A comparison of mechanisms for improving TCP performance over wireless links

Abstract

Reliable transport protocols such as TCP are tuned to perform well in traditional networks where packet losses occur mostly because of congestion. However, networks with wireless and other lossy links also suffer from significant losses due to bit errors and handoffs. TCP responds to all losses by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless and lossy systems. In this paper, we compare several schemes designed to improve the performance of TCP in such networks. We classify these schemes into three broad categories: end-to-end protocols, where loss recovery is performed by the sender; link-layer protocols, that provide local reliability; and split-connection protocols, that break the end-to-end connection into two parts at the base station. We present the results of several experiments performed in both LAN and WAN environments, using throughput and goodput as the metrics for comparison.Our results show that a reliable link-layer protocol that is TCP-aware provides very good performance. Furthermore, it is possible to achieve good performance without splitting the end-to-end connection at the base station. We also demonstrate that selective acknowledgments and explicit loss notifications result in significant performance improvements.

Transport Layer Protocols for Mobile Ad Hoc Networks

“…The enhancements are classified and compared in terms of the way in which they attempt to improve the TCP performance. This is in contrast to the previous studies on TCP [5,6] which classify enhancements into end-to-end proposals (only the sender and the receiver attempt to handle losses and thus maintain the end-to-end semantics of TCP), link-layer proposals (the link layer tries to hide the characteristics of lossy wireless links from the transport layer), and split-connection proposals (splitting the TCP connection between the mobile host and the fixed host into two separate connections and handling them separately).…”

“…In contrast with many of the previous efforts that classify and compare TCP enhancements by their type [5,6] (i.e., end-to-end proposals, link-layer proposals, and split-connection proposals), they are classified as per the strategy used in order to improve the TCP performance.…”

Multi-layer loss recovery in TCP over optical burst-switched networks

“…The Snoop protocol [11] for wireless networks addresses the issues of TCP end-to-end semantics violation. Snoop works by deploying an agent at the base station and performing retransmissions of lost segments over the wireless portion based on duplicate TCP acknowledgments (which it also suppresses).…”

“…In order to minimize the dupack as much as possible, the lost packet is retransmitted to burstification process as soon as the loss is detected at edge node where Snoop is implemented. For additional details about the implementation of Snoop refer [11].…”

“…Snoop uses two important functions for implementing its functionality, snoop_data() and snoop_ack() [11]. In the forward direction, the snoop_data() function processes and caches the packets before OBS burstification at the OBS ingress.…”