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RFC 8321


Alternate-Marking Method for Passive and Hybrid Performance Monitoring

Part 2 of 2, p. 18 to 33
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4.  Considerations

   This section highlights some considerations about the methodology.

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4.1.  Synchronization

   The Alternate-Marking technique does not require a strong
   synchronization, especially for packet loss and two-way delay
   measurement.  Only one-way delay measurement requires network devices
   to have synchronized clocks.

   Color switching is the reference for all the network devices, and the
   only requirement to be achieved is that all network devices have to
   recognize the right batch along the path.

   If the length of the measurement period is L time units, then all
   network devices must be synchronized to the same clock reference with
   an accuracy of +/- L/2 time units (without considering network
   delay).  This level of accuracy guarantees that all network devices
   consistently match the color bit to the correct block.  For example,
   if the color is toggled every second (L = 1 second), then clocks must
   be synchronized with an accuracy of +/- 0.5 second to a common time

   This synchronization requirement can be satisfied even with a
   relatively inaccurate synchronization method.  This is true for
   packet loss and two-way delay measurement, but not for one-way delay
   measurement, where clock synchronization must be accurate.

   Therefore, a system that uses only packet loss and two-way delay
   measurement does not require synchronization.  This is because the
   value of the clocks of network devices does not affect the
   computation of the two-way delay measurement.

4.2.  Data Correlation

   Data correlation is the mechanism to compare counters and timestamps
   for packet loss, delay, and delay variation calculation.  It could be
   performed in several ways depending on the Alternate-Marking
   application and use case.  Some possibilities are to:

   o  use a centralized solution using NMS to correlate data; and

   o  define a protocol-based distributed solution by introducing a new
      protocol or by extending the existing protocols (e.g., see RFC
      6374 [RFC6374] or the Two-Way Active Measurement Protocol (TWAMP)
      as defined in RFC 5357 [RFC5357] or the One-Way Active Measurement
      Protocol (OWAMP) as defined in RFC 4656 [RFC4656]) in order to
      communicate the counters and timestamps between nodes.

   In the following paragraphs, an example data correlation mechanism is
   explained and could be used independently of the adopted solutions.

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   When data is collected on the upstream and downstream nodes, e.g.,
   packet counts for packet loss measurement or timestamps for packet
   delay measurement, and is periodically reported to or pulled by other
   nodes or an NMS, a certain data correlation mechanism SHOULD be in
   use to help the nodes or NMS tell whether any two or more packet
   counts are related to the same block of markers or if any two
   timestamps are related to the same marked packet.

   The Alternate-Marking Method described in this document literally
   splits the packets of the measured flow into different measurement
   blocks; in addition, a Block Number (BN) could be assigned to each
   such measurement block.  The BN is generated each time a node reads
   the data (packet counts or timestamps) and is associated with each
   packet count and timestamp reported to or pulled by other nodes or
   NMSs.  The value of a BN could be calculated as the modulo of the
   local time (when the data are read) and the interval of the marking
   time period.

   When the nodes or NMS see, for example, the same BNs associated with
   two packet counts from an upstream and a downstream node,
   respectively, it considers that these two packet counts correspond to
   the same block, i.e., these two packet counts belong to the same
   block of markers from the upstream and downstream nodes.  The
   assumption of this BN mechanism is that the measurement nodes are
   time synchronized.  This requires the measurement nodes to have a
   certain time synchronization capability (e.g., the Network Time
   Protocol (NTP) [RFC5905] or the IEEE 1588 Precision Time Protocol
   (PTP) [IEEE-1588]).  Synchronization aspects are further discussed in
   Section 4.1.

4.3.  Packet Reordering

   Due to ECMP, packet reordering is very common in an IP network.  The
   accuracy of a marking-based PM, especially packet loss measurement,
   may be affected by packet reordering.  Take a look at the following

   Block   :    1    |    2    |    3    |    4    |    5    |...

                        Figure 5: Packet Reordering

   In Figure 5, the packet stream for Node R1 isn't being reordered and
   can be safely assigned to interval blocks, but the packet stream for
   Node R2 is being reordered; so, looking at the packet with the marker

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   of "B" in block 3, there is no safe way to tell whether the packet
   belongs to block 2 or block 4.

   In general, there is the need to assign packets with the marker of
   "B" or "A" to the right interval blocks.  Most of the packet
   reordering occurs at the edge of adjacent blocks, and they are easy
   to handle if the interval of each block is sufficiently large.  Then,
   it can be assumed that the packets with different markers belong to
   the block that they are closer to.  If the interval is small, it is
   difficult and sometimes impossible to determine to which block a
   packet belongs.

   To choose a proper interval is important, and how to choose a proper
   interval is out of the scope of this document.  But an implementation
   SHOULD provide a way to configure the interval and allow a certain
   degree of packet reordering.

5.  Applications, Implementation, and Deployment

   The methodology described in the previous sections can be applied in
   various situations.  Basically, the Alternate-Marking technique could
   be used in many cases for performance measurement.  The only
   requirement is to select and mark the flow to be monitored; in this
   way, packets are batched by the sender, and each batch is alternately
   marked such that it can be easily recognized by the receiver.

   Some recent Alternate-Marking Method applications are listed below:

   o  IP Flow Performance Measurement (IPFPM): this application of the
      marking method is described in [COLORING].  As an example, in this
      document, the last reserved bit of the Flag field of the IPv4
      header is proposed to be used for marking, while a solution for
      IPv6 could be to leverage the IPv6 extension header for marking.

   o  OAM Passive Performance Measurement: In [RFC8296], two OAM bits
      from the Bit Index Explicit Replication (BIER) header are reserved
      for the Passive performance measurement marking method.
      [PM-MM-BIER] details the measurement for multicast service over
      the BIER domain.  In addition, the Alternate-Marking Method could
      also be used in a Service Function Chaining (SFC) domain.  Lastly,
      the application of the marking method to Network Virtualization
      over Layer 3 (NVO3) protocols is considered by [NVO3-ENCAPS].

   o  MPLS Performance Measurement: RFC 6374 [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.  [MPLS-FLOW] discusses the desired capabilities for

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      MPLS flow identification in order to perform a better in-band
      performance monitoring of user data packets.  A method of
      accomplishing identification is Synonymous Flow Labels (SFLs)
      introduced in [SFL-FRAMEWORK], while [SYN-FLOW-LABELS] describes
      performance measurements in RFC 6374 with SFL.

   o  Active Performance Measurement: [ALT-MM-AMP] describes how to
      extend the existing Active Measurement Protocol, in order to
      implement the Alternate-Marking methodology.  [ALT-MM-SLA]
      describes an extension to the Cisco SLA Protocol Measurement-Type

   An example of implementation and deployment is explained in the next
   section, just to clarify how the method can work.

5.1.  Report on the Operational Experiment

   The method described in this document, also called Packet Network
   Performance Monitoring (PNPM), has been invented and engineered in
   Telecom Italia.

   It is important to highlight that the general description of the
   methodology in this document is a consequence of the operational
   experiment.  The fundamental elements of the technique have been
   tested, and the lessons learned from the operational experiment
   inspired the formalization of the Alternate-Marking Method as
   detailed in the previous sections.

   The methodology has been used experimentally in Telecom Italia's
   network and is applied to multicast IPTV channels or other specific
   traffic flows with high QoS requirements (i.e., Mobile Backhauling
   traffic realized with a VPN MPLS).

   This technology has been employed by leveraging functions and tools
   available on IP routers, and it's currently being used to monitor
   packet loss in some portions of Telecom Italia's network.  The
   application of this method for delay measurement has also been
   evaluated in Telecom Italia's labs.

   This section describes how the experiment has been executed,
   particularly, how the features currently available on existing
   routing platforms can be used to apply the method, in order to give
   an example of implementation and deployment.

   The operational test, described herein, uses the flow-based strategy,
   as defined in Section 3.  Instead, the link-based strategy could be
   applied to a physical link or a logical link (e.g., an Ethernet VLAN
   or an MPLS Pseudowire (PW)).

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   The implementation of the method leverages the available router
   functions, since the experiment has been done by a Service Provider
   (as Telecom Italia is) on its own network.  So, with current router
   implementations, only QoS-related fields and features offer the
   required flexibility to set bits in the packet header.  In case a
   Service Provider only uses the three most-significant bits of the
   DSCP field (corresponding to IP Precedence) for QoS classification
   and queuing, it is possible to use the two least-significant bits of
   the DSCP field (bit 0 and bit 1) to implement the method without
   affecting QoS policies.  That is the approach used for the
   experiment.  One of the two bits (bit 0) could be used to identify
   flows subject to traffic monitoring (set to 1 if the flow is under
   monitoring, otherwise, it is set to 0), while the second (bit 1) can
   be used for coloring the traffic (switching between values 0 and 1,
   corresponding to colors A and B) and creating the blocks.

   The experiment considers a flow as all the packets sharing the same
   source IP address or the same destination IP address, depending on
   the direction.  In practice, once the flow has been defined, traffic
   coloring using the DSCP field can be implemented by configuring an
   access-list on the router output interface.  The access-list
   intercepts the flow(s) to be monitored and applies a policy to them
   that sets the DSCP field accordingly.  Since traffic coloring has to
   be switched between the two values over time, the policy needs to be
   modified periodically.  An automatic script is used to perform this
   task on the basis of a fixed timer.  The automatic script is loaded
   on board of the router and automatizes the basic operations that are
   needed to realize the methodology.

   After the traffic is colored using the DSCP field, all the routers on
   the path can perform the counting.  For this purpose, an access-list
   that matches specific DSCP values can be used to count the packets of
   the flow(s) being monitored.  The same access-list can be installed
   on all the routers of the path.  In addition, network flow
   monitoring, such as provided by IPFIX [RFC7011], can be used to
   recognize timestamps of the first/last packet of a batch in order to
   enable one of the alternatives to measure the delay as detailed in
   Section 3.3.

   In Telecom Italia's experiment, the timer is set to 5 minutes, so the
   sequence of actions of the script is also executed every 5 minutes.
   This value has shown to be a good compromise between measurement
   frequency and stability of the measurement (i.e., the possibility of
   collecting all the measures referring to the same block).

   For this experiment, both counters and any other data are collected
   by using the automatic script that sends these out to an NMS.  The
   NMS is responsible for packet loss calculation, performed by

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   comparing the values of counters from the routers along the flow
   path(s).  A 5-minute timer for color switching is a safe choice for
   reading the counters and is also coherent with the reporting window
   of the NMS.

   Note that the use of the DSCP field for marking implies that the
   method in this case works reliably only within a single management
   and operation domain.

   Lastly, the Telecom Italia experiment scales up to 1000 flows
   monitored together on a single router, while an implementation on
   dedicated hardware scales more, but it was tested only in labs for

5.1.1.  Metric Transparency

   Since a Service Provider application is described here, the method
   can be applied to end-to-end services supplied to customers.  So it
   is important to highlight that the method MUST be transparent outside
   the Service Provider domain.

   In Telecom Italia's implementation, the source node colors the
   packets with a policy that is modified periodically via an automatic
   script in order to alternate the DSCP field of the packets.  The
   nodes between source and destination (included) have to use an
   access-list to count the colored packets that they receive and

   Moreover, the destination node has an important role: the colored
   packets are intercepted and a policy restores and sets the DSCP field
   of all the packets to the initial value.  In this way, the metric is
   transparent because outside the section of the network under
   monitoring, the traffic flow is unchanged.

   In such a case, thanks to this restoring technique, network elements
   outside the Alternate-Marking monitoring domain (e.g., the two
   Provider Edge nodes of the Mobile Backhauling VPN MPLS) are totally
   unaware that packets were marked.  So this restoring technique makes
   Alternate Marking completely transparent outside its monitoring

6.  Hybrid Measurement

   The method has been explicitly designed for Passive measurements, but
   it can also be used with Active measurements.  In order to have both
   end-to-end measurements and intermediate measurements (Hybrid
   measurements), two endpoints can exchange artificial traffic flows
   and apply Alternate Marking over these flows.  In the intermediate

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   points, artificial traffic is managed in the same way as real traffic
   and measured as specified before.  So the application of the marking
   method can also simplify the Active measurement, as explained in

7.  Compliance with Guidelines from RFC 6390

   RFC 6390 [RFC6390] defines a framework and a process for developing
   Performance Metrics for protocols above and below the IP layer (such
   as IP-based applications that operate over reliable or datagram
   transport protocols).

   This document doesn't aim to propose a new Performance Metric but
   rather a new Method of Measurement for a few Performance Metrics that
   have already been standardized.  Nevertheless, it's worth applying
   guidelines from [RFC6390] to the present document, in order to
   provide a more complete and coherent description of the proposed
   method.  We used a combination of the Performance Metric Definition
   template defined in Section 5.4 of [RFC6390] and the Dependencies
   laid out in Section 5.5 of that document.

   o  Metric Name / Metric Description: as already stated, this document
      doesn't propose any new Performance Metrics.  On the contrary, it
      describes a novel method for measuring packet loss [RFC7680].  The
      same concept, with small differences, can also be used to measure
      delay [RFC7679] and jitter [RFC3393].  The document mainly
      describes the applicability to packet loss measurement.

   o  Method of Measurement or Calculation: according to the method
      described in the previous sections, the number of packets lost is
      calculated by subtracting the value of the counter on the source
      node from the value of the counter on the destination node.  Both
      counters must refer to the same color.  The calculation is
      performed when the value of the counters is in a steady state.
      The steady state is an intrinsic characteristic of the marking
      method counters because the alternation of color makes the
      counters associated with each color still one at a time for the
      duration of a marking period.

   o  Units of Measurement: the method calculates and reports the exact
      number of packets sent by the source node and not received by the
      destination node.

   o  Measurement Point(s) with Potential Measurement Domain: the
      measurement can be performed between adjacent nodes, on a per-link
      basis, or along a multi-hop path, provided that the traffic under
      measurement follows that path.  In case of a multi-hop path, the
      measurements can be performed both end-to-end and hop-by-hop.

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   o  Measurement Timing: the method has a constraint on the frequency
      of measurements.  This is detailed in Section 3.2, where it is
      specified that the marking period and the guard band interval are
      strictly related each other to avoid out-of-order issues.  That is
      because, in order to perform a measurement, the counter must be in
      a steady state, and this happens when the traffic is being colored
      with the alternate color.  As an example, in the experiment of the
      method, the time interval is set to 5 minutes, while other
      optimized implementations can also use a marking period of a few

   o  Implementation: the experiment of the method uses two encodings of
      the DSCP field to color the packets; this enables the use of
      policy configurations on the router to color the packets and
      accordingly configure the counter for each color.  The path
      followed by traffic being measured should be known in advance in
      order to configure the counters along the path and be able to
      compare the correct values.

   o  Verification: both in the lab and in the operational network, the
      methodology has been tested and experimented for packet loss and
      delay measurements by using traffic generators together with
      precision test instruments and network emulators.

   o  Use and Applications: the method can be used to measure packet
      loss with high precision on live traffic; moreover, by combining
      end-to-end and per-link measurements, the method is useful to
      pinpoint the single link that is experiencing loss events.

   o  Reporting Model: the value of the counters has to be sent to a
      centralized management system that performs the calculations; such
      samples must contain a reference to the time interval they refer
      to, so that the management system can perform the correct
      correlation; the samples have to be sent while the corresponding
      counter is in a steady state (within a time interval); otherwise,
      the value of the sample should be stored locally.

   o  Dependencies: the values of the counters have to be correlated to
      the time interval they refer to; moreover, because the experiment
      of the method is based on DSCP values, there are significant
      dependencies on the usage of the DSCP field: it must be possible
      to rely on unused DSCP values without affecting QoS-related
      configuration and behavior; moreover, the intermediate nodes must
      not change the value of the DSCP field not to alter the

   o  Organization of Results: the Method of Measurement produces

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   o  Parameters: currently, the main parameter of the method is the
      time interval used to alternate the colors and read the counters.

8.  IANA Considerations

   This document has no IANA actions.

9.  Security Considerations

   This document specifies a method to perform measurements in the
   context of a Service Provider's network and has not been developed to
   conduct Internet measurements, so it 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.

   There are two types of security concerns: potential harm caused by
   the measurements and potential harm to the measurements.

   o  Harm caused by the measurement: the measurements described in this
      document are Passive, so there are no new packets injected into
      the network causing potential harm to the network itself and to
      data traffic.  Nevertheless, the method implies modifications on
      the fly to a header or encapsulation of the data packets: this
      must be performed in a way that doesn't alter the quality of
      service experienced by packets subject to measurements and that
      preserves stability and performance of routers doing the
      measurements.  One of the main security threats in OAM protocols
      is network reconnaissance; an attacker can gather information
      about the network performance by passively eavesdropping on OAM
      messages.  The advantage of the methods described in this document
      is that the marking bits are the only information that is
      exchanged between the network devices.  Therefore, Passive
      eavesdropping on data-plane traffic does not allow attackers to
      gain information about the network performance.

   o  Harm to the Measurement: the measurements could be harmed by
      routers altering the marking of the packets or by an attacker
      injecting artificial traffic.  Authentication techniques, such as
      digital signatures, may be used where appropriate to guard against
      injected traffic attacks.  Since the measurement itself may be
      affected by routers (or other network devices) along the path of
      IP packets intentionally altering the value of marking bits of
      packets, as mentioned above, the mechanism specified in this
      document can be applied just in the context of a controlled
      domain; thus, the routers (or other network devices) are locally
      administered and this type of attack can be avoided.  In addition,
      an attacker can't gain information about network performance from

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      a single monitoring point; it must use synchronized monitoring
      points at multiple points on the path, because they have to do the
      same kind of measurement and aggregation that Service Providers
      using Alternate Marking must do.

   The privacy concerns of network measurement are limited because the
   method only relies on information contained in the header or
   encapsulation without any release of user data.  Although information
   in the header or encapsulation is metadata that can be used to
   compromise the privacy of users, the limited marking technique in
   this document seems unlikely to substantially increase the existing
   privacy risks from header or encapsulation metadata.  It might be
   theoretically possible to modulate the marking to serve as a covert
   channel, but it would have a very low data rate if it is to avoid
   adversely affecting the measurement systems that monitor the marking.

   Delay attacks are another potential threat in the context of this
   document.  Delay measurement is performed using a specific packet in
   each block, marked by a dedicated color bit.  Therefore, a
   man-in-the-middle attacker can selectively induce synthetic delay
   only to delay-colored packets, causing systematic error in the delay
   measurements.  As discussed in previous sections, the methods
   described in this document rely on an underlying time synchronization
   protocol.  Thus, by attacking the time protocol, an attacker can
   potentially compromise the integrity of the measurement.  A detailed
   discussion about the threats against time protocols and how to
   mitigate them is presented in RFC 7384 [RFC7384].

10.  References

10.1.  Normative References

              IEEE, "IEEE Standard for a Precision Clock Synchronization
              Protocol for Networked Measurement and Control Systems",
              IEEE Std 1588-2008.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393,
              DOI 10.17487/RFC3393, November 2002,

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   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,

   [RFC7679]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Delay Metric for IP Performance Metrics
              (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
              2016, <>.

   [RFC7680]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Loss Metric for IP Performance Metrics
              (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
              2016, <>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

10.2.  Informative References

              Fioccola, G., Clemm, A., Bryant, S., Cociglio, M.,
              Chandramouli, M., and A. Capello, "Alternate Marking
              Extension to Active Measurement Protocol", Work in
              Progress, draft-fioccola-ippm-alt-mark-active-01, March

              Fioccola, G., Clemm, A., Cociglio, M., Chandramouli, M.,
              and A. Capello, "Alternate Marking Extension to Cisco SLA
              Protocol RFC6812", Work in Progress, draft-fioccola-ippm-
              rfc6812-alt-mark-ext-01, March 2016.

   [COLORING] Chen, M., Zheng, L., Mirsky, G., Fioccola, G., and T.
              Mizrahi, "IP Flow Performance Measurement Framework", Work
              in Progress, draft-chen-ippm-coloring-based-ipfpm-
              framework-06, March 2016.

              Chen, M., Zheng, L., and G. Mirsky, "IP Flow Performance
              Measurement Report", Work in Progress, draft-chen-ippm-
              ipfpm-report-01, April 2016.

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              Cociglio, M., Capello, A., Bonda, A., and L. Castaldelli,
              "A method for IP multicast performance monitoring", Work
              in Progress, draft-cociglio-mboned-multicast-pm-01,
              October 2010.

              Bryant, S., Pignataro, C., Chen, M., Li, Z., and G.
              Mirsky, "MPLS Flow Identification Considerations", Work in
              Progress, draft-ietf-mpls-flow-ident-06, December 2017.

              Fioccola, G., Cociglio, M., Sapio, A., and R. Sisto,
              "Multipoint Alternate Marking method for passive and
              hybrid performance monitoring", Work in Progress,
              draft-fioccola-ippm-multipoint-alt-mark-01, October 2017.

              Boutros, S., Ganga, I., Garg, P., Manur, R., Mizrahi, T.,
              Mozes, D., Nordmark, E., Smith, M., Aldrin, S., and I.
              Bagdonas, "NVO3 Encapsulation Considerations", Work in
              Progress, draft-ietf-nvo3-encap-01, October 2017.

              Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda,
              "A packet based method for passive performance
              monitoring", Work in Progress, draft-tempia-opsawg-p3m-04,
              February 2014.

              Mirsky, G., Zheng, L., Chen, M., and G. Fioccola,
              "Performance Measurement (PM) with Marking Method in Bit
              Index Explicit Replication (BIER) Layer", Work in
              Progress, draft-ietf-bier-pmmm-oam-03, October 2017.

   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, DOI 10.17487/RFC5357, October 2008,

   [RFC5481]  Morton, A. and B. Claise, "Packet Delay Variation
              Applicability Statement", RFC 5481, DOI 10.17487/RFC5481,
              March 2009, <>.

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   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,

   [RFC6390]  Clark, A. and B. Claise, "Guidelines for Considering New
              Performance Metric Development", BCP 170, RFC 6390,
              DOI 10.17487/RFC6390, October 2011,

   [RFC6703]  Morton, A., Ramachandran, G., and G. Maguluri, "Reporting
              IP Network Performance Metrics: Different Points of View",
              RFC 6703, DOI 10.17487/RFC6703, August 2012,

   [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,

   [RFC7276]  Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
              Weingarten, "An Overview of Operations, Administration,
              and Maintenance (OAM) Tools", RFC 7276,
              DOI 10.17487/RFC7276, June 2014,

   [RFC7384]  Mizrahi, T., "Security Requirements of Time Protocols in
              Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
              October 2014, <>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <>.

   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <>.

              Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S.,
              and G. Mirsky, "Synonymous Flow Label Framework", Work in
              Progress, draft-ietf-mpls-sfl-framework-00, August 2017.

Top      Up      ToC       Page 32 
              Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S.,
              Mirsky, G., and G. Fioccola, "RFC6374 Synonymous Flow
              Labels", Work in Progress, draft-ietf-mpls-rfc6374-sfl-01,
              December 2017.


   The previous IETF specifications describing this technique were:

   The authors would like to thank Alberto Tempia Bonda, Domenico
   Laforgia, Daniele Accetta, and Mario Bianchetti for their
   contribution to the definition and the implementation of the method.

   The authors would also thank Spencer Dawkins, Carlos Pignataro, Brian
   Haberman, and Eric Vyncke for their assistance and their detailed and
   precious reviews.

Authors' Addresses

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


   Alessandro Capello
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148


   Mauro Cociglio
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148


Top      Up      ToC       Page 33 
   Luca Castaldelli
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148


   Mach(Guoyi) Chen
   Huawei Technologies


   Lianshu Zheng
   Huawei Technologies


   Greg Mirsky
   United States of America


   Tal Mizrahi
   6 Hamada St.