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Versions: (draft-browne-sfc-nsh-timestamp) 00 01 02

Network Working Group                                          R. Browne
Internet Draft                                               A. Chilikin
Intended status: Standards Track                                   Intel
Expires: February 2018                                        T. Mizrahi
                                                                 Marvell
                                                         August 31, 2017


                    Network Service Header KPI Stamping
                   draft-browne-sfc-nsh-kpi-stamp-02.txt


Abstract

   This draft describes a method of inserting Key Performance Indicators
   (KPIs) into Network Service Header (NSH) encapsulated packets or
   frames on service chains. This method may be used to monitor latency
   and QoS configuration to identify problems with virtual links
   (vlinks), Virtual Network Functions (VNFs) or Physical Network
   Functions (PNFs) on the Rendered Service Path (RSP).

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on February 28, 2018.

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. Terminology....................................................3
      2.1. Requirement Language......................................3
      2.2. Definition of Terms.......................................3
      2.3. Abbreviations.............................................5
   3. NSH KPI Stamping...............................................6
      3.1. Prerequisites.............................................8
      3.2. Operation................................................10
         3.2.1. Flow Selection......................................11
         3.2.2. SCP Interface.......................................11
      3.3. Performance Considerations...............................12
   4. NSH KPIStamping Encapsulation.................................13
      4.1. KPIstamping Encapsulation (Detection Mode)...............13
      4.2. NSH Timestamping Encapsulation (Extended Mode)...........16
      4.3. NSH QoS Stamping Encapsulation (Extended Mode)...........19
   5. Hybrid Models.................................................22
      5.1. Targeted VNF Stamp.......................................23
   6. Fragmentation Considerations..................................23
   7. Security Considerations.......................................24
   8. Open Items for WG Discussion..................................24
   9. IANA Considerations...........................................25
   10. Contributors.................................................25
   11. Acknowledgments..............................................25
   12. References...................................................26
      12.1. Normative References....................................26
      12.2. Informative References..................................26

1. Introduction

   Network Service Header (NSH), as defined by [NSH], defines a method
   to insert a service-aware header in between payload and transport
   headers. This allows a great deal of flexibility and programmability
   in the forwarding plane allowing user flows to be programmed on-the-
   fly for the appropriate Service Functions (SFs).


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   Whilst NSH promises a compelling vista of operational agility for
   Service Providers, many service providers are concerned about losing
   service and configuration visibility in the transition from physical
   appliance SFs to virtualized SFs running in the Network Function
   Virtualization (NFV) domain. This concern increases when we consider
   that many service providers wish to run their networks seamlessly in
   'hybrid' mode, whereby they wish to mix physical and virtual SFs and
   run services seamlessly between the two domains.

   This draft describes a generic method to monitor and debug service
   chains in terms of application latency and QoS configuration of the
   flows within a service chain. This method is compliant with hybrid
   architectures in which VNFs and PNFs are freely mixed in the service
   chain. This method also is flexible to monitor the performance and
   configuration of an entire chain or part thereof as desired. Please
   refer to [NSH] as background architecture for the method described in
   this document.

   In particular, this draft proposes mechanisms to detect and debug
   performance issues based on timestamping flows within a chain and to
   detect and debug QoS configuration on the chain. The method described
   here is easily extensible to monitoring other KPIs also.

   The method described in this draft is not an OAM protocol like
   [Y.1731] or [Y.1564] for example. As such it does not define new OAM
   packet types or operation. Rather it monitors the service chain
   performance and configuration for subscriber payloads and indicates
   subscriber QoE rather than out-of-band infrastructure metrics.

2. Terminology

2.1. Requirement 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 [RFC2119].

2.2. Definition of Terms

   Classification: Locally instantiated policy and
   customer/network/service profile matching of traffic flows for
   identification of appropriate outbound forwarding actions.

   First Stamping Node (FSN): Mark packets correctly. Must understand 5
   tuple information in order to match Stamping Controller flow table.




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   Last Stamping Node (LSN): Reads all MD & export to system performance
   statistics agent or repository. Should also send NSH header - the
   Service Index (SI) will indicate if a PNF(s) was at the end of the
   chain. The LSN changes the SPI in order that the underlay routes the
   metadata back directly to the KPI database (KPIDB).

   Network Node/Element:  Device that forwards packets or frames based
   on outer header information. In most cases is not aware of the
   presence of NSH.

   Network Overlay:  Logical network built on top of existing network
   (the underlay).  Packets are encapsulated or tunneled to create the
   overlay network topology.

   Network Service Header:  Data plane header added to frames/packets.
   The header contains information required for service chaining, as
   well as metadata added and consumed by network nodes and service
   elements.

   NSH Proxy:  Acts as a gateway: removes and inserts SH on behalf of a
   service function that is not NSH aware.

   Service Classifier:  Function that performs classification and
   imposes an NSH.  Creates a service path.  Non-initial (i.e.
   subsequent) classification can occur as needed and can alter, or
   create a new service path.

   Service Function (SF):  A function that is responsible for specific
   treatment of received packets.  A service function can act at the
   network layer or other OSI layers.  A service function can be virtual
   instance or be embedded in a physical network element. One of
   multiple service functions can be embedded in the same network
   element. Multiple instances of the service function can be enabled in
   the same administrative domain.

   Service Function Chain (SFC):  A service function chain defines an
   ordered set of service functions that must be applied to packets
   and/or frames selected as a result of classification. The implied
   order may not be a linear progression as the architecture allows for
   nodes that copy to more than one branch.  The term service chain is
   often used as shorthand for service function chain.

   Service Function Path (SFP):  The instantiation of a SFC in the
   network. Packets follow a service function path from a classifier
   through the requisite service functions.




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   Stamping Controller SC: The SC may be part of the service chaining
   application, SDN controller, NFVO or any MANO entity. For clarity we
   define the SC separately here as the central logic that decides what
   packets to stamp and how. The SC instructs the classifier on how to
   build the NSH header.

   Stamp Control Plane (SCP): the control plane between the FSN and the
   SC.

   Key Performance Indicator Database (KPIDB): external storage of
   Metadata for reporting, trend analysis etc.



2.3. Abbreviations

   DEI      Drop Eligible Indicator

   DSCP     Differentiated Services Code Point

   FSN      First Stamping Node

   KPI      Key Performance Indicator

   KPIDB    Key Performance Indicator Database

   LSN      Last Stamping Node

   MD       Metadata

   NFV      Network Function Virtualization

   NFVI-PoP NFV Infrastructure Point of Presence

   NIC      Network Interface Card

   NSH      Network Service Header

   OAM      Operations, Administration, and Maintenance

   PCP      Priority Code Point

   PNF      Physical Network Function

   PNFN     Physical Network Function Node

   QoE      Quality of Experience


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   QoS      Quality of Service

   QS       QoS Stamp

   RSP      Rendered Service Path

   SC       Stamping Controller

   SCL      Service Classifier

   SCP      Stamp Control Plane

   SI       Service Index

   SF       Service Function

   SFC      Service Function Chain

   SFN      Service Function Node

   SFP      Service Function Path

   SSI      Stamp Service Index

   TC       Traffic Class

   TS       Timestamp

   VLAN     Virtual Local Area Network

   VNF      Virtual Network Function

   vSwitch  Virtual Switch



3. NSH KPI Stamping

   A typical KPI stamping architecture is presented in Figure 1.










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       Stamping
      Controller
         |                                                     KPIDB
         | SCP Interface                                        |
       ,---.             ,---.              ,---.              ,---.
      /     \           /     \            /     \            /     \
     (  SCL  )-------->(  SF1  )--------->(  SF2  )--------->(  SFN  )
      \ FSN /           \     /            \     /            \ LSN /
       `---'             `---'              `---'              `---'
                Figure 1: Logical roles in NSH KPI Stamping

   The Stamping Controller (SC) will most probably be part of the SFC
   controller but is explained separately in this document for clarity.
   The SC is responsible for initiating start/stop stamp requests to the
   SCL or FSN, and also for distributing NSH stamping policy into the
   service chain via the Stamping Control Plane (SCP) interface.

   The First Stamp Node (FSN) will typically be part of the SCL but
   again is called out as separate logical entity for clarity. The FSN
   is responsible for marking NSH MD fields for the correct flow with
   the appropriate NSH fields. This tells all upstream nodes how to
   behave in terms of stamping at VNF ingress, egress or both, or
   ignoring the stamp NSH metadata completely. The FSN also writes the
   Reference Time value, a (possibly inaccurate) estimate of the current
   time-of-day, into the header, allowing the {chain:flow} performance
   to be compared to previous samples for offline analysis. The FSN
   should return an error to the SC if not synchronized to the current
   time-of-day and forward the packet along the service-chain unchanged.

   SF1, SF2 stamp the packets as dictated by the FSN and process the
   payload as per normal.

   Note 1: The exact location of the stamp creation may not be in
           the VNF itself, as referenced in Section 3.3.

   Note 2: Special cases exist where some of the SFs (PNFs or VNFs) are
           NSH-unaware. This is covered in Section 5.

   The Last Stamp Node (LSN) should strip the entire header and forward
   the raw packet to the IP next hop. The LSN also exports NSH stamp
   information to the KPI Database (KPIDB) for offline analysis; the LSN
   may either export the stamping information of all packets, or a
   subset based on packet sampling. In fully virtualized environments
   the LSN will be co-located with the VNF that decrements the NSH




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   Service Index to zero. Corner cases exist whereby this is not the
   case and is covered in section 5.



3.1. Prerequisites

   Timestamping presents a set of prerequisites not required to QoS-
   Stamp. In order to guarantee metadata accuracy, all servers hosting
   VNFs should be synchronized from a centralized stable clock. As it is
   assumed that PNFs do not timestamp there is no need for them to
   synchronize. There are two possible levels of synchronization:

   Level A: Low accuracy time-of-day synchronization, based on
            NTP [RFC5905].

   Level B: High accuracy synchronization (typically on the order of
            microseconds), based on [IEEE1588].

   Each platform SHOULD have a level A synchronization, and MAY have a
   level B synchronization.

   Level A requires each platform (including the Stamp Controller) to
   synchronize its system real-time-clock to an NTP server. This is used
   to mark the metadata in the chain, using the <Reference Time> field
   in the NSH KPIstamp header (Section 4.2). This timestamp is written
   to the NSH header by the first SF in the chain. NTP accuracy can vary
   by several milliseconds between locations. This is not an issue as
   the Reference Time is merely being used as a reference inserted into
   the KPIDB for performance monitoring.

   Level B synchronization requires each platform to be synchronized to
   a Primary Reference Clock (PRC) using the Precision Time Protocol
   [IEEE1588]. A platform MAY also use Synchronous Ethernet ([G.8261],
   [G.8262], [G.8264]), allowing more accurate frequency
   synchronization.

   If a SF is not synchronized at the moment of timestamping, it should
   indicate synch status in the NSH header. This is described in more
   detail in section 4.

   By synchronizing the network in this way, the timestamping operation
   is independent of the current RSP, whether the entire chain is served
   by one NFVI-PoP or by multiple. Indeed the timestamp MD can indicate
   where a chain has been moved due to a resource starvation event as
   indicated in 0 below, between VNF 3 and VNF 4 at time B.



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   Delay
    |                                  v
    |                           v
    |                                  x
    |                           x            x = reference time A
    |                    xv                  v = reference time B
    |             xv
    |      xv
    |______|______|______|______|______|_____
          VNF1   VNF2  VNF3   VNF4    VNF5

               Figure 2: Flow performance in a service chain



   For QoS Stamping it is desired that the SCL or FSN be synchronized in
   order to provide reference time for offline analysis, but this is not
   a hard requirement (they may be in holdover or free-run state for
   example). Subsequent upstream platforms do not need to be
   synchronized for QoS Stamping operation as described below

   QoS stamping can be used to check consistency of configuration across
   the entire chain or part thereof. This will allow quick
   identification of QoS mismatches across multiple L2/L3 fields which
   otherwise is a manual, expert-led consuming process.



    |
    |
    |                                  xy
    |                           xy           x = ingress QoS sum
    |                    xv                  v = egress QoS sum
    |             xv                         y = egress QoS sum miss
    |      xv
    |______|______|______|______|______|_____
          VNF1   VNF2  VNF3   VNF4    VNF5

             Figure 3: Flow QoS Consistency in a service chain





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   Referring to figure 3 above, x, v and y are notional sum values of
   the QoS configuration of the flow within a given chain. As the
   encapsulation of the flow can change from hop to hop in terms of VLAN
   header(s), MPLS labels, DSCP(s) these values are used to compare
   consistency of configuration from for example payload DSCP through
   overlay and underlay QoS settings in VLAN IEEE 802.1Q bits, TC MPLS
   bits and infrastructure DSCPs.

   The above figure indicates that at VNF4 in the chain, the egress QoS
   marking is inconsistent. That is, the ingress QoS settings does not
   match the egress. The method described here will indicate which QoS
   field(s) is inconsistent, and whether this is ingress (whereby the
   underlay has incorrectly marked and queued the packet) or egress
   (where the VNF has incorrectly marked and queued the packet.



3.2. Operation



   KPIstamping detection mode uses MD type 2. This involves the SFC
   classifier stamping the flow at chain ingress, and no subsequent
   stamps being applied, rather each VNF upstream can compare its local
   condition with the ingress value and take appropriate action.
   Therefore detection mode is very efficient in terms of header size
   that does not grow after the classification. This is further
   explained in section 4.1.

   Section 3.5 of [NSH] (draft-ietf-sfc-nsh-10) defines NSH metadata
   type 2 encapsulation as per the figure below In KPIstamped detection
   and extended mode, flows will use this format.

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Ver|O|C|R|R|R|R|R|R|   Length  |  MD-type=0x2  | Next Protocol |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Service Path ID                      | Service Index |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           MD Class            |C|    Type     |R|     Len     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Variable Metadata                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   Figure 5: NSH MD type 2 Encapsulation


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3.2.1. Flow Selection

   The SC should maintain a list of flows within each service chain to
   be monitored. This flow table should be in the format SPI:5 tuple ID.
   The SC should map these pairs to unique Flow IDs per service chain
   within the extended NSH header specified in this draft. The SC should
   instruct the FSN to initiate timestamping on flow table match. The SC
   may also tell the classifier the duration of the timestamping
   operation, either by a number of packets in the flow or by a time
   duration.

   In this way the system can monitor the performance of the all en-
   route traffic, or an individual subscriber in a chain, or just a
   specific application or QoS class the subscriber is running.

   The SC should write the list of monitored flows into the KPIDB for
   correlation of performance and configuration data. Thus, when the
   KPIDB receives data from the LSN it understands to which flow the
   data pertains.

   The association of source IP to subscriber identity is outside the
   scope of this draft and will vary by network application. For
   example, the method of association of a source IP to IMSI in mobile
   cores will be different to how a CPE with NAT function may be chained
   in an enterprise NFV application.

3.2.2. SCP Interface

   A new Stamp control plane (SCP) interface is required between the SC
   and the FSN or classifier. This interface:

   o     Queries the SFC classifier for a list of active chains and
      flows

   o     Communicates which chains and flows to stamp. This can be a
      specific {chain:flow} combination or include wildcards for
      monitoring subscribers across multiple chains or multiple flows
      within one chain.

   o     How the stamp should be applied (ingress, egress, both or
      specific).






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   o     Typically SCP timestamps flows for a certain duration for trend
      analysis, but only stamps one packet of each QoS class in a chain
      periodically (perhaps once per day or after a network change).
      Therefore timestamping is generally applied to a much larger set
      of packets than QoS stamping

   o     When to stop stamping, either after a certain number of packets
      or duration.

   Exact specification of SCP is for further study.

3.3. Performance Considerations

   This draft does not mandate a specific stamping implementation
   method, and thus NSH KPI stamping can either be performed by hardware
   mechanisms, or by software. If software-based stamping is used,
   applying and operating on the stamps themselves incur an additional
   small delay in the service chain. However, it can be assumed that
   these additional delays are all relative for the flow in question.
   This is only pertinent for timestamping mode, and not for QoS
   stamping mode. Thus, whist the absolute timestamps may not be fully
   accurate for normal non-timestamped traffic they can be assumed to be
   relative.

   It is assumed that the method described in this document would only
   operate on a small percentage of user flows. The service provider may
   choose a flexible policy in the SC to timestamp a selection of user-
   plane every minute for example to highlight any performance issues.
   Alternatively, the LSN may selectively export a subset of the
   KPIstamps it receives, based on a predefined sampling method. Of
   course the SC can stress test an individual flow or chain should a
   deeper analysis be required. We can expect that this type of deep
   analysis has an impact on the performance of the chain itself whilst
   under investigation. The impact will be dependent on vendor
   implementation and outside the scope of this document.

   For QoS stamping the method described here is even less intrusive, as
   you would not typically need to QoS stamp multiple packets in a flow
   rather periodically (perhaps once per day) check one packet in a
   chain per QoS class.

   The KPIstamp may be applied at various parts of the NFV architecture.
   The VNF, hypervisor, vSwitch or NIC are all potential locations that
   can append the packet with the requested KPIstamp. Whilst it is
   desirable to stamp as close as possible to the VNF for accuracy, the
   exact location of the stamp application is outside the scope of this
   document, but should be consistent across the individual SC domain.


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4. NSH KPIStamping Encapsulation



   KPI stamping uses NSH MD type 0x02 for detection of anomalies and
   extended mode for root cause analysis of KPI violations. These are
   further explained in this section.



4.1. KPIstamping Encapsulation (Detection Mode)



   The generic NSH MD type 2 allocation for KPI Stamping (detection
   mode) is shown below. This is the format we propose for KPI anomaly
   detection.



     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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ver|O|C|R|R|R|R|R|R|   Length  |  MD type=0x2  | Next Protocol |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Service Path Identifier              | Service Index |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    MD  Class=KPI Monitoring   |C| Type=TSD    |R|     Len     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |C|     KPIType  |      SI      |           Flow ID             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |                      Threshold KPI Value                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       Ingress KPIStamp                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        Figure 6: Generic NSH KPI Encapsulation (Detection Mode)




   Relevant fields in header that the FSN must implement:


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   o     The O bit should not be set as we are operating on subscriber
      packets

   o     The C bit should be set indicating critical metadata exists

   o     The MD type must be set to 0x2

   o     The MD Class must be set to 0x0210 (General KPI Monitoring) as
      requested in Section 9. The stamp type is defined as per below:

       o Type = 0x00 Reserved.

       o Type = 0x01 Timestamp Detection

   o     The MSB of the Type field must be set to zero. Thus if a
      receiver along the path does not understand the KPIstamping
      protocol it will pass the packet transparently and not drop. This
      scheme allows for extensibility to the mechanism described in this
      document to other KPI collections and operations.

   In the first header the SFC classifier may program a KPI threshold
   value. This is a value that when exceeded, requires the SF to set the
   C bit and insert the current SI value into the SI field. The KPI type
   is the type of KPI stamp inserted into the header as per section 9.

   The flow ID is inserted into the header by the SFC classifier in
   order to correlate flow data in the KPIDB for offline analysis. The
   last two mandatory context headers are reserved for the KPIStamp.
   This is the KPI value at the chain ingress at the SFC classifier.

   As an example operation, say we are using KPI type 0x01 (timestamp)
   when a service function (SFn) receives the packet it can compare
   current local timestamp (it first checks that it is synchronized to
   network PRC) with chain ingress timestamp to calculate the latency in
   the chain. If this value exceeds the timestamp threshold, it then
   sets the C bit inserts its SI and returns the NSH header to the
   KPIDB. This effectively tells the system that at SFn the packet
   violated the KPI threshold. All subsequent upstream SFs perform no
   NSH KPI operation as the flow has already been marked in violation
   via the C bit. Please refer to figure 9 for timestamp format.

   When this occurs the SFC control plane system would then invoke the
   KPI extended mode, which uses a more sophisticated (and intrusive)
   method to isolate KPI violation root cause as described below.

   Note: Whilst detection mode is a valuable tool for latency actions,
   we feel that it is not justified to build the logic into the KPI


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   system for QoS configuration. As QoS stamping is done infrequently
   and on a tiny percentage of user plane, it is more practical to use
   extended mode only for service chain QoS verification.

   The generic NSH MD type 2 KPI Stamping header extended mode is shown
   below. This is the format we propose for performance monitoring of
   service chain issues with respect to QoS configuration and latency.



    0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ver|O|C|R|R|R|R|R|R|   Length  |  MD type=0x2  |   NextProto   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Service Path ID                      | Service Index |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    MD  Class=KPI Monitoring   |C| Type=KPI    |R|     Len     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |I|E|T|R|R|R|SSI| Service Index |           Flow ID             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Reference Time                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |I|E|K|K|K|K|K|K|                Reserved                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        KPI Value (LSN)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |I|E|K|K|K|K|K|K|                Reserved                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        KPI Value (FSN)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 7: Generic KPI Encapsulation (Extended Mode)



   As per section 9, we propose a new MD class 0x0210 to indicate KPI
   MD. Within this class we define 2 types for QoS and timestamp MD to
   be reported along the service chain. The K bits are KPI specific
   bits, for example, SYN for timestamping.




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4.2. NSH Timestamping Encapsulation (Extended Mode)

   The NSH timestamping encapsulation 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Ver|O|C|R|R|R|R|R|R|   Length  |  MD-type=0x2  |   NextProto   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Service Path ID                      | Service Index |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    MD  Class=KPI Monitoring   |C| Type=TS     |R|     Len     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |I|E|T|R|R|R|SSI| Service Index |           Flow ID             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |              Reference Time (T bit is set)                    |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |I|E|R|R|R| Syn | Service Index |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |             Ingress Timestamp (I bit is set)(LSN)             |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              Egress Timestamp (E bit is set)(LSN)             |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |I|E|R|R|R| Syn | Service Index |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |                 Ingress Timestamp (I bit is set)  (FSN)       |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Egress Timestamp (E bit is set)  (FSN)        |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 8: NSH Timestamp Encapsulation (Extended Mode)




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   Relevant fields in header that the FSN must implement:

   o     The O bit should not be set as we are operating on subscriber
      packets

   o     The C bit should be set indicating critical metadata exists

   o     The MD type must be set to 0x2

   o     The MD Class must be set to 0x0210 (General KPI Monitoring) as
      requested in Section 9. The stamp type is defined as per below:

       o Type = 0x00 Reserved

       o Type = 0x01 Timestamp Detection

       o Type = 0x02 Timestamp Extended

       o Type = 0x03 QoSStamp Extended

       o Type = 0x04 to 0x7F: Experimental

   o     The MSB of the Type field must be set to zero. Thus if a
      receiver along the path does not understand the KPIstamping
      protocol it will pass the packet transparently and not drop. This
      scheme allows for extensibility to the mechanism described in this
      document to other KPI collections and operations.

   The FSN KPIstamp metadata starts with Stamping Configuration Header.
   This header contains the Stamp Service Index (SSI) field which must
   be set to one of the following values:

   o     0x0 KPIstamp mode, no Service index specified in the Stamp
      Service Index field.

   o     0x1 KPIUstamp Hybrid mode is selected, Stamp Service Index
      contains LSN Service index. This is used when PNFs or NSH-unaware
      SFs are used at the tail of the chain. If SSI=0x1, then the value
      in the type field informs the chain which SF should act as the
      LSN.









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   o     0x2 KPIstamp Specific mode is selected, Stamp Service Index
      contains the targeted Service Index. In this case the Stamp
      Service Index field indicates which SF is to be stamped. Both
      ingress and egress stamps are performed when the SI=SSI on the
      chain. For timestamping mode, the FSN will also apply the
      Reference Time and Ingress Timestamp. This will indicate the delay
      along the entire service chain to the targeted SF. This method may
      also be used as a light implementation to monitor end-to-end
      service chain performance whereby the targeted SF is the LSN. This
      is not applicable to QoSStamping mode.

   The Flow ID is a unique 16 bit identifier written into the header by
   the classifier. This allow 65536 flows to be concurrently stamped on
   any given NSH service chain (SPI). Flow IDs are not written by
   subsequent SFs in the chain. The FSN may export monitored flow IDs to
   the KPIDB for correlation.

   The E bit should be set if Egress stamp is requested.

   The I bit should be set if Ingress stamp is requested.

   The T bit should be set if Reference Time follows Stamping
   Configuration Header.

   Reference Time is the wall clock of the FSN, and may be used for
   historical comparison of SC performance. If the FSN is not Level A
   synchronized (see Section 3.1) it should inform the SC over the SCP
   interface. The Reference Time is represented in 64-bit NTP format
   [RFC5905].

   Each stamping Node adds stamping metadata which consist of Stamping
   Reporting Header and timestamps.

   The E bit should be set if Egress stamp is reported.

   The I bit should be set if Ingress stamp is reported.

   With respect to timestamping mode, the Syn bits are an indication of
   the synchronization status of the node performing the timestamp and
   must be set to one of the following values:

   o     In Synch: 0x00

   o     In holdover: 0x01

   o     In free run: 0x02



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   o     Out of Synch: 0x03

   If the network node is out of synch or in free run no timestamp is
   applied by the node (but other timestamp MD is applied) and the
   packet is processed normally.

   If FSN is out of synch or in free run timestamp request rejected and
   not propagated though the chain. The FSN should inform the SC in such
   an event over the SCP interface.

   The outer service index value is copied into the stamp metadata to
   help cater for hybrid chains that's are a mix of VNFs and PNFs or
   through SFs that do not understand NSH. Thus if a flow transits
   through a PNF or an NSH-unaware node the delta in the inner service
   index between timestamps will indicate this.

   The Ingress Timestamp and Egress Timestamp are represented in 64-bit
   NTP format [RFC5905]. The corresponding bits (I and E) reported in
   the Stamping Reporting Header of the node's metadata.

   The 64-bit timestamp format [RFC5905] is presented 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            Seconds                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            Fraction                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 9: NTP [RFC5905] 64-bit Timestamp Format



4.3. NSH QoS Stamping Encapsulation (Extended Mode)

   Packets have a variable QoS stack. That is for example the same
   payload IP can have a very different stack in the access part of the
   network to the core. This is most apparent in mobile networks where
   for example in an access circuit we would have 2 layers of
   infrastructure IP header (DSCP) - one transport-based and the other
   IPsec-based, in addition to multiple MPLS and VLAN tags. The same
   packet as it leaves the PGW Gi egress interface may be very much
   simplified in terms of overhead and related QoS fields.

   Because of this variability we need to build extra meaning into the
   QoS headers - they are not for example all PTP timestamps of a fixed


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   length as in the case of timestamping, rather they are variable
   lengths and types. Also they can be changed on the underlay at any
   time without knowledge by the SFC system. Therefore each VNF must be
   able to ascertain and record its ingress and egress QoS configuration
   on the fly.

   The suggested QoS type, lengths are as below. The type is 4 bits
   long.



   Q Type(QT)  Value       Length      Comment

   IVLAN       0x01        4 Bits      Ingress VLAN (PCP + DEI)

   EVLAN       0x02        4 Bits      Egress VLAN

   IQINQ       0x03        8 Bits      Ingress QinQ (2x PCP+DEI)

   EQINQ       0x04        8 Bits      Egress QinQ

   IMPLS       0x05        3 Bits      Ingress Label

   EMPLS       0x06        3 Bits      Egress Label

   IMPLS       0x07        6 Bits      2 Ingress Labels (2x EXP)

   EMPLS       0x08        6 Bits      2 Egress Labels

   IDSCP       0x09        8 Bits      Ingress DSCP

   EDSCP       0x0A        8 Bits      Egress DSCP



For stacked headers such as MPLS and 802.1ad, we extract the QoS
relevant data from the header and insert into one QoS value in order to
be more efficient on packet size. This for MPLS we represent both EXP
fields in one QoS value, and both 802.1p priority and drop precedence in
one QoS value as indicated above.









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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Ver|O|C|R|R|R|R|R|R|   Length  |  MD-type=0x2  | NextProto=0x0 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Service Path ID                      | Service Index |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          MD Class= KPI        |C|   Type= QoS |R|     Len     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |R|R|T|R|R|R|SSI| Service Index |           Flow ID             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |              Reference Time (T bit is set)                    |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |R|R|R|R|R|R|R|R| Service Index |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |   QT  |    QoS Value  |R|R|R|E|  QT   | QoS Value     |R|R|R|E|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |R|R|R|R|R|R|R|R| Service Index |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |   QT  |   QoS Value   |R|R|R|E|  QT   | QoS Value     |R|R|R|E|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 10: NSH QoS Configuration Encapsulation (Extended Mode)

   The encapsulation above is very similar to that detailed in section
   4.1 with the following exceptions

   -  I and E bits are not required as we wish to walk the full QoS
     stack at ingress and egress at every SF.

   -  Syn status bits are not required

   -  The QT (QoS Type) and QoS value are as outlined in the table above

   -  The E bit at the tail of each QoS context field indicates if this
     is the last egress QoS stamp for a given SF. This should coincide
     with SI=0 at the LSN, whereby the packet is truncated and the NSH
     MD sent to the KPIDB and the subscriber raw IP packet forwarded to
     the underlay next hop.



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   Note: It is possible to compress the frame structure to better
   utilize the header, but this would come at the expense of crossing
   byte boundaries. For ease of implementation, and that QoS stamping is
   applied on an extremely small subset of user plane traffic, we
   believe the above structure is a pragmatic compromise between header
   efficiency and ease of implementation.



5. Hybrid Models

   A hybrid chain may be defined as a chain whereby there is a mix of
   NSH-aware and NSH-unaware SFs. This may be the case if some PNFs are
   used in the chain or if VNFs are used that do not support NSH.

Example 1. PNF in the middle

        Stamp
     Controller
         |                                                      KPIDB
         | SCP Interface                                        |
       ,---.             ,---.              ,---.              ,---.
      /     \           /     \            /     \            /     \
     (  SCL  )-------->(  SF1  )--------->(  SF2  )--------->(  SFN  )
      \ FSN /           \     /            \ PNF1/            \ LSN /
       `---'             `---'              `---'              `---'
                Figure 11: Hybrid chain with PNF in middle

   In this example the FSN begins operation and sets the SI to 3, SF1
   decrements this to 2 and passes the flow to an SFC proxy (not shown).

   The proxy strips the NSH header and passes to the PNF. On receipt
   back from the PNF the Proxy decrements the SI and passes the packet
   onto the LSN with a SI=1.

   After the LSN processes the traffic it knows it is the last node on
   the chain from the SI value and exports the entire NSH header and all
   metadata to the KPIDB. The payload is forwarded to the next hop on
   the underlay minus the NSH header. The TS information packet may be
   given a new SPI to act as a homing tag to transport the timestamp
   data back to the KPIDB.







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Example 2. PNF at the end

      Stamp
   Controller
         |                                                      KPIDB
         | SCP Interface                                        |
       ,---.             ,---.              ,---.              ,---.
      /     \           /     \            /     \            /     \
     (  SCL  )-------->(  SF1  )--------->(  SF2  )--------->(  PNFN )
      \ FSN /           \     /            \ LSN /            \     /
       `---'             `---'              `---'              `---'
                  Figure 12: Hybrid Chain with PNF at end

   In this example the FSN begins operation and sets the SI to 3, the
   SSI field set to 0x1, and the type to 1. Thus when SF2 receives the
   packet with SI=1, it understands that it is expected to take on the
   role of the LSN as it is the last NSH-aware node in the chain.

5.1. Targeted VNF Stamp

   For the majority of flows within the service chain, stamps (ingress,
   egress or both) will be carried out at each hop until the SI
   decrements to zero and the NSH header and Stamp MD is exported to the
   KPIDB. There may exist however the need to just test a particular VNF
   (perhaps after a scale out operation, software upgrade or underlay
   change for example). In this case the FSN should mark the NSH header
   as follows:

   SSI field is set to 0x2. Type is set to the expected SI at the SF in
   question. When outer SI is equal to the SSI, stamps are applied at SF
   ingress and egress, and the NSH header and MD are exported to the
   KPIDB.



6. Fragmentation Considerations

   The method described in this draft does not support fragmentation.
   The SC should return an error should a stamping request from an
   external system exceed MTU limits and require fragmentation.

   Depending on the length of the payload and the type of KPIstamp and
   chain length, this will vary for each packet.





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   In most service provider architectures we would expect a SI << 10,
   and that may include some PNFs in the chain which do not add
   overhead. Thus for typical IMIX packet sizes we expect to able to
   perform timestamping on the vast majority of flows without
   fragmenting. Thus the classifier can have a simple rule to only allow
   KPIstamping on packet sizes less than 1200 bytes for example.



7. Security Considerations

   The security considerations of NSH in general are discussed in [NSH].

   The use of in-band timestamping, as defined in this document, can be
   used as a means for network reconnaissance. By passively
   eavesdropping to timestamped traffic, an attacker can gather
   information about network delays and performance bottlenecks.

   The NSH timestamp is intended to be used by various applications to
   monitor the network performance and to detect anomalies. Thus, a man-
   in-the-middle attacker can maliciously modify timestamps in order to
   attack applications that use the timestamp values. For example, an
   attacker could manipulate the SFC classifier operation, such that it
   forwards traffic through 'better' behaving chains. Furthermore, if
   timestamping is performed on a fraction of the traffic, an attacker
   can selectively induce synthetic delay only to timestamped packets,
   causing systematic error in the measurements.

   Similarly, if an attacker can modify QoS stamps, erroneous values may
   be imported into the KPIDB, resulting is further misconfiguration and
   subscriber QoE impairment.

   An attacker that gains access to the SCP can enable time and QoS
   stamping for all subscriber flows, thereby causing performance
   bottlenecks, fragmentation, or outages.

   As discussed in previous sections, NSH timestamping relies on an
   underlying time synchronization protocol. Thus, by attacking the time
   protocol an attack can potentially compromise the integrity of the
   NSH timestamp. A detailed discussion about the threats against time
   protocols and how to mitigate them is presented in [RFC7384].



8. Open Items for WG Discussion

   o     Specification and operation of SCP


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   o     AOB



9. IANA Considerations

MD Class Allocation

   MD classes are defined in [NSH].

   IANA is requested allocate a new MD class value:

   0x0210 KPI General Monitoring, stamping types and QoS types.

10. Contributors

   This document originated as draft-browne-sfc-nsh-timestamp-00 and had
   the following co-authors and contributors. We would like to thank and
   recognize them and their contributions.

   Yoram Moses

   Technion

   moses@ee.technion.ac.il



   Brendan Ryan

   Intel Corporation

   brendan.ryan@intel.com



11. Acknowledgments

   This document was prepared using 2-Word-v2.0.template.dot.

   The authors would like to thank Ramki Krishnan and Anoop Ghanwani
   from Dell for their reviews and comments on this draft.







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12. References

12.1. Normative References

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

   [NSH]         Quinn, P., Elzur, U., Pignataro, C., "Network Service
                 Header", draft-ietf-sfc-nsh-19 (work in progress),
                 August 2017.

12.2. Informative References

   [IEEE1588]    IEEE TC 9 Instrumentation and Measurement Society,
                 "1588 IEEE Standard for a Precision Clock
                 Synchronization Protocol for Networked Measurement and
                 Control Systems Version 2", IEEE Standard, 2008.

   [RFC5226]     Narten, T. and H. Alvestrand, "Guidelines for Writing
                 an IANA Considerations Section in RFCs", BCP 26, RFC
                 5226, May 2008.

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

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

   [Y.1731]      ITU-T Recommendation G.8013/Y.1731, "OAM Functions and
                 Mechanisms for Ethernet-based Networks", August 2015.

   [Y.1564]      ITU-T Recommendation Y.1564, "Ethernet service
                 activation test methodology", March 2011.

   [G.8261]      ITU-T Recommendation G.8261/Y.1361, "Timing and
                 synchronization aspects in packet networks", August
                 2013.

   [G.8262]      ITU-T Recommendation G.8262/Y.1362, "Timing
                 characteristics of a synchronous Ethernet equipment
                 slave clock", January 2015.

   [G.8264]      ITU-T Recommendation G.8264/Y.1364, "Distribution of
                 timing information through packet networks", May 2014.




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Authors' Addresses

   Rory Browne
   Intel
   Dromore House
   Shannon
   Co.Clare
   Ireland

   Email: rory.browne@intel.com



   Andrey Chilikin
   Intel
   Dromore House
   Shannon
   Co.Clare
   Ireland

   Email: andrey.chilikin@intel.com



   Tal Mizrahi
   Marvell
   6 Hamada St.
   Yokneam, 20692 Israel

   Email: talmi@marvell.com



















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