Residence Time Measurment in MPLS network
draft-mirsky-mpls-residence-time-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Greg Mirsky , John Drake , Stewart Bryant , Sasha Vainshtein | ||
| Last updated | 2014-04-21 | ||
| Replaced by | draft-ietf-mpls-residence-time, RFC 8169 | ||
| RFC stream | (None) | ||
| Formats | |||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-mirsky-mpls-residence-time-01
MPLS Working Group G. Mirsky
Internet-Draft Ericsson
Intended status: Standards Track J. Drake
Expires: October 23, 2014 Juniper Networks
S. Bryant
Cisco Systems
A. Vainshtein
ECI Telecom
April 21, 2014
Residence Time Measurment in MPLS network
draft-mirsky-mpls-residence-time-01
Abstract
This document specifies G-ACh based Residence Time Measurement and
how it can be used by time synchronization protocols being
transported over MPLS domain.
Status of this Memo
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This Internet-Draft will expire on October 23, 2014.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . . 3
2. Residence Time Measurement . . . . . . . . . . . . . . . . . . 4
3. G-ACh for Residence Time Measurement . . . . . . . . . . . . . 4
4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
Time synchronization protocols, Network Time Protocol version 4
(NTPv4) [RFC5905] and Precision Time Protocol (PTP) Version 2, a.k.a.
IEEE-1588 v.2, can be used to syncronized clocks across network
domain. In some scenarios calculation of time packet of time
syncronization protocol spends within a node, called Resident Time,
can improve accuracy of clock syncronization. This document defines
new Generalized Associated Channel (G-ACh) that can be used in Multi-
Protocol Label Switching (MPLS) network to measure Residence Time
over Label Switched Path (LSP) or Pseudo-wire (PW). Transport of
packets of a time synchronization protocol over MPLS domain is
outside of scope of this document.
1.1. Conventions used in this document
1.1.1. Terminology
MPLS: Multi-Protocol Label Switching
ACH: Associated Channel
TTL: Time-to-Live
G-ACh: Generic Associated Channel
GAL: Generic Associated Channel Label
NTP: Network Time Protocol
PTP: Precision Time Protocol
PW: Pseudo-wire
LSP: Label Switched Path
OAM: Operations, Administration, and Maintenance
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].
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2. Residence Time Measurement
Packet Loss and Delay Measurement for MPLS Networks [RFC6374] can be
used to measure one-way or two-way end-to-end propagation delay over
LSP or PW. But none of these metrics is useful for time
syncronization across a network. For example, PTPv2 uses "residence
time", time it takes for a PTPv2 packet to transit a node, not delay
of propagation over a link connected to a port receiving the PTP
event message.
3. G-ACh for Residence Time Measurement
RFC 5586 [RFC5586] and RFC 6423 [RFC6423] extended applicability of
PW Associated Channel (ACH) [RFC5085] to LSPs. G-ACh presents
mechanism to transport OAM and other control messages and trigger
their processing by arbitrary transient LSRs through controlled use
of Time-to-Live (TTL) value.
Packet format for Residence Time Measurement presented in Figure 1
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | RTM Channel |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Scratch Pad |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload |
| |
. .
Figure 1: G-ACh packet format for Residence Time Measurement
Version field is set to 0, as defined in RFC 4385 [RFC4385].
Reserved field must be set to 0 on trnsmit and ignored at reception.
Residence Time Measurement (RTM) G-ACh - value to be allocated by
IANA. Scratch pad - 8 octets long field that can be used to
accumulate residence time the packet spends traversing the node.
Payload - optional field. May be used to transport a packet of time
synchronization protocol.
4. Theory of Operation
An LSP ingress LSR, based on information collected through IGP
extensions that are outside of scope of this document, select to use
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use Residence Time Measurement G-ACh. The LSR then would use GAL and
G-ACh header. The LSR will zero out Scratch Pad field and set TTL
value so that TTL expiration will be at the next RTM capable
downstream LSR.
Upon expiration of RTM packet an LSR would substract local time value
from the value in the Scratch Pad field and processes the packet
according to label stack information. If the packet to be forwarded,
the LSR will set TTL value so that the TTL expiration takes place at
the next RTM-capable downstream LSR. The LSR adds local time value
to the value in the Scratch Pad field as close to the start of packet
transmition as possible.
LSP terminating LSR may use value accumulated in the Scratch Pad
field as time correction as it represent sum of Residence Time of all
traveresed RTM capable LSR between end points of the LSP. For
example, egress LSR may be PTP Boundary Clock syncronized to a Master
Clock and as Slave Clock will use accumulated in the Scratch Pad
Field value to update PTP's Correction Field.
5. IANA Considerations
IANA is requested to reserve a new G-ACh as follows:
+-------+----------------------------+---------------+
| Value | Description | Reference |
+-------+----------------------------+---------------+
| X | Residence Time Measurement | This document |
+-------+----------------------------+---------------+
Table 1: New Residence Time Measurement
6. Security Considerations
Routers that support Residence Time Measurement are subject to the
same security considerations as defined in [RFC5586] and [RFC6423].
7. Acknowledgements
TBD
8. References
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8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, February 2006.
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC6423] Li, H., Martini, L., He, J., and F. Huang, "Using the
Generic Associated Channel Label for Pseudowire in the
MPLS Transport Profile (MPLS-TP)", RFC 6423,
November 2011.
8.2. Informative References
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, September 2011.
Authors' Addresses
Greg Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
John Drake
Juniper Networks
Email: jdrake@juniper.net
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Stewart Bryant
Cisco Systems
Email: stbryant@cisco.com
Alexander Vainshtein
ECI Telecom
Email: Alexander.Vainshtein@ecitele.com
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