Impact of False RTT Estimation on TCP Performance over Wireless Links

Presented in the paper is the simulation based study of the TCP performance issue over a Heterogeneous (with first link as wireless link) Network. In Wireless Network packet loss occur due to link failure (disconnection) and high bit errors. Frequent disconnection is considered as one of the major issues in the Wireless Network. WLAN uses IEEE 802.11 MAC protocol and it uses retransmission policy to hide the wireless losses from TCP sender. Over an erroneous wireless link, recovery of the packet loss is attempted first using local retransmission policy. Authors first investigate the effect of wireless losses on different TCP parameters, resulted in to degradation of End -- to -- End performance. By analyzing basic MAC loss recovery mechanism, authors are able to show how extended loss recovery at MAC results in to false RTT estimation and hence delays TCP loss recovery.