CDN Loop Prevention
draft-ietf-httpbis-cdn-loop-00

Document Type Active Internet-Draft (httpbis WG)
Last updated 2018-08-16
Replaces draft-cdn-loop-prevention
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HTTP Working Group                                              S. Ludin
Internet-Draft                                       Akamai Technologies
Intended status: Standards Track                           M. Nottingham
Expires: February 17, 2019                                        Fastly
                                                             N. Sullivan
                                                              Cloudflare
                                                         August 16, 2018

                          CDN Loop Prevention
                     draft-ietf-httpbis-cdn-loop-00

Abstract

   This specification defines the CDN-Loop request header field for
   HTTP.

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 February 17, 2019.

Copyright Notice

   Copyright (c) 2018 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
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   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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  The CDN-Loop Request Header Field . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   In modern deployments of HTTP servers, it is common to interpose
   Content Delivery Networks (CDNs) to improve end-user perceived
   latency, reduce operational costs, and improve scalability and
   reliability of services.

   Often, more than one CDN is in use by any one server; this happens
   for a variety of reasons, such as cost savings, arranging for
   failover should one CDN have issues, or to directly compare their
   services.

   As a result, it is not unknown for CDNs to be configured in a "loop"
   accidentally; because routing is achieved through a combination of
   DNS and forwarding rules, and site configurations are sometimes
   complex and managed by several parties.

   When this happens, it is difficult to debug.  Additionally, it
   sometimes isn't accidental; loops between multiple CDNs be used as an
   attack vector (e.g., see [loop-attack]), especially if one CDN
   unintentionally strips the loop detection headers of another.

   HTTP defines the Via header field in [RFC7230], Section 5.7.1 for
   "tracking message forwards, avoiding request loops, and identifying
   the protocol capabilities of senders along the request/response
   chain."

   In theory, Via could be used to identify these loops.  However, in
   practice it is not used in this fashion, because some HTTP servers
   use Via for other purposes - in particular, some implementations
   disable some HTTP/1.1 features when the Via header is present.

   This specification defines the CDN-Loop request header field for
   HTTP, to address this shortcoming.

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2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
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