Internet DRAFT - draft-mirsky-ippm-time-format
draft-mirsky-ippm-time-format
Network Working Group G. Mirsky
Internet-Draft Ericsson
Intended status: Standards Track I. Meilik
Expires: August 12, 2016 Broadcom
February 9, 2016
Support of IEEE-1588 time stamp format in Two-Way Active Measurement
Protocol (TWAMP)
draft-mirsky-ippm-time-format-03
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on August 12, 2016.
Copyright Notice
Copyright (c) 2016 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.
Mirsky & Meilik Expires August 12, 2016 [Page 1]
Internet-Draft 1588 time stamp format in TWAMP February 2016
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 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Timestamp Format Negotiation in Setting Up Connection in
TWAMP . . . . . . . . . . . . . . . . . . . . . . . . . . 5
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 . . . . . . . . . . . . . . . . . . . . 7
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]. NTP, when used over Internet, typically
achieves clock accuracy of about 5ms to 100ms. Surveys conducted
recently suggest that 90% devices achieve accuracy of better than 100
ms and 99% - better than 1 sec. It should be noted that NTP
synchronizes clocks on the control plane, not on data plane.
Distribution of clock wiitin a node may be supported by independent
NTP domain or via interprocess communication in multiprocessor
distributed system. And of mentioned solutions will be subject to
additional queuing delays that negatively affect data plane clock
accuracy.
Precision Time Protocol (PTP) [IEEE.1588.2008] has gained wide
support since the development of OWAMP and TWAMP. PTP, using on-path
support and other mechanisms, allows sub-microsecond clock accuracy.
PTP is now supported in multiple implementations of fast forwarding
engines and thus accuracy achieved by PTP is the accuracy of clock in
data plane. Thus providing option to use more accurate clock as
source of time stamps for IP performance measurement is one of
advantages this proposal helps to achive. Another advantage realized
by simplification of hardware in data plane. To support OWAMP or
TWAMP test protocol time stamps must be converted from PTP to NTP.
Mirsky & Meilik Expires August 12, 2016 [Page 2]
Internet-Draft 1588 time stamp format in TWAMP February 2016
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.
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.
Mirsky & Meilik Expires August 12, 2016 [Page 3]
Internet-Draft 1588 time stamp format in TWAMP February 2016
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
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.
Mirsky & Meilik Expires August 12, 2016 [Page 4]
Internet-Draft 1588 time stamp format in TWAMP February 2016
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
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.
Mirsky & Meilik Expires August 12, 2016 [Page 5]
Internet-Draft 1588 time stamp format in TWAMP February 2016
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.
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 Lakshmikanthan and Suchit Bansal for
their insightful suggestions. The authors would like to thank David
Allan for his thorough review and thoughtful comments.
Mirsky & Meilik Expires August 12, 2016 [Page 6]
Internet-Draft 1588 time stamp format in TWAMP February 2016
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,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<http://www.rfc-editor.org/info/rfc4656>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<http://www.rfc-editor.org/info/rfc5357>.
[RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the
Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
DOI 10.17487/RFC5618, August 2009,
<http://www.rfc-editor.org/info/rfc5618>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<http://www.rfc-editor.org/info/rfc5905>.
[RFC6038] Morton, A. and L. Ciavattone, "Two-Way Active Measurement
Protocol (TWAMP) Reflect Octets and Symmetrical Size
Features", RFC 6038, DOI 10.17487/RFC6038, October 2010,
<http://www.rfc-editor.org/info/rfc6038>.
Authors' Addresses
Greg Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
Mirsky & Meilik Expires August 12, 2016 [Page 7]
Internet-Draft 1588 time stamp format in TWAMP February 2016
Israel Meilik
Broadcom
Email: israel@broadcom.com
Mirsky & Meilik Expires August 12, 2016 [Page 8]
