![]() Snoop proxies detect losses by monitoring TCP transmissions for duplicate acknowledgements. It is designed to hide interference or collision-based packet loss over a wireless link. The Snoop proxy is an example of an integrated proxy. As TCP acknowledgements are cumulatively acknowledged some can be decimated or filtered to improve performance. In this scenario, the speed at which the modem can return TCP acknowledgements can be a limiting factor. A common example is satellite broadband where a downstream satellite link provides significantly greater bandwidths than the upstream dialup modem link. In asymmetric links the upstream and downstream rates vary widely. This allows the end systems to run unmodified and can overcome some problems with TCP window sizes on the end systems being set too low for satellite communications.Īck filtering or decimation is used on highly asymmetric links. Split TCP intercepts TCP connections from the end systems and terminates them. The end systems use standard TCP with no modifications, and do not need to know of the existence of the PEPs in between. Split TCP functions by breaking the end-to-end connection into multiple connections and using different parameters to transfer data across the different legs. A typical system uses Split TCP PEPs to improve TCP performance over a satellite link. Split TCP is typically used to solve TCP problems with large round-trip delay times. Each is used to solve a link related problem. There are a range of different types of PEPs. Asymmetric PEPs operate differently in each direction, which can cause, for example, only one link direction performance to be enhanced. Symmetric PEPs use identical behavior in both directions the actions taken by the PEP occur independent from which interface a packet is received. Symmetry: A PEP implementation may be symmetric or asymmetric.This is quite common in commercial PEP devices, which act as a black box, using more or less open protocols to communicate between them in the place of TCP. ![]() Integrated PEP will run on a single box, while distributed PEP will require to be installed on both sides of the link that cause the performance degradation. Distribution: PEPs can be either integrated or distributed.This is based on the OSI level of implementation of the PEP. In the latter case, the proxy controls the transmissions of the TCP segments in both directions, by ack filtering and reconstruction in the existing connection (see protocol spoofing). ![]() In the first case, the proxy pretends to be the opposite endpoint of the connection in each direction, literally splitting the connection into two.
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