, a link from source to destination devices and
intermediate nodes are used to transmit packets simultaneously. This enhances the channel
efficiency and reduces the total delay for transmission across a packet network as compared to
message switching.

5.6.4 Cell Switching

Cell switching, associated with Asynchronous Transmission Mode (ATM) is considered to be a
high speed switching technology to overcome the speed problems for real time applications.
Cell switching uses a connection-oriented packet-switched network. In cell switching, a connection
is known as signaling. The cell switching uses a fixed length of packets of 53 bytes out of which
5 bytes are reserved for header. The packet switching technique uses variable length packets.
Like packet switching, the cell switching technique also divided the message into smaller packets
but of fixed length. The advantages are high performance, common LAN/WAN architecture,
multimedia support, dynamic bandwidth and scalability. High performance is achieved because
of the use of hardware switches. The cell switching also possesses connection-oriented service
features of circuit switching. The connection oriented virtual circuits for each phase allocates
specified resources for different streams of traffic.

5.6.5 Difference between Circuit Switching and Packet Switching

The concept and idea of switching data (into circuit switching network) into the small blocks or
packets according to the match of their size, content or structure was firstly represented by “Paul
Baran” in early years of 1960’s. On other hand, Packet switching which is also known as virtual
switching is also in the content of the feature of networking.
Circuit Switching Vs. Packet switching is actually defines the differences between the two different
methods of switching. Circuit Vs. Packet Switching is an absolute comparison between the both
switching. Circuit Vs. Packet switching is taking place on the basis of different features of the
two different kinds of switching. The difference of old and the new technology use is also a main
comparative feature between the both which supports Circuit switching Vs. Packet Switching.

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