wdiff rfc8186.alt-original rfc8186.txt

Network Working Group
Internet Engineering Task Force (IETF) G. Mirsky
Internet-Draft
Request for Comments: 8186 ZTE Corp.
Intended status:
Category: Standards Track I. Meilik
Expires: October 14, 2017
ISSN: 2070-1721 Broadcom
April 12,
June 2017

Support of the IEEE-1588 time stamp format Timestamp Format in a
Two-Way Active Measurement Protocol (TWAMP)
draft-ietf-ippm-twamp-time-format-06

Abstract

This document describes an OPTIONAL feature for active performance
measurement protocols allowing that allows use of the Precision Time Protocol
time stamp
timestamp format defined in IEEE-1588v2-2008, as an alternative to
the Network Time Protocol that is currently used.

Status of This Memo

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This Internet-Draft will expire on October 14, 2017.
http://www.rfc-editor.org/info/rfc8186.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used Used in this document 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 . . . . . . . . . . . . . . . . . . . . . . . . . Connection Setup . 4
2.2. Timestamp Format Negotiation in Setting Up Connection in TWAMP . . . . . . . . . . . . . . . . . . . . . . . . . Connection Setup . 5
2.3. OWAMP-Test and TWAMP-Test Update Updates . . . . . . . . . . . . 5
2.3.1. Consideration for TWAMP Light mode Mode . . . . . . . . . 6
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements Normative References . . . . . . . . . . . . . . . . . . . . 7
Acknowledgements . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 8

1. Introduction

The One-Way Active Measurement Protocol (OWAMP) [RFC4656] defines
that only the NTP [RFC5905] format [RFC5905] of a time stamp timestamp can be used in OWAMP-
Test the
OWAMP-Test protocol. The 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 timestamps are expected to follow the 64-bit
long 64-bit-long
NTP format [RFC5905]. NTP, when used over the Internet, typically
achieves clock accuracy of about 5ms within 5 ms to 100ms. 100 ms. Surveys conducted
recently suggest that 90% of devices achieve accuracy of better than 100
ms and 99% - of devices achieve accuracy better than 1 sec. It should
be noted that NTP synchronizes clocks on the control plane, not on
data plane. Distribution of clock within a node may be supported by
an independent NTP domain or via interprocess communication in a
multiprocessor distributed system. Any of the mentioned solutions
will be subject to additional queuing delays that negatively affect data plane
data-plane clock accuracy.

The Precision Time Protocol (PTP) [IEEE.1588.2008] [IEEE-1588] 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 fast-forwarding engines;
thus, accuracy achieved by PTP is the accuracy of the clock in the
data plane. An Having an option to use a more accurate clock as a
source of
time stamps timestamps for IP performance measurements is one of the
advantages of this
specification's advantages. specification. Another advantage is realized by
simplification of hardware in the data plane. To support OWAMP or TWAMP
TWAMP, test protocol time stamps timestamps must be converted from PTP to NTP.
That requires resources, use of micro-code microcode 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 the IEEE-1588v2 time stamp timestamp format as an optional alternative to
the NTP time stamp timestamp format.

One of the goals of this specification is not only to allow end-
points endpoints
of a test session to use a timestamp format other than NTP NTP, but to
support backwards compatibility with nodes that do not yet support
this extension.

1.1. Conventions used Used in this document 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].
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

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 has
been used to identify and select specific communication capabilities.
At the same time time, the Modes field has been recognized and used as an
extension mechanism [RFC6038]. The new feature requires one bit
position for the 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 endpoint of the test session, Session-
Sender
Session-Sender and Session-Receiver (for OWAMP) or Session-Reflector, Session-Reflector
(for TWAMP), that supports this extension MUST be capable to interpret of
interpreting the NTP and PTPv2 timestamp formats. If the end-point endpoint
does not support this extension, then the value of the PTPv2
Timestamp flag MUST be 0 because it is in Must Be Zero field. If the
value of the PTPv2 Timestamp flags flag is 0, then the advertising node can
use and interpret only the NTP timestamp format. Implementations of
OWAMP and/or TWAMP MAY provide a configuration knob to bypass the
timestamp format negotiation process and to use the locally configured
values instead.

Use of PTPv2 Timestamp flags is discussed in the following sub-
sections.
subsections. For details on the assigned values and bit positions positions,
see the Section 3.

2.1. Timestamp Format Negotiation in Setting Up Connection in OWAMP Connection Setup

In OWAMP-Test [RFC4656] [RFC4656], the Session-Receiver and/or Fetch-Client
interpret collected timestamps. Thus, the Server uses the Modes
field timestamp format to indicate which formats the Session-Receiver
is capable to interpret. of interpreting. 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 the timestamp
formats the Session-Sender can use. The rules of for setting timestamp
flags in the Modes field in server greeting Server Greeting and Set-Up-Response
messages and interpreting them are as follows:

o If the Session-Receiver supports this extension, then the Server
that establishes test sessions on its behalf MUST set the PTPv2
Timestamp flag to 1 in the server greeting Server Greeting message per the
requirement listed in Section 2. Otherwise, the PTPv2 Timestamp
flag will be set to 0 to indicate that the Session-Receiver
interprets only the NTP format.

o If the Control-Client receives a greeting message with the PTPv2
Timestamp flag set to 0, then the Session-Sender MUST use the NTP
format for the timestamp in the test session session, and Control-Client the Control-
Client SHOULD set the PTPv2 Timestamp flag to 0 in accordance with
[RFC4656]. If the Session-Sender cannot use NTP timestamps, then
the Control-
Client Control-Client SHOULD close the TCP connection associated with
the OWAMP-
Control OWAMP-Control session.

o If the Control-Client receives a greeting message with the PTPv2
Timestamp flag set to 1 and the Session-Sender can set the
timestamp in PTPv2 format, then the Control-Client MUST set the
PTPv2 Timestamp flag to 1 in the Modes field in the Set-Up-Response Set-Up-
Response message and the Session-Sender MUST use PTPv2 timestamp
format.

o If the Session-Sender doesn't support this extension and can set
the timestamp only in NTP format, format only, then the PTPv2 Timestamp flag in
the Modes field in the Set-Up-Response message will be set to 0 as
part of the Must Be Zero field and the Session-Sender will use the
NTP format.

If OWAMP-Control uses Fetch-Session commands, then selection and use
of one or another timestamp format or another is a local decision for both
Session-Sender and Session-Receiver.

2.2. Timestamp Format Negotiation in Setting Up Connection in TWAMP Connection Setup

In TWAMP-Test [RFC5357] [RFC5357], the Session-Sender interprets collected
timestamps. Hence, in the Modes field field, a Server advertises timestamp
formats that the Session-Reflector can use in the 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 flag values to indicate which the format that will be used
by the Session-Reflector. The rules of setting and interpreting flag
values are as follows:

o The Server MUST set to 1 value of the PTPv2 Timestamp flag value to 1 in its
greeting message if the Session-Reflector can set the timestamp in
the PTPv2 format.
Otherwise Otherwise, the PTPv2 Timestamp flag MUST be set
to 0.

o If the value of the PTPv2 Timestamp flag in the received server greeting Server
Greeting message equals is 0, then the Session-Reflector does not support
this extension and will use the NTP timestamp format. The
Control-Client SHOULD set the PTPv2 Timestamp flag to 0 in the
Set-Up-Response message in accordance with [RFC5357]. [RFC4656].

o The Control-Client MUST set the PTPv2 Timestamp flag value to 1 in
the Modes field in the Set-Up-Response message if the Server
advertised ability
of that the Session-Reflector has the ability to use the
PTPv2 format for timestamps.
Otherwise Otherwise, the flag MUST be set to
0.

o If the values value of the PTPv2 Timestamp flag in the Set-Up-Response
message equals is 0, then that means that the Session-Sender can only
interpret the NTP timestamp format. Then Therefore, the Session-Reflector Session-
Reflector MUST use the NTP timestamp format. If the Session-Reflector Session-
Reflector does not support the NTP format format, then the Server and MUST
close the TCP connection associated with the TWAMP-Control
session.

2.3. OWAMP-Test and TWAMP-Test Update Updates

Participants of a test session need to indicate which timestamp
format is being used. The specification is to use Currently, the Z field in the Error Estimate
defined in Section 4.1.2 of [RFC4656]. The new
interpretation of [RFC4656] is used for this purpose.
However, this document extends the Error Estimate is in addition to it specifying
error estimate and synchronization, Error Estimate indicates indicate the
format of a collected timestamp. And this timestamp, in addition to the estimate of error
and synchronization. This specification also changes the semantics
of the Z bit field, the one field (the field between S and Scale fields, fields) to be
referred to as the Timestamp format and format; the value MUST be set per the
following: as
follows:

o 0 - NTP 64 bit 64-bit format of a timestamp; timestamp.

o 1 - PTPv2 truncated PTPv2-truncated format of a timestamp.

As a result of this value of the Z field from the Error Estimate, the
Sender Error Estimate (in TWAMP) or Send Error Estimate (in OWAMP)
and Receive Error Estimate SHOULD NOT be ignored and MUST be used
when calculating delay and
delay variation delay-variation metrics based on collected
timestamps.

2.3.1. Consideration for TWAMP Light mode Mode

This document does not specify how the Session-Sender and Session-
Reflector in TWAMP Light mode are informed of the timestamp format to
be used. It is assumed that, for example, configuration could be
used to direct the Session-Sender and Session-Reflector respectively to use the
timestamp format per their capabilities and rules listed in
Section 2.2.

3. IANA Considerations

The TWAMP-Modes registry defined in [RFC5618].

IANA is requested to reserve has registered a new PTPv2 Timestamp in the "TWAMP-Modes"
registry [RFC5618] as follows:

+--------------+------------------+---------------------+-----------+

Table 1: New Timestamp Capability

4. Security Considerations

Use of particular format of a particular timestamp format in a 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] [RFC4656] and
[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. Normative References

[IEEE.1588.2008]
"Standard

[IEEE-1588]
IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
IEEE Standard 1588, March 2008. Std 1588-2008, DOI 10.1109/IEEESTD.2008.4579760.

[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>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.

Acknowledgements

The authors would like to thank Ramanathan Lakshmikanthan and Suchit
Bansal for their insightful suggestions. The authors would also like
to thank David Allan for his thorough review and thoughtful comments.

Authors' Addresses

Greg Mirsky
ZTE Corp.

Email: gregimirsky@gmail.com

Israel Meilik
Broadcom

Email: israel@broadcom.com