MPLS S. Bryant
Internet-Draft G. Swallow
Intended status: Standards Track S. Sivabalan
Expires: April 20, 2016 Cisco Systems
G. Mirsky
Ericsson
M. Chen
Z. Li
Huawei
October 18, 2015
RFC6374 Synonymous Flow Labels
draft-bryant-mpls-rfc6374-sfl-00
Abstract
This document describes a method of providing flow identification
information when making RFC6374 performance measurements. This
allows RFC6374 measurements to be made on multi-point to point LSPs
and allows the measurement of flows within an MPLS construct using
RFC6374.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 20, 2016.
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Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. RFC6374 Packet Loss Measurement with SFL . . . . . . . . . . 3
3.1. RFC6374 SFL TLV . . . . . . . . . . . . . . . . . . . . . 5
4. The Application of SFL to other PM Types . . . . . . . . . . 6
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
[I-D.bryant-mpls-flow-ident] describes the requirement for
introducing flow identities when using RFC6374 [RFC6374] packet Loss
Measurements (LM). In summary RFC6374 uses the LM packet as the
packet accounting demarcation point. Unfortunately this gives rise
to a number of problems that may lead to significant packet
accounting errors in certain situations. For example:
1. Where a flow is subjected to Equal Cost Multi-Path (ECMP)
treatment packets can arrive out of order with respect to the LM
packet.
2. Where a flow is subjected to ECMP treatment, packets can arrive
at different hardware interfaces, thus requiring reception of an
LM packet on one interface to trigger a packet accounting action
on a different interface which may not be co-located with it.
This is a difficult technical problem to address with the
required degree of accuracy.
3. Even where there is no ECMP (for example on RSVP-TE, MPLS-TP LSPs
and PWs) local processing may be distributed over a number of
processor cores, leading to synchronization problems.
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4. Link aggregation techniques may also lead to synchronization
issues.
5. Some forwarder implementations have a long pipeline between
processing a packet and incrementing the associated counter again
leading to synchronization difficulties.
An approach to mitigating these synchronization issue is described in
[I-D.tempia-ippm-p3m] and
[I-D.chen-ippm-coloring-based-ipfpm-framework] in which packets are
batched by the sender and each batch is marked in some way such that
adjacent batches can be easily recognized by the receiver.
An additional problem arises where the LSP is a multi-point to point
LSP, since MPLS does not include a source address in the packet.
Network management operations require the measurement of packet loss
between a source and destination. It is thus necessary to introduce
some source specific information into the packet to identify packet
batches from a specific source.
draft-bryant-mpls-sfl-framework specifies a method of encoding per
flow instructions in an MPLS label stack using a technique called
Synonymous Flow Labels (SFL) in which labels which mimic the
behaviour of other labels provide the packet batch identifiers and
enable the per batch packet accounting. This memo specifies how SFLs
are used to perform RFC6374 performance measurements.
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].
3. RFC6374 Packet Loss Measurement with SFL
The packet format of an RFC6374 Query message using SFLs is shown in
Figure 1.
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+-------------------------------+
| |
| LSP |
| Label |
+-------------------------------+
| |
| Synonymous Flow |
| Label |
+-------------------------------+
| |
| |
| RFC6374 Measurement Message |
| |
| +-------------------------+ |
| | | |
| | RFC6374 Fixed | |
| | Header | |
| | | |
| +-------------------------+ |
| | | |
| | Optional SFL TLV | |
| | | |
| +-------------------------+ |
| | | |
| | Optional Return | |
| | Information | |
| | | |
| +-------------------------+ |
| |
+-------------------------------+
Figure 1: RFC6734 Query Packet with SFL
The MPLS label stack is exactly the same as that used for the user
data service packets being instrumented except for the replacement of
the appropriate label with an SFL . The RFC6374 measurement message
consists of the three components, the RFC6374 fixed header as
specified in [RFC6374] carried over the ACH channel type specified
the type of measurement being made (currently: loss, delay or loss
and delay) as specified in RFC6374.
Two optional TLVs MAY also be carried if needed. The first is the
SFL TLV specified in Section 3.1. This is used to provide the
implementation with a reminder of the SFL that was used to carry the
RFC6374 message. This is needed because a number of MPLS
implementations do not provide the MPLS label stack to the MPLS OAM
handler. This TLV is required if RFC6374 messages are sent over UDP
(draft-bryant-mpls-RFC6374-over-udp). This TLV MUST be included
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unless, by some method outside the scope of this document, it is
known that this information is not needed by the RFC6374 Responder.
The second set of information that may be needed is the return
information that allows the responder send the RFC6374 response to
the Querier. This is not needed if the response is requested in-band
and the MPLS construct being measured is a point to point LSP, but
otherwise MUST be carried. The return address TLV is defined in
RFC6378 and the optional UDP Return Object is defined in
[I-D.ietf-mpls-rfc6374-udp-return-path].
3.1. RFC6374 SFL TLV
[Editor's Note we need to review the following in the light of
further thoughts on the associated signaling protocol(s). I am
fairly confident that we need all the fields other than SFL Batch and
SFL Index. The Index is useful in order to map between the label and
information associated with the FEC. The batch is part of the
lifetime management process]
The required RFC6374 SFL TLV is shown in Figure 2. This contains the
SFL that was carried in the label stack, the FEC that was used to
allocate the SFL and the index into the batch of SLs that were
allocated for the FEC that corresponds to this SFL.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |MBZ| SFL Batch | SFL Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SFL | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: SFL TLV
Where:
Type Type is set to Synonymous Flow Label (SFL-TLV).
Length The length of the TLV as specified in [RFC6374].
MBZ MUST be sent as zero and ignored on receive.
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SFL Batch The SFL batch that this SFL was allocated as part of
(see draft-bryant-mpls-sfl-control)
SPL Index The index into the list of SFLs that were assigned
against the FEC that corresponds to the SFL.
SFL The SFL used to deliver this packet. This is an MPLS
label which is a component of a label stack entry as
defined in Section 2.1 of [RFC3032].
Reserved MUST be sent as zero and ignored on receive.
FEC The Forwarding Equivalence Class that was used to
request this SFL. This is encoded as per
Section 3.4.1 of
This information is needed to allow for operation with hardware that
discards the MPLS label stack before passing the remainder of the
stack to the OAM handler. By providing both the SFL and the FEC plus
index into the array of allocated SFLs a number of implementation
types are supported.
4. The Application of SFL to other PM Types
SFL can be used to enable other types of PM in addition to loss.
Delay, Delay Variation and Throughput may be calculated based on
measurement results collected through Loss and Delay Measurement test
sessions. Further details will be provided in a future version of
this draft.
5. Privacy Considerations
The inclusion of originating and/or flow information in a packet
provides more identity information and hence potentially degrades the
privacy of the communication. Whilst the inclusion of the additional
granularity does allow greater insight into the flow characteristics
it does not specifically identify which node originated the packet
other than by inspection of the network at the point of ingress, or
inspection of the control protocol packets. This privacy threat may
be mitigated by encrypting the control protocol packets, regularly
changing the synonymous labels and by concurrently using a number of
such labels.
6. Security Considerations
The issue noted in Section 5 is a security consideration. There are
no other new security issues associated with the MPLS dataplane. Any
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control protocol used to request SFLs will need to ensure the
legitimacy of the request.
7. IANA Considerations
IANA is request to allocate a new TLV from the 0-127 range on the
MPLS Loss/Delay Measurement TLV Object Registry:
Type Description Reference
---- --------------------------------- ---------
TBD Synonymous Flow Label This
A value of 4 is recommended.
8. Acknowledgements
TBD
9. References
9.1. Normative References
[I-D.ietf-mpls-rfc6374-udp-return-path]
Bryant, S., Sivabalan, S., and S. Soni, "RFC6374 UDP
Return Path", draft-ietf-mpls-rfc6374-udp-return-path-04
(work in progress), August 2015.
[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>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<http://www.rfc-editor.org/info/rfc3032>.
9.2. Informative References
[I-D.bryant-mpls-flow-ident]
Bryant, S., Pignataro, C., Chen, M., Li, Z., and G.
Mirsky, "MPLS Flow Identification", draft-bryant-mpls-
flow-ident-02 (work in progress), September 2015.
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[I-D.chen-ippm-coloring-based-ipfpm-framework]
Chen, M., Zheng, L., Mirsky, G., and G. Fioccola, "IP Flow
Performance Measurement Framework", draft-chen-ippm-
coloring-based-ipfpm-framework-04 (work in progress), July
2015.
[I-D.tempia-ippm-p3m]
Capello, A., Cociglio, M., Fioccola, G., Castaldelli, L.,
and A. Bonda, "A packet based method for passive
performance monitoring", draft-tempia-ippm-p3m-01 (work in
progress), September 2015.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374,
DOI 10.17487/RFC6374, September 2011,
<http://www.rfc-editor.org/info/rfc6374>.
Authors' Addresses
Stewart Bryant
Cisco Systems
Email: stbryant@cisco.com
George Swallow
Cisco Systems
Email: swallow@cisco.com
Siva Sivabalan
Cisco Systems
Email: msiva@cisco.com
Greg Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
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Zhenbin(Robin) Li
Huawei
Email: lizhenbin@huawei.com
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