CDN Loop Detection
draft-ietf-httpbis-cdn-loop-02

Document Type Active Internet-Draft (httpbis WG)
Last updated 2019-02-14 (latest revision 2019-02-03)
Replaces draft-cdn-loop-prevention
Stream IETF
Intended RFC status Proposed Standard
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Send notices to Patrick McManus <mcmanus@ducksong.com>, Tommy Pauly <tpauly@apple.com>
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HTTP Working Group                                              S. Ludin
Internet-Draft                                       Akamai Technologies
Intended status: Standards Track                           M. Nottingham
Expires: August 8, 2019                                           Fastly
                                                             N. Sullivan
                                                              Cloudflare
                                                       February 04, 2019

                           CDN Loop Detection
                     draft-ietf-httpbis-cdn-loop-02

Abstract

   This document defines the CDN-Loop request header field for HTTP.
   CDN-Loop addresses an operational need that occurs when an HTTP
   request is intentionally forwarded between Content Delivery Networks
   (CDNs), but is then accidentally or maliciously re-routed back into
   the original CDN causing a non-terminating loop.  The new header
   field can be used to identify the error and terminate the loop.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 8, 2019.

Copyright Notice

   Copyright (c) 2019 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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   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.  Relationship to Via . . . . . . . . . . . . . . . . . . .   3
     1.2.  Conventions and Definitions . . . . . . . . . . . . . . .   3
   2.  The CDN-Loop Request Header Field . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   In modern deployments of HTTP servers, it is common to interpose
   Content Delivery Networks (CDNs) in front of origin servers 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 a given origin.  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 forwarding 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 can be used
   as an attack vector (e.g., see [loop-attack]), especially if one CDN
   unintentionally strips the loop detection headers of another.

   This specification defines the CDN-Loop HTTP request header field to
   help detect such attacks and accidents among implementing forwarding
   CDNs, by disallowing its modification by their customers.

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1.1.  Relationship to Via

   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."

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