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Versions: 00                                                            
Network Working Group                                              X. Fu
Internet-Draft                                                  M. Betts
Intended status: Standards Track                                 Q. Wang
Expires: January 5, 2012                                             ZTE
                                                              D. McDysan
                                                                A. Malis
                                                                 Verizon
                                                            July 4, 2011


     Framework for latency and loss traffic engineering application
              draft-fuxh-ccamp-delay-loss-te-framework-00

Abstract

   Latency and packet loss is such requirement that must be achieved
   according to the Service Level Agreement (SLA) / Network Performance
   Objective (NPO) between customers and service providers.  Latency and
   packet loss can be associated with different service level.  The user
   may select a private line provider based on the ability to meet a
   latency and loss SLA.

   The key driver for latency and loss is stock/commodity trading
   applications that use data base mirroring.  A few milli seconds and
   packet loss can impact a transaction.  Financial or trading companies
   are very focused on end-to-end private pipe line latency
   optimizations that improve things 2-3 ms.  Latency/loss and
   associated SLA is one of the key parameters that these "high value"
   customers use to select a private pipe line provider.  Other key
   applications like video gaming, conferencing and storage area
   networks require stringent latency, loss and bandwidth.

   This document describes requirements to communicate latency and
   packet loss as a traffic engineering performance metric in today's
   network which is consisting of potentially multiple layers of packet
   transport network and optical transport network in order to meet the
   latency/loss SLA between service provider and his customers.

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/.




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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on January 5, 2012.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Conventions Used in This Document  . . . . . . . . . . . .  4
   2.  Latency and Loss Report  . . . . . . . . . . . . . . . . . . .  4
   3.  Requirements Identification  . . . . . . . . . . . . . . . . .  5
   4.  Control Plane Implication  . . . . . . . . . . . . . . . . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10






































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1.  Introduction

   Current operation and maintenance mode of latency and packet loss
   measurement is high in cost and low in efficiency.  The latency and
   packet loss can only be measured after the connection has been
   established, if the measurement indicates that the latency SLA is not
   met then another path is computed, setup and measured.  This "trial
   and error" process is very inefficient.  To avoid this problem a
   means of making an accurate prediction of latency and packet loss
   before a path is establish is required.

   This document describes the requirements and control plane
   implication to communicate latency and packet loss as a traffic
   engineering performance metric in today's network which is consisting
   of potentially multiple layers of packet transport network and
   optical transport network in order to meet the latency and packet
   loss SLA between service provider and his customers.

1.1.  Conventions Used in This Document

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


2.  Latency and Loss Report

   This section isn't going to say how latency or packet loss is
   measured.  How to measure has been provided in ITU-T [Y.1731],
   [G.709] and [ietf-mpls-loss-delay].  It's purpose is to define what
   it is sufficiently clear that mechanisms could be defined to measure
   it, and so that independent implementations will report the same
   thing.  If control plane wish to define the ability to report latency
   and packet loss, control plane must be clear what it are reporting.

   Packet/Frame loss probability is expressed as a percentage of the
   number of service packets/frames not delivered divided by the total
   number of service frames during time interval T. Loss is always
   measured by sending a measurement packet or frame from measurement
   point to its reception and recception sending back a response.

   The link of latecny is the time interval between the propagation of
   an electrical signal and its reception.  Latency is always measured
   by sending a measurement packet or frame from measurement point to
   its reception.  In some usages, latency is measured by sending a
   packet/frame that is returned to the sender and the round-trip time
   is considered the latency of bidirectional co-routed or associated
   LSP.  One way time is considered as the latency of unidirectional



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   LSP.  The one way latency may not be half of the round-trip latency
   in the case that the transmit and receive directions of the path are
   of unequal lengths.

   Control plane should report two components of the delay, "static" and
   "dynamic".  The dynamic component is caused by traffic loading.  What
   is reporting for "dynamic" portion is approximation.

   Latency on a connection has two sources: Node latency which is caused
   by the node as a result of process time in each node and: Link
   latency as a result of packet/frame transit time between two
   neighbouring nodes or a FA-LSP/Composit Link [CL-REQ].  The average
   latency of node should be reported.  It is simpler to add node
   latency to the link delay vs. carrying a separate parameter and does
   not hide any important information.  Latency variation is a parameter
   that is used to indicate the variation range of the latency value.
   Latency, latecny variation value must be reported as a average value
   which is calculated by data plane.


3.  Requirements Identification

   End-to-end service optimization based on latency and packet loss is a
   key requirement for service provider.  This type of function will be
   adopted by their "premium" service customers.  They would like to pay
   for this "premium" service.  Latency and loss on a route level will
   help carriers' customers to make his provider selection decision.
   Following key requirements associated with latency and loss is
   identified.

   o  REQ #1: The solution MUST provide a means to communicate latency,
      latency variation and packet loss of links and nodes as a traffic
      engineering performance metric into IGP.

   o  REQ #2: Latency, latency variation and packet loss may be
      unstable, for example, if queueing latency were included, then IGP
      could become unstable.  The solution MUST provide a means to
      control latency and loss IGP message advertisement and avoid
      unstable when the latency, latency variation and packet loss value
      changes.

   o  REQ #3: Path computation entity MUST have the capability to
      compute one end-to-end path with latency and packet loss
      constraint. for example, it has the capability to compute a route
      with X amount bandwidth with less than Y ms of latency and Z%
      packet loss limit based on the latency and packet loss traffic
      engineering database.  It MUST also support the path computation
      with routing constraints combination with pre-defined priorities,



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      e.g., SRLG diversity, latency, loss and cost.

   o  REQ #4: One end-to-end LSP may traverses some Composite Links [CL-
      REQ].  Even if the transport technology (e.g., OTN) implementing
      the component links is identical, the latency and packet loss
      characteristics of the component links may differ.  In order to
      assign the LSP to one of component links with different latency
      and packet loss characteristics, the solution SHOULD provide a
      means to indicate that a traffic flow should select a component
      link with minimum latency and/or packet loss, maximum acceptable
      latency and/or packet loss value and maximum acceptable delay
      variation value as specified by protocol.  The endpoints of
      Composite Link will take these parameters into account for
      component link selection or creation.

   o  REQ #5: One one end-to-end LSP may traverse a server layer.  There
      will be some latency and packet loss constraint requirement for
      the segment route in server layer.  The solution SHALL provide a
      means to indicate FA selection or FA-LSP creation with minimum
      latency and/or packet loss, maximum acceptable latency and/or
      packet loss value and maximum acceptable delay variation value.
      The boundary nodes of FA-LSP will take these parameters into
      account for FA selection or FA-LSP creation.

   o  REQ #6: The solution SHOULD provide a means to accumulate (e.g.,
      sum) of latency information of links and nodes along one LSP
      across multi-domain (e.g., Inter-AS, Inter-Area or Multi-Layer) so
      that an latency validation decision can be made at the source
      node.  One-way and round-trip latency collection along the LSP by
      signaling protocol and latency verification at the end of LSP
      should be supported.  The accumulation of the delay is "simple"
      for the static component i.e. its a linear addition, the dynamic/
      network loading component is more interesting and would involve
      some estimate of the "worst case".  However, method of deriving
      this worst case appears to be more in the scope of Network
      Operator policy than standards i.e. the operator needs to decide,
      based on the SLAs offered, the required confidence level.

   o  REQ #7: Some customers may insist on having the ability to re-
      route if the latency and loss SLA is not being met.  If a
      "provisioned" end-to-end LSP latency and/or loss could not meet
      the latency and loss agreement between operator and his user, The
      solution SHOULD support pre-defined or dynamic re-routing to
      handle this case based on the local policy.  The latency
      performance of pre-defined protection or dynamic re-routing LSP
      MUST meet the latency SLA parameter.





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   o  REQ #8: If a "provisioned" end-to-end LSP latency and/or loss
      performance is improved because of some segment performance
      promotion, the solution SHOULD support the re-routing to optimize
      latency and/or loss end-to-end cost.

   o  REQ #9: As a result of the change of latency and loss in the LSP,
      current LSP may be frequently switched to a new LSP with a
      appropriate latency and packet loss value.  In order to avoid
      this, the solution SHOULD indicate the switchover of the LSP
      according to maximum acceptable change latency and packet loss
      value.


4.  Control Plane Implication

   o  The latency and packet loss performance metric MUST be advertised
      into path computation entity by IGP (etc., OSPF-TE or IS-IS-TE) to
      perform route computation and network planning based on latecny
      and packet loss SLA target.  Latency, latecny variation and packet
      loss value MUST be reported as a average value which is calculated
      by data plane.  Latency and packet loss characteristics of these
      links and nodes may change dynamically.  In order to control IGP
      messaging and avoid being unstable when the latency, latency
      variation and packet loss value changes, a threshold and a limit
      on rate of change MUST be configured to control plane.  If any
      latency and packet loss values change and over than the threshold
      and a limit on rate of change, then the change MUST be notified to
      the IGP again.

   o  Link latency attribute may also take into account the latency of a
      network element (node), i.e., the latency between the incoming
      port and the outgoing port of a network element.  If the link
      attribute is to include node latency AND link latency, then when
      the latency calculation is done for paths traversing links on the
      same node then the node latency can be subtracted out.

   o  When the Composite Links [CL-REQ] is advertised into IGP, there
      are following considerations.

      *  The latency and packet loss of composite link may be the range
         (e.g., at least minimum and maximum) latency value of all
         component links.  It may also be the maximum latency value of
         all component links.  In these cases, only partial information
         is transmited in the IGP.  So the path computation entity has
         insufficient information to determine whether a particular path
         can support its latency and packet loss requirements.  This
         leads to signaling crankback.  So IGP may be extended to
         advertise latency and packet of each component link within one



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         Composite Link having an IGP adjacency.

   o  One end-to-end LSP (e.g., in IP/MPLS or MPLS-TP network) may
      traverse a FA-LSP of server layer (e.g., OTN rings).  The boundary
      nodes of the FA-LSP SHOULD be aware of the latency and packet loss
      information of this FA-LSP.

      *  If the FA-LSP is able to form a routing adjacency and/or as a
         TE link in the client network, the total latency and packet
         loss value of the FA-LSP can be as an input to a transformation
         that results in a FA traffic engineering metric and advertised
         into the client layer routing instances.  Note that this metric
         will include the latency and packet loss of the links and nodes
         that the trail traverses.

      *  If total latency and packet loss information of the FA-LSP
         changes (e.g., due to a maintenance action or failure in OTN
         rings), the boundary node of the FA-LSP will receive the TE
         link information advertisement including the latency and packet
         value which is already changed and if it is over than the
         threshold and a limit on rate of change, then it will compute
         the total latency and packet value of the FA-LSP again.  If the
         total latency and packet loss value of FA-LSP changes, the
         client layer MUST also be notified about the latest value of
         FA.  The client layer can then decide if it will accept the
         increased latency and packet loss or request a new path that
         meets the latency and packet loss requirement.

   o  Restoration, protection and equipment variations can impact
      "provisioned" latency and packet loss (e.g., latency and packet
      loss increase).  The change of one end-to-end LSP latency and
      packet loss performance MUST be known by source and/or sink node.
      So it can inform the higher layer network of a latency and packet
      loss change.  The latency or packet loss change of links and nodes
      will affect one end-to-end LSP's total amount of latency or packet
      loss.  Applications can fail beyond an application-specific
      threshold.  Some remedy mechanism could be used.

      *  Pre-defined protection or dynamic re-routing could be triggered
         to handle this case.  In the case of predefined protection,
         large amounts of redundant capacity may have a significant
         negative impact on the overall network cost.  Service provider
         may have many layers of pre-defined restoration for this
         transfer, but they have to duplicate restoration resources at
         significant cost.  Solution should provides some mechanisms to
         avoid the duplicate restoration and reduce the network cost.
         Dynamic re-routing also has to face the risk of resource
         limitation.  So the choice of mechanism MUST be based on SLA or



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         policy.  In the case where the latency SLA can not be met after
         a re-route is attempted, control plane should report an alarm
         to management plane.  It could also try restoration for several
         times which could be configured.


5.  Security Considerations

   The use of control plane protocols for signaling, routing, and path
   computation of latency and loss opens security threats through
   attacks on those protocols.  The control plane may be secured using
   the mechanisms defined for the protocols discussed.  For further
   details of the specific security measures refer to the documents that
   define the protocols ([RFC3473], [RFC4203], [RFC4205], [RFC4204], and
   [RFC5440]).  [GMPLS-SEC] provides an overview of security
   vulnerabilities and protection mechanisms for the GMPLS control
   plane.


6.  IANA Considerations

   This document makes not requests for IANA action.


7.  References

7.1.  Normative References

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

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, December 2001.

   [RFC3473]  Berger, L., "Generalized Multi-Protocol Label Switching
              (GMPLS) Signaling Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.

   [RFC3477]  Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
              in Resource ReSerVation Protocol - Traffic Engineering
              (RSVP-TE)", RFC 3477, January 2003.

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

   [RFC4203]  Kompella, K. and Y. Rekhter, "OSPF Extensions in Support



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              of Generalized Multi-Protocol Label Switching (GMPLS)",
              RFC 4203, October 2005.

7.2.  Informative References

   [CL-REQ]   C. Villamizar, "Requirements for MPLS Over a Composite
              Link", draft-ietf-rtgwg-cl-requirement-02 .

   [G.709]    ITU-T Recommendation G.709, "Interfaces for the Optical
              Transport Network (OTN)", December 2009.

   [Y.1731]   ITU-T Recommendation Y.1731, "OAM functions and mechanisms
              for Ethernet based networks", Feb 2008.

   [ietf-mpls-loss-delay]
              D. Frost, "Packet Loss and Delay Measurement for MPLS
              Networks", draft-ietf-mpls-loss-delay-03 .


Authors' Addresses

   Xihua Fu
   ZTE

   Email: fu.xihua@zte.com.cn


   Malcolm Betts
   ZTE

   Email: malcolm.betts@zte.com.cn


   Qilei Wang
   ZTE

   Email: wang.qilei@zte.com.cn


   Dave McDysan
   Verizon

   Email: dave.mcdysan@verizon.com








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   Andrew Malis
   Verizon

   Email: andrew.g.malis@verizon.com















































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