CIP Transport Protocols
RFC 2653

Document Type RFC - Proposed Standard (August 1999; No errata)
Authors Jeff Allen  , Roland Hedberg  , Paul Leach 
Last updated 2013-03-02
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Network Working Group                                          J. Allen
Request for Comments: 2653                         WebTV Networks, Inc.
Category: Standards Track                                      P. Leach
                                                             R. Hedberg
                                                            August 1999

                        CIP Transport Protocols

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.


   This document specifies three protocols for transporting CIP
   requests, responses and index objects, utilizing TCP, mail, and HTTP.
   The objects themselves are defined in [CIP-MIME] and the overall CIP
   architecture is defined in [CIP-ARCH].

1.   Protocol

   In this section, the actual protocol for transmitting CIP index
   objects and maintaining the mesh is presented. While companion
   documents ([CIP-ARCH] and [CIP-MIME]) describe the concepts involved
   and the formats of the CIP MIME objects, this document is the
   authoritative definition of the message formats and transfer
   mechanisms of CIP used over TCP, HTTP and mail.

1.1  Philosophy

   The philosophy of the CIP protocol design is one of building-block
   design. Instead of relying on bulky protocol definition tools, or
   ad-hoc text encodings, CIP draws on existing, well understood
   Internet technologies like MIME, RFC-822, Whois++, FTP, and SMTP.
   Hopefully this will serve to ease implementation and consensus

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RFC 2653                CIP Transport Protocols              August 1999

   building. It should also stand as an example of a simple way to
   leverage existing Internet technologies to easily implement new
   application-level services.

1.2  Conventions

   The key words "MUST" and "MAY" in this document are to be interpreted
   as described in "Key words for use in RFCs to Indicate Requirement
   Levels" [KEYWORDS].

   Formal syntax is defined using ABNF [ABNF].

   In examples octets sent by the sender-CIP are preceded by ">>> " and
   those sent by the receiver-CIP by "<<< ".

2  MIME message exchange mechanisms

   CIP relies on interchange of standard MIME messages for all requests
   and replies. These messages are passed over a bidirectional, reliable
   transport system. This document defines transport over reliable
   network streams (via TCP), via HTTP, and via the Internet mail

   The CIP server which initiates the connection (conventionally
   referred to as a client) will be referred to below as the sender-CIP.
   The CIP server which accepts a sender-CIP's incoming connection and
   responds to the sender-CIP's requests is called a receiver-CIP.

2.1  The Stream Transport

   CIP messages are transmitted over bi-directional TCP connections via
   a simple text protocol. The transaction can take place over any TCP
   port, as specified by the mesh configuration. There is no "well known
   port" for CIP transactions. All configuration information in the
   system must include both a hostname and a port.

   All sender-CIP actions (including requests, connection initiation,
   and connection finalization) are acknowledged by the receiver-CIP
   with a response code. See section 2.1.1 for the format of these
   codes, a list of the responses a CIP server may generate, and the
   expected sender-CIP action for each.

   In order to maintain backwards compatibility with existing Whois++
   servers, CIPv3 sender-CIPs MUST first verify that the newer protocol
   is supported. They do this by sending the following illegal Whois++
   system command: "# CIP-Version: 3<cr><lf>". On existing Whois++
   servers implementing version 1 and 2 of CIP, this results in a 500-
   series response code, and the server terminates the connection.  If

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RFC 2653                CIP Transport Protocols              August 1999

   the server implements CIPv3, it MUST instead respond with response
   code 300. Future versions of CIP can be correctly negotiated using
   this technique with a different string (i.e. "CIP-Version: 4"). An
   example of this short interchange is given below.

   Note: If a sender-CIP can safely assume that the server implements
   CIPv3, it may choose to send the "# CIP-Version: 3" string and
   immediately follow it with the CIPv3 request. This optimization,
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