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

"Shahram Davari" <davari@broadcom.com> Fri, 02 August 2013 10:24 UTC

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From: Shahram Davari <davari@broadcom.com>
To: "<stbryant@cisco.com>" <stbryant@cisco.com>
Thread-Topic: [mpls] Comments on draft-ietf-tictoc-1588overmpls
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Date: Fri, 02 Aug 2013 10:23:33 +0000
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Subject: Re: [TICTOC] [mpls] Comments on draft-ietf-tictoc-1588overmpls
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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" <stbryant@cisco.com> wrote:

> 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
>   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 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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> 
> 
> 
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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: davari@broadcom.com
> 
> 
>   Amit Oren
>   Broadcom Corp.
>   San Jose, CA  95134
>   USA
> 
>   Email: amito@broadcom.com
> 
> 
>   Manav Bhatia
>   Alcatel-Lucent
>   Bangalore,
>   India
> 
>   Email: manav.bhatia@alcatel-lucent.com
> 
> 
>   Peter Roberts
>   Alcatel-Lucent
>   Kanata,
>   Canada
> 
>   Email: peter.roberts@alcatel-lucent.com
> 
> 
>   Laurent Montini
>   Cisco Systems
>   San Jose CA
>   USA
> 
>   Email: lmontini@cisco.com
> 
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>   Luca
>   Cisco Systems
>   San Jose CA
>   USA
> 
>   Email: lmartini@cisco.com
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> -- 
> For corporate legal information go to:
> 
> http://www.cisco.com/web/about/doing_business/legal/cri/index.html
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