The document discusses packet switching as an efficient technology for digital data communications, contrasting it with traditional circuit switching used for voice communications. It describes two primary types of packet switching: datagram and virtual circuit, and explains their operational principles, including packet transmission, control information, and the roles of switching nodes in a network. The conclusion emphasizes the adaptability of packet switching for managing data traffic, especially when dealing with unreliable connections and variable data rates.

1. PAPER NAME : COMPUTER NETWORKS
STAFF NAME : MISS.S.MANIMOZHI MCA,M.Phil,PHD.,
CLASS : III BCA A
SEMESTER : VI
UNIT : III
TOPIC : PACKET SWITCHING

3.  Networks are used to interconnect many devices.
 We have checked with Local Area Networks.
 Now, wide area networks
 Since the invention of the telephone, circuit switching has been
the dominant technology for voice communications.
 Since 1970, packet switching has evolved substantially for
digital data communications. It was designed to provide a
more efficient facility than circuit switching for bursty data
traffic.
 Two types of packet switching:
 Datagram (such as today’s Internet)
 Virtual circuit (such as Frame Relay, ATM)

4.  Long detachment broadcast between stations (called
“end campaign”) is usually done over a set of
connections of switching nodes.
 Switching nodes do not concern with satisfied of
information. Their rationale is to have the resources for
a switching flair that will move the data from node to
nodule during they accomplish their goal(the end
device.
 A gathering of nodes and relatives forms a
communications network.
 In a switched infrastructure set of connections report
inward bound the network from a station are running
scared to the goal by being switched from node to node.

6.  Nodes may attach to additional nodes, or to
some stations.
 set of connections is frequently partly
connected
 However, several neglected relatives are enviable for
reliability.
 Two unlike switching technologies
 Circuit switch
 Packet switch

7.  Incompetence
 Direct capacity is dedicated for the whole duration of a correlation
 If no data, capacity is wasted
 Delay
 Long initial delay: circuit establishment takes time
 Low data delay: after the circuit institution in sequence is
transmit at a fixed data rate with no setback other than the
transmission delay.
 The delay at each node is insignificant.
 Residential for voice traffic (public phone network) but can
also applied to information traffic.
 For voice connections, the resulting circuit will enjoy a elevated
percentage of operation because most of the time one party or the
other is talking.

8. Subscribers: the campaign that attach to the network.
Subscriber loop: the link between the subscriber and the network
interactions: the switching centers in the report mill. End office: the switching
center that directly wires subscribers. Trunks: the undergrowth between
exchanges. They carry several voice-regularity circuits using either FDM or
synchronous TDM.

9.  Predicament of course switching
 designed for voice overhaul
 Resources dedicated to a finicky call
 For information communication, much of the
occasion the connection is idle (say, web browsing)
 information rate is preset
 Both ends must operate at the same rate during the
total stage of relation.
 Packet switching is intended to tackle these
troubles.

10.  information are transmit in short packets
 classically at the order of 1000 bytes
 Longer messages are split into sequence of packets
 Each packet contain a segment of user information plus some
control info
 Control info contain at least
 Routing (addressing) info, so as to be routed to the planned
objective.
 Recall the content of an IP subtitle!
 store and forward
 On each switching node, packets are received, stored
momentarily (buffered) and agreed on to the next node.

12.  A station break long communication into
packet.
 Packets are sent out to the system successively,
one at a occasion
 How will the system switch this torrent of
packet as it challenge to direction them through
the network and transport them to the
intended objective?
 Two approach
 Datagram approach
 Virtual circuit approach

13.  every one packet is treated discretely with no
position to packet that have departed before.
 Each node choose the next node on a packet’s path.
 Packets can take any potential direction.
 Packets may land at the receiver out of order.
 packet may go missing.
 It is up to the head put to rearrange packets
and accept up from missing carton
 Example: Internet

14.  In practical route, a preplanned route is
established before any packets are sent, then all
packets follow the same route.
 Each packet contains a practical route
identifier in its place of objective attend to and
each node on the pre conventional route knows
where to forward such packets.
 The node need not make a navigation decision for
each pack.
 Example: X.25, Frame Relay, ATM
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16.  implicit circuit
 System can provide sequencing (packets arrive at the same
order) and error control (retransmission between two nodes).
 Packets are frontward more speedily
 Based on the virtual circuit identifier
 No navigation decisions to make
 Less unswerving
 If a node fails, all fundamental circuits that pass through that node
fail.
 Datagram
 No call complex phase
 Good for burs T v data, such as Web application
 More plastic
 If a node fails, packet may find an interchange route
 Routing can be used to avoid congested parts of the system
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17. CONCLUSION
A router in fact is a switch that create
association between an participation and production
port and an electrical switch connect the input to the
production to the liveliness flow .