Effect of link level impairments on transmission control protocol in military networks

Tactical networks is a heterogeneous network which facilitates information sharing and data exchange among military tactical force units. The tactical communication depends on factors such as network characteristics, communication media resources, operational mobility, terrain etc. The key challenge is to address typical military communication network constraints such as limited bandwidth and latency, narrow effective communication range, intermittent communication links. Performance of the transport layer protocols is heavily affect by some of the link level impairments like high loss rates, long & variable delays and intermittent. Any random packet loss in the network is considered as congestion by TCP in the network and in order to overcome this congestion and packet-loss TCP employs the congestion control algorithm resulting in poor bandwidth usage of already scarce bandwidth. Similar for the intermittency the transport protocol must detect intermittencies and quickly adjust to intermittent paths it carry mission-critical data in military networks. Heterogeneous communication link (starting from High Frequencies or Very High Frequencies radio sets to satellite links) between sources to destination results is long and variable delays. The interaction of these long delays with the standard TCP slow-start and congestion-avoidance algorithms will damage the TCP performance. A critical survey has been done on various TCP variants to find out which is the best suitable protocol (and variants) under varying impairments for tactical networks.