The IESG has approved the following document:
- '0-RTT TCP Convert Protocol'
  (draft-ietf-tcpm-converters-19.txt) as Experimental RFC

This document is the product of the TCP Maintenance and Minor Extensions
Working Group.

The IESG contact persons are Mirja Kühlewind and Magnus Westerlund.

A URL of this Internet Draft is:
https://datatracker.ietf.org/doc/draft-ietf-tcpm-converters/





Technical Summary

This document specifies an application proxy, called Transport Converter, to 
assist the deployment of TCP extensions such as Multipath TCP. This proxy is 
designed to avoid inducing extra delay when involved in a network-assisted 
connection (that is, 0-RTT). This specification assumes an explicit model, 
where the proxy is explicitly configured on hosts. The proxy can be installed 
in managed networks by a network operator, for instance to help the deployment 
of Multipath TCP.

Working Group Summary

While Multipath TCP is an important use case, the Convert Protocol can actually 
be used for several TCP extensions. As the protocol is highly related to TCP 
standards and not specific to Multipath TCP, it was decided to home this 
document in the TCPM working group. The TCPM working group requests publication 
as Experimental document because the protocol targets controlled environments 
in which all network attachments are managed by the same administrative entity.

Document Quality

The document has been presented and discussed repeatedly in TCPM and as a 
result the protocol has changed several times. One frequently discussed design 
choice is whether and how to use TCP Fast Open (TFO). Appendix C explains the 
rationale for the final solution. There have also been some discussions whether 
such a proxy is really useful and needed. Some few contributors to the working 
group were not convinced by the MPTCP use case. During WGLC, Philip Eardley 
(chair of the MPTCP WG) has performed a comprehensive review, which was 
subsequently addressed in a number of document updates. The shepherd has 
reviewed the document before WGLC and verified that all WGLC comments are 
addressed. In addition to that, several contributors from vendors and network 
operators have explicitly expressed their support before and during WGLC. It 
has also been mentioned that the protocol is of interest to 3GPP. In TCPM, 
there is very strong but not unanimous support for publication as experimental 
document.

There is at least one known implementation: Tessares has an open-sourced a 
library (https://github.com/Tessares/libconvert) and a closed-source Hybrid 
Access Gateway (HAG) that uses this library directly to act as an MPTCP 
Converter. Korea Telekom (KT) has reported to TCPM the results of a PoC using 
these implementations (see 
https://tessares.pr.co/181810-kt-tessares-successfully-test-5g-low-latency-multi-radio-access-technology-in-a-commercial-5g-network).
 Other vendors have also expressed interest, but there is no publicly known 
second implementation.

Personnel

The document shepherd is Michael Scharf. The responsible Area Director is Mirja 
Kuehlewind.


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