TCP In the IPSEC Environment

Abstract

Satellite based networks can transport data for diverse set of applications. Most Internet applications which use Transmission Control Protocol (TCP) need special handling for efficient operation at high speeds. Recently, support for IPSEC is getting widespread in IPv4 networks and it is likely to be mandatory in future IPv6 networks. However when IPSEC is used, TCP headers will be encrypted. High speed TCP connections can suffer from poor performance over networks with high latency, which is the case for geosynchronous satellite links. Performance enhancing proxies (PEP) serve to optimize protocol performance over satellite links by examining and suitably processing TCP headers. Since IPSEC obscures the TCP headers which proxies rely upon, the two technologies are incompatible. This paper describes the salient points of TCP over satellite links, performance enhancing proxies, and describes in detail the TCP enhancements necessary for its efficient operation in the combined IPSEC and satellite environment. The standardization for such a TCP profile being carried out in the Telecommunications Industry Association (TIA) under their Satellite Communications Division will be briefly described. The performance comparison of the different TCP enhancements is also discussed.