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Versions: 00 01 02 03 04 draft-ietf-ippm-multipoint-alt-mark

IPPM Working Group                                      G. Fioccola, Ed.
Internet-Draft                                               M. Cociglio
Intended status: Experimental                             Telecom Italia
Expires: December 31, 2018                                      A. Sapio
                                                                R. Sisto
                                                   Politecnico di Torino
                                                           June 29, 2018


 Multipoint Alternate Marking method for passive and hybrid performance
                               monitoring
               draft-fioccola-ippm-multipoint-alt-mark-04

Abstract

   The Alternate Marking method, as presented in RFC 8321 [RFC8321], can
   be applied only to point-to-point flows because it assumes that all
   the packets of the flow measured on one node are measured again by a
   single second node.  This document aims to generalize and expand this
   methodology to measure any kind of unicast flows, whose packets can
   follow several different paths in the network, in wider terms a
   multipoint-to-multipoint network.  For this reason the technique here
   described is called Multipoint Alternate Marking.  Some definitions
   here introduced extend the scope of RFC 5644 [RFC5644] in the context
   of alternate marking schema.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 https://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 31, 2018.



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Copyright Notice

   Copyright (c) 2018 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
   (https://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.  Correlation with RFC5644  . . . . . . . . . . . . . . . . . .   4
   3.  Flow classification . . . . . . . . . . . . . . . . . . . . .   4
   4.  Multipoint Performance Measurement  . . . . . . . . . . . . .   6
     4.1.  Monitoring Network  . . . . . . . . . . . . . . . . . . .   7
   5.  Multipoint Packet Loss  . . . . . . . . . . . . . . . . . . .   8
   6.  Network Clustering  . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Algorithm for Cluster partition . . . . . . . . . . . . .  10
   7.  Timing Aspects  . . . . . . . . . . . . . . . . . . . . . . .  12
   8.  Multipoint Delay and Delay Variation  . . . . . . . . . . . .  14
     8.1.  Delay measurements on multipoint paths basis  . . . . . .  14
       8.1.1.  Single Marking measurement  . . . . . . . . . . . . .  14
     8.2.  Delay measurements on single packets basis  . . . . . . .  14
       8.2.1.  Single and Double Marking measurement . . . . . . . .  14
       8.2.2.  Hashing selection method  . . . . . . . . . . . . . .  15
   9.  An SDN enabled Performance Management . . . . . . . . . . . .  17
   10. Examples of application . . . . . . . . . . . . . . . . . . .  17
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  18
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  18
     14.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   The alternate marking method, as presented until now, is applicable
   to a point-to-point path; so the extension proposed in this document
   explains the most general case of multipoint-to-multipoint path and




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   enables flexible and adaptive performance measurements in a managed
   network.

   The Alternate Marking methodology described in RFC 8321 [RFC8321] has
   the property to synchronize measurements in different points
   maintaining the coherence of the counters.  So it is possible to show
   what is happening in every marking period for each monitored flow.
   The monitoring parameters are the packet counter and timestamps of a
   flow for each marking period.

   There are some applications of the alternate marking method where
   there are a lot of monitored flows and nodes.  Multipoint Alternate
   Marking aims to reduce these values and makes the performance
   monitoring more flexible in case a detailed analysis is not needed.
   For instance, by considering n measurement points and m monitored
   flows,the order of magnitude of the packet counters for each time
   interval is n*m*2 (1 per color).  If both n and m are high values the
   packet counters increase a lot and Multipoint Alternate Marking
   offers a tool to control these parameters.

   The approach presented in this document is applied only to unicast
   flows and not to multicast.  BUM (Boradcast Unkown Unicast Multicast)
   traffic is not considered here, because traffic replication is not
   covered by the Multipoint Alternate Marking method.

   Alternate Marking method works by definition for multipoint to
   multipoint paths but the network clustering approach presented in
   this document is the formalization of how to implement this property
   and it allows a flexible and optimized performance measurement
   support.

   Without network clustering, it is possible to apply alternate marking
   only for all the network or per single flow.  Instead, with network
   clustering, it is possible to use the network clusters partition at
   different levels to perform the needed degree of detail.  In some
   circumstances it is possible to monitor a Multipoint Network by
   analyzing the Network Clustering, without examining in depth.  In
   case of problems (packet loss is measured or the delay is too high)
   the filtering criteria could be specified more in order to perform a
   detailed analysis by using a different combination of clusters up to
   a per-flow measurement as described in RFC 8321 [RFC8321].

   An application could be the Software Defined Network (SDN) paradigm
   where the SDN Controllers are the brains of the network and can
   manage flow control to the switches and routers and, in the same way,
   can calibrate the performance measurements depending on the
   necessity.  An SDN Controller Application can orchestrate how deep
   the network performance monitoring is setup.



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2.  Correlation with RFC5644

   RFC 5644 [RFC5644] is limited to active measurements using a single
   source packet or stream, and observations of corresponding packets
   along the path (spatial), at one or more destinations (one-to-group),
   or both.  Instead, the scope of this memo is to define multiparty
   metrics for passive and hybrid measurements in a group-to-group
   topology with multiple sources and destinations.

   RFC 5644 [RFC5644] introduces metric names that can be reused also
   here but have to be extended and rephrased to be applied to the
   alternate marking schema:

   a.  the multiparty metrics are not only one-to-group metrics but can
       be also group-to-group metrics;

   b.  the spatial metrics, used for measuring the performance of
       segments of a source to destination path, are applied here to
       group-to-group segments (called Clusters).

3.  Flow classification

   An unicast flow is identified by all the packets having a set of
   common characteristics.  This definition is inspired by RFC 7011
   [RFC7011].

   As an example, by considering a flow as all the packets sharing the
   same source IP address or the same destination IP address, it is easy
   to understand that the resulting pattern will not be a point-to-point
   connection, but a point-to-multipoint or multipoint-to-point
   connection.

   In general a flow can be defined by a set of selection rules used to
   match a subset of the packets processed by the network device.  These
   rules specify a set of headers fields (Identification Fields) and the
   relative values that must be found in matching packets.

   The choice of the identification fields directly affects the type of
   paths that the flow would follow in the network.  In fact, it is
   possible to relate a set of identification fields with the pattern of
   the resulting graphs, as listed in Figure 1.

   A TCP 5-tuple usually identifies flows following either a single path
   or a point-to-point multipath (in case of load balancing).  On the
   contrary, a single source address selects flows following a point-to-
   multipoint, while a multipoint-to-point can be the result of a
   matching on a single destination address.  In case a selection rule
   and its reverse are used for bidirectional measurements, they can



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   correspond to a point-to-multipoint in one direction and a
   multipoint-to-point in the opposite direction.

   In this way the flows to be monitored are selected into the
   monitoring points using packet selection rules, that can also change
   the pattern of the monitored network.

   The alternate marking method is applicable only to a single path (and
   partially to a one-to-one multipath), so the extension proposed in
   this document is suitable also for the most general case of
   multipoint-to-multipoint, which embraces all the other patterns of
   Figure 1.


          point-to-point single path
              +------+      +------+      +------+
          ---<>  R1  <>----<>  R2  <>----<>  R3  <>---
              +------+      +------+      +------+

          point-to-point multipath
                           +------+
                          <>  R2  <>
                         / +------+ \
                        /            \
              +------+ /              \ +------+
          ---<>  R1  <>                <>  R4  <>---
              +------+ \              / +------+
                        \            /
                         \ +------+ /
                          <>  R3  <>
                           +------+

          point-to-multipoint
                                      +------+
                                     <>  R4  <>---
                                    / +------+
                          +------+ /
                         <>  R2  <>
                        / +------+ \
              +------+ /            \ +------+
          ---<>  R1  <>              <>  R5  <>---
              +------+ \              +------+
                        \ +------+
                         <>  R3  <>
                          +------+ \
                                    \ +------+
                                     <>  R6  <>---
                                      +------+



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          multipoint-to-point
              +------+
          ---<>  R1  <>
              +------+ \
                        \ +------+
                        <>  R4  <>
                        / +------+ \
              +------+ /            \ +------+
          ---<>  R2  <>              <>  R4  <>---
              +------+              / +------+
                          +------+ /
                         <>  R5  <>
                        / +------+
              +------+ /
          ---<>  R3  <>
              +------+

          multipoint-to-multipoint
              +------+                +------+
          ---<>  R1  <>              <>  R6  <>---
              +------+ \            / +------+
                        \ +------+ /
                         <>  R4  <>
                          +------+ \
              +------+              \ +------+
          ---<>  R2  <>             <>  R7  <>---
              +------+ \            / +------+
                        \ +------+ /
                         <>  R5  <>
                        / +------+ \
              +------+ /            \ +------+
          ---<>  R3  <>              <>  R8  <>---
              +------+                +------+



                       Figure 1: Flow classification

4.  Multipoint Performance Measurement

   By Using the "traditional" alternate marking method only point-to-
   point paths can be monitored.  To have an IP (TCP/UDP) flow that
   follows a point-to-point path we have to define, with a specific
   value, 5 identification fields (IP Source, IP Destination, Transport
   Protocol, Source Port, Destination Port).

   Multipoint Alternate Marking enables the performance measurement for
   multipoint flows selected by identification fields without any



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   constraints (even the entire network production traffic).  It is also
   possible to use multiple marking points for the same monitored flow.

4.1.  Monitoring Network

   The Monitoring Network is deduced from the Production Network, by
   identifying the nodes of the graph that are the measurement points,
   and the links that are the connections between measurement points.

   There are some techniques that can help with the building of the
   monitoring network (as an example it is possible to mention
   [I-D.amf-ippm-route]).  In general there are different options: the
   monitoring network can be obtained by considering all the possible
   paths for the traffic or also by checking the traffic sometimes and
   update the graph consequently.

   So a graph model of the monitoring network can be built according to
   the alternate marking method: the monitored interfaces and links are
   identified.  Only the measurement points and links where the traffic
   has flowed have to be represented in the graph.

   The following figure shows a simple example of a Monitoring Network
   graph:




























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                                                    +------+
                                                   <>  R6  <>---
                                                  / +------+
                           +------+     +------+ /
                          <>  R2  <>---<>  R4  <>
                         / +------+ \   +------+ \
                        /            \            \ +------+
              +------+ /   +------+   \ +------+   <>  R7  <>---
          ---<>  R1  <>---<>  R3  <>---<>  R5  <>   +------+
              +------+ \   +------+ \   +------+ \
                        \            \            \ +------+
                         \            \            <>  R8  <>---
                          \            \            +------+
                           \            \
                            \            \ +------+
                             \            <>  R9  <>---
                              \            +------+
                               \
                                \ +------+
                                 <>  R10 <>---
                                  +------+



                    Figure 2: Monitoring Network Graph

   Each monitoring point is characterized by the packet counter that
   refers only to a marking period of the monitored flow.

   The same is applicable also for the delay but it will be described in
   the following sections.

5.  Multipoint Packet Loss

   Since all the packets of the considered flow leaving the network have
   previously entered the network, the number of packets counted by all
   the input nodes is always greater or equal than the number of packets
   counted by all the output nodes.

   And in case of no packet loss occurring in the marking period, if all
   the input and output points of the network domain to be monitored are
   measurement points, the sum of the number of packets on all the
   ingress interfaces and on all the egress interfaces is the same.  In
   this circumstance, if no packet loss occurs, the intermediate
   measurement points have only the task to split the measurement.

   It is possible to define the Network Packet Loss (for 1 flow, for 1
   period): <<In a packet network, the number of lost packets is the



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   number of packets counted by the input nodes minus the number of
   packets counted by the output nodes>>.  This is true for every packet
   flow in each marking period.

   The Monitored Network Packet Loss with n input nodes and m output
   nodes is given by:

   PL = (PI1 + PI2 +...+ PIn) - (PO1 + PO2 +...+ POm)

   where:

   PL is the Network Packet Loss (number of lost packets)

   PIi is the Number of packets flowed through the i-th Input node in
   this period

   POj is the Number of packets flowed through the j-th Output node in
   this period

   The equation is applied on a per-time-interval basis.

6.  Network Clustering

   The previous Equation can determine the number of packets lost
   globally in the monitored network, exploiting only the data provided
   by the counters in the input and output nodes.

   In addition it is also possible to leverage the data provided by the
   other counters in the network to converge on the smallest
   identifiable subnetworks where the losses occur.  These subnetworks
   are named Clusters.

   A Cluster graph is a subnetwork of the entire Monitoring Network
   graph that still satisfies the packet loss equation where PL in this
   case is the number of packets lost in the Cluster.

   For this reason a Cluster should contain all the arcs emanating from
   its input nodes and all the arcs terminating at its output nodes.
   This ensures that we can count all the packets (and only those)
   exiting an input node again at the output node, whatever path they
   follow.

   In a completely monitored network (a network where every network
   interface is monitored), each network device corresponds to a Cluster
   and each physical link corresponds to two Clusters (one for each
   direction).





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   Clusters can have different sizes depending on flow filtering
   criteria adopted.

   Moreover, sometimes Clusters can be optionally simplified.  For
   example when two monitored interfaces are divided by a single router
   (one is the input interface and the other is the output interface and
   the router has only these two interfaces), instead of counting
   exactly twice, upon entering and leaving, it is possible to consider
   a single measurement point (in this case we do not care of the
   internal packet loss of the router).

6.1.  Algorithm for Cluster partition

   A simple algorithm can be applied in order to split our monitoring
   network into Clusters.  It is a two-step algorithm:

   o  Group the links where there is the same starting node;

   o  Join the grouped links with at least one ending node in common.

   In our monitoring network graph example it is possible to identify
   the Clusters partition by applying this two-step algorithm.

   The first step identifies the following groups:

   1.  Group 1: (R1-R2), (R1-R3), (R1-R10)

   2.  Group 2: (R2-R4), (R2-R5)

   3.  Group 3: (R3-R5), (R3-R9)

   4.  Group 4: (R4-R6), (R4-R7)

   5.  Group 5: (R5-R8)

   And then, the second step builds the Clusters partition (in
   particular we can underline that Group 2 and Group 3 connect
   together, since R5 is in common):

   1.  Cluster 1: (R1-R2), (R1-R3), (R1-R10)

   2.  Cluster 2: (R2-R4), (R2-R5), (R3-R5), (R3-R9)

   3.  Cluster 3: (R4-R6), (R4-R7)

   4.  Cluster 4: (R5-R8)

   In the end the following 4 Clusters are obtained:



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          Cluster 1
                           +------+
                          <>  R2  <>---
                         / +------+
                        /
              +------+ /   +------+
          ---<>  R1  <>---<>  R3  <>---
              +------+ \   +------+
                        \
                         \
                          \
                           \
                            \
                             \
                              \
                               \
                                \ +------+
                                 <>  R10 <>---
                                  +------+


          Cluster 2
              +------+     +------+
          ---<>  R2  <>---<>  R4  <>---
              +------+ \   +------+
                        \
              +------+   \ +------+
          ---<>  R3  <>---<>  R5  <>---
              +------+ \   +------+
                        \
                         \
                          \
                           \
                            \ +------+
                             <>  R9  <>---
                              +------+


          Cluster 3
                          +------+
                         <>  R6  <>---
                        / +------+
              +------+ /
          ---<>  R4  <>
              +------+ \
                        \ +------+
                         <>  R7  <>---
                          +------+



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          Cluster 4
              +------+
          ---<>  R5  <>
              +------+ \
                        \ +------+
                         <>  R8  <>---
                          +------+



                        Figure 3: Clusters example

   There are Clusters with more than 2 nodes and two-nodes Clusters.  In
   the two-nodes Clusters the loss is on the link (Cluster 4).  In more-
   than-2-nodes Clusters the loss is on the Cluster but we cannot know
   in which link (Cluster 1, 2, 3).

   In this way the calculation of packet loss can be made on Cluster
   basis.  Note that CIR(Committed Information Rate) and EIR(Excess
   Information Rate) can also be deduced on Cluster basis.

   Obviously, by combining some Clusters in a new connected subnetwork
   (called Super Cluster) the Packet Loss Rule is still true.

   In this way in a very large network there is no need to configure
   detailed filter criteria to inspect the traffic.  You can check
   multipoint network and only in case of problems you can go deep with
   a step-by-step cluster analysis, but only for the cluster or
   combination of clusters where the problem happens.

7.  Timing Aspects

   The mark switching approach based on a fixed timer is considered in
   this document.

   So, if we analyze a multipoint-to-multipoint path with more than one
   marking node, it is important to recognize the reference measurement
   interval.  In general the measurement interval for describing the
   results is the interval of the marking node that is more aligned with
   the start of the measurement, as reported in the following figure.











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           time -> start         stop
           T(R1)   |-------------|
           T(R2)     |-------------|
           T(R3)        |------------|


                      Figure 4: Measurement Interval

   T(R1) is the measurement interval and this is essential in order to
   be compatible and make comparison with other active/passive/hybrid
   Packet Loss metrics.

   That is why, when we expand to multipoint-to-multipoint flows, we
   have to consider that all source nodes mark the traffic.

   Regarding the timing aspects of the methodology, RFC 8321 [RFC8321]
   already describes two contributions that are taken into account: the
   clock error between network devices and the network delay between
   measurement points.

   But we should now consider an additional contribution.  Since all
   source nodes mark the traffic, the source measurement intervals can
   be of different lengths and with different offsets and this mismatch
   m can be added to d, as shown in figure.


   ...BBBBBBBBB | AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA | BBBBBBBBB...
                |<======================================>|
                |                   L                    |
   ...=========>|<==================><==================>|<==========...
                |         L/2                L/2         |
                |<=><===>|                      |<===><=>|
                  m   d  |                      |  d   m
                         |<====================>|
                       available counting interval


               Figure 5: Timing Aspects for Multipoint paths

   So the misalignment between the marking source routers gives an
   additional constraint and the value of m is added to d (that already
   includes clock error and network delay).

   In the end, the condition that must be satisfied to enable the method
   to function properly is that the available counting interval must be
   > 0, and that means: L - 2m - 2d > 0 for each measurement point on
   the multipoint path.  Therefore, the mismatch between measurement
   intervals must satisfy this condition.



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8.  Multipoint Delay and Delay Variation

   The same line of reasoning can be applied to Delay and Delay
   Variation.  It is important to highlight that both delay and delay
   variation measurements make sense in a multipoint path.  The Delay
   Variation is calculated by considering the same packets selected for
   measuring the Delay.

   In general, it is possible to perform delay and delay variation
   measurements on multipoint paths basis or on single packets basis:

   o  Delay measurements on multipoint paths basis means that the delay
      value is representative of an entire multipoint path (e.g. whole
      multipoint network, a cluster or a combination of clusters).

   o  Delay measurements on single packets basis means that you can use
      multipoint path just to easily couple packets between inputs and
      output nodes of a multipoint path, as it is described in the
      following sections.

8.1.  Delay measurements on multipoint paths basis

8.1.1.  Single Marking measurement

   Mean delay and mean delay variation measurements can also be
   generalized to the case of multipoint flows.  It is possible to
   compute the average one-way delay of packets, in one block, in a
   cluster or in the entire monitored network.

   The average latency can be measured as the difference between the
   weighted averages of the mean timestamps of the sets of output and
   input nodes.

8.2.  Delay measurements on single packets basis

8.2.1.  Single and Double Marking measurement

   Delay and delay variation measurements relative to only one picked
   packet per period (both single and double marked) can be performed in
   the Multipoint scenario with some limitations:

      Single marking based on the first/last packet of the interval
      would not work, because it would not be possible to agree on the
      first packet of the interval.

      Double marking or multiplexed marking would work, but each
      measurement would only give information about the delay of a
      single path.  However, by repeating the measurement multiple



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      times, it is possible to get information about all the paths in
      the multipoint flow.  This can be done in case of point-to-
      multipoint path but it is more difficult to achieve in case of
      multipoint-to-multipoint path because of the multiple source
      routers.

   if we would perform a delay measurement for more than one picked
   packet in the same marking period and, especially, if we want to get
   delay mesurements on multipoint-to-multipoint basis, both single and
   double marking method are not useful in the Multipoint scenario,
   since they would not be representative of the entire flow.  The
   packets can follow different paths with various delays and in general
   it can be very difficult to recognize marked packets in a multipoint-
   to-multipoint path especially in case they are more than one per
   period.

   A desirable option is to monitor simultaneously all the paths of a
   multipoint path in the same marking period and, for this purpose,
   hashing can be used as reported in the next Section.

8.2.2.  Hashing selection method

   RFC 5474 [RFC5474] and RFC 5475 [RFC5475] introduce sampling and
   filtering techniques for IP Packet Selection.

   The hash-based selection methodologies for delay measurement can work
   in a multipoint-to-multipoint path and can be used both coupled to
   mean delay or stand alone.

   [I-D.mizrahi-ippm-compact-alternate-marking] introduces how to use
   the Hash method combined with alternate marking method for point-to-
   point flows.  It is also called Mixed Hashed Marking: the coupling of
   marking method and hashing technique is very useful because the
   marking batches anchor the samples selected with hashing and this
   simplifies the correlation of the hashing packets along the path.

   It is possible to use a basic hash or a dynamic hash method.  One of
   the challenges of the basic approach is that the frequency of the
   sampled packets may vary considerably.  For this reason the dynamic
   approach has been introduced for point-to-point flow in order to have
   the desired and almost fixed number of samples for each measurement
   period.  In the hash-based sampling, alternate marking is used to
   create periods, so that hash-based samples are divided into batches,
   allowing to anchor the selected samples to their period.  Moreover in
   the dynamic hash-based sampling, by dynamically adapting the length
   of the hash value, the number of samples is bounded in each marking
   period.  This can be realized by choosing the maximum number of
   samples (NMAX) to be catched in a marking period.  The algorithm



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   starts with only few hash bits, that permit to select a greater
   percentage of packets (e.g. with 0 bit of hash all the packets are
   sampled, with 1 bit of hash half of the packets are sampled, and so
   on).  When the number of selected packets reaches NMAX, a hashing bit
   is added.  As a consequence, the sampling proceeds at half of the
   original rate and also the packets already selected that don't match
   the new hash are discarded.  This step can be repeated iteratively.
   It is assumed that each sample includes the timestamp (used for delay
   measurement) and the hash value, allowing the management system to
   match the samples received from the two measurement points.  The
   dynamic process statistically converges at the end of a marking
   period and the final number of selected samples is between NMAX/2 and
   NMAX.  Therefore, the dynamic approach paces the sampling rate,
   allowing to bound the number of sampled packets per sampling period.

   In a multipoint environment the behaviour is similar to point-to
   point flow.  In particular, in the context of multipoint-to-
   multipoint flow, the dynamic hash could be the solution to perform
   delay measurements on specific packets and to overcome the single and
   double marking limitations.

   The management system receives the samples including the timestamps
   and the hash value from all the MPs, and this happens both for point-
   to-point and for multipoint-to-multipoint flow.  Then the longest
   hash used by MPs is deduced and it is applied to couple timestamps of
   same packets of 2 MPs of a point-to-point path or of input and output
   MPs of a Cluster (or a Super Cluster or the entire network).  But
   some considerations are needed: if there isn't packet loss the set of
   input samples is always equal to the set of output samples.  In case
   of packet loss the set of output samples can be a subset of input
   samples but the method still works because, at the end, it is easy to
   couple the input and output timestamps of each catched packet using
   the hash (in particular the "unused part of the hash" that should be
   different for each packet).

   In summary, the basic hash is logically similar to the double marking
   method, and in case of point-to-point path double marking and basic
   hash selection are equivalent.  The dynamic approach scales the
   number of measurements per interval, and it would seem that double
   marking would also work well if we reduced the interval length, but
   this can be done only for point-to-point path and not for multipoint
   path, where we cannot couple the picked packets in a multipoint
   paths.  So, in general, if we want to get delay mesurements on
   multipoint-to-multipoint path basis and want to select more than one
   packet per period, double marking cannot be used because we could not
   be able to couple the picked packets between input and output nodes.
   On the other hand we can do that by using hashing selection.




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9.  An SDN enabled Performance Management

   The Multipoint Alternate Marking framework that is introduced in this
   document adds flexibility to PM because it can reduce the order of
   magnitude of the packet counters.  This allows an SDN Orchestrator to
   supervise, control and manage PM in large networks.

   The monitoring network can be considered as a whole or can be split
   in Clusters, that are the smallest subnetworks (group-to-group
   segments), maintaining the packet loss property for each subnetwork.
   They can also be combined in new connected subnetworks at different
   levels depending on the detail we want to achieve.

   An SDN Controller can calibrate Performance Measurements.  It can
   start without examining in depth.  In case of necessity (packet loss
   is measured or the delay is too high), the filtering criteria could
   be immediately specified more in order to perform a partition of the
   network by using Clusters and/or different combinations of Clusters.
   In this way the problem can be localized in a specific Cluster or in
   a single combination of Clusters and a more detailed analysis can be
   performed step-by-step by successive approximation up to a point-to-
   point flow detailed analysis.

   In addition an SDN Controller could also collect the measurement
   history.

10.  Examples of application

   There are three application fields where it may be useful to take
   into consideration the Multipoint Alternate Marking:

   o  VPN: The IP traffic is selected on IP source basis in both
      directions.  At the end point WAN interface all the output traffic
      is counted in a single flow.  The input traffic is composed by all
      the other flows aggregated for source address.  So, by considering
      n end-points, the monitored flows are n (each flow with 1 ingress
      point and (n-1) egress points) instead of n*(n-1) flows (each
      flow, with 1 ingress point and 1 egress point);

   o  Mobile Backhaul: LTE traffic is selected, in the Up direction, by
      the EnodeB source address and, in Down direction, by the EnodeB
      destination address because the packets are sent from the Mobile
      Packet Core to the EnodeB.  So the monitored flow is only one per
      EnodeB in both directions;

   o  OTT(Over The Top) services: The traffic is selected, in the Down
      direction by the source addresses of the packets sent by OTT
      Servers.  In the opposite direction (Up) by the destination IP



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      addresses of the same Servers.  So the monitoring is based on a
      single flow per OTT Servers in both directions.

11.  Security Considerations

   This document specifies a method to perform measurements that does
   not directly affect Internet security nor applications that run on
   the Internet.  However, implementation of this method must be mindful
   of security and privacy concerns, as explained in RFC 8321 [RFC8321].

12.  Acknowledgements

   The authors would like to thank Al Morton, Tal Mizrahi, Rachel Huang
   for the precious contribution.

13.  IANA Considerations

   tbc

14.  References

14.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5644]  Stephan, E., Liang, L., and A. Morton, "IP Performance
              Metrics (IPPM): Spatial and Multicast", RFC 5644,
              DOI 10.17487/RFC5644, October 2009,
              <https://www.rfc-editor.org/info/rfc5644>.

   [RFC8321]  Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
              L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
              "Alternate-Marking Method for Passive and Hybrid
              Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
              January 2018, <https://www.rfc-editor.org/info/rfc8321>.

14.2.  Informative References

   [I-D.amf-ippm-route]
              Alvarez-Hamelin, J., Morton, A., and J. Fabini, "Advanced
              Unidirectional Route Assessment", draft-amf-ippm-route-01
              (work in progress), October 2017.






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   [I-D.mizrahi-ippm-compact-alternate-marking]
              Mizrahi, T., Arad, C., Fioccola, G., Cociglio, M., Chen,
              M., Zheng, L., and G. Mirsky, "Compact Alternate Marking
              Methods for Passive and Hybrid Performance Monitoring",
              draft-mizrahi-ippm-compact-alternate-marking-01 (work in
              progress), March 2018.

   [RFC5474]  Duffield, N., Ed., Chiou, D., Claise, B., Greenberg, A.,
              Grossglauser, M., and J. Rexford, "A Framework for Packet
              Selection and Reporting", RFC 5474, DOI 10.17487/RFC5474,
              March 2009, <https://www.rfc-editor.org/info/rfc5474>.

   [RFC5475]  Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
              Raspall, "Sampling and Filtering Techniques for IP Packet
              Selection", RFC 5475, DOI 10.17487/RFC5475, March 2009,
              <https://www.rfc-editor.org/info/rfc5475>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

Authors' Addresses

   Giuseppe Fioccola (editor)
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148
   Italy

   Email: giuseppe.fioccola@telecomitalia.it


   Mauro Cociglio
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148
   Italy

   Email: mauro.cociglio@telecomitalia.it










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   Amedeo Sapio
   Politecnico di Torino
   Corso Duca degli Abruzzi, 24
   Torino  10129
   Italy

   Email: amedeo.sapio@polito.it


   Riccardo Sisto
   Politecnico di Torino
   Corso Duca degli Abruzzi, 24
   Torino  10129
   Italy

   Email: riccardo.sisto@polito.it



































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