draft-ietf-avtcore-clksrc-10.txt   draft-ietf-avtcore-clksrc-11.txt 
Audio/Video Transport Core A. Williams Audio/Video Transport Core A. Williams
Maintenance Audinate Maintenance Audinate
Internet-Draft K. Gross Internet-Draft K. Gross
Intended status: Standards Track AVA Networks Intended status: Standards Track AVA Networks
Expires: September 15, 2014 R. van Brandenburg Expires: September 26, 2014 R. van Brandenburg
H. Stokking H. Stokking
TNO TNO
March 14, 2014 March 25, 2014
RTP Clock Source Signalling RTP Clock Source Signalling
draft-ietf-avtcore-clksrc-10 draft-ietf-avtcore-clksrc-11
Abstract Abstract
NTP format timestamps are used by several RTP protocols for NTP format timestamps are used by several RTP protocols for
synchronisation and statistical measurements. This memo specifies synchronisation and statistical measurements. This memo specifies
SDP signalling identifying timestamp reference clock sources and SDP SDP signalling identifying timestamp reference clock sources and SDP
signalling identifying the media clock sources in a multimedia signalling identifying the media clock sources in a multimedia
session. session.
Requirements Language Requirements Language
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 15, 2014. This Internet-Draft will expire on September 26, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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7. Security Considerations 7. Security Considerations
Entities receiving and acting upon an SDP message should note that a Entities receiving and acting upon an SDP message should note that a
session description cannot be trusted unless it has been obtained by session description cannot be trusted unless it has been obtained by
an authenticated transport protocol from a known and trusted source. an authenticated transport protocol from a known and trusted source.
Many different transport protocols may be used to distribute session Many different transport protocols may be used to distribute session
description, and the nature of the authentication will differ from description, and the nature of the authentication will differ from
transport to transport. For some transports, security features are transport to transport. For some transports, security features are
often not deployed. In case a session description has not been often not deployed. In case a session description has not been
obtained in a trusted manner, the endpoint SHOULD exercise care obtained in a trusted manner, the endpoint should exercise care
because, among other attacks, the media sessions received may not be because, among other attacks, the media sessions received may not be
the intended ones, the destination where media is sent to may not be the intended ones, the destination where media is sent to may not be
the expected one, any of the parameters of the session may be the expected one, any of the parameters of the session may be
incorrect. incorrect.
Incorrect reference or media clock parameters may cause devices or Incorrect reference or media clock parameters may cause devices or
streams to synchronize to unintended clock sources. Normally this streams to synchronize to unintended clock sources. Normally this
simply results in failure to establish a session or failure to simply results in failure to establish a session or failure to
synchronize once connected. Enough devices fraudulently assigned to synchronize once connected. Enough devices fraudulently assigned to
a specific clock source (e.g. a particular IEEE 1588 grandmaster) a specific clock source (e.g. a particular IEEE 1588 grandmaster)
may, however, constitute a successful denial of service attack on may, however, constitute a successful denial of service attack on
that source. Devices MAY wish to validate the integrity of the clock that source. Devices MAY wish to validate the integrity of the clock
description through some means before connecting to unfamiliar clock description through some means before connecting to unfamiliar clock
sources. sources.
The timestamp reference clocks negotiated by this protocol are used The timestamp reference clocks negotiated by this protocol are used
to provide media timing information to RTP. Negotiated timestamp to provide media timing information to RTP. Negotiated timestamp
reference clocks SHOULD NOT be relied upon to provide a secure time reference clocks should not be relied upon to provide a secure time
reference for security critical operations (e.g. the expiration of reference for security critical operations (e.g. the expiration of
public key certificates). public key certificates).
8. IANA Considerations 8. IANA Considerations
This document defines two new SDP attributes: 'ts-refclk' and This document defines two new SDP attributes: 'ts-refclk' and
'mediaclk', within the existing Internet Assigned Numbers Authority 'mediaclk', within the existing Internet Assigned Numbers Authority
(IANA) registry of SDP Parameters. (IANA) registry of SDP Parameters.
This document also defines a new IANA registry subordinate to the This document also defines a new IANA registry subordinate to the
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