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Versions: (draft-mirsky-mpls-residence-time) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 8169

MPLS Working Group                                             G. Mirsky
Internet-Draft                                                S. Ruffini
Intended status: Standards Track                                 E. Gray
Expires: September 19, 2016                                     Ericsson
                                                                J. Drake
                                                        Juniper Networks
                                                               S. Bryant
                                                           Cisco Systems
                                                           A. Vainshtein
                                                             ECI Telecom
                                                          March 18, 2016


               Residence Time Measurement in MPLS network
                   draft-ietf-mpls-residence-time-06

Abstract

   This document specifies G-ACh based Residence Time Measurement and
   how it can be used by time synchronization protocols being
   transported over MPLS domain.

   Residence time is the variable part of propagation delay of timing
   and synchronization messages and knowing what this delay is for each
   message allows for a more accurate determination of the delay to be
   taken into account in applying the value included in a PTP event
   message.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 19, 2016.







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Copyright Notice

   Copyright (c) 2016 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
   (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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Conventions used in this document . . . . . . . . . . . .   3
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   4
   2.  Residence Time Measurement  . . . . . . . . . . . . . . . . .   4
   3.  G-ACh for Residence Time Measurement  . . . . . . . . . . . .   5
     3.1.  PTP Packet Sub-TLV  . . . . . . . . . . . . . . . . . . .   6
   4.  Control Plane Theory of Operation . . . . . . . . . . . . . .   7
     4.1.  RTM Capability  . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  RTM Capability Sub-TLV  . . . . . . . . . . . . . . . . .   8
     4.3.  RTM Capability Advertisement in OSPFv2  . . . . . . . . .   9
     4.4.  RTM Capability Advertisement in OSPFv3  . . . . . . . . .   9
     4.5.  RTM Capability Advertisement in IS-IS . . . . . . . . . .   9
     4.6.  RSVP-TE Control Plane Operation to Support RTM  . . . . .  10
     4.7.  RTM_SET TLV . . . . . . . . . . . . . . . . . . . . . . .  11
       4.7.1.  RTM_SET Sub-TLVs  . . . . . . . . . . . . . . . . . .  13
   5.  Data Plane Theory of Operation  . . . . . . . . . . . . . . .  15
   6.  Applicable PTP Scenarios  . . . . . . . . . . . . . . . . . .  16
   7.  One-step Clock and Two-step Clock Modes . . . . . . . . . . .  16
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     8.1.  New RTM G-ACh . . . . . . . . . . . . . . . . . . . . . .  19
     8.2.  New RTM TLV Registry  . . . . . . . . . . . . . . . . . .  19
     8.3.  New RTM Sub-TLV Registry  . . . . . . . . . . . . . . . .  20
     8.4.  RTM Capability sub-TLV in OSPFv2  . . . . . . . . . . . .  20
     8.5.  RTM Capability sub-TLV in OSPFv3  . . . . . . . . . . . .  20
     8.6.  IS-IS RTM Application ID  . . . . . . . . . . . . . . . .  21
     8.7.  RTM_SET Sub-object RSVP Type and sub-TLVs . . . . . . . .  21
     8.8.  RTM_SET Attribute Flag  . . . . . . . . . . . . . . . . .  22
     8.9.  New Error Codes . . . . . . . . . . . . . . . . . . . . .  22
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  23



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   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  23
     11.2.  Informative References . . . . . . . . . . . . . . . . .  24
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction

   Time synchronization protocols, e.g., Network Time Protocol version 4
   (NTPv4) [RFC5905] and Precision Time Protocol (PTP) Version 2
   [IEEE.1588.2008] define timing messages that can be used to
   synchronize clocks across a network domain.  Measurement of the
   cumulative time one of these timing messages spends transiting the
   nodes on the path from ingress node to egress node is termed
   Residence Time and it is used to improve the accuracy of clock
   synchronization.  (I.e., it is the sum of the difference between the
   time of receipt at an ingress interface and the time of transmission
   from an egress interface for each node along the path from ingress
   node to egress node.)  This document defines a new Generalized
   Associated Channel (G-ACh) value and an associated residence time
   measurement (RTM) packet that can be used in a Multi-Protocol Label
   Switching (MPLS) network to measure residence time over a Label
   Switched Path (LSP).

   Although it is possible to use RTM over an LSP instantiated using
   LDP, that is outside the scope of this document.  Rather, this
   document describes RTM over an LSP signaled using RSVP-TE [RFC3209]
   because the LSP's path can be either explicitly specified or
   determined during signaling.

   Comparison with alternative proposed solutions such as
   [I-D.ietf-tictoc-1588overmpls] is outside the scope of this document.

1.1.  Conventions used in this document

1.1.1.  Terminology

   MPLS: Multi-Protocol Label Switching

   ACH: Associated Channel

   TTL: Time-to-Live

   G-ACh: Generic Associated Channel

   GAL: Generic Associated Channel Label

   NTP: Network Time Protocol




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   ppm: parts per million

   PTP: Precision Time Protocol

   LSP: Label Switched Path

   OAM: Operations, Administration, and Maintenance

   RRO: Record Route Object

   RTM: Residence Time Measurement

   IGP: Internal Gateway Protocol

1.1.2.  Requirements Language

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

2.  Residence Time Measurement

   Packet Loss and Delay Measurement for MPLS Networks [RFC6374] can be
   used to measure one-way or two-way end-to-end propagation delay over
   LSP or PW.  But these measurements are insufficient for use in some
   applications, for example, time synchronization across a network as
   defined in the Precision Time Protocol (PTP).  In PTPv2
   [IEEE.1588.2008] residence times is accumulated in the
   correctionField of the PTP event message, as defined in
   [IEEE.1588.2008], or in the associated follow-up message (or
   Delay_Resp message associated with the Delay_Req message) in case of
   two-step clocks (see the detailed discussion in Section 7).

   IEEE 1588 uses this residence time to correct the transit time from
   ingress node to egress node, effectively making the transit nodes
   transparent.

   This document proposes a mechanism that can be used as one of types
   of on-path support for a clock synchronization protocol or to perform
   one-way measurement of residence time.  The proposed mechanism
   accumulates residence time from all nodes that support this extension
   along the path of a particular LSP in Scratch Pad field of an RTM
   packet Figure 1.  This value can then be used by the egress node to
   update, for example, the correctionField of the PTP event packet
   carried within the RTM packet prior to performing its PTP processing.





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3.  G-ACh for Residence Time Measurement

   RFC 5586 [RFC5586] and RFC 6423 [RFC6423] define the G-ACh to extend
   the applicability of the PW Associated Channel (ACH) [RFC5085] to
   LSPs.  G-ACh provides a mechanism to transport OAM and other control
   messages over an LSP.  Processing of these messages by select transit
   nodes is controlled by the use of the Time-to-Live (TTL) value in the
   MPLS header of these messages.

   The packet format for Residence Time Measurement (RTM) is presented
   in Figure 1

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 1|Version|   Reserved    |           RTM G-ACh           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                        Scratch Pad                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            Type               |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                             Value                             |
    ~                                                               ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 1: RTM G-ACh packet format for Residence Time Measurement

   o  First four octets are defined as G-ACh Header in [RFC5586]

   o  The Version field is set to 0, as defined in RFC 4385 [RFC4385].

   o  The Reserved field MUST be set to 0 on transmit and ignored on
      receipt.

   o  The RTM G-ACh field, value (TBA1) to be allocated by IANA,
      identifies the packet as such.

   o  The Scratch Pad field is 8 octets in length.  It is used to
      accumulate the residence time spent in each RTM capable node
      transited by the packet on its path from ingress node to egress
      node.  The first RTM-capable node MUST initialize the Scratch Pad
      field with its residence time measurement.  Its format is IEEE
      double precision and its units are nanoseconds.  Note that
      depending on whether the timing procedure is one-step or two-step
      operation (Section 7), the residence time is either for the timing
      packet carried in the Value field of this RTM packet or for an



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      associated timing packet carried in the Value field of another RTM
      packet.

   o  The Type field identifies the type and encapsulation of a timing
      packet carried in the Value field, e.g., NTP [RFC5905] or PTP
      [IEEE.1588.2008].  IANA will be asked to create a sub-registry in
      Generic Associated Channel (G-ACh) Parameters Registry called
      "MPLS RTM TLV Registry".

   o  The Length field contains the length, in octets , of the of the
      timing packet carried in the Value field.

   o  The optional Value field MAY carry a packet of the time
      synchronization protocol identified by Type field.  It is
      important to note that the packet may be authenticated or
      encrypted and carried over LSP edge to edge unchanged while the
      residence time is accumulated in the Scratch Pad field.

   o  The TLV MUST be included in the RTM message, even if the length of
      the Value field is zero.

3.1.  PTP Packet Sub-TLV

   Figure 2 presents format of a PTP sub-TLV that MUST be included in
   the Value field of an RTM packet preceding the carried timing packet
   when the timing packet is PTP.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             Type              |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Flags                         |PTPType|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            Port ID                            |
    |                                                               |
    |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               |           Sequence ID         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 2: PTP Sub-TLV format

   where Flags field has format








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     0                   1                   2
     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |S|                      Reserved                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 3: Flags field format of PTP Packet Sub-TLV

   o  The Type field identifies PTP sub-TLV defined in the Table 19
      Values of messageType field in [IEEE.1588.2008].

   o  The Length field of the PTP sub-TLV contains the number of octets
      of the Value field and MUST be 20.

   o  The Flags field currently defines one bit, the S-bit, that defines
      whether the current message has been processed by a 2-step node,
      where the flag is cleared if the message has been handled
      exclusively by 1-step nodes and there is no follow-up message, and
      set if there has been at least one 2-step node and a follow-up
      message is forthcoming.

   o  The PTPType indicates the type of PTP packet carried in the TLV.
      PTPType is the messageType field of the PTPv2 packet whose values
      are defined in the Table 19 [IEEE.1588.2008].

   o  The 10 octets long Port ID field contains the identity of the
      source port.

   o  The Sequence ID is the sequence ID of the PTP message carried in
      the Value field of the message.

4.  Control Plane Theory of Operation

   The operation of RTM depends upon TTL expiry to deliver an RTM packet
   from one RTM capable interface to the next along the path from
   ingress node to egress node.  This means that a node with RTM capable
   interfaces MUST be able to compute a TTL which will cause the expiry
   of an RTM packet at the next node with RTM capable interfaces.

4.1.  RTM Capability

   Note that the RTM capability of a node is with respect to the pair of
   interfaces that will be used to forward an RTM packet.  In general,
   the ingress interface of this pair must be able to capture the
   arrival time of the packet and encode it in some way such that this
   information will be available to the egress interface.





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   The supported modes (1-step verses 2-step) of any pair of interfaces
   is then determined by the capability of the egress interface.  For
   both modes, the egress interface implementation MUST be able to
   determine the precise departure time of the same packet and determine
   from this, and the arrival time information from the corresponding
   ingress interface, the difference representing the residence time for
   the packet.

   An interface with the ability to do this and update the associated
   Scratch Pad in real-time (i.e. while the packet is being forwarded)
   is said to be 1-step capable.

   Hence while both ingress and egress interfaces are required to
   support RTM for the pair to be RTM-capable, it is the egress
   interface that determines whether or not the node is 1-step or 2-step
   capable with respect to the interface-pair.

   The RTM capability used in the sub-TLV shown in Figure 4 is thus
   associated with the egress port of the node making the advertisement,
   while the ability of any pair of interfaces that includes this egress
   interface to support any mode of RTM depends on the ability of that
   interface to record packet arrival time in some way that can be
   conveyed to and used by that egress interface.

   When a node uses an IGP to carry the RTM capability sub-TLV, the sub-
   TLV MUST reflect the RTM capability (1-step or 2-step) associated
   with egress interfaces.

4.2.  RTM Capability Sub-TLV

   The format for the RTM Capabilities sub-TLV is presented in Figure 4

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              Type             |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | RTM |                       Reserved                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 4: RTM Capability sub-TLV

   o  Type values TBA2 and TBA3 will be assigned by IANA from
      appropriate registries for OSPFv2 and OSPFv3 respectively.

   o  Length MUST be set to 4.





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   o  RTM (capability) - is a three-bit long bit-map field with values
      defined as follows:

      *  0b001 - one-step RTM supported;

      *  0b010 - two-step RTM supported;

      *  0b100 - reserved.

   o  Reserved field must be set to all zeroes on transmit and ignored
      on receipt.

   [RFC4202] explains that the Interface Switching Capability Descriptor
   describes switching capability of an interface.  For bi-directional
   links, the switching capabilities of an interface are defined to be
   the same in either direction.  I.e., for data entering the node
   through that interface and for data leaving the node through that
   interface.  That principle SHOULD be applied when a node advertises
   RTM Capability.

   A node that supports RTM MUST be able to act in two-step mode and MAY
   also support one-step RTM mode.  Detailed discussion of one-step and
   two-step RTM modes in Section 7.

4.3.  RTM Capability Advertisement in OSPFv2

   The capability to support RTM on a particular link (interface) is
   advertised in the OSPFv2 Extended Link Opaque LSA described in
   Section 3 [RFC7684] via the RTM Capability sub-TLV.

   Its Type value will be assigned by IANA from the OSPF Extended Link
   TLV Sub-TLVs registry that will be created per [RFC7684] request.

4.4.  RTM Capability Advertisement in OSPFv3

   The capability to support RTM on a particular link (interface) is
   advertised in the OSPFv3 be Intra-Area-Prefix TLV, IPv6 Link-Local
   Address TLV, or the IPv4 Link-Local Address TLV described in
   [I-D.ietf-ospf-ospfv3-lsa-extend] via the RTM Capability sub-TLV.

4.5.  RTM Capability Advertisement in IS-IS

   The capability to support RTM on a particular link (interface) is
   advertised in the GENINFO TLV described in [RFC6823] via the RTM
   Capability sub-TLV.

   With respect to the Flags field of the GENINFO TLV:




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   o  The S bit MUST be cleared to prevent the RTM Capability sub-TLV
      from leaking between levels.

   o  The D bit of the Flags field MUST be cleared as required by
      [RFC6823].

   o  The I bit and the V bit MUST be set accordingly depending on
      whether RTM capability being advertised is for an IPv4 or an IPv6
      interface.

   Application ID (TBA4) will be assigned from the Application
   Identifiers for TLV 251 IANA registry.  The RTM Capability sub-TLV
   MUST be included in GENINFO TLV in Application Specific Information.

4.6.  RSVP-TE Control Plane Operation to Support RTM

   Throughout this document we refer to a node as RTM capable node when
   at least one of its interfaces is RTM capable.  Figure 5 provides an
   example of roles a node may have with respect to RTM capability:

    -----     -----     -----     -----     -----     -----     -----
    | A |-----| B |-----| C |-----| D |-----| E |-----| F |-----| G |
    -----     -----     -----     -----     -----     -----     -----

                        Figure 5: RTM capable roles

   o  A is a Boundary Clock with its egress port in Master state.  Node
      A transmits IP encapsulated timing packets whose destination IP
      address is G.

   o  B is the ingress LER for the MPLS LSP and is the first RTM capable
      node.  It creates RTM packets and in each it places a timing
      packet, possibly encrypted, in the Value field and initializes the
      Scratch Pad field with its residence time measurement

   o  C is a transit node that is not RTM capable.  It forwards RTM
      packets without modification.

   o  D is RTM capable transit node.  It updates the Scratch Pad filed
      of the RTM packet without updating of the timing packet.

   o  E is a transit node that is not RTM capable.  It forwards RTM
      packets without modification.

   o  F is the egress LER and the last RTM capable node.  It processes
      the timing packet carried in the Value field using the value in
      the Scratch Pad field.  It updates the Correction field of the PTP




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      message with the value in the Scratch Pad field of the RTM ACH,
      and removes the RTM ACH encapsulation.

   o  G is a Boundary Clock with its ingress port in Slave state.  Node
      G receives PTP messages.

   An ingress node that is configured to perform RTM along a path
   through an MPLS network to an egress node verifies that the selected
   egress node has an interface that supports RTM via the egress node's
   advertisement of the RTM Capability sub-TLV.  In the Path message
   that the ingress node uses to instantiate the LSP to that egress node
   it places LSP_ATTRIBUTES Object [RFC5420] with RTM_SET Attribute Flag
   set Section 8.8 which indicates to the egress node that RTM is
   requested for this LSP.  RTM_SET Attribute Flag SHOULD NOT be set in
   the LSP_REQUIRED_ATTRIBUTES object [RFC5420] , unless it is known
   that all nodes support RTM, because a node that does not recognize
   RTM_SET Attribute Flag would reject the Path message.

   If egress node receives Path message with RTM_SET Attribute Flag in
   LSP_ATTRIBUTES object, it MUST include initialized RRO [RFC3209] and
   LSP_ATTRIBUTES object where RTM_SET Attribute Flag is set and RTM_SET
   TLV Section 4.7 is initialized.  When Resv message received by
   ingress node the RTM_SET TLV will contain an ordered list, from
   egress node to ingress node, of the RTM capable node along the LSP's
   path.

   After the ingress node receives the Resv, it MAY begin sending RTM
   packets on the LSP's path.  Each RTM packet has its Scratch Pad field
   initialized and its TTL set to expire on the closest downstream RTM
   capable node.

   It should be noted that RTM can also be used for LSPs instantiated
   using [RFC3209] in an environment in which all interfaces in an IGP
   support RTM.  In this case the RTM_SET TLV and LSP_ATTRIBUTES Object
   MAY be omitted.

4.7.  RTM_SET TLV

   RTM capable interfaces can be recorded via RTM_SET TLV.  The RTM_SET
   sub-object format is of generic Type, Length, Value (TLV), presented
   in Figure 6 .










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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Type     |     Length    |          Reserved           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                             Value                           ~
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 6: RTM_SET TLV format

   Type value (TBA5) will be assigned by IANA from its Attributes TLV
   Space sub-registry.

   The Length contains the total length of the sub-object in bytes,
   including the Type and Length fields.

   Reserved field must be zeroed on initiation and ignored on receipt.

   The content of an RTM_SET TLV is a series of variable-length sub-
   TLVs.  Only a single RTM_SET can be present in the LSP_ATTRIBUTES
   object.  The sub-TLVs are defined in Section 4.7.1 below.

   The following processing procedures apply to every RTM capable node
   along the LSP that in this paragraph is referred as node for sake of
   brevity.  Each node MUST examine Resv message whether RTM_SET
   Attribute Flag in the LSP_ATTRIBUTES object is set.  If the RTM_SET
   flag set, the node MUST inspect the LSP_ATTRIBUTES object for
   presence of RTM_SET TLV.  If more than one found, then the LSP setup
   MUST fail with generation of the ResvErr message with Error Code
   Duplicate TLV Section 8.9 and Error Value that contains Type value in
   its 8 least significant bits.  If no RTM_SET TLV has been found, then
   the LSP setup MUST fail with generation of the ResvErr message with
   Error Code RTM_SET TLV Absent Section 8.9.  If one RTM_SET TLV has
   been found the node will use the ID of the first node in the RTM_SET
   in conjunction with the RRO to compute the hop count to its
   downstream node with reachable RTM capable interface.  If the node
   cannot find matching ID in RRO, then it MUST try to use ID of the
   next node in the RTM_SET until it finds the match or reaches the end
   of RTM_SET TLV.  If match have been found, then the calculated value
   is used by the node as TTL value in outgoing label to reach the next
   RTM capable node on the LSP.  Otherwise, the TTL value MUST be set to
   255.  The node MUST add RTM_SET sub-TLV with the same address it used
   in RRO sub-object at the beginning of the RTM_SET TLV in associated
   outgoing Resv message before forwarding it upstream.

   There are scenarios when some information is removed from an RRO due
   to policy processing (e.g., as may happen between providers) or RRO



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   is limited due to size constraints .  Such changes affect the core
   assumption of the method to control processing of RTM packets.  RTM
   SHOULD NOT be used if it is not guaranteed that RRO contains complete
   information.

4.7.1.  RTM_SET Sub-TLVs

   The RTM Set sub-object contains an ordered list, from egress node to
   ingress node, of the RTM capable nodes along the LSP's path.

   The contents of a RTM_SET sub-object are a series of variable-length
   sub-TLVs.  Each sub-TLV has its own Length field.  The Length
   contains the total length of the sub-TLV in bytes, including the Type
   and Length fields.  The Length MUST always be a multiple of 4, and at
   least 8 (smallest IPv4 sub-object).

   Sub-TLVs are organized as a last-in-first-out stack.  The first -out
   sub-TLV relative to the beginning of RTM_SET TLV is considered the
   top.  The last-out sub-TLV is considered the bottom.  When a new sub-
   TLV is added, it is always added to the top.  Only a single RTM_SET
   sub-TLV with the given Value field MUST be present in the RTM_SET
   TLV.  If more than one sub-TLV is found the LSP setup MUST fail with
   the generation of a ResvErr message with the Error Code "Duplicate
   sub-TLV" Section 8.9 and Error Value contains 16-bit value composed
   of (Type of TLV, Type of sub-TLV).

   Three kinds of sub-TLVs for RTM_SET are currently defined.

4.7.1.1.  IPv4 Sub-TLV

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Type     |     Length    |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       IPv4 address                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 7: IPv4 sub-TLV format

   Type

      0x01 IPv4 address

   Length

      The Length contains the total length of the sub-TLV in bytes,
      including the Type and Length fields.  The Length is always 8.



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   IPv4 address

      A 32-bit unicast host address.

   Reserved

      Zeroed on initiation and ignored on receipt.

4.7.1.2.  IPv6 Sub-TLV

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Type     |     Length    |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                             |
    |                         IPv6 address                        |
    |                                                             |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 8: IPv6 sub-TLV format

   Type

      0x02 IPv6 address

   Length

      The Length contains the total length of the sub-TLV in bytes,
      including the Type and Length fields.  The Length is always 20.

   IPv6 address

      A 128-bit unicast host address.

   Reserved

      Zeroed on initiation and ignored on receipt.

4.7.1.3.  Unnumbered Interface Sub-TLV










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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Type     |     Length    |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Node ID                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Interface ID                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 9: IPv4 sub-TLV format

   Type

      0x03 Unnumbered interface

   Length

      The Length contains the total length of the sub-TLV in bytes,
      including the Type and Length fields.  The Length is always 12.

   Node ID

      The Node ID interpreted as Router ID as discussed in the Section 2
      [RFC3477].

   Interface ID

      The identifier assigned to the link by the node specified by the
      Node ID.

   Reserved

      Zeroed on initiation and ignored on receipt.

5.  Data Plane Theory of Operation

   After instantiating an LSP for a path using RSVP-TE [RFC3209] as
   described in Section 4.6 or as described in the second paragraph of
   Section 4 and in Section 4.6, ingress node MAY begin sending RTM
   packets to the first downstream RTM capable node on that path.  Each
   RTM packet has its Scratch Pad field initialized and its TTL set to
   expire on the next downstream RTM-capable node.  Each RTM-capable
   node on the explicit path receives an RTM packet and records the time
   at which it receives that packet at its ingress interface as well as
   the time at which it transmits that packet from its egress interface;
   this should be done as close to the physical layer as possible to
   ensure precise accuracy in time determination.  The RTM-capable node



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   determines the difference between those two times; for 1-step
   operation, this difference is determined just prior to or while
   sending the packet, and the RTM-capable egress interface adds it to
   the value in the Scratch Pad field of the message in progress.  Note,
   for the purpose of calculating a residence time, a common free
   running clock synchronizing all the involved interfaces may be
   sufficient, as, for example, 4.6 ppm accuracy leads to 4.6 nanosecond
   error for residence time on the order of 1 millisecond.

   For 2-step operation, the difference between packet arrival time (at
   an ingress interface) and subsequent departure time (from an egress
   interface) is determined at some later time prior to sending a
   subsequent follow-up message, so that this value can be used to
   update the correctionField in the follow-up message.

   See Section 7 for further details on the difference between 1-step
   and 2-step operation.

   The last RTM-capable node on the LSP MAY then use the value in the
   Scratch Pad field to perform time correction, if there is no follow-
   up message.  For example, the egress node may be a PTP Boundary Clock
   synchronized to a Master Clock and will use the value in the Scratch
   Pad field to update PTP's correctionField.

6.  Applicable PTP Scenarios

   The proposed approach can be directly integrated in a PTP network
   based on the IEEE 1588 delay request-response mechanism.  The RTM
   capable node nodes act as end-to-end transparent clocks, and
   typically boundary clocks, at the edges of the MPLS network, use the
   value in the Scratch Pad field to update the correctionField of the
   corresponding PTP event packet prior to performing the usual PTP
   processing.

7.  One-step Clock and Two-step Clock Modes

   One-step mode refers to the mode of operation where an egress
   interface updates the correctionField value of an original event
   message.  Two-step mode refers to the mode of operation where this
   update is made in a subsequent follow-up message.

   Processing of the follow-up message, if present, requires the
   downstream end-point to wait for the arrival of the follow-up message
   in order to combine correctionField values from both the original
   (event) message and the subsequent (follow-up) message.  In a similar
   fashion, each 2-step node needs to wait for the related follow-up
   message, if there is one, in order to update that follow-up message




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   (as opposed to creating a new one.  Hence the first node that uses
   2-step mode MUST do two things:

   1.  Mark the original event message to indicate that a follow-up
       message will be forthcoming (this is necessary in order to

          Let any subsequent 2-step node know that there is already a
          follow-up message, and

          Let the end-point know to wait for a follow-up message;

   2.  Create a follow-up message in which to put the RTM determined as
       an initial correctionField value.

   IEEE 1588v2 [IEEE.1588.2008] defines this behavior for PTP messages.

   Thus, for example, with reference to the PTP protocol, the PTPType
   field identifies whether the message is a Sync message, Follow_up
   message, Delay_Req message, or Delay_Resp message.  The 10 octet long
   Port ID field contains the identity of the source port, that is, the
   specific PTP port of the boundary clock connected to the MPLS
   network.  The Sequence ID is the sequence ID of the PTP message
   carried in the Value field of the message.

   PTP messages also include a bit that indicates whether or not a
   follow-up message will be coming.  This bit, once it is set by a
   2-step mode device, MUST stay set accordingly until the original and
   follow-up messages are combined by an end-point (such as a Boundary
   Clock).

   Thus, an RTM packet, containing residence time information relating
   to an earlier packet, also contains information identifying that
   earlier packet.

   For compatibility with PTP, RTM (when used for PTP packets) must
   behave in a similar fashion.  To do this, a 2-step RTM capable egress
   interface will need to examine the S-bit in the Flags field of the
   PTP sub-TLV (for RTM messages that indicate they are for PTP) and -
   if it is clear (set to zero), it MUST set it and create a follow-up
   PTP Type RTM message.  If the S bit is already set, then the RTM
   capable node MUST wait for the RTM message with the PTP type of
   follow-up and matching originator and sequence number to make the
   corresponding residence time update to the Scratch Pad field.

   In practice an RTM operating according to two-step clock behaves like
   a two-steps transparent clock.





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   A 1-step capable RTM node MAY elect to operate in either 1-step mode
   (by making an update to the Scratch Pad field of the RTM message
   containing the PTP even message), or in 2-step mode (by making an
   update to the Scratch Pad of a follow-up message when its presence is
   indicated), but MUST NOT do both.

   Two main subcases can be identified for an RTM node operating as a
   two-step clock:

   A) If any of the previous RTM capable node or the previous PTP clock
   (e.g. the BC connected to the first node), is a two-step clock, the
   residence time is added to the RTM packet that has been created to
   include the associated PTP packet (i.e. follow-up message in the
   downstream direction), if the local RTM-capable node is also
   operating as a two-step clock.  This RTM packet carries the related
   accumulated residence time and the appropriate values of the Sequence
   Id and Port Id (the same identifiers carried in the packet processed)
   and the Two-step Flag set to 1.

   Note that the fact that an upstream RTM-capable node operating in the
   two-step mode has created a follow-up message does not require any
   subsequent RTM capable node to also operate in the 2-step mode, as
   long as that RTM-capable node forwards the follow-up message on the
   same LSP on which it forwards the corresponding previous message.

   A one-step capable RTM node MAY elect to update the RTM follow-up
   message as if it were operating in two-step mode, however, it MUST
   NOT update both messages.

   A PTP event packet (sync) is carried in the RTM packet in order for
   an RTM node to identify that residence time measurement must be
   performed on that specific packet.

   To handle the residence time of the Delay request message on the
   upstream direction, an RTM packet must be created to carry the
   residence time on the associated downstream Delay Resp message.

   The last RTM node of the MPLS network in addition to update the
   correctionField of the associated PTP packet, must also properly
   handle the two-step flag of the PTP packets.

   B) When the PTP network connected to the MPLS and RTM node, operates
   in one-step clock mode, the associated RTM packet must be created by
   the RTM node itself.  The associated RTM packet including the PTP
   event packet needs now to indicate that a follow up message will be
   coming.





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   The last RTM node of the LSP, if it receives an RTM message with a
   PTP payload indicating a follow-up message will be forthcoming, must
   generate a follow-up message and properly set the two-step flag of
   the PTP packets.

8.  IANA Considerations

8.1.  New RTM G-ACh

   IANA is requested to reserve a new G-ACh as follows:

          +-------+----------------------------+---------------+
          | Value |        Description         | Reference     |
          +-------+----------------------------+---------------+
          | TBA1  | Residence Time Measurement | This document |
          +-------+----------------------------+---------------+

                  Table 1: New Residence Time Measurement

8.2.  New RTM TLV Registry

   IANA is requested to create sub-registry in Generic Associated
   Channel (G-ACh) Parameters Registry called "MPLS RTM TLV Registry".
   All code points in the range 0 through 127 in this registry shall be
   allocated according to the "IETF Review" procedure as specified in
   [RFC5226] .  Remaining code points are allocated according to the
   table below.  This document defines the following new values RTM TLV
   type s:

   +-----------+-----------------------------+-------------------------+
   | Value     |         Description         | Reference               |
   +-----------+-----------------------------+-------------------------+
   | 0         |           Reserved          | This document           |
   | 1         |          No payload         | This document           |
   | 2         |       PTPv2, Ethernet       | This document           |
   |           |        encapsulation        |                         |
   | 3         |  PTPv2, IPv4 Encapsulation  | This document           |
   | 4         |  PTPv2, IPv6 Encapsulation  | This document           |
   | 5         |             NTP             | This document           |
   | 6-127     |           Reserved          | IETF Consensus          |
   | 128 - 191 |           Reserved          | First Come First Served |
   | 192 - 255 |           Reserved          | Private Use             |
   +-----------+-----------------------------+-------------------------+

                           Table 2: RTM TLV Type






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8.3.  New RTM Sub-TLV Registry

   IANA is requested to create sub-registry in MPLS RTM TLV Registry,
   requested in Section 8.2, called "MPLS RTM Sub-TLV Registry".  All
   code points in the range 0 through 127 in this registry shall be
   allocated according to the "IETF Review" procedure as specified in
   [RFC5226] .  Remaining code points are allocated according to the
   table below.  This document defines the following new values RTM sub-
   TLV types:

           +-----------+-------------+-------------------------+
           | Value     | Description | Reference               |
           +-----------+-------------+-------------------------+
           | 0         |   Reserved  | This document           |
           | 1         |  PTP 2-step | This document           |
           | 2-127     |   Reserved  | IETF Consensus          |
           | 128 - 191 |   Reserved  | First Come First Served |
           | 192 - 255 |   Reserved  | Private Use             |
           +-----------+-------------+-------------------------+

                         Table 3: RTM Sub-TLV Type

8.4.  RTM Capability sub-TLV in OSPFv2

   IANA is requested to assign a new type for RTM Capability sub-TLV
   from OSPFv2 Extended Link TLV Sub-TLVs registry as follows:

                +-------+----------------+---------------+
                | Value |  Description   | Reference     |
                +-------+----------------+---------------+
                | TBA2  | RTM Capability | This document |
                +-------+----------------+---------------+

                      Table 4: RTM Capability sub-TLV

8.5.  RTM Capability sub-TLV in OSPFv3

   IANA is requested to assign a new type for RTM Capability sub-TLV
   from future OSPFv3 Extended-LSA Sub-TLVs registry that would be part
   of OSPFv3 IANA registry as follows:

                +-------+----------------+---------------+
                | Value |  Description   | Reference     |
                +-------+----------------+---------------+
                | TBA3  | RTM Capability | This document |
                +-------+----------------+---------------+

                      Table 5: RTM Capability sub-TLV



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8.6.  IS-IS RTM Application ID

   IANA is requested to assign a new Application ID for RTM from the
   Application Identifiers for TLV 251 registry as follows:

                  +-------+-------------+---------------+
                  | Value | Description | Reference     |
                  +-------+-------------+---------------+
                  | TBA4  |     RTM     | This document |
                  +-------+-------------+---------------+

                     Table 6: IS-IS RTM Application ID

8.7.  RTM_SET Sub-object RSVP Type and sub-TLVs

   IANA is requested to assign a new Type for RTM_SET sub-object from
   Attributes TLV Space sub-registry as follows:

   +-----+------------+-----------+---------------+---------+----------+
   | Typ |    Name    |  Allowed  | Allowed  on   | Allowed | Referenc |
   | e   |            | on  LSP_A | LSP_REQUIRED_ |  on LSP | e        |
   |     |            | TTRIBUTES |   ATTRIBUTES  | Hop Att |          |
   |     |            |           |               | ributes |          |
   +-----+------------+-----------+---------------+---------+----------+
   | TBA |  RTM_SET   |    Yes    |       No      |    No   | This     |
   | 5   | sub-object |           |               |         | document |
   +-----+------------+-----------+---------------+---------+----------+

                     Table 7: RTM_SET Sub-object Type

   IANA requested to create new sub-registry for sub-TLV types of
   RTM_SET sub-object as follows:

      +-----------+----------------------+-------------------------+
      | Value     |     Description      | Reference               |
      +-----------+----------------------+-------------------------+
      | 0         |       Reserved       |                         |
      | 1         |     IPv4 address     | This document           |
      | 2         |     IPv6 address     | This document           |
      | 3         | Unnumbered interface | This document           |
      | 4-127     |       Reserved       | IETF Consensus          |
      | 128 - 191 |       Reserved       | First Come First Served |
      | 192 - 255 |       Reserved       | Private Use             |
      +-----------+----------------------+-------------------------+

                 Table 8: RTM_SET object sub-object types





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8.8.  RTM_SET Attribute Flag

   IANA is requested to assign new flag from Attribute Flags registry

   +-----+--------+-----------+------------+-----+-----+---------------+
   | Bit |  Name  | Attribute | Attribute  | RRO | ERO | Reference     |
   | No  |        |   Flags   | Flags Resv |     |     |               |
   |     |        |    Path   |            |     |     |               |
   +-----+--------+-----------+------------+-----+-----+---------------+
   | TBA | RTM_SE |    Yes    |    Yes     |  No |  No | This document |
   | 6   |   T    |           |            |     |     |               |
   +-----+--------+-----------+------------+-----+-----+---------------+

                      Table 9: RTM_SET Attribute Flag

8.9.  New Error Codes

   IANA is requested to assign new Error Codes from Error Codes and
   Globally-Defined Error Value Sub-Codes registry

            +------------+--------------------+---------------+
            | Error Code |      Meaning       | Reference     |
            +------------+--------------------+---------------+
            | TBA7       |   Duplicate TLV    | This document |
            | TBA8       | Duplicate sub-TLV  | This document |
            | TBA9       | RTM_SET TLV Absent | This document |
            +------------+--------------------+---------------+

                         Table 10: New Error Codes

9.  Security Considerations

   Routers that support Residence Time Measurement are subject to the
   same security considerations as defined in [RFC5586] .

   In addition - particularly as applied to use related to PTP - there
   is a presumed trust model that depends on the existence of a trusted
   relationship of at least all PTP-aware nodes on the path traversed by
   PTP messages.  This is necessary as these nodes are expected to
   correctly modify specific content of the data in PTP messages and
   proper operation of the protocol depends on this ability.

   As a result, the content of the PTP-related data in RTM messages that
   will be modified by intermediate nodes cannot be authenticated, and
   the additional information that must be accessible for proper
   operation of PTP 1-step and 2-step modes MUST be accessible to
   intermediate nodes (i.e. - MUST NOT be encrypted in a manner that
   makes this data inaccessible).



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   While it is possible for a supposed compromised node to intercept and
   modify the G-ACh content, this is an issue that exists for nodes in
   general - for any and all data that may be carried over an LSP - and
   is therefore the basis for an additional presumed trust model
   associated with existing LSPs and nodes.

   The ability for potentially authenticating and/or encrypting RTM and
   PTP data that is not needed by intermediate RTM/PTP-capable nodes is
   for further study.

   Security requirements of time protocols are provided in RFC 7384
   [RFC7384].

10.  Acknowledgements

   Authors want to thank Loa Andersson, Lou Berger and Acee Lindem for
   their thorough reviews, thoughtful comments and, most of, patience.

11.  References

11.1.  Normative References

   [I-D.ietf-ospf-ospfv3-lsa-extend]
              Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
              LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-09
              (work in progress), November 2015.

   [IEEE.1588.2008]
              "Standard for a Precision Clock Synchronization Protocol
              for Networked Measurement and Control Systems",
              IEEE Standard 1588, March 2008.

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

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <http://www.rfc-editor.org/info/rfc3209>.

   [RFC3477]  Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
              in Resource ReSerVation Protocol - Traffic Engineering
              (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003,
              <http://www.rfc-editor.org/info/rfc3477>.





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   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
              February 2006, <http://www.rfc-editor.org/info/rfc4385>.

   [RFC5085]  Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
              Circuit Connectivity Verification (VCCV): A Control
              Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
              December 2007, <http://www.rfc-editor.org/info/rfc5085>.

   [RFC5420]  Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A.
              Ayyangarps, "Encoding of Attributes for MPLS LSP
              Establishment Using Resource Reservation Protocol Traffic
              Engineering (RSVP-TE)", RFC 5420, DOI 10.17487/RFC5420,
              February 2009, <http://www.rfc-editor.org/info/rfc5420>.

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

   [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,
              <http://www.rfc-editor.org/info/rfc5905>.

   [RFC6423]  Li, H., Martini, L., He, J., and F. Huang, "Using the
              Generic Associated Channel Label for Pseudowire in the
              MPLS Transport Profile (MPLS-TP)", RFC 6423,
              DOI 10.17487/RFC6423, November 2011,
              <http://www.rfc-editor.org/info/rfc6423>.

   [RFC6823]  Ginsberg, L., Previdi, S., and M. Shand, "Advertising
              Generic Information in IS-IS", RFC 6823,
              DOI 10.17487/RFC6823, December 2012,
              <http://www.rfc-editor.org/info/rfc6823>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <http://www.rfc-editor.org/info/rfc7684>.

11.2.  Informative References








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   [I-D.ietf-tictoc-1588overmpls]
              Davari, S., Oren, A., Bhatia, M., Roberts, P., and L.
              Montini, "Transporting Timing messages over MPLS
              Networks", draft-ietf-tictoc-1588overmpls-07 (work in
              progress), October 2015.

   [RFC4202]  Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
              <http://www.rfc-editor.org/info/rfc4202>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <http://www.rfc-editor.org/info/rfc6374>.

   [RFC7384]  Mizrahi, T., "Security Requirements of Time Protocols in
              Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
              October 2014, <http://www.rfc-editor.org/info/rfc7384>.

Authors' Addresses

   Greg Mirsky
   Ericsson

   Email: gregory.mirsky@ericsson.com


   Stefano Ruffini
   Ericsson

   Email: stefano.ruffini@ericsson.com


   Eric Gray
   Ericsson

   Email: eric.gray@ericsson.com








Mirsky, et al.         Expires September 19, 2016              [Page 25]


Internet-Draft         Residence Time Measurement             March 2016


   John Drake
   Juniper Networks

   Email: jdrake@juniper.net


   Stewart Bryant
   Cisco Systems

   Email: stbryant@cisco.com


   Alexander Vainshtein
   ECI Telecom

   Email: Alexander.Vainshtein@ecitele.com



































Mirsky, et al.         Expires September 19, 2016              [Page 26]


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