One document matched: draft-mirsky-ippm-time-format-01.txt
Differences from draft-mirsky-ippm-time-format-00.txt
Network Working Group G. Mirsky
Internet-Draft S. Bansal
Intended status: Standards Track Ericsson
Expires: January 4, 2016 R. Lakshmikanthan
I. Meilik
Broadcom
July 3, 2015
Support of IEEE-1588 time stamp format in Two-Way Active Measurement
Protocol (TWAMP)
draft-mirsky-ippm-time-format-01
Abstract
This document describes an OPTIONAL feature for active performance
measurement protocols allowing use of time stamp format defined in
IEEE-1588v2-2008.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 4, 2016.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. OWAMP and TWAMP Extensions . . . . . . . . . . . . . . . . . 3
2.1. Timestamp Format Negotiation in Setting Up Connection in
OWAMP . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Timestamp Format Negotiation in Setting Up Connection in
TWAMP . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. OWAMP-Test and TWAMP-Test Update . . . . . . . . . . . . 5
2.3.1. Consideration for TWAMP Light mode . . . . . . . . . 6
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
One-Way Active Measurement Protocol (OWAMP) [RFC4656] defines that
only the NTP [RFC5905] format of a time stamp can be used in OWAMP-
Test protocol. Two-Way Active Measurement Protocol (TWAMP) [RFC5357]
adopted the OWAMP-Test packet format and extended it by adding a
format for a reflected test packet. Both the sender's and
reflector's packets time stamps are expected to follow the 64-bit
long NTP format [RFC5905].
Precision Time Protocol (PTP) [IEEE.1588.2008] has gained wide
support since the development of OWAMP and TWAMP. PTP is now
supported in multiple implementations of fast forwarding engines. As
result, to support OWAMP or TWAMP test protocol time stamps must be
converted from PTP to NTP. That requires resources, use of micro-
code or additional processing elements, that are always limited. To
address this, this document proposes optional extensions to Control
and Test protocols to support use of IEEE-1588v2 time stamp format as
optional alternative to the NTP time stamp format.
One of the goals of this proposal is not only allow end-points of a
test session to use other than NTP timestamp but to support backwards
compatibility with nodes that do not yet support this extension.
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1.1. Conventions used in this document
1.1.1. Terminology
IPPM: IP Performance Measurement
NTP: Network Time Protocol
PTP: Precision Time Protocol
TWAMP: Two-Way Active Measurement Protocol
OWAMP: One-Way Active Measurement Protocol
1.1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
2. OWAMP and TWAMP Extensions
OWAMP connection establishment follows the procedure defined in
Section 3.1 of [RFC4656] and additional steps in TWAMP described in
Section 3.1 of [RFC5357]. In these procedures the Modes field been
used to identify and select specific communication capabilities. At
the same time the Modes field been recognized and used as extension
mechanism [RFC6038]. The new feature requires one bit position for
Server and Control-Client to negotiate which timestamp format can be
used in some or all test sessions invoked with this control
connection. The end-point of the test session, Session-Sender and
Session-Receiver or Session-Reflector, that supports this extension
MUST be capable to interpret NTP and PTPv2 timestamp formats. If the
end-point does not support this extension, then the value of PTPv2
Timestamp flag MUST be 0 because it is in Must Be Zero field. If
value of PTPv2 Timestamp flags is 0, then the advertising node can
use and interpret only NTP timestamp format.
Use of PTPv2 Timestamp flags discussed in the following sub-sections.
For details on the assigned values and bit positions see the
Section 3.
2.1. Timestamp Format Negotiation in Setting Up Connection in OWAMP
In OWAMP-Test [RFC4656] it is the Session-Receiver and/or Fetch-
Client that are interpreting collected timestamps. Thus announced by
a Server in the Modes field timestamp format indicates which formats
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the Session-Receiver is capable to interpret. The Control-Client
inspects values set by the Server for timestamp formats and sets
values in the Modes field of the Set-Up-Response message according to
timestamp formats Session-Sender is capable of using. The rules of
setting timestamp flags in Modes field in server greeting and Set-Up-
Response messages and interpreting them are as follows:
o The Server that establishes test sessions for Session-Receiver
that supports this extension MUST set PTPv2 Timestamp flag to 1 in
the server greeting message according to the requirement listed in
Section 2.
o If PTPv2 Timestamp flag of the server greeting message that the
Control-Client receives has value 0, then the Session-Sender MUST
use NTP format for timestamp in the test session and Control-
Client SHOULD set PTPv2 Timestamp flag to 0 in accordance with
[RFC4656]. If the Session-Sender cannot use NTP timestamps, then
the Control-Client SHOULD close the TCP connection associated with
the OWAMP-Control session.
o If the Session-Sender can set timestamp in PTPv2 format, then the
Control-Client MUST set the PTPv2 Timestamp flag to 1in Modes
field in the Set-Up-Response message and the Session-Sender MUST
set timestamp in PTPv2 timestamp format. Otherwise the Control-
Client MUST set the PTPv2 Timestamp flag in the Set-Up-Response
message to 0.
o Otherwise, if the Session-Sender can set timestamp in NTP format,
then the Session-Sender MUST set timestamp in NTP timestamp
format. Otherwise the Control-Client SHOULD close the TCP
connection associated with the OWAMP-Control session..
If values of both NTP and PTPv2 Timestamp flags in the Set-Up-
Response message are equal to 0, then that indicates that the
Control-Client can set timestamp only in NTP format.
If OWAMP-Control uses Fetch-Session commands, then selection and use
of one or another timestamp format is local decision for both
Session-Sender and Session-Receiver.
2.2. Timestamp Format Negotiation in Setting Up Connection in TWAMP
In TWAMP-Test [RFC5357] it is the Session-Sender that is interpreting
collected timestamps. Hence, in the Modes field a Server advertises
timestamp formats that the Session-Reflector can use in TWAMP-Test
message. The choice of the timestamp format to be used by the
Session-Sender is a local decision. The Control-Client inspects the
Modes field and sets timestamp flags values to indicate which format
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will be used by the Session-Reflector. The rules of setting and
interpreting flag values are as follows:
o Server MUST set to 1 value of PTPv2 Timestamp flag in its greeting
message if Session-Reflector can set timestamp in PTPv2 format.
Otherwise the PTPv2 Timestamp flag MUST be set to 0.
o If value of the PTPv2 Timestamp flag in received server greeting
message equals 0, then Session-Reflector does not support this
extension and will use NTP timestamp format. Control-Client
SHOULD set PTPv2 Timestamp flag to 0 in Set-Up-Response message in
accordance with [RFC5357].
o Control-Client MUST set PTPv2 Timestamp flag value to 1 in Modes
field in the Set-Up-Response message if Server advertised ability
of the Session-Reflector to use PTPv2 format for timestamps.
Otherwise the flag MUST be set to 0.
o If the values of PTPv2 Timestamp flag in the Set-Up-Response
message equals 0, then that means that Session-Sender can only
interpret NTP timestamp format. Then the Session-Reflector MUST
use NTP timestamp format. If the Session-Reflector does not
support NTP format for timestamps then Server and SHOULD close the
TCP connection associated with the TWAMP-Control session.
2.3. OWAMP-Test and TWAMP-Test Update
Participants of a test session need to indicate which timestamp
format being used. The proposal is to use Z field in Error Estimate
defined in Section 4.1.2 of [RFC4656]. The new interpretation of the
Error Estimate is in addition to it specifying error estimate and
synchronization, Error Estimate indicates format of a collected
timestamp. And this proposal changes the semantics of the Z bit
field, the one between S and Scale fields, to be referred as
Timestamp format and value MUST be set according to the following:
o 0 - NTP 64 bit format of a timestamp;
o 1 - PTPv2 truncated format of a timestamp.
As result of this value of the Z field from Error Estimate, Sender
Error Estimate or Send Error Estimate and Receive Error Estimate
SHOULD NOT be ignored and MUST be used when calculating delay and
delay variation metrics based on collected timestamps.
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2.3.1. Consideration for TWAMP Light mode
This document does not specify how Session-Sender and Session-
Reflector in TWAMP Light mode are informed of timestamp format to be
used. It is assumed that, for example, configuration could be used
to direct Session-Sender and Session-Reflector respectively to use
timestamp format according to their capabilities and rules listed in
Section 2.2.
3. IANA Considerations
The TWAMP-Modes registry defined in [RFC5618].
IANA is requested to reserve a new PTPv2 Timestamp as follows:
+--------------+------------------+---------------------+-----------+
| Value | Description | Semantics | Reference |
+--------------+------------------+---------------------+-----------+
| TBA1 | PTPv2 Timestamp | bit position TBA2 | This |
| (proposed | Capability | (proposed 8) | document |
| 256) | | | |
+--------------+------------------+---------------------+-----------+
Table 1: New Timestamp Capability
4. Security Considerations
Use of particular format of a timestamp in test session does not
appear to introduce any additional security threat to hosts that
communicate with OWAMP and/or TWAMP as defined in [RFC4656],
[RFC5357] respectively. The security considerations that apply to
any active measurement of live networks are relevant here as well.
See the Security Considerations sections in [RFC4656] and [RFC5357].
5. Acknowledgements
The authors would like to thank David Allan for his thorough review
and thoughtful comments.
6. Normative References
[IEEE.1588.2008]
"Standard for a Precision Clock Synchronization Protocol
for Networked Measurement and Control Systems", IEEE
Standard 1588, March 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
[RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the
Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
August 2009.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC6038] Morton, A. and L. Ciavattone, "Two-Way Active Measurement
Protocol (TWAMP) Reflect Octets and Symmetrical Size
Features", RFC 6038, October 2010.
Authors' Addresses
Greg Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
Suchit Bansal
Ericsson
Email: suchit.bansal@ericsson.com
Ramanathan Lakshmikanthan
Email: ramlak@gmail.com
Israel Meilik
Broadcom
Email: israel@broadcom.com
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