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Known Issues and Best Practices for the Use of Long Polling and Streaming in Bidirectional HTTP
RFC 6202

Internet Engineering Task Force (IETF)                         S. Loreto
Request for Comments: 6202                                      Ericsson
Category: Informational                                   P. Saint-Andre
ISSN: 2070-1721                                                    Cisco
                                                              S. Salsano
                                        University of Rome "Tor Vergata"
                                                              G. Wilkins
                                                                 Webtide
                                                              April 2011

                    Known Issues and Best Practices
    for the Use of Long Polling and Streaming in Bidirectional HTTP

Abstract

   On today's Internet, the Hypertext Transfer Protocol (HTTP) is often
   used (some would say abused) to enable asynchronous, "server-
   initiated" communication from a server to a client as well as
   communication from a client to a server.  This document describes
   known issues and best practices related to such "bidirectional HTTP"
   applications, focusing on the two most common mechanisms: HTTP long
   polling and HTTP streaming.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6202.

Loreto, et al.                Informational                     [Page 1]
RFC 6202                   Bidirectional HTTP                 April 2011

Copyright Notice

   Copyright (c) 2011 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
   (http://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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  HTTP Long Polling  . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Definition . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  HTTP Long Polling Issues . . . . . . . . . . . . . . . . .  5
   3.  HTTP Streaming . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Definition . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  HTTP Streaming Issues  . . . . . . . . . . . . . . . . . .  8
   4.  Overview of Technologies . . . . . . . . . . . . . . . . . . . 10
     4.1.  Bayeux . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.2.  BOSH . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.3.  Server-Sent Events . . . . . . . . . . . . . . . . . . . . 13
   5.  HTTP Best Practices  . . . . . . . . . . . . . . . . . . . . . 13
     5.1.  Limits to the Maximum Number of Connections  . . . . . . . 13
     5.2.  Pipelined Connections  . . . . . . . . . . . . . . . . . . 14
     5.3.  Proxies  . . . . . . . . . . . . . . . . . . . . . . . . . 14
     5.4.  HTTP Responses . . . . . . . . . . . . . . . . . . . . . . 15
     5.5.  Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . 15
     5.6.  Impact on Intermediary Entities  . . . . . . . . . . . . . 16
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 18

Loreto, et al.                Informational                     [Page 2]
RFC 6202                   Bidirectional HTTP                 April 2011

1.  Introduction

   The Hypertext Transfer Protocol [RFC2616] is a request/response
   protocol.  HTTP defines the following entities: clients, proxies, and

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