The impact of IPsec on DoD Teleport throughput efficiency

The DoD Teleport program., a component of the Global Information Grid (GIG), provides the warfighter with access to the DoD terrestrial network via satellite communications. In accordance with GIG net-centric initiatives, the Teleport program must transition from its current circuit-based architecture to a future IP-based architecture. The GIG will use a DoD implementation of IPsec to provide security through end-to-end encryption. The use of IP and its associated protocols, including IPsec may have a significant effect on the throughput achievable with wireless systems, especially satellite communication systems. Unlike the landline components of the GIG, satellite links are characterized by long delays, limited bandwidth, and non-negligible bit error rates. The purpose of this paper is to summarize some of the issues that will affect the throughput efficiency (bit/s per Hz) achievable on Teleport satellite links. GIG data links are expected to utilize TCP as their primary transport layer protocol. The problems associated with the use of TCP over satellite links are well-known and are associated with the TCP slow start and congestion avoidance algorithms. Performance enhancing proxies (PEP) provide perhaps the best solution to this problem, but PEP provide no benefit if the TCP headers are encrypted. In this paper, we estimate the effects of TCP on the throughput efficiency achieved on Teleport satellite links and discuss possible ways to mitigate this problem. Voice-over-IP (VoIP) and in particular, secure VoIP presents yet another challenge. The overhead associated with the protocols used to implement secure VoIP (IP, UDP, RTP, IPsec, etc.) can be an order of magnitude greater than the voice data being transported. Furthermore, increasing the packet size also increases the channel delay, the queuing delay, and the sensitivity to errors. We provide some examples of the overhead that might be incurred on Teleport satellite links and discuss techniques that can be used to minimize the overhead (e.g., header compression techniques and PDU concatenation). We compare the effectiveness of various combinations of these techniques.