Inner Space for all TCP Options (Kitchen Sink Draft - to be Split Up)

Document Type Expired Internet-Draft (individual)
Author Bob Briscoe 
Last updated 2015-09-10 (latest revision 2015-03-09)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document describes an experimental redesign of TCP's extensibility mechanism. It aims to traverse most known middleboxes including connection splitters, by making it possible to tunnel all TCP options within the TCP Data. It provides a choice between in- order and out-of-order delivery for TCP options. In-order delivery is a useful new facility for options that control datastream processing. Out-of-order delivery has been the norm for TCP options until now, and is necessary for options involved with acknowledging data, otherwise flow control can deadlock. TCP's original design limits TCP option space to 40B. In the new design there is no such arbitrary limit, other than the maximum size of a segment. The TCP client can immediately start to use the extra option space optimistically from the very first SYN segment, by using a dual handshake. The dual handshake is designed to prevent a legacy server from getting confused and sending the control options to the application as user-data. The dual handshake is only one strategy - a single handshake will usually suffice once deployment is underway. In summary, the protocol should allow new TCP options to be introduced i) with minimal middlebox traversal problems; ii) with incremental deployment from legacy servers; iii) with zero handshaking delay iv) with a choice of in-order and out-of-order delivery v) without arbitrary limits on available space.


Bob Briscoe (

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