Internet DRAFT - draft-jansky-alc-timestamp-extension
draft-jansky-alc-timestamp-extension
Network Working Group M. Jansky
Internet-Draft T. Pohjolainen
Expires: April 4, 2006 Nokia
October 2005
NTP Timestamp Extension for ALC
draft-jansky-alc-timestamp-extension-00.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 4, 2006.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document defines a variable length ALC PI specific LCT Header
Extension, NTP Timestamp Header (EXT_NTP). This extension can be
used within an ALC session for multiple purposes, for example, to
signal the last moment of time there was a change in the session.
Jansky & Pohjolainen Expires April 4, 2006 [Page 1]
Internet-Draft NTP Timestamp Extension for ALC October 2005
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. NTP Timestamp Header . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. Normative references . . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 7
Jansky & Pohjolainen Expires April 4, 2006 [Page 2]
Internet-Draft NTP Timestamp Extension for ALC October 2005
1. Requirements notation
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 [1].
2. Introduction
This document defines a variable length ALC PI specific LCT Header
Extension, NTP Timestamp Header (EXT_NTP) [2]. This extension can be
used within an ALC session for multiple purposes. The semantics of
the EXT_NTP can be declared within the Header Extension itself
(through the "Use" field).
Although the specification of EXT_NTP does not limit the use of the
timestamp information any particular use, this specification defines
one use - the signaling of the last moment of time there was a change
in the session. The purpose of that use of the EXT_NTP extension is
to allow the sender of the ALC session to signal changes in the
session for the receivers of the session. This is particularly
useful in the cases where the receivers of the ALC session
sporadically enter and leave the session. In such cases the receiver
may receive the session for a period of time, stop reception for
another period of time and continue reception again. Examples of
such cases are relatively long ALC sessions that deliver a number of
Transport Objects so that the number of Transport Objects dynamically
changes, or, cases where the receiver has temporary connection to the
transmission medium.
3. NTP Timestamp Header
NTP Timestamp Header (EXT_NTP) is a variable length, ALC PI specific
LCT Header Extension [2]. The Header Extension Type (HET) for the
extension is 65. Its format is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET = 65 | HEL = 2 | Use | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Header Extension Type (HET), 8 bits:
Jansky & Pohjolainen Expires April 4, 2006 [Page 3]
Internet-Draft NTP Timestamp Extension for ALC October 2005
Value of this field MUST be set to 65.
Header Extension Length (HEL), 8 bits:
The length of the whole Header Extension field, expressed in
multiples of 32-bit words. For EXT_NTP, this field MUST be set to 2.
Use, 8 bits:
This field expresses the exact semantics how the sender of the ALC
session intens the receiver to interpret the use of the timestamp.
This specification defines the semantics for the case when "Use"
equals "0". Other values for this field are possible but not in
scope of this specification.
Reserved, 8 bits:
This field is reserved for future use and SHOULD be set to 0.
NTP Timestamp, 32 bits:
The value of this field is to be interpreted as the seconds-part (32
most significant bits) of NTP timestamp [3]. When the field When use
equals "0", this timestamp signals the NTP time the ALC session was
last changed. That is, it expresses the last moment of time a
Transport Object was added to the session for delivery.
The EXT_NTP MAY be carried in any ALC packet delivered within the ALC
session. This specification does not define further guidelines on
how frequently or when to use the EXT_NTP as these choices are
depenent on the usage scenario of the extension.
4. Security Considerations
As the NTP Timestamp Header is to be used with ALC packets within ALC
sessions, the security considerations of ALC apply. Beyond that,
there are no further security considerations related to this header
extension.
5. Normative references
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[2] Luby, M., Gemmell, J., Vicisano, L., Rizzo, L., Handley, M., and
J. Crowcroft, "Layered Coding Transport (LCT) Building Block",
RFC 3451, December 2002.
Jansky & Pohjolainen Expires April 4, 2006 [Page 4]
Internet-Draft NTP Timestamp Extension for ALC October 2005
[3] Mills, D., "Network Time Protocol (Version 3), Specification,
Implementation and Analysis", RFC 1305, March 1992.
Jansky & Pohjolainen Expires April 4, 2006 [Page 5]
Internet-Draft NTP Timestamp Extension for ALC October 2005
Authors' Addresses
Martin Jansky
Nokia
Itamerenkatu 11-13
Helsinki FIN-00180
Finland
Email: martin.jansky@nokia.com
Topi Pohjolainen
Nokia
Itamerenkatu 11-13
Helsinki FIN-00180
Finland
Email: topi.pohjolainen@nokia.com
Jansky & Pohjolainen Expires April 4, 2006 [Page 6]
Internet-Draft NTP Timestamp Extension for ALC October 2005
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Jansky & Pohjolainen Expires April 4, 2006 [Page 7]
