Transport Control Protocol (TCP) Issues in MANET

Transport Control Protocol (TCP) is designed and optimized for wired networks

Problem:

It assumes that every packet loss is due to congestion and takes the congestion control action by reducing window size. This mechanism of TCP reduces the throughput when wireless loss occurs.

Solution:

A Loss Differentiation Algorithm (LDA) algorithm named spike scheme, solves this issue. The spike scheme differentiates congestion and wireless losses using round trip time as a measure. So after detecting losses if it is due to a wireless loss, congestion window will not be decreased. Thus, the throughput of the network is greater with LDA than the original TCP.

Solution in NS2

 
  • Data transmission can be established in the mobile network using tcp connection.

  • Inbuilt variable cwnd_ (congestion window size) can be accessed under the mobile scenario. tcp.cc file can be modified such that, cwnd_ adjustment based on rtt (round trip time) value. Value of the rtt variable will be different for congestion and wireless loss condition. Ns2 is rebuilt after modification of tcp.cc file with spike scheme.

  • Throughput result can be compared between original tcp implementation and modified tcp implementation in the network.

Related Project Titles:

 
  • “End-to-end differentiation of congestion and wireless losses” IEEE TRANSACTIONS ON NETWORKING.