Theory of operations - Mature Packet Switching Protocols

1. Theory of Operations
1. Traffic Characteristics
2. X.25 Packet Switching Operation
By: Pradnya Saval
Asst. Professor, TCET
Mumbai

2. Traffic Characteristics
• To understand packet switching protocols following details must be known:
• Types of traffic for transport
• Characteristics of traffic
• Bursty Traffic:
• Data Transmission with duration of less than 5 seconds.
• Often travels in one direction rather than equally in both direction.
• Eg: HTTP browsing

3. Traffic Characteristics
• Packet Switching networks accommodate traffic that is not delay-
sensitive.
• Two primary requirements for packet networks are burstiness
and delay-insensitive traffic.
• Due to dynamic allocation of bandwidth technique used by
packet switching, bursty delay-insensitive traffic is ideal for
transport over a packet switching network.

4. • The figure shows that:
• Low speed terminal users at site A, B and C.
• High Speed user host.
• Terminals could use low speed X.3 circuits to
request information downloads from the host.
• Terminal traffic is very light (low-bandwidth
usage) compared to the data traffic from the
host (high-bandwidth usage).
• The single 56Kbps multiplexed X.25 line from
the host into the packet switching network
depicts the efficiency of asymmetrical traffic
patterns where the host will transmit much
more traffic than it receives.

5. X.25 Packet Switching Operation

6. X.25 Packet Switching Operation (Cont..)
• Packet Switching Network shows 6 nodes (1-6) each with 3 users (terminal A, B,
and C)
• Each user device is acting as a DTE and each network node is acting as a DCE.
• Packets are routed based on the routing table via different paths.
• Reassembly is done at the receiving node.
• The DTE device transmits data to the network via synchronous mode
X.25protocol.
• Error checking and retransmission is done at every node.