RFC7355
Internet Engineering Task Force (IETF) G. Salgueiro Request for Comments: 7355 Cisco Updates: 6873 V. Pascual Category: Informational A. Roman ISSN: 2070-1721 S. Garcia
Quobis
September 2014
Indicating WebSocket Protocol as a Transport in the Session Initiation Protocol (SIP) Common Log Format (CLF)
Abstract
RFC 7118 specifies a WebSocket subprotocol as a reliable real-time transport mechanism between Session Initiation Protocol (SIP) entities to enable usage of SIP in web-oriented deployments. This document updates the SIP Common Log Format (CLF), defined in RFC 6873, with a new "Transport Flag" for such SIP WebSocket transport.
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/rfc7355.
Copyright Notice
Copyright (c) 2014 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.
Contents
Introduction
The WebSocket protocol RFC6455 enables bidirectional message exchange between clients and servers on top of a persistent TCP connection (optionally secured with TLS RFC5246). The initial protocol handshake makes use of HTTP RFC7230 semantics, allowing the WebSocket protocol to reuse existing transport connections.
RFC 7118 RFC7118 defines a WebSocket subprotocol for transporting SIP messages between a WebSocket client and server.
SIP messages can be logged using the Common Log Format defined in RFC 6873 RFC6873. In order to make such SIP CLF logging possible for SIP messages transported over the WebSocket protocol, a new WebSocket "Transport Flag" ('W') must be added to the "Transport Flags" already defined in RFC 6873 RFC6873 (i.e., UDP, TCP, and SCTP).
This document updates RFC 6873 RFC6873 by defining a new SIP CLF "Transport Flag" value for WebSocket.
Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119.
Document Conventions
This document contains several examples of SIP CLF records showing messages over plain and secure WebSocket connections. The formatting described in this document does not permit the examples to be unambiguously rendered due to the constraints imposed by the formatting rules for RFCs. To avoid ambiguity and to meet the RFC layout requirements, this document uses the <allOneLine/> markup convention established in RFC4475. This markup convention is described in detail in Section 3 of RFC 6873 RFC6873 and used throughout that document for representing the syntax of SIP CLF records.
Usage of the WebSocket Transport Flag
Section 4.2 of RFC6873 RFC6873 specifies the mandatory fields in a SIP CLF record. The fourth and fifth bytes of the five-byte "Flags Field" are the "Transport Flag" and the "Encryption Flag", respectively. SIP messages transported over both a plain and secure WebSocket connection can be clearly distinguished by appropriately setting these two flag fields.
The currently registered values of the "Transport Flag" (Section 9.2 of RFC 6873) are UDP ('U'), TCP ('T'), and SCTP ('S'). This document defines and registers a new "Transport Flag" value 'W' for WebSocket transport of SIP messages and consequently updates RFC 6873 RFC6873 and the IANA "SIP CLF Transport Flag Values" registry.
SIP CLF records of messages transported over a plain WebSocket connection (WS) MUST set the "Transport Flag" to this new 'W' value and the "Encryption Flag" value to 'U' (Unencrypted). SIP CLF records of messages transported over a secure WebSocket (WSS) connection (i.e., WS over TLS) MUST set the "Transport Flag" to this new 'W' value and the "Encryption Flag" value to 'E' (Encrypted).
Examples
The following examples show sample SIP CLF records logged for SIP messages transported over both plain and secure WebSocket connections.
SIP over WebSocket (WS)
The following example represents a SIP INVITE request sent over a plain WebSocket connection. For the sake of brevity, the Session Description Protocol (SDP) RFC4566 body is omitted.
INVITE sip:[email protected] SIP/2.0 Via: SIP/2.0/WS df7jal23ls0d.invalid;branch=z9hG4bK56sdasks From: sip:[email protected];tag=asdyka899 To: sip:[email protected] Call-ID: asidkj3ss CSeq: 1 INVITE Max-Forwards: 70 Date: Thu, 6 Feb 2014 15:02:03 GMT Supported: path, outbound, gruu Route: <sip:proxy.example.com:80;transport=ws;lr> Contact: <sip:[email protected];gr=urn:uuid:f81-7dec-14a06cf1;ob> Content-Type: application/sdp Content-Length: 418
Shown below is approximately how this message would appear as a single record in a SIP CLF logging file if encoded according to the syntax described in RFC6873. Due to RFC conventions, this log entry has been split into five lines, instead of the two lines that actually appear in a log file; and the tab characters have been padded out using spaces to simulate their appearance in a text terminal.
A0000E7,0053005C005E00720080009200A600A800BE00C800D200DE00E7 <allOneLine> 1328821153.010 RORWU 1 INVITE - sip:[email protected] 192.0.2.10:80 192.0.2.200:56485 sip:[email protected] - sip:[email protected] asdyka899 asidkj3ss S1781761-88 C67651-11 </allOneLine>
A bit-exact version of the actual log entry is provided here, Base64 encoded RFC4648, using the uuencode utility.
begin-base64 644 clf_ws_record QTAwMDBFNywwMDUzMDA1QzAwNUUwMDcyMDA4MDAwOTIwMEE2MDBBODAwQkUwMEM4MDBE MjAwREUwMEU3CjEzMjg4MjExNTMuMDEwCVJPUldVCTEgSU5WSVRFCS0Jc2lwOmJvYkBl eGFtcGxlLmNvbQkxOTIuMC4yLjEwOjgwCTE5Mi4wLjIuMjAwOjU2NDg1CXNpcDpib2JA ZXhhbXBsZS5jb20JLQlzaXA6YWxpY2VAZXhhbXBsZS5jb20JYXNkeWthODk5CWFzaWRr ajNzcwlTMTc4MTc2MS04OAlDNjc2NTEtMTEKCg==
==
The original SIP CLF format can be obtained by reversing the effects of uuencode by simply applying the uudecode transform. Additionally, to recover the unencoded file, the Base64 text above may be passed as input to the following perl script (the output should be redirected to a file).
- !/usr/bin/perl
use strict;
my $bdata = "";
use MIME::Base64;
while(<>)
{
if (/begin-base64 644 clf_ws_record/ .. /-- ==== --/)
{
if ( m/^\s*[^\s]+\s*$/)
{
$bdata = $bdata . $_;
}
}
}
print decode_base64($bdata);
SIP over Secure WebSocket (WSS)
The following example represents a SIP INVITE request sent over a
secure WebSocket connection (i.e., WebSocket over TLS RFC5246).
For the sake of brevity, the SDP body is omitted.
INVITE sip:[email protected] SIP/2.0
Via: SIP/2.0/WSS df7jal23ls0d.invalid;branch=z9hG4bK56sdasks
From: sip:[email protected];tag=asdyka899
To: sip:[email protected]
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 70
Date: Thu, 6 Feb 2014 15:02:03 GMT
Supported: path, outbound, gruu
Route: <sip:proxy.example.com:443;transport=ws;lr>
Contact: <sip:[email protected];gr=urn:uuid:f81-7dec-14a06cf1;ob>
Content-Type: application/sdp
Content-Length: 439
Shown below is approximately how this message would appear as a
single record in a SIP CLF logging file if encoded according to the
syntax described in RFC6873. Due to RFC conventions, this log
entry has been split into five lines, instead of the two lines that
actually appear in a log file; and the tab characters have been
padded out using spaces to simulate their appearance in a text
terminal.
A0000E8,0053005C005E00720081009300A700A900BF00C900D300DF00E8
<allOneLine>
1328821153.010 RORWE 1 INVITE - sip:[email protected]
192.0.2.10:443 192.0.2.200:56485 sip:[email protected] -
sip:[email protected]:5060 asdyka899 asidkj3ss S1781761-88
C67651-11
</allOneLine>
A bit-exact version of the actual log entry is provided here, Base64
encoded.
begin-base64 644 clf_ws_record
QTAwMDBFOCwwMDUzMDA1QzAwNUUwMDcyMDA4MTAwOTMwMEE3MDBBOTAwQkYwMEM5MDBE
MzAwREYwMEU4CjEzMjg4MjExNTMuMDEwCVJPUldVCTEgSU5WSVRFCS0Jc2lwOmJvYkBl
eGFtcGxlLmNvbQkxOTIuMC4yLjEwOjQ0MwkxOTIuMC4yLjIwMDo1NjQ4NQlzaXA6Ym9i
QGV4YW1wbGUuY29tCS0Jc2lwOmFsaWNlQGV4YW1wbGUuY29tCWFzZHlrYTg5OQlhc2lk
a2ozc3MJUzE3ODE3NjEtODgJQzY3NjUxLTExCgo=
==
Security Considerations
This document merely adds a new "Transport Flag" value for the
WebSocket protocol. This value may be set in a SIP CLF record, but
its use does not intrinsically introduce any new security
considerations. When logging protocol information, such as with SIP
CLF, there are a myriad of security, privacy, and data protection
issues to consider. These are exhaustively described in RFC 6872
RFC6872 and RFC 6873 RFC6873.
Any security considerations specific to the WebSocket protocol or its
application as a transport for SIP are detailed in the relevant
specifications (the WebSocket protocol RFC6455 and SIP over
WebSockets RFC7118) and are considered outside the scope of this
document.
IANA Considerations
This document defines a new value ('W') for SIP CLF "Transport Flag".
IANA has registered this value in the "SIP CLF Transport Flag Values"
registry, as shown in Table 1 below.
+-------+--------------------+--------------------+
| Value | Transport Protocol | Reference |
+-------+--------------------+--------------------+
| W | WebSocket | RFC 7118, RFC 7355 |
+-------+--------------------+--------------------+
Table 1: IANA-Registered SIP CLF Transport Flag
Acknowledgements
The authors would like to thank Vijay Gurbani for shepherding this
document and Area Director Richard Barnes for his sponsorship. This
work benefitted from the thorough review and constructive comments of
Richard Barnes, Barry Leiba, Benoit Claise, Pete Resnick, Stephen
Farrel, and Vijay Gurbani.
References
Normative References
RFC2119 Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
RFC6455 Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC
6455, December 2011.
RFC6872 Gurbani, V., Burger, E., Anjali, T., Abdelnur, H., and O.
Festor, "The Common Log Format (CLF) for the Session
Initiation Protocol (SIP): Framework and Information
Model", RFC 6872, February 2013.
RFC6873 Salgueiro, G., Gurbani, V., and A. Roach, "Format for the
Session Initiation Protocol (SIP) Common Log Format
(CLF)", RFC 6873, February 2013.
RFC7118 Baz Castillo, I., Millan Villegas, J., and V. Pascual,
"The WebSocket Protocol as a Transport for the Session
Initiation Protocol (SIP)", RFC 7118, January 2014.
Informative References
RFC4475 Sparks, R., Hawrylyshen, A., Johnston, A., Rosenberg, J.,
and H. Schulzrinne, "Session Initiation Protocol (SIP)
Torture Test Messages", RFC 4475, May 2006.
RFC4566 Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
RFC4648 Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
RFC5246 Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
RFC7230 Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230, June
2014.
Authors' Addresses
Gonzalo Salgueiro
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
EMail: [email protected]
Victor Pascual
Quobis
EMail: [email protected]
Anton Roman
Quobis
EMail: [email protected]
Sergio Garcia Ramos
Quobis
EMail: [email protected]
