Greasing HTTP
draft-nottingham-http-grease-01

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Network Working Group                                      M. Nottingham
Internet-Draft                                           October 8, 2020
Intended status: Best Current Practice
Expires: April 11, 2021

                             Greasing HTTP
                    draft-nottingham-http-grease-01

Abstract

   Like many network protocols, HTTP is vulnerable to ossification of
   its extensibility points.  This draft explains why HTTP ossification
   is a problem and establishes guidelines for exercising those
   extensions by 'greasing' the protocol to combat it.

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   The issues list for this draft can be found at
   https://github.com/mnot/I-D/labels/http-grease [1].

   The most recent (often, unpublished) draft is at
   https://mnot.github.io/I-D/http-grease/ [2].

   Recent changes are listed at https://github.com/mnot/I-D/commits/gh-
   pages/http-grease [3].

   See also the draft's current status in the IETF datatracker, at
   https://datatracker.ietf.org/doc/draft-nottingham-http-grease/ [4].

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 April 11, 2021.

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Copyright Notice

   Copyright (c) 2020 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  Ossification and HTTP . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Greasing HTTP Request Header Fields . . . . . . . . . . .   4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     4.2.  Informative References  . . . . . . . . . . . . . . . . .   6
     4.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Like many network protocols, HTTP is vulnerable to ossification of
   its extensibility points.  Ossification happens when a significant
   number of the systems that generate, transmit, handle, or consume the
   protocol don't accept a new extension, thereby making it more
   difficult to deploy extensions.

   For example, TCP has effectively been ossified by middleboxes that
   assume that new TCP options will not be deployed; likewise, the
   Protocol field in IP has been effectively ossified as well, since so
   many networks will only accept TCP or UDP traffic.

   Addressing this issue is important; protocol extensibility allows
   adaptation to new circumstances as well as application to new use
   cases.  Inability to deploy new extensions creates pressure to misuse
   the protocol - often leading to undesirable side effects - or to use
   other protocols, reducing the value that the community gets from a
   shared, standard protocol.

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   While there are a few ways that protocol designers can mitigate
   ossification, this document focuses on a technique that's well suited
   to many of the ossification risks in HTTP: 'greasing' extensibility
   points by exercising them, so that they don't become 'rusted shut.'

   [RFC8701]) pioneered greasing techniques in IETF protocols; this
   document explains how they apply to HTTP.  It focuses on generic HTTP
   features; other documents cover versioned extensibility points (e.g.,