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Versions: (draft-bryant-mpls-rfc6374-sfl) 00

MPLS Working Group                                             S. Bryant
Internet-Draft                                                   M. Chen
Intended status: Standards Track                                   Z. Li
Expires: December 14, 2017                                        Huawei
                                                              G. Swallow
                                                            S. Sivabalan
                                                           Cisco Systems
                                                               G. Mirsky
                                                               ZTE Corp.
                                                             G. Fioccola
                                                          Telecom Italia
                                                           June 12, 2017


                     RFC6374 Synonymous Flow Labels
                     draft-ietf-mpls-rfc6374-sfl-00

Abstract

   This document describes a method of making RFC6374 performance
   measurements on flows carried over an MPLS Label Switched path.  This
   allows loss and delay 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.

   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 December 14, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   3.  RFC6374 Packet Loss Measurement with SFL  . . . . . . . . . .   4
   4.  RFC6374 Single Packet Delay Measurement . . . . . . . . . . .   4
   5.  Data Service Packet Delay Measurement . . . . . . . . . . . .   4
   6.  Some Simplifying Rules  . . . . . . . . . . . . . . . . . . .   6
   7.  Multiple Packet Delay Characteristics . . . . . . . . . . . .   6
     7.1.  Method 1: Time Buckets  . . . . . . . . . . . . . . . . .   7
     7.2.  Method 2 Classic Standard Deviation . . . . . . . . . . .   9
       7.2.1.  RFC6374 Multi-Packet Delay Measurement Message Format  10
     7.3.  Per Packet Delay Measurement  . . . . . . . . . . . . . .  11
     7.4.  Average Delay . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Sampled Measurement . . . . . . . . . . . . . . . . . . . . .  13
   9.  Carrying RFC6374 Packets over an LSP using an SFL . . . . . .  13
     9.1.  RFC6374 SFL TLV . . . . . . . . . . . . . . . . . . . . .  15
   10. Applicability to Pro-active and On-demand Measurement . . . .  16
   11. RFC6374 Combined Loss-Delay Measurement . . . . . . . . . . .  16
   12. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  16
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  17
   14. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
     14.1.  Allocation of PW Associated Channel Type . . . . . . . .  17
     14.2.  MPLS Loss/Delay TLV Object . . . . . . . . . . . . . . .  17
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     15.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   [RFC6374] was originally designed for use as an OAM protocol for use
   with MPLS Transport Profile (MPLS-TP) [RFC5921] LSPs.  MPLS-TP only
   supports point-to-point and point-to-multi-point LSPs.  This document
   describes how to use RFC6374 in the general MPLS case, and also
   introduces a number of more sophisticated measurements of
   applicability to both cases.




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   [I-D.ietf-mpls-flow-ident] describes the requirement for introducing
   flow identities when using RFC6374 [RFC6374] packet Loss Measurements
   (LM).  In summary RFC6374 uses the loss-measurement (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.

   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.

   [I-D.bryant-mpls-sfl-framework] describes 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




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   are used to perform RFC6374 packet loss and RFC6374 delay
   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 data service packets of the flow being instrumented are grouped
   into batches, and all the packets within a batch are marked with the
   SFL [I-D.ietf-mpls-flow-ident] corresponding to that batch.  The
   sender counts the number of packets in the batch.  When the batch has
   completed and the sender is confident that all of the packets in that
   batch will have been received, the sender issues an RFC6374 Query
   message to determine the number actually received and hence the
   number of packets lost.  The RFC6374 Query message is sent using the
   same SFL as the co-responding batch of data service packets.  The
   format of the Query and Response packet is described in Section 9.

4.  RFC6374 Single Packet Delay Measurement

   RFC6374 describes how to measure the packet delay by measuring the
   transit time of an RFC6374 packet over an LSP.  Such a packet may not
   need to be carried over an SFL since the delay over a particular LSP
   should be a function of the TC bits.

   However where SFLs are being used to monitor packet loss or where
   label inferred scheduling is used [RFC3270] then the SFL would be
   REQUIRED to ensure that the RFC6374 packet which was being used as a
   proxy for a data service packet experienced a representative delay.
   The format of an RFC6374 packet carried over the LSP using an SFL is
   shown in Section 9.

5.  Data Service Packet Delay Measurement

   Where it is desired to more thoroughly instrument a packet flow and
   to determine the delay of a number of packets it is undesirable to
   send a large number of RFC6374 packets acting as proxy data service
   packets Section 4.  A method of directly measuring the delay
   characteristics of a batch of packets is therefore needed.

   Given the long intervals over which it is necessary to measure packet
   loss, it is not necessarily the case that the batch times for the two
   measurement types would be identical.  This it is proposed that the



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   two measurements are relatively independent.  The notion that they
   are relatively independent arises for the potential for the two
   batches to overlap in time, in which case either the delay batch time
   will need to be cut short or the loss time will need to be extended
   to allow correct reconciliation of the various counters.

   The problem is illustrated in Figure 1 below:

   (1) AAAAAAAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB

    SFL Marking of a packet batch for loss measurement

   (2) AADDDDAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB

    SFL Marking of a subset if the packets for delay

   (3) AAAAAAAADDDDBBBBBBBBAAAAAAAAAABBBBBBBBBB

    SFL Marking of a subset of the packets across a
    packet loss measurement boundary

   (4) AACDCDCDAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB

    The case of multiple delay measurements within
    a packet loss measurement

                  Figure 1: RFC6734 Query Packet with SFL

   In case 1 of Figure 1 we show the case were loss measurement alone is
   being carried out on the flow under analysis.  For illustrative
   purposes consider that in the time interval being analyzed, 10
   packets always flow.

   Now consider case 2 of Figure 1 where a small batch of packets need
   to analyzed for delay.  These are marked with a different SFL type
   indicating that they are to be monitored for both loss and delay.
   The SFL=A indicates loss batch A, SFL=D indicates a batch of packets
   that are to be instrumented for delay, but SFL D is synonymous with
   SFL A, which in turn is synonymous with the underlying FEC.  Thus a
   packet marked D will be accumulated into the A loss batch, into the
   delay statistics and will be forwarded as normal.  Whether the packet
   is actually counted twice (for loss and delay) or whether the two
   counters are reconciled during reporting is a local matter.

   Now consider case 3 of Figure 1 where a small batch of packets are
   marked for delay across a loss batch boundary.  These packets need to
   considered as part of batch A or a part of batch B, and any RFC6374




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   Query needs to take place after all the packets A or D (which ever
   option is chosen) have arrived at the receiving LSR.

   Now consider case 4 of Figure 1.  Here we have a case where it is
   required to take a number of delay measurements within a batch of
   packets that we are measuring for loss.  To do this we need two SFLs
   for delay (C and D) and alternate between them (on a delay batch by
   delay batch basis) for the purposes of measuring the delay
   characteristics of the different batches of packets.

6.  Some Simplifying Rules

   It is possible to construct a large set of overlapping measurement
   type, in terms of loss, delay, loss and delay and batch overlap.  If
   we allow all combination of cases, this leads to configuration,
   testing and implementation complexity and hence increased operation
   and capital cost.  The following simplifying rules represent the
   default case:

   1.  Any system that needs to measure delay MUST be able to measure
       loss.

   2.  Any system that is to measure delay MUST be configured to measure
       loss.  Whether the loss statistics are collected or not is a
       local matter.

   3.  A delay measurement MAY start at any point during a loss
       measurement batch, subject to rule 4.

   4.  A delay measurement interval MUST be short enough that it will
       complete before the enclosing loss batch completes.

   5.  The duration of a second delay (D in Figure 1 batch must be such
       that all packets from the packets belonging to a first delay
       batch (C in Figure 1)will have been received before the second
       delay batch completes.

   Given that the sender controls both the start and duration of a loss
   and a delay packet batch, these rules are readily implemented in the
   control plane.

7.  Multiple Packet Delay Characteristics

   A number of methods are described.  The expectation is that the MPLS
   WG possibly with the assistance of the IPPM WG will select one or
   maybe more than one of these methods for standardization.

   Three Methods are discussed:



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   1.  Time Buckets

   2.  Classic Standard Deviation

   3.  Average Delay

7.1.  Method 1: Time Buckets

   In this method the receiving LSR measures the inter-packet gap,
   classifies the delay into a number of delay buckets and records the
   number of packets in each bucket.  As an example, if the operator
   were concerned about packets with a delay of up to 1us, 2us, 4us,
   8us, and over 8us then there would be five buckets and packets that
   arrived up to 1us would cause the 1us bucket counter to increase,
   between 1us and 2us the 2us bucket counter would increase etc.  In
   practice it might be better in terms of processing and potential
   parallelism if, when a packet had a delay relative to its predecessor
   of 2us both the up to 1us and the 2us counter were incremented and
   any more detailed information was calculated in the analytics system.

   This method allows the operator to see more structure in the jitter
   characteristics than simply measuring the average jitter, and avoids
   the complication of needing to perform a per packet multiply, but
   will probably need to time intervals between buckets to be
   programmable by the operator.

   The packet format of an RFC6374 Bucket Jitter Measurement Message is
   shown below:























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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Flags |  Control Code |        Message Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  QTF  |  RTF  | RPTF  |              Reserved                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Session Identifier          |    DS     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Number of     |      Reserved                                 |
   | Buckets       |                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Interval in 10ns units                      |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Number pkts in Bucket                       |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   ~                           TLV Block                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 2: Bucket Jitter Measurement Message Format

   The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF,
   Session Identifier, and DS Fields are as defined in section 3.7 of
   RFC6374.  The remaining fields are as follows:

   o Number of Buckets in the measurement

   o Reserved must be sent as zero and ignored on receipt

   o Interval in 10ns units is the inter-packet interval for
     this bucket

   o Number Pkts in Bucket is the number of packets found in
     this bucket.

   There will be a number of Interval/Number pairs depending on the
   number of buckets being specified by the Querier.  If an RFC6374
   message is being used to configure the buckets, (i.e. the responder
   is creating or modifying the buckets according to the intervals in
   the Query message), then the Responder MUST respond with 0 packets in
   each bucket until it has been configured for a full measurement
   period.  This indicates that it was configured at the time of the



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   last response message, and thus the response is valid for the whole
   interval.  As per the [RFC6374] convention the Number of pkts in
   Bucket fields are included in the Query message and set to zero.

   Out of band configuration is permitted by this mode of operation.

   Note this is a departure from the normal fixed format used in
   RFC6374.  We need to establish if this is problematic or not.

   This RFC6374 message is carried over an LSP in the way described in
   [RFC6374] and over an LSP with an SFL as described in Section 9.

7.2.  Method 2 Classic Standard Deviation

   In this method, provision is made for reporting the following delay
   characteristics:

   1.  Number of packets in the batch (n).

   2.  Sum of delays in a batch (S)

   3.  Maximum Delay.

   4.  Minimum Delay.

   5.  Sum of squares of Inter-packet delay (SS).

   Characteristic's 1 and 2 give the mean delay.  Measuring the delay of
   each pair in the batch is discussed in Section 7.3.

   Characteristics 3 and 4 give the outliers.

   Characteristics 1, 2 and 5 can be used to calculate the variance of
   the inter-packet gap and hence the standard deviation giving a view
   of the distribution of packet delays and hence the jitter.  The
   equation for the variance (var) is given by:

   var = (SS - S*S/n)/(n-1)

   There is some concern over the use of this algorithm for measuring
   variance, because SS and S*S/n can be similar numbers, particularly
   where variance is low.  However the method commends it self by not
   requiring a division in the hardware.  A future version of this
   document will look at using improved statistical methods such as the
   assumed mean.






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7.2.1.  RFC6374 Multi-Packet Delay Measurement Message Format

   The packet format of an RFC6374 Multi-Packet Delay Measurement
   Message is shown below:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Flags |  Control Code |        Message Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  QTF  |  RTF  | RPTF  |              Reserved                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Session Identifier          |    DS     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Number of Packets                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Sum of Delays for Batch                     |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Minimum Delay                           |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Maximum Delay                           |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Sum of squares of Inter-packet delay           |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   ~                           TLV Block                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 3: Multi-packet Delay Measurement Message Format

   The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF,
   Session Identifier, and DS Fields are as defined in section 3.7 of
   RFC6374.  The remaining fields are as follows:













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   o Number of Packets is the number of packets in this batch

   o Sum of Delays for Batch is the duration of the batch in the
     time measurement format specified in the RTF field.

   o Minimum Delay is the minimum inter-packet gap observed during
     the batch in the time format specified in the RTF field.

   o Maximum Delay is the maximum inter-packet gap observed during
     the batch in the time format specified in the RTF field.

   This RFC6374 message is carried over an LSP in the way described in
   [RFC6374] and over an LSP with an SFL as described in Section 9.

7.3.  Per Packet Delay Measurement

   If detailed packet delay measurement is required then it might be
   possible to record the inter-packet gap for each packet pair.  In
   other that exception cases of slow flows or small batch sizes, this
   would create a large demand on storage in the instrumentation system,
   bandwidth to such a storage system and bandwidth to the analytics
   system.  Such a measurement technique is outside the scope of this
   document.

7.4.  Average Delay

   Introduced in [I-D.ietf-ippm-alt-mark] is the concept of a one way
   delay measurement in which the average time of arrival of a set of
   packets is measured.  In this approach the packet is time-stamped at
   arrival and the Responder returns the sum of the time-stamps and the
   number of times-tamps.  From this the analytics engine can determine
   the mean delay.  An alternative model is that the Responder returns
   the time stamp of the first and last packet and the number of
   packets.  This method has the advantage of allowing the average delay
   to be determined at a number of points along the packet path and
   allowing the components of the delay to be characterized.

   The packet format of an RFC6374 Average Delay Measurement Message is
   shown below:












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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Flags |  Control Code |        Message Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  QTF  |  RTF  | RPTF  |              Reserved                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Session Identifier          |    DS     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Number of Packets                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Time of First Packet                     |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Time of Last Packet                      |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Sum of Timestamps of Batch                  |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ~                                                               ~
   ~                           TLV Block                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 4: Average Delay Measurement Message Format

   The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF,
   Session Identifier, and DS Fields are as defined in section 3.7 of
   RFC6374.  The remaining fields are as follows:

   o Number of Packets is the number of packets in this batch.

   o Time of First Packet is the time of arrival of the first
     packet in the batch.

   o Time of Last Packet is the time of arrival of the last
     packet in the batch.

   o Sum of Timestamps of Batch.

   This RFC6374 message is carried over an LSP in the way described in
   [RFC6374] and over an LSP with an SFL as described in Section 9.  As
   is the convention with RFC6374, the Query message contains
   placeholders for the Response message.  The placeholders are sent as
   zero.




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8.  Sampled Measurement

   In the discussion so far it has been assumed that we would measure
   the delay characteristics of every packet in a delay measurement
   interval defined by an SL of constant colour.  In
   [I-D.ietf-ippm-alt-mark] the concept of a sampled measurement is
   considered.  That is the Responder only measures a packet at the
   start of a group of packets being marked for delay measurement by a
   particular colour, rather than every packet in the marked batch.  A
   measurement interval is not defined by the duration of a marked batch
   of packets but the interval between a pair of RFC6374 packets taking
   a readout of the delay characteristic.  This approach has the
   advantage that the measurement is not impacted by ECMP effects.

9.  Carrying RFC6374 Packets over an LSP using an SFL

   The packet format of an RFC6374 Query message using SFLs is shown in
   Figure 5.

































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   +-------------------------------+
   |                               |
   |             LSP               |
   |            Label              |
   +-------------------------------+
   |                               |
   |        Synonymous Flow        |
   |            Label              |
   +-------------------------------+
   |                               |
   |            GAL                |
   |                               |
   +-------------------------------+
   |                               |
   |      ACH Type = 0xA           |
   |                               |
   +-------------------------------+
   |                               |
   |  RFC6374 Measurement Message  |
   |                               |
   |  +-------------------------+  |
   |  |                         |  |
   |  |     RFC6374 Fixed       |  |
   |  |     Header              |  |
   |  |                         |  |
   |  +-------------------------+  |
   |  |                         |  |
   |  |      Optional SFL TLV   |  |
   |  |                         |  |
   |  +-------------------------+  |
   |  |                         |  |
   |  |      Optional Return    |  |
   |  |      Information        |  |
   |  |                         |  |
   |  +-------------------------+  |
   |                               |
   +-------------------------------+

                  Figure 5: 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 inclusion of
   the GAL [RFC5586] to allow the receiver to distinguish between normal
   data packets and OAM packets.  Since the packet loss measurements are
   being made on the data service packets, an RFC6374 direct loss
   measurement is being made, and which is indicated by the type field
   in the ACH (Type = 0x000A).




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   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 9.1.  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
   [RFC7876].  This TLV MUST be included 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 [RFC7876].

9.1.  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 6.  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 6: SFL TLV



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   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.

   SFL Batch The SFL batch that this SFL was allocated as part
             of see [I-D.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 TBD

   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.

10.  Applicability to Pro-active and On-demand Measurement

   A future version of the this document will discuss the applicability
   of the various methods to pro-active and on-demand Measurement.

11.  RFC6374 Combined Loss-Delay Measurement

   This mode of operation is not currently supported by this
   specification.

12.  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



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   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.

13.  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
   control protocol used to request SFLs will need to ensure the
   legitimacy of the request.

14.  IANA Considerations

14.1.  Allocation of PW Associated Channel Type

   As per the IANA considerations in [RFC5586], IANA is requested to
   allocate the following Channel Type in the "PW Associated Channel
   Type" registry:

   Value  Description                        TLV Follows  Reference
   -----  ---------------------------------  -----------  ---------
   TBD    RFC6374 Bucket Jitter Measurement     No        This


   TBD    RFC6374 Multi-Packet Delay            No        This
          Measurement

   TBD    RFC6374 Average Delay Measurement     No        This

14.2.  MPLS Loss/Delay TLV Object

   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.

15.  References

15.1.  Normative References







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   [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>.

   [RFC5586]  Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
              "MPLS Generic Associated Channel", RFC 5586,
              DOI 10.17487/RFC5586, June 2009,
              <http://www.rfc-editor.org/info/rfc5586>.

   [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>.

   [RFC7876]  Bryant, S., Sivabalan, S., and S. Soni, "UDP Return Path
              for Packet Loss and Delay Measurement for MPLS Networks",
              RFC 7876, DOI 10.17487/RFC7876, July 2016,
              <http://www.rfc-editor.org/info/rfc7876>.

15.2.  Informative References

   [I-D.bryant-mpls-sfl-control]
              Bryant, S., Swallow, G., and S. Sivabalan, "MPLS Flow
              Identification Considerations", draft-bryant-mpls-sfl-
              control-01 (work in progress), March 2017.

   [I-D.bryant-mpls-sfl-framework]
              Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S.,
              and G. Mirsky, "Synonymous Flow Label Framework", draft-
              bryant-mpls-sfl-framework-04 (work in progress), April
              2017.

   [I-D.chen-ippm-coloring-based-ipfpm-framework]
              Chen, M., Zheng, L., Mirsky, G., Fioccola, G., and T.
              Mizrahi, "IP Flow Performance Measurement Framework",
              draft-chen-ippm-coloring-based-ipfpm-framework-06 (work in
              progress), March 2016.








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   [I-D.ietf-ippm-alt-mark]
              Fioccola, G., Capello, A., Cociglio, M., Castaldelli, L.,
              Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
              "Alternate Marking method for passive performance
              monitoring", draft-ietf-ippm-alt-mark-04 (work in
              progress), March 2017.

   [I-D.ietf-mpls-flow-ident]
              Bryant, S., Pignataro, C., Chen, M., Li, Z., and G.
              Mirsky, "MPLS Flow Identification Considerations", draft-
              ietf-mpls-flow-ident-04 (work in progress), February 2017.

   [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-03 (work in
              progress), March 2016.

   [RFC3270]  Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
              P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
              Protocol Label Switching (MPLS) Support of Differentiated
              Services", RFC 3270, DOI 10.17487/RFC3270, May 2002,
              <http://www.rfc-editor.org/info/rfc3270>.

   [RFC5921]  Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
              L., and L. Berger, "A Framework for MPLS in Transport
              Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
              <http://www.rfc-editor.org/info/rfc5921>.

Authors' Addresses

   Stewart Bryant
   Huawei

   Email: stewart.bryant@gmail.com


   Mach Chen
   Huawei

   Email: mach.chen@huawei.com


   Zhenbin Li
   Huawei

   Email: lizhenbin@huawei.com




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   George Swallow
   Cisco Systems

   Email: swallow.ietf@gmail.com


   Siva Sivabalan
   Cisco Systems

   Email: msiva@cisco.com


   Gregory Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com


   Giuseppe Fioccola
   Telecom Italia

   Email: giuseppe.fioccola@telecomitalia.it





























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