Aggregated Option for SYN Option Space Extension
draft-nishida-tcpm-agg-syn-ext-00
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Active Internet-Draft (individual)
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Yoshifumi Nishida
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2021-02-02
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On Agenda |
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tcpm at IETF-110
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Network Working Group Y. Nishida
Internet-Draft Amazon Web Services
Intended status: Standards Track February 2, 2021
Expires: August 6, 2021
Aggregated Option for SYN Option Space Extension
draft-nishida-tcpm-agg-syn-ext-00
Abstract
TCP option space is scarce resource as its max length is limited to
40 bytes. This limitation becomes more significant in SYN segments
as all options used in a connection should be exchanged during SYN
negotiations. This document proposes a new SYN option negotiation
scheme that provide a feature to compress TCP options in SYN segments
and provide more option space. The proposed scheme does not update
the format of TCP header nor transmit any additional SYN or SYN-like
segments so that it has lower risks for middlebox interventions. In
addition, by combining another proposal for option space extension,
it is possible to provide further option space.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 6, 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Nishida Expires August 6, 2021 [Page 1]
Internet-Draft Aggregated Option February 2021
carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. Basic Design . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Aggregated Option . . . . . . . . . . . . . . . . . . . . 4
3.2. Additional Information Exchange Using 3rd ACK Segments . 6
3.3. Examples of Option Exchanges with Aggregated Options . . 7
4. Option Bits Registration . . . . . . . . . . . . . . . . . . 9
5. Discussions . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Incremental Deployments for Aggregated Option . . . . . . 10
5.2. Middlebox Considerations . . . . . . . . . . . . . . . . 10
5.3. Which Options are Aggregatable . . . . . . . . . . . . . 10
5.4. Further Extensions . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7.1. Aggregated Option . . . . . . . . . . . . . . . . . . . . 11
7.2. Option Bits Registry for Aggregated Option . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
TCP option space is scarce resource as its max length is limited to
40 bytes. This limitation is a nominal issue especially for SYN
segment. This is because although a TCP endpoint can send only one
SYN segment to the peer, SYN segments need to contain all options
expected to be used for the connection. As a result, the current SYN
option space tends to be congested. Many TCP connections use MSS
[RFC0793], Timestamp and Window Scale [RFC7323], SACK Permitted
options [RFC2018] which already consume 19 bytes (10 + 4 + 3 + 2).
In addition to them, if a connection wants to use Multipath TCP
[RFC8684], it requires additional 4-12 bytes for MP_CAPABLE or 12-16
bytes for MP_JOIN option. Similarly, TCP Fast Open [RFC7413] and TCP
AO [RFC5925] require additional 6-18 bytes and 16 bytes respectively.
Moreover, Experimental Option Format defined in [RFC6994] consumes
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