Subject: [mpls] Comments on draft-ietf-tictoc-1588overmpls

From: Stewart Bryant <[email-masked]>
Date: Fri, 02 Aug 2013 11:01:58 +0100

Talking to John Drake about this, an alternative general
model is for the LSP is that it is an LSP that timestamps
the packet and then passes it to an application associated
with the LSP at that hop.

This has a lot of merit.

If however we think about it some more we have a
type of network service chaining going on here and
so we don't need an LSP per say, because the path
and instruction can be in the packet.

In other words a general solution  to the problem
is to define an LSP with the properties that the
packet is passed one hop, timestamped and delivered
to the associated application.

How this is MPLS construct is used to support time
tranfer is entirely within the scope of TICTOC, but
at the MPLS layer we have a clean reusable network
service.

- Stewart

============
SB> This draft does not seem to provide a precise definition
SB> the properties of the new LSP type that it wishes to
SB> define, in particular it does it define the PHB of those
SB> LSPs, nor the full interaction with the MPLS
SB> architecture.
SB>
SB> I have not tracked TICTOC for a while but I thought that
SB> the original plan was to define the concept of an offset
SB> into a packet to do the correction.
SB>
SB> It is disappointing that the opportunity was not taken
SB> to define a timing shim inside the timing LSP so that
SB> a time correction could be added to any packet such that
SB> the MPLS system was isolated from the details of the
SB> complexity of the particular time transfer type.

SB> I think that much more clarify is needed in terms of
SB> definition of the new LSP type, since it is unclear
SB> from this text how to implement one.
SB>
SB> There are a lot of other MPLS services such as
SB> LSP ping that need to be considered.
SB>
SB> Please see inline for more comments. However these
SB> comments are made in the context of the text as written
SB> whilst I have a fundamental concern that this approach
SB> lacks an MPLS architectural soundness that need
SB> greater thought with significant impact on the
SB> draft.

- Stewart

TICTOC Working Group                                           S. Davari
Internet-Draft                                                   A. Oren
Intended status: Standards Track                          Broadcom Corp.
Expires: December 17, 2013                                     M. Bhatia
                                                               P. Roberts
                                                           Alcatel-Lucent
                                                               L. Montini
                                                               L. Martini
                                                            Cisco Systems
                                                            June 15, 2013

             Transporting Timing messages over MPLS Networks
                    draft-ietf-tictoc-1588overmpls-05

Abstract

    This document defines the method for transporting Timing messages
    such as PTP and NTP over an MPLS network.  The method allows for the
    easy identification of these PDUs at the port level to allow for port

SB> What is a port

    level processing of these PDUs in both LERs and LSRs.

    The basic idea is to transport Timing messages inside dedicated MPLS
    LSPs.  These LSPs only carry Timing messages and possibly Control and
    Management packets, but they do not carry customer traffic.

SB> More specifically they only carry traffic associated with the
SB> timing service and its support.
SB> The question arose WRT BFD - surely BFD is allowed, BUT surely
SB> also it gets carried in a structure that causes it to get
SB> timestamped.

    Two methods for transporting Timing messages over MPLS are defined.

SB> Perhaps the right approach is to define the new LSP type and then
SB> seperately to define  the mapping of the various timing services
SB> over that LSP type.

    The first method is to transport Timing messages directly over the
    dedicated MPLS LSP via UDP/IP encapsulation, which is suitable for
    MPLS networks.  The second method is to transport Timing messages
    inside a PW via Ethernet encapsulation.

SB> I think that we should note that there are some
SB> h/w reasons for this preference. A clean sheet approach
SB> would have been to use PTP over MPLS with no intermediate
SB> layers.

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
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    Drafts is at http://datatracker.ietf.org/drafts/current/.

    Internet-Drafts are draft documents valid for a maximum of six months
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    material or to cite them other than as "work in progress."

    This Internet-Draft will expire on December 17, 2013.

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Copyright Notice

    Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . .  5

    2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  7

    3.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  8

    4.  Timing over MPLS Architecture  . . . . . . . . . . . . . . . .  9

    5.  Dedicated LSPs for Timing messages . . . . . . . . . . . . . . 12

    6.  Timing over LSP Encapsulation  . . . . . . . . . . . . . . . . 13
      6.1.  Timing over UDP/IP over MPLS Encapsulation . . . . . . . . 13
      6.2.  Timing over PW Encapsulation . . . . . . . . . . . . . . . 13
      6.3.  Other Timing Encapsulation methods . . . . . . . . . . . . 14

    7.  Timing message Processing  . . . . . . . . . . . . . . . . . . 15

    8.  Protection and Redundancy  . . . . . . . . . . . . . . . . . . 16

    9.  ECMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

    10. PHP  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

    11. Entropy  . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

    12. OAM, Control and Management  . . . . . . . . . . . . . . . . . 20

    13. QoS Considerations . . . . . . . . . . . . . . . . . . . . . . 21

    14. FCS and Checksum Recalculation . . . . . . . . . . . . . . . . 22

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    15. Behavior of LER/LSR  . . . . . . . . . . . . . . . . . . . . . 23
      15.1. Behavior of Timing-capable/aware LER . . . . . . . . . . . 23
      15.2. Behavior of Timing-capable/aware LSR . . . . . . . . . . . 23
      15.3. Behavior of non-Timing-capable/aware LSR . . . . . . . . . 24

    16. Other considerations . . . . . . . . . . . . . . . . . . . . . 25

    17. Security Considerations  . . . . . . . . . . . . . . . . . . . 26

    18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27

    19. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 28

    20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
      20.1. Normative References . . . . . . . . . . . . . . . . . . . 29
      20.2. Informative References . . . . . . . . . . . . . . . . . . 29

    Appendix 1.  Routing extensions for Timing-aware Routers . . . . . 32

    Appendix 2.  Signaling Extensions for Creating Timing LSPs . . . . 33

    Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34

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    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 [RFC2119].

    When used in lower case, these words convey their typical use in
    common language, and are not to be interpreted as described in
    RFC2119 [RFC2119].

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1.  Introduction

    The objective of Precision Time Protocol (PTP) and Network Timing
    Protocol (NTP) are to synchronize independent clocks running on
    separate nodes of a distributed system.

    [IEEE-1588] defines PTP messages for frequency, phase and time
    synchronization.  The PTP messages include PTP PDUs over UDP/IP
    (Annex D and E of [IEEE-1588]) and PTP PDUs over Ethernet (Annex F of
    [IEEE-1588]).

SB> Sure BUT it is acknowledged that IEEE is open to the definition
SB> of other PTP mappings if they provide better optimisation.

    This document defines mapping and transport of the PTP
    messages defined in [IEEE-1588] over MPLS/MPLS-TP networks.  PTP
    defines several clock types: ordinary clocks, boundary clocks, end-
    to-end transparent clocks, and peer-to-peer transparent clocks.
    Transparent clocks require intermediate nodes to update correction
    field inside PTP message that reflects the transit time in the node.

    [RFC5905] defines NTP messages for clock and time synchronization.
    The PTP messages (PDUs) are transported over UDP/IP.  This document
SB> Should that be NTP messages?
SB> It needs to be made clear as soon as you introduce NTP that
SB> they use different time representations.

    defines mapping and transport of the NTP messages defined in
    [RFC5905] over MPLS networks.

    One key attribute of all of these Timing messages is that the Time
    stamp processing should occur as close as possible to the actual
    transmission and reception at the physical port interface.  This
    targets optimal time and/or frequency recovery by avoiding variable
    delay introduced by queues internal to the clocks.

SB> As I recall NTP has no epoch point defined, and I am not sure
SB> where that point is in the case of PTP in this mapping
SB> Hopefully this will get defined in due course.

    To facilitate the fast and efficient recognition of Timing messages
    at the port level when the Timing messages are carried over MPLS
    LSPs,

SB> Over a new LSP type with time optimied characteristics

    this document defines the specific encapsulations that should
    be used.
SB> Hopefully it will also define the PHP

    In addition, it can be expected that there will exist LSR/
    LERs where only a subset of the physical ports will have the port-
    based Timing message processing capabilities.
SB> Do you need to clarify that this only works at base and not in
SB> a label heirarchy.

    In order to ensure
    that the LSPs carrying Timing packets always enter and exit ports
    with this capability, routing extensions are defined to advertise
    this capability on a port basis and to allow for the establishment of
    LSPs that only transit such ports.  While this path establishment
    restriction may be applied only at the LER Ingress and/or egress
    ports, it becomes more important when using transparent clock capable
    LSRs in the path.
SB> I do not understand the implications of the last
SB> sentences - starting ", it becomes"

    Port based Timing message processing involves Timing message
    recognition.  Once the Timing messages are recognized they can be
    modified based on the reception or transmission Time-stamp.

    This document provides two methods for transporting Timing messages
    over MPLS.  One is applicable to MPLS environment and the other one
    is applicable to MPLS/MPLS-TP environment

SB> I think the sentence is incomplete.

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    The solution involves transporting Timing messages over dedicated
    LSPs called Timing LSPs.  These LSPs carry Timing messages and MAY
    carry Management and control messages, but not data plane client
    traffic.

SB> It is not clear why this restriction applies.

    Timing LSPs can be established statically or via signaling.
SB> s/statically/by provisioning/network management/

    Extensions to control plane (OSPF, ISIS, etc.) is required to enable
    routers to distribute their Timing processing capabilities over MPLS
    to other routers.  However such extensions are outside the scope of
    this document.

    When signaling is used to setup the PTP LSP, Extensions to signaling
SB> is it a PTP LSP or a Timing LSP?

    protocols (e.g., RSVP-TE) are required for establishing PTP LSPs.
    However such extensions are outside the scope of this document.

SB> for mpls-tp GMPLS is the signalling protocol

    While the techniques included herein allow for the establishment of
    paths optimized to include Time-stamping capable links, the
    performance of the Slave clocks is outside the scope of this
    document.

    At the time of publishing this specification, Transparent Clocking
    (TC) is only defined for PTP.  Therefore at this time any part of
    this specification that talks about Transparent Clocking applies only
    to PTP.

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2.  Terminology

    1588: The timing and synchronization as defined by IEEE 1588.

SB> I think that there is a more formal name for the 1588 group
SB> that needs to be used here.
SB> Also do we need to talk about 1588-200? as there is
SB> an update in progress

    NTP: The timing and synchronization protocol defined by IETF RFC-1305
    and RFC-5905.

    PTP: The timing and synchronization protocol used by 1588.
SB> need the proper name for 1588

    Master Clock: The source of 1588 timing to a set of slave clocks.

    Master Port: A port on a ordinary or boundary clock that is in Master
    state.  This is the source of timing toward slave ports.

SB> I am not sure the reader knows what a port is

    Slave Clock: A receiver of 1588 timing from a master clock.

    Slave Port: A port on a boundary clock or ordinary clock that is
    receiving timing from a master clock.

    Ordinary Clock: A device with a single PTP port.

    Transparent Clock.  A device that measures the time taken for a PTP
    event message to transit the device and then updates the
    correctionField of the message with this transit time.

    Boundary Clock: A device with more than one PTP port.  Generally
    boundary clocks will have one port in slave state to receive timing
    and then other ports in master state to re-distribute the timing.

    PTP LSP: An LSP dedicated to carry PTP messages

SB> PTP or timing?

    PTP PW: A PW within a PTP LSP that is dedicated to carry PTP
    messages.

SB> Ah I don't think that PWE3 know what one of these is

    CW: Pseudowire Control Word

    LAG: Link Aggregation

    ECMP: Equal Cost Multipath

    CF: Correction Field, a field inside certain PTP messages (message
    type 0-3)that holds the accumulative transit time inside intermediate
    switches

    Timing messages: Timing Protocol messages that are exchanged between
    routers in order to establish a synchronized clock.

SB> A number of these definitions look like copies of IEEE1588
SB> definitions. We need to provide references and note the
SB> priority of the IEEE base reference.

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3.  Problem Statement

    [IEEE-1588] has defined methods for transporting PTP messages over
    Ethernet and IP networks.  [RFC5905] has defined the method of
    transporting NTP messages over IP networks.  There is a need to
    transport Timing messages over MPLS networks while supporting the
    Transparent Clock (TC), Boundary Clock (BC) and Ordinary Clock (OC)
    functionality in the LER and LSRs in the MPLS network.

    There are multiple ways of transporting Timing over MPLS.  However,
    there is a requirement to limit the possible encapsulation options to
    simplify the Timing message identification and processing required at
    the port level.

    When Timing-awareness is needed, Timing messages should not be
    transported over LSPs or PWs that are carrying customer traffic
    because LSRs perform Label switching based on the top label in the
    stack.

SB> Have you explained why?

    To detect Timing messages inside such LSPs require special
    hardware to do deep packet inspection at line rate.  Even if such
    hardware exists, the payload can't be deterministically identified by
    LSRs because the payload type is a context of the PW label, and the
    PW label and its context are only known to the Edge routers (PEs/
    LERs); LSRs dont know what is a PWs payload (Ethernet, ATM, FR, CES,
    etc).  Even if one restricts an LSP to only carry Ethernet PWs, the
    LSRs dont have the knowledge of whether PW Control Word (CW) is
    present or not and therefore can not deterministically identify the
    payload.

    A generic method is defined in this document that does not require
    deep packet inspection at line rate, and can deterministically
    identify Timing messages.  This method can be used to detect Timing
    Messages in both one-step and two-step clock implementations of
    ordinary, boundary and transparent clocks.

SB> Needs a ref and I am sure many MPLS specialists will not understand
SB> the msg types.

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4.  Timing over MPLS Architecture

    Timing messages are exchange between Timing ports on ordinary and

SB> Have you defined a timing port?

    boundary clocks.  Boundary clocks terminate the Timing messages and
    act as master for other boundary clocks or for slave clocks.  End-to-
    End Transparent clocks do not terminate the Timing messages but they
    do modify the contents of the Timing messages as they transit across
    the transparent clock.

    Master/Slave clocks (OCs), Boundary Clocks (BC) and Transparent Clock

    (TC) could be implemented in either LERs or LSRs.

SB> LER and LSR need to be expanded

    An example is shown in Figure 1, where the LERs act as Ordinary Clock
    (OC) and are the initiating/terminating point for Timing messages.
    The ingress LER encapsulates the Timing messages in Timing LSP and
    the Egress LER terminates the Timing LSP.  The LSRs act as
    Transparent Clock (TC) and just update the Timing field in the Timing
    messages.

       +--------+     +-------+     +-------+     +-------+     +--------+
       |Switch, |     |       |     |       |     |       |     |Switch, |
       | Router |-----|  LER  |-----|  LSR  |-----|  LER  |-----| Router |
       |        |     |  OC   |     |  TC   |     |  OC   |     |        |
       +--------+     +-------+     +-------+     +-------+     +--------+
                      /                                 \
       +-------+     /                                   \     +-------+
       |  LER  |    /                                     \    |  LER  |
       | Master|---/                                       \---| Slave |
       | Clock |                                               | Clock |
       +-------+                                               +-------+

      Figure (1) - Deployment example 1 of timing over MPLS network

    Another example is shown in Figure2, where LERs terminate the Timing
    messages received from switch/routers that are outside of the MPLS
    network acting as OC or BC.  In this example LERs regenerate the
    clock and initiate timing messages encapsulated in Timing LSP toward
    the MPLS network, while the LSRs act as Transparent Clock (TC) and
    just update the Timing field in the Timing messages, which are
    already encapsulated in Timing LSPs.

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      +--------+     +-------+     +-------+     +-------+     +--------+
      |Switch, |     |       |     |       |     |       |     |Switch, |
      | Router |-----|  LER  |-----|  LSR  |-----|  LER  |-----| Router |
      | OC/BC  |     |  BC   |     |  TC   |     |  BC   |     | OC/BC  |
      +--------+     +-------+     +-------+     +-------+     +--------+

      Figure (2) - Deployment example 2 of timing over MPLS network

    Another example is shown in Figure 3, where LERs do not terminate the
    Timing messages received from switch/routers that are outside of the
    MPLS network acting as OC, TC or BC.  The LERs act as TC and update
    the Timing field in the Timing messages as they transit the LER,
    while encapsulating them in timing LSP.  The LSRs also act as
    Transparent Clock (TC) and just update the Timing field in the Timing
    messages which are already encapsulated in Timing LSPs.

       +--------+     +-------+     +-------+     +-------+     +--------+
       |Switch, |     |       |     |       |     |       |     |Switch, |
       | Router |-----|  LER  |-----|  LSR  |-----|  LER  |-----| Router |
       |OC/TC/BC|     |  TC   |     |  TC   |     |  TC   |     |OC/TC/BC|
       +--------+     +-------+     +-------+     +-------+     +--------+

     Figure (3) - Deployment example 3 of timing over MPLS network

    Another example is shown in Figure 4, where LERs and LSRs support
    Boundary Clocks.  A single-hop LSP is created between two adjacent
    LSRs engaged in BC operation.  Other methods such as PTP transport
    over Ethernet MAY be used for transporting timing messages if the
    link between the two routers is Ethernet.

      +--------+     +-------+     +-------+     +-------+     +--------+
      |Switch, |     |       |     |       |     |       |     |Switch, |
      | Router |-----|  LER  |-----|  LSR  |-----|  LER  |-----| Router |
      | OC/BC  |     |  BC   |     |  BC   |     |  BC   |     | OC/BC  |
      +--------+     +-------+     +-------+     +-------+     +--------+

    Figure (4) - Deployment example 3 of timing over MPLS network

    An MPLS domain MAY serve multiple customers.  In these cases the MPLS
    domain (maintained by a service provider) may provide timing services
    to multiple customers, each having their own Timing domain.

    The Timing over MPLS architecture assumes full mesh of Timing LSPs
    between all LERs supporting this specification.

SB> Note sure this is right - the salves surely do not need to
SB> exchange timing amongst themselves

    It supports
    Point-to- point (VPWS) and Multipoint (VPLS) services.

SB> What does that mean? You do not carry user data traffic?
SB> Maybe it's the ordering of the statemnets that is causing
SB> confusion.

    This means
    that a customer may purchase a Point-to-point Timing service between
    two customer sites or a Multipoint Timing service between more than

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    two customer sites.

    The Timing over MPLS architecture supports P2P or P2MP Timing LSPs.
    This means that the Timing Multicast messages such as PTP Multicast
    event messages can be transported over P2MP Timing LSP or be
    replicated and transported over many P2P Timing LSPs.

SB> Note we do not yet have a definition of a P2MP mpls-tp LSP
SB> nor a P2MP PW, although we are close.

    Timing messages, that do not require Time stamping or Correction
    Field update MAY be transported over Timing LSPs to simplify hardware
    and software.

    PTP Announce messages that determine the Timing LSP terminating point
    behavior such as BC/OC/TC SHOULD be transported over the Timing LSP
    to simplify hardware and software.

SB> have you defined and referenced PTP announce msgs?

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5.  Dedicated LSPs for Timing messages

    Many methods have been considered for identifying the Timing messages
    when they are encapsulated in MPLS such as using GAL/G-ACH or a new
    reserved label.  These methods were not attractive since they either
    required deep packet inspection at line rate in the intermediate LSRs
    or they required use of a scarce new reserved label.  Also one of the
    goals was to reuse existing OAM mechanisms.

SB> RLs = SPLs are not so rare now. In any case needs a ref.

    The method defined in this document can be used by LER and LSRs to
    identify Timing messages in MPLS tunnels by just looking at the top
    label in the MPLS label stack, which only carry Timing messages as
    well as OAM, but not data plane client traffic.

    Compliant implementations MUST use dedicated LSPs to carry Timing
    messages over MPLS.

SB> I think that we need a definition of the properies of these LSPs

    These LSPs are herein referred to as "Timing
    LSPs" and the labels associated with these LSPs as "Timing LSP
    labels".  The Timing LSPs that runs between Ingress and Egress LERs
    MUST be co-routed.  Alternatively, a single bidirectional co-routed
    LSP can be used.

SB> I though that you said you could use M2MP LSPs - these are not
SB> bidirectional.

    Co-routing of the two directions is required to limit the difference
    in the delays in the Master clock to Slave clock direction compared
    to the Slave clock to Master clock direction.  The Timing LSP MAY be
    MPLS/MPLS-TP LSP.

    The Timing LSPs could be configured or signaled via RSVP-TE/GMPLS.
    New Extensions to RSVP-TE/GMPLS TLVs are required; however they are
    outside the scope of this document.

    The Timing LSPs MAY carry essential MPLS/MPLS-TP OAM traffic such as
    BFD and LSP Ping but the LSP data plane client plane traffic MUST be
    Timing packets only.

SB> Why?

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6.  Timing over LSP Encapsulation

The encapsulations is not LSP is it?

    This document defines two methods for carrying Timing messages over
    MPLS.  The first method is carrying UDP/IP encapsulated Timing
    messages over Timing LSPs, and the second method, is carrying
    Ethernet encapsulated Timing messages over Ethernet PWs inside Timing
    LSPs.

6.1.  Timing over UDP/IP over MPLS Encapsulation

    The simplest method of transporting Timing messages over MPLS is to
    encapsulate Timing PDUs in UDP/IP and then encapsulate them in Timing
    LSP.  This format is shown in Figure 4.

                     +----------------------+
                     |   Timing LSP Label   |
                     +----------------------+
                     |        IPv4/6        |
                     +----------------------+
                     |         UDP          |
                     +----------------------+
                     |     Timing PDU       |
                     +----------------------+

       Figure (4) - Timing over UDP/IP over MPLS Encapsulation

    This encapsulation is very simple and is useful when the network
    between Timing Master Clock and Slave Clock is MPLS network.

SB> Simple is a judgement call

    In order for an LER/LSR to process Timing messages, the Timing LSP
    Label must be at the top label of the label stack.  The LER/LSR MUST
    know that the Timing LSP Label is used for carrying Timing messages.
    This can be accomplished via static configuration or via RSVP-TE
    signaling.

    The UDP/IP encapsulation of PTP MUST follow Annex D and E of
    [IEEE-1588].  While the UDP/IP encapsulation of NTP MUST follow
    [RFC5905].

6.2.  Timing over PW Encapsulation

    Another method of transporting Timing over MPLS networks is by
    encapsulating Timing PDUs in PW which in turn is transported over
    Timing LSPs.  In case of PTP, Ethernet PW encapsulation [RFC4448],
    shown in Fig 5(A) MUST be used and the Ethernet encapsulation of PTP
    MUST follow Annex F of [IEEE-1588].

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    The RAW mode or Tagged mode defined in [RFC4448] MAY be used and the
    Payload MUST have 0, 1, or 2 VLAN tags (S-VLAN and C-VLAN).  The
    Timing over PW encapsulation MUST use the Control Word (CW) as
    specified in [RFC4448] to ensure proper detection of PTP messages
    inside the MPLS packets for Timing over LSP and Timing over PW
    encapsulation.

SB> That needs explanation

    The use of Sequence Number in the CW is optional.

SB> Given that s/n are never in practice deployed, you could probably
SB> simplify things by sayig that they are not used.

    Timing over PW encapsulation for NTP MUST use NTP over UDP/IP over PW
    (the IP PW discussed in [RFC4447]) shown in Fig 5(B).

                     +----------------+  +----------------+
                      |Timing LSP Label|  |Timing LSP Label|
                      +----------------+  +----------------+
                      |    PW Label    |  |    PW Label    |
                      +----------------+  +----------------+
                      |  Control Word  |  |      IP        |
                      +----------------+  +----------------+
                      |    Ethernet    |  |      UDP       |
                      |     Header     |  +----------------+
                      +----------------+  |   Timing PDU   |
                      |S-VLAN(Optional)|  |                |
                      +----------------+  +----------------+
                      |C-VLAN(Optional)|        (B)
                      +----------------+
                      |   Timing PDU   |
                      |                |
                      +----------------+
                             (A)

               Figure (5) - Timing over PW Encapsulations

    In order for an LSR to process PTP messages, the top label of the
    label stack (the Tunnel Label) MUST be a Timing label.

S> You said that before.

6.3.  Other Timing Encapsulation methods

    In future other timing encapsulation methods may be introduced, such
    as a new shim header after the Bottom of Stack to carry the Timing
    information.  Such new encapsulations are outside the scope of this
    document.

SB> Taking a pure MPLS pov, you can simplify a lot of the text
SB> out of the definition of the LSP

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SB> I think we need a section on LSP processing

7.  Timing message Processing

    Each Timing protocol such as PTP and NTP, define their set of Timing
    messages.  For example PTP defines SYNC, DELAY_REQ, DELAY_RESP,
    FOLLOW_UP, etc messages.

    Some of the Timing messages require time stamping or correction field
    update at port level and some dont.  It is the job of the LER/LSR to
    parse the timing message and find out the type of the Timing message
    and decide whether and how to Time- stamp it (e.g., BC) or update
    correction field(e.g., TC).

SB> AAAAAAAAAAAH. Surely this is the function of the PTP prcessing
SB> function rather than the LER?

    For example the following PTP messages (called Event messages)
    require time-stamping or correction field update:

    o  SYNC

    o  DELAY_REQ (Delay Request)

    o  PDELAY_REQ (Peer Delay Request)

    o  PDELAY_RESP (Peer Delay Response)

    SYNC and DELAY_REQ are exchanged between Master Clock and Slave Clock
    and MUST be transported over PTP LSPs.  PDELAY_REQ and PDELAY_RESP
    are exchanged between adjacent PTP clocks (i.e.  Master, Slave,
    Boundary, or Transparent) and SHOULD be transported over single hop
    PTP LSPs.  If Two Step PTP clocks are present, then the FOLLOW_UP,
    and PDELAY_RESP_FOLLOW_UP messages MUST also be transported over the
    PTP LSPs.

    For a given instance of 1588 protocol, SYNC and DELAY_REQ MUST be
    transported over two PTP LSPs that are in opposite directions.  These
    PTP LSPs, which are in opposite directions MUST be congruent and co-
    routed.  Alternatively, a single bidirectional co-routed LSP can be
    used.

    Except as indicated above for the two-step PTP clocks, Non-Event PTP
    message types do not need to be processed by intermediate routers.
    These message types MAY be carried in PTP Tunnel LSPs.

SB> Are you saying that a timing P router has to be msg type sensitive?

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8.  Protection and Redundancy

SB> This is a bit of a jump - I don't know how the LSP itself works yet!

    In order to ensure continuous uninterrupted operation of slave
    clocks, usually as a general practice, slave clocks (or ports) track
    redundant master clocks.

    It is the responsibility of the network operator to ensure that
    physically disjoint Timing LSPs are established between a slave clock
    (or port) and redundant master clocks (or ports).

    When a slave clock (or port) listens to redundant master clocks or
    ports, any prolonged Timing LSP outage will trigger the slave clock
    or port to switch to a redundant master clock or port.

    LSP/PW protection such as Linear protection Switching (1:1, 1+1),
    Ring protection switching or MPLS Fast Reroute (FRR) generally switch
    alternative path that usually cause a change in delay, which if
    undetected by slave clock can reduce accuracy of the slave clock.

    Therefore protection switching MAY be used, as long as phase jumps
    upon switchover due to differences in path latency are detected and
    compensated for (such compensation not being required if BCs or peer-
    peer TCs are used throughout).

    Note that any protection or reroute mechanism that adds additional
    MPLS label to the label stack, such as Facility Backup Fast Reroute,
    MUST ensure that the pushed label is also a Timing Label to ensure
    recognition of the MPLS frame as containing Timing messages, as it
    transits the backup path.

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9.  ECMP

    To ensure the optimal operation of slave clocks and avoid error
    introduced by forward and reverse path delay asymmetry, the physical
    path for Timing messages from master clock to slave Clock and vice
    versa must be the same for all Event Timing messages listed in
    section 7.

    Therefore the Timing LSPs MUST not be subject to ECMP (Equal Cost
    Multipath).

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10.  PHP

    To ensure that the label on the top of the label stack is the Timing
    LSP Label, PHP MUST not be used.

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11.  Entropy

    To ensure all Timing messages in a Timing LSP take the same path,
    Entropy Label MUST NOT be used for the Timing LSP[RFC6790] and
    Entropy Label MUST NOT be used for the PWs that are carried inside
    Timing LSP [RFC6391].

SB> This is incorrect - you mean that all msgs of the same timing
SB> flow need to have the same EL value.

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12.  OAM, Control and Management

    In order to monitor Timing LSPs and their encapsulated PWs, they MUST
    be able to carry OAM and management messages.  These management
    messages MUST be differentiated from Timing messages via already
    defined IETF methods.

    For example BFD [RFC5880], [RFC5884] and LSP-Ping [RFC4389] MAY run
    over PTP LSPs via UDP/IP encapsulation or via GAL/G-ACH.  These
    Management protocols can easily be identified by the UDP Destination
    Port number or by GAL/G-ACH respectively.

    Also BFD, LSP-Ping and other management messages MAY run over the PWs
    encapsulated in Timing LSP via one of the defined VCCVs (Type 1, 3 or
    4) [RFC5085] (note that VCCV Type 2 using Router Alert Label is going
    to be deprecated by IETF).  In this case G-ACH, PW label (TTL=1) or
    GAL-ACH are used to identify such management messages.

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13.  QoS Considerations

    In network deployments where not every LSR/LER is Timing-aware, it is
    important to reduce the impact of the non-Timing-aware LSR/LERs on
    the timing recovery in the slave clock.  The Timing messages are time
    critical and must be treated with the highest priority.  Therefore
    Timing over MPLS messages must be treated with the highest priority
    in the routers.  This can be achieved by proper setup of Timing LSPs.

    It is recommended that the Timing LSPs are setup or configured
    properly to indicate EF-PHB [RFC3246]for the CoS and Green [RFC2697]
    for drop eligibility.

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14.  FCS and Checksum Recalculation

    When time-stamp generation and timing packet adjustment is performed
    near the physical port hardware, the process MUST include
    recalculation of the Ethernet FCS.

SB> The above is confusing - an LSR always recomputes the link layer
SB> CRC which may or may not be Ethernet.

    Also FCS retention for the
    payload Ethernet described in [RFC4720] MUST NOT be used.

    For UDP/IP encapsulation mode of Timing over MPLS, the UDP checksum
    may be required as per UDP transport standards.

SB> You really need to be working on getting the IPv6 C?S computation
SB> removed from PTP msgs.

    When UDP checksum is used, each Timing-aware LER/LSR must either
    incrementally update the UDP checksum after Time stamping or
    Correction Field update or verify the UDP checksum on reception from
    upstream and recalculate the checksum completely on transmission to
    downstream node after Time stamping or Correction Field update.

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15.  Behavior of LER/LSR

    Timing-capable/aware LERs and LSRs are routers that have one or more

SB> You mean physical interfaces?

    interfaces that can perform Timing operations (OC/BC/TC) on Timing
    packets and are configured to do so.  Timing-capable/aware LERs and
    LSRs can advertise their Timing-capability per-interface via control
    plane such as OSPF or IS-IS.
SB> ISIS and OSPF are routing protocols.

   The Timing-capable/aware LERs can then
    signals Timing LSPs via RSVP-TE signaling.  Alternatively the Timing
    capability of LER and LSRs may be configured in a centralized
    controller and the Timing LSP may be setup using manual configuration
    or other methods such as SDN.

SB> it can also be configured individually rather then through
SB> a cebtral controllwe

15.1.  Behavior of Timing-capable/aware LER

    When a Timing-capable/aware LER behaves as a Transparent clock and
    receives a Timing message from a Timing-capable/aware non-MPLS
    interface, the LER updates the Correction Field (CF) and encapsulates
    and forwards the timing message over previously established Timing
    LSP.

SB> You need to call out the details so that people properly
SB> understand the definition of the new LSP.

    Also when a Timing message is received from a Timing-capable/
    aware MPLS interface, LER updates the Correction Filed (CF) and
    decapsulates the MPLS encapsulation and forwards the timing message
    to a non-MPLS interface.

    When a Timing-capable/aware LER behaves as a Boundary clock and
    receives a Timing message from a Timing-capable/aware non MPLS
    interface, the LER Timestamps the Timing packet and sends it to the
    LERs Boundary clock processing module.  Also when a Timing message is
    received from a Timing- capable/aware MPLS interface, the LER
    Timestamps the Timing packet and sends it to the LERs Boundary clock
    processing module.

    When a Timing-capable/aware LER behaves as an Ordinary Clock toward
    the MPLS network, and receives a Timing message from a Timing-
    capable/aware MPLS interface, the LER Timestamps the Timing packet
    and sends it to the LERs Ordinary clock processing module.

15.2.  Behavior of Timing-capable/aware LSR

    When a Timing-capable/aware LSR behaves as a Transparent clock and
    receives a Timing message from a Timing-capable/aware MPLS interface,
    The LSR updates the Correction Filed (CF) and forwards the timing
    message over another MPLS interface.

    When a Timing-capable/aware LSR behaves as a Boundary clock and
    receives a Timing message from a Timing-capable/aware MPLS interface.
    The LSR performs the functions of a Boundary Clock in terminating the
    received Timing message and re-generating a new timing message over
    another (or the same) MPLS interface.

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15.3.  Behavior of non-Timing-capable/aware LSR

    It is most beneficial when all LSRs in the path of a Timing LSP be
    timing-Capable/aware LSRs.  This would ensure the highest quality
    time and clock synchronization by Timing Slave Clocks.  However, this
    specification does not mandate that all LSRs in path of a Timing LSP
    be Timing- capable/aware.

    Non-Timing-capable/aware LSRs just switch the packets encapsulated in
    Timing LSPs and dont perform any Timing operation (TC or BC).
    However as explained in QoS section the Timing over MPLS packets MUST
    be still be treated with the highest priority based on their Traffic
    Class (TC) marking.

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16.  Other considerations

    [IEEE-1588] defines an optional peer-to-peer Transparent clocking
    that requires peer delay measurement between two adjacent Timing-
    capable/ aware routers/switches.  Peer delay measurement messages
    need to be time stamped and terminated by the Timing-capable/aware
    routers/ switches.  This means that two adjacent LSRs may be engaged
    in a peer delay measurement.

    For transporting such peer delay measurement messages a single-hop
    LSP SHOULD to be created between the two adjacent LSRs engaged in
    peer delay measurement to carry peer delay measurement messages.
    Other methods such as PTP transport over Ethernet MAY be used for
    transporting peer delay measurement messages if the link between the
    two routers is Ethernet.

    In Peer-to-peer transparent clocking (P2P TC), a Timing-capable/ ware
    routers/switches MUST maintain a list of all the neighbors it needs
    to send a PDelay_Req to, where each neighbor corresponds to a timing
    LSP.

    The use of Explicit Null Label (Label= 0 or 2) is acceptable as long
    as either the Explicit Null label is the bottom of stack label
    (applicable only to UDP/IP encapsulation) or the label below the
    Explicit Null label is a PTP label.

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17.  Security Considerations

    MPLS PW security considerations in general are discussed in [RFC3985]
    and [RFC4447],and those considerations also apply to this document.

    An experimental security protocol is defined in [IEEE-1588].The PTP
    security extension and protocol provides group source authentication,
    message integrity, and replay attack protection for PTP messages.

    When the MPLS network (provider network) serves multiple customers,
    it is important to maintain and process each customers clock and
    Timing messages separately from other customers to ensure there is no
    cross- customer effect.  For example if an LER BC is synchronized to
    a specific grandmaster, belonging to customer A, then the LER MUST
    use that BC clock only for customer A to ensure that customer A
    cannot attack other customers by manipulating its time.

    Timing messages MAY be encrypted or authenticated, provided that the
    LERs/LSRs that are Timing capable/aware can authenticate/ decrypt the
    timing messages.

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18.  Acknowledgements

    The authors would like to thank Ron Cohen, Yaakov Stein, Tal Mizrahi,
    Stefano Ruffini, Peter Meyer, and other members of IETF for reviewing
    and providing feedback on this draft.

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19.  IANA Considerations

    There are no IANA requirements in this specification.

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20.  References

20.1.  Normative References

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

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

    [RFC3985]  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
               Edge (PWE3) Architecture", RFC 3985, March 2005.

    [RFC4389]  Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
               Proxies (ND Proxy)", RFC 4389, April 2006.

    [RFC4447]  Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
               Heron, "Pseudowire Setup and Maintenance Using the Label
               Distribution Protocol (LDP)", RFC 4447, April 2006.

    [RFC4448]  Martini, L., Rosen, E., El-Aawar, N., and G. Heron,
               "Encapsulation Methods for Transport of Ethernet over MPLS
               Networks", RFC 4448, April 2006.

    [RFC4720]  Malis, A., Allan, D., and N. Del Regno, "Pseudowire
               Emulation Edge-to-Edge (PWE3) Frame Check Sequence
               Retention", RFC 4720, November 2006.

    [RFC5085]  Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
               Connectivity Verification (VCCV): A Control Channel for
               Pseudowires", RFC 5085, December 2007.

    [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
               (BFD)", RFC 5880, June 2010.

    [RFC5884]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
               "Bidirectional Forwarding Detection (BFD) for MPLS Label
               Switched Paths (LSPs)", RFC 5884, June 2010.

20.2.  Informative References

    [I-D.ietf-pwe3-fat-pw]
               Bryant, S., Filsfils, C., Drafz, U., Kompella, V., Regan,
               J., and S. Amante, "Flow Aware Transport of Pseudowires
               over an MPLS Packet Switched Network",
               draft-ietf-pwe3-fat-pw-07 (work in progress), July 2011.

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    [ISO]      ISO/IEC 10589:1992, "Intermediate system to Intermediate
               system routeing information exchange protocol for use in
               conjunction with the Protocol for providing the
               Connectionless-mode Network Service (ISO 8473)".

    [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
               dual environments", RFC 1195, December 1990.

    [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

    [RFC2697]  Heinanen, J. and R. Guerin, "A Single Rate Three Color
               Marker", RFC 2697, September 1999.

    [RFC3246]  Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
               J., Courtney, W., Davari, S., Firoiu, V., and D.
               Stiliadis, "An Expedited Forwarding PHB (Per-Hop
               Behavior)", RFC 3246, March 2002.

    [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
               (TE) Extensions to OSPF Version 2", RFC 3630,
               September 2003.

    [RFC3784]  Smit, H. and T. Li, "Intermediate System to Intermediate
               System (IS-IS) Extensions for Traffic Engineering (TE)",
               RFC 3784, June 2004.

    [RFC4970]  Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
               Shaffer, "Extensions to OSPF for Advertising Optional
               Router Capabilities", RFC 4970, July 2007.

    [RFC4971]  Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
               System to Intermediate System (IS-IS) Extensions for
               Advertising Router Information", RFC 4971, July 2007.

    [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
               Topology (MT) Routing in Intermediate System to
               Intermediate Systems (IS-ISs)", RFC 5120, February 2008.

    [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
               Engineering", RFC 5305, October 2008.

    [RFC5329]  Ishiguro, K., Manral, V., Davey, A., and A. Lindem,
               "Traffic Engineering Extensions to OSPF Version 3",
               RFC 5329, September 2008.

    [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
               for IPv6", RFC 5340, July 2008.

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

    [RFC6391]  Bryant, S., Filsfils, C., Drafz, U., Kompella, V., Regan,
               J., and S. Amante, "Flow-Aware Transport of Pseudowires
               over an MPLS Packet Switched Network", RFC 6391,
               November 2011.

    [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
               L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
               RFC 6790, November 2012.

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1.  Routing extensions for Timing-aware Routers

    MPLS-TE routing relies on extensions to OSPF [RFC2328] [RFC5340] and
    IS-IS [ISO] [RFC1195] in order to advertise Traffic Engineering (TE)
    link information used for constraint-based routing.

    Indeed, it is useful to advertise data plane TE router link
    capabilities, such as the capability for a router to be Timing-aware.
    This capability MUST then be taken into account during path
    computation to prefer or even require links that advertise themselves
    as Timing-aware.  In this way the path can ensure the entry and exit
    points into the LERs and, if desired, the links into the LSRs are
    able to perform port based time-stamping thus minimizing their impact
    on the performance of the slave clock.

    extensions are required to OSPF and IS-IS in order to advertise
    Timing-aware capabilities of a link.  Such extensions are outside the
    scope of this document; however such extension SHOULD be able to
    signal the following information per Router Link:

    o  Capable of processing PTP, NTP or other Timing flows

    o  Capable of performing Transparent Clock operation

    o  Capable of performing Boundary Clock operation

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2.  Signaling Extensions for Creating Timing LSPs

    RSVP-TE signaling MAY be used to setup the timing LSPs.  When RSVP-TE
    is used to setup Timing LSPs, some information that indicates that
    the LSP is carrying Timing flows MUST be included in the new
    Extensions to RSVP-TE:

    The following information MAY also be included in the new Extensions
    to RSVP-TE:

    o  Offset from Bottom of Stack (BoS) to the start of the Time-stamp
       field

    o  Number of VLANs in case of PW encapsulation

    o  Timestamp field Type

       *  Correction Field, Timestamp

    o  Timestamp Field format

       *  64-bit PTPv1, 80-bit PTPv2, 32-bit NTP, 64-bit NTP, 128-bit
          NTP, etc.

    Note that in case the above optional information is signaled with
    RSVP-TE for a Timing LSP, all the Timing packets carried in that LSP
    must have the same signaled characteristics.  For example if
    Timestamp format is signaled as 64-bit PTPv1, then all Timing packets
    must use 64-bit PTPv1 time-stamp.

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Authors' Addresses

    Shahram Davari
    Broadcom Corp.
    San Jose, CA  95134
    USA

    Email: [email-masked]

    Amit Oren
    Broadcom Corp.
    San Jose, CA  95134
    USA

    Email: [email-masked]

    Manav Bhatia
    Alcatel-Lucent
    Bangalore,
    India

    Email: [email-masked]

    Peter Roberts
    Alcatel-Lucent
    Kanata,
    Canada

    Email: [email-masked]

    Laurent Montini
    Cisco Systems
    San Jose CA
    USA

    Email: [email-masked]

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    Luca
    Cisco Systems
    San Jose CA
    USA

    Email: [email-masked]

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-- 
For corporate legal information go to:

http://www.cisco.com/web/about/doing_business/legal/cri/index.html

---

From: "Shahram Davari" <[email-masked]>
Date: Fri, 2 Aug 2013 10:23:33 +0000

Hi Stewart

We have already looked at similar approach. The issue with one hop LSP is that not all LSRs are 1588 capable. One of the requirements is for non-1588 capable routers to just switch the packet normally.

Regards,
Shahram

On Aug 2, 2013, at 12:02 PM, "Stewart Bryant" <[email-masked]> wrote:

> _______________________________________________
> mpls mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mpls
>

---

From: John E Drake <[email-masked]>
Date: Fri, 2 Aug 2013 10:51:41 +0000

Shahram,

The LSPs would be between LSRs that are 1588 capable, so they could be one or more hops.

Yours Irrespectively,

John

> -----Original Message-----
> From: Shahram Davari [mailto:[email-masked]]
> Sent: Friday, August 02, 2013 3:24 AM
> To: <[email-masked]>
> Cc: [email-masked]; [email-masked]; int-
> [email-masked]; [email-masked]; draft-ietf-tictoc-
> [email-masked]; John E Drake; [email-masked];
> [email-masked]
> Subject: Re: [mpls] Comments on draft-ietf-tictoc-1588overmpls
> 
> Hi Stewart
> 
> We have already looked at similar approach. The issue with one hop LSP
> is that not all LSRs are 1588 capable. One of the requirements is for
> non-1588 capable routers to just switch the packet normally.
> 
> Regards,
> Shahram
> 
> 
> > Internet-Draft                                                   A.
> Oren
> >                                                              P.
> Roberts
> >                                                          Alcatel-
> Lucent
> >                                                              L.
> Montini
> >                                                              L.
> Martini
> >                                                           Cisco
> Systems
> >                                                           June 15,
> 2013

> >      +-------+     /                                   \     +-------
> +
> >      |  LER  |    /                                     \    |  LER
> |
> >      | Clock |                                               | Clock
> |
> >      +-------+                                               +-------
> +

---

From: "Shahram Davari" <[email-masked]>
Date: Fri, 2 Aug 2013 13:42:18 +0000

Hi John

In that case I fail to understand the difference between your proposal and the current draft.

In both cases you need a special LSP to tell the HW to Timestamp the packet and I assume you need to use RSVPTE to sign it. That is what the draft does.

Regards,
Shahram

---

From: Greg Mirsky <[email-masked]>
Date: Fri, 2 Aug 2013 18:04:58 +0200

Hi Shahram,
I think that John suggested creation of LSPs interconnecting all
1588-capable nodes. It is absolutely not what current document defines but
that reminds me of what I've suggested around November of 2011.
Regards,
Greg
On Aug 2, 2013 6:43 AM, "Shahram Davari" <[email-masked]> wrote:

> In both cases you need a special LSP to tell the HW to Timestamp the
> packet and I assume you need to use RSVPTE to sign it. That is what the
> draft does.
>
> Regards,
> Shahram
>
>