Traffic Engineering architecture for services aware MPLS
draft-fuxh-mpls-delay-loss-te-framework-03

Network Working Group                                              X. Fu
Internet-Draft                                                       ZTE
Intended status: Standards Track                               V. Manral
Expires: May 17, 2012                              Hewlett-Packard Corp.
                                                              D. McDysan
                                                                A. Malis
                                                                 Verizon
                                                            S. Giacalone
                                                         Thomson Reuters
                                                                M. Betts
                                                                 Q. Wang
                                                                     ZTE
                                                                J. Drake
                                                        Juniper Networks
                                                       November 14, 2011

        Traffic Engineering architecture for services aware MPLS
               draft-fuxh-mpls-delay-loss-te-framework-03

Abstract

   With more and more enterprises using cloud based services, the
   distances between the user and the applications are growing.  A lot
   of the current applications are designed to work across LAN's and
   have various inherent assumptions.  For multiple applications such as
   High Performance Computing and Electronic Financial markets, the
   response times are critical as is packet loss, while other
   applications require more throughput.

   [RFC3031] describes the architecture of MPLS based networks.  This
   draft extends the MPLS architecture to allow for latency, loss and
   jitter as properties.  It describes requirements and control plane
   implication for 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 make a accurate end-to-end latency and
   loss prediction before a path is established.

   Note MPLS architecture for Multicast will be taken up in a future
   version of the draft.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC 2119].

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Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on May 17, 2012.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Architecture requirements overview . . . . . . . . . . . . . .  4
     2.1.  Communicate Latency and Loss as TE Metric  . . . . . . . .  4
     2.2.  Requirement for Composite Link . . . . . . . . . . . . . .  5
     2.3.  Requirement for Hierarchy LSP  . . . . . . . . . . . . . .  5
     2.4.  Latency Accumulation and Verification  . . . . . . . . . .  5
     2.5.  Restoration, Protection and Rerouting  . . . . . . . . . .  6
   3.  End-to-End Latency . . . . . . . . . . . . . . . . . . . . . .  6
   4.  End-to-End Jitter  . . . . . . . . . . . . . . . . . . . . . .  8
   5.  End-to-End Loss  . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Protocol Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  Control Plane Implication  . . . . . . . . . . . . . . . . . .  9
     7.1.  Implications for Routing . . . . . . . . . . . . . . . . .  9
     7.2.  Implications for Signaling . . . . . . . . . . . . . . . . 11
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     11.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13

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1.  Introduction

   In High Frequency trading for Electronic Financial markets, computers
   make decisions based on the Electronic Data received, without human
   intervention.  These trades now account for a majority of the trading
   volumes and rely exclusively on ultra-low-latency direct market
   access.

   Extremely low latency measurements for MPLS LSP tunnels are defined
   in [draft-ietf-mpls-loss-delay].  They allow a mechanism to measure
   and monitor performance metrics for packet loss, and one-way and two-
   way delay, as well as related metrics like delay variation and
   channel throughput.

   The measurements are however effective only after the LSP is created
   and cannot be used by MPLS Path computation engine to define paths
   that have the latest latency.  This draft defines the architecture
   used, so that end-to-end tunnels can be set up based on latency, loss
   or jitter characteristics.

   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.

2.  Architecture requirements overview

2.1.  Communicate Latency and Loss as TE Metric

   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.

   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.

   In the case where it is known that either the changes are too
   frequent or there is a backup which is preferred, we can put the node
   or the link in unusable state for services requiring a particular
   service capability.  This unusable state is on a capability basis and
   not a global basis.

   Path computation entity MUST have the capability to compute one end-

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   to-end path with latency and packet loss constraint.  For example, it
   has the capability to compute a route with X amount of bandwidth with
   less than Y ms of latency and less than 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, e.g., SRLG diversity,
   latency, loss, jitter and cost.  If the performance of link exceeds
   its configured maximum threshold, path computation entity may not
   select this kind of link although end-to-end performance is still
   met.

2.2.  Requirement for Composite Link

   One end-to-end LSP may traverses some Composite Links [CL-REQ].  Even
   if the transport technology (e.g., OTN) component links are
   identical, the latency and packet loss characteristics of the
   component links may differ.

   The solution MUST 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.  The exact details for
   component links will be taken up seperately and are not part of this
   document.

2.3.  Requirement for Hierarchy LSP

   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 MUST 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.

2.4.  Latency Accumulation and Verification

   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.

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   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.

2.5.  Restoration, Protection and Rerouting

   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 (e.g., make-before-break) to handle
   this case based on the local policy.  In revertive behaviour is
   supported, the original LSP must not be released and is monitored by
   control plane.  When the end-to-end performance is repaired, the
   service is restored to the original LSP.

   The solution should support to move one end-to-end path away from any
   link whose performance exceeds the configured maximum threshold.  The
   anomalous path can be switch to protection path or rerouted to new
   path because of end-to-end performance couldn't meet any more.

   If a "provisioned" end-to-end LSP latency and/or loss performance is
   improved (i.e., beyond a configurable minimum value) because of some
   segment performance promotion, the solution SHOULD support the re-
   routing to optimize latency and/or loss end-to-end cost.

   The latency performance of pre-defined protection or dynamic re-
   routing LSP MUST meet the latency SLA parameter.  The difference of
   latency value between primary and protection/restoration path SHOULD
   be zero.

   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.

3.  End-to-End Latency

   Procedures to measure latency and loss has been provided in ITU-T
   [Y.1731], [G.709] and [ietf-mpls-loss-delay].  The control plane can
   be independent of the mechanism used and different mechanisms can be
   used for measurement based on different standards.

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   Latency on a path 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/ Composite Link [CL-REQ].

   Latency or one-way delay is the time it takes for a packet within a
   stream going from measurement point 1 to measurement point 2.

   The architecture uses assumption that the sum of the latencies of the
   individual components approximately adds up to the average latency of
   an LSP.  Though using the sum may not be perfect, it however gives a
   good approximation that can be used for Traffic Engineering (TE)
   purposes.

   The total latency of an LSP consists of the sum of the latency of the
   LSP hop, as well as the average latency of switching on a device,
   which may vary based on queuing and buffering.

   Hop latency can be measured by getting the latency measurement
   between the egress of one MPLS LSR to the ingress of the nexthop LSR.
   This value may be constant for most part, unless there is protection
   switching, or other similar changes at a lower layer.

   The switching latency on a device, can be measured internally, and
   multiple mechanisms and data structures to do the same have been
   defined.  Add references to papers by Verghese, Kompella, Duffield.
   Though the mechanisms define how to do flow based measurements, the
   amount of information gathered in such a case, may become too
   cumbersome for the Path Computation element to effectively use.

   An approximation of Flow based measurement is the per DSCP value,
   measurement from the ingress of one port to the egress of every other
   port in the device.

   Another approximation that can be used is per interface DSCP based
   measurement, which can be an agrregate of the average measurements
   per interface.  The average can itself be calculated in ways, so as
   to provide closer approximation.

   For the purpose of this draft it is assumed that the node latency is
   a small factor of the total latency in the networks where this
   solution is deployed.  The node latency is hence ignored for the
   benefit of simplicity.

   The average link delay over a configurable interval should be
   reported by data plane in micro-seconds.

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4.  End-to-End Jitter

   Jitter or Packet Delay Variation of a packet within a stream of
   packets is defined for a selected pair of packets in the stream going
   from measurement point 1 to measurement point 2.

   The architecture uses assumption that the sum of the jitter of the
   individual components approximately adds up to the average jitter of
   an LSP.  Though using the sum may not be perfect, it however gives a
   good approximation that can be used for Traffic Engineering (TE)
   purposes.

   There may be very less jitter on a link-hop basis.

   The buffering and queuing within a device will lead to the jitter.
   Just like latency measurements, jitter measurements can be
   appproximated as either per DSCP per port pair (Ingresss and Egress)
   or as per DSCP per egress port.

   For the purpose of this draft it is assumed that the node latency is
   a small factor of the total latency in the networks where this
   solution is deployed.  The node latency is hence ignored for the
   benefit of simplicity.

   The jitter is measured in terms of 10's of nano-seconds.

5.  End-to-End Loss

   Loss or Packet Drop probability of a packet within a stream of
   packets is defined as the number of packets dropped within a given
   interval.

   The architecture uses assumption that the sum of the loss of the
   individual components approximately adds up to the average loss of an
   LSP.  Though using the sum may not be perfect, it however gives a
   good approximation that can be used for Traffic Engineering (TE)
   purposes.

   There may be very less loss on a link-hop basis, except in case of
   physical link issues.

   The buffering and queuing mechanisms within a device will decide
   which packet is to be dropped.  Just like latency and jitter
   measurements, the loss can best be appproximated as either per DSCP
   per port pair (Ingresss and Egress) or as per DSCP per egress port.

   The loss is measured in terms of the number of packets per million

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   packets.

6.  Protocol Considerations

   The protocol metrics above can be sent in IGP protocol packets RFC
   3630.  They can then be used by the Path Computation engine to decide
   paths with the desired path properties.

   As Link-state IGP information is flooded throughout an area, frequent
   changes can cause a lot of control traffic.  To prevent such
   flooding, data should only be flooded when it crosses a certain
   configured maximum.

   A seperate measurement should be done for an LSP when it is UP.  Also
   LSP's path should only be recalculated when the end-to-end metrics
   changes in a way it becomes more than desired.

7.  Control Plane Implication

7.1.  Implications for Routing

   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 latency 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 latency and loss
   change of link MUST be notified to the IGP again.  The receiving node
   detrimines whether the link affects any of these LSPs for which it is
   ingress.  If there are, it must determine whether those LSPs still
   meet end-to-end performance objectives.

   A minimum value MUST be configured to control plane.  If the link
   performance improves beyond a configurable minimum value, it must be
   re-advertised.  The receiving node detrimines whether a "provisioned"
   end-to-end LSP latency and/or loss performance is improved because of

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   some segment performance promotion.

   It is sometimes important for paths that desire low latency is to
   avoid nodes that have a significant contribution to latency.  Control
   plane should report two components of the delay, "static" and
   "dynamic".  The dynamic component is always caused by traffic loading
   and queuing.  The "dynamic" portion SHOULD be reported as an
   approximate value.  It should be a fixed latency through the node
   without any queuing.  Link latency attribute should also take into
   account the latency of node, i.e., the latency between the incoming
   port and the outgoing port of a network element.  Half of the fixed
   node latency can be added to each link.

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

   o  One option is that 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 or
      average latency value of all component links.  In both 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.

   o  Another option is that latency and packet loss of each component
      link within one Composite Link could be advertised but having only
      one IGP adjacency.

   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-

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   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.

7.2.  Implications for Signaling

   In order to assign the LSP to one of component links with different
   latency and loss characteristics, RSVP-TE message needs to carry a
   indication of request minimum latency and/or packet loss, maximum
   acceptable latency and/or packet loss value and maximum acceptable
   delay variation value for the component link selection or creation.
   The composite link will take these parameters into account when
   assigning traffic of LSP to a component link.

   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).  There will be some
   latency and packet loss constraint requirement for the segment route
   in server layer.  So RSVP-TE message needs to carry a indication of
   request 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.

   RSVP-TE needs to be extended to accumulate (e.g., sum) 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
   verification can be made at end points.  One-way and round-trip
   latency collection along the LSP by signaling protocol can be
   supported.  So the end points of this LSP can verify whether the
   total amount of latency could meet the latency agreement between
   operator and his user.  When RSVP-TE signaling is used, the source
   can determine if the latency requirement is met much more rapidly
   than performing the actual end-to-end latency measurement.

   Restoration, protection and equipment variations can impact
   "provisioned" latency and packet loss (e.g., latency and packet loss
   increase).  For example, restoration/provisioning action in transport
   network that increases latency seen by packet network observable by
   customers, possibly violating SLAs.  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 LSPs 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

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   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 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.

8.  IANA Considerations

   No new IANA consideration are raised by this document.

9.  Security Considerations

   This document raises no new security issues.

10.  Acknowledgements

   TBD.

11.  References

11.1.  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.

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

11.2.  Informative References

   [CL-REQ]   C. Villamizar, "Requirements for MPLS Over a Composite
              Link", draft-ietf-rtgwg-cl-requirement-04 .

   [EXPRESS-PATH]
              S. Giacalone, "OSPF Traffic Engineering (TE) Express
              Path", draft-giacalone-ospf-te-express-path-01 .

   [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

   Vishwas Manral
   Hewlett-Packard Corp.
   191111 Pruneridge Ave.
   Cupertino, CA  95014
   US

   Phone: 408-447-1497
   Email: vishwas.manral@hp.com
   URI:

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   Dave McDysan
   Verizon

   Email: dave.mcdysan@verizon.com

   Andrew Malis
   Verizon

   Email: andrew.g.malis@verizon.com

   Spencer Giacalone
   Thomson Reuters
   195 Broadway
   New York, NY  10007
   US

   Phone: 646-822-3000
   Email: spencer.giacalone@thomsonreuters.com
   URI:

   Malcolm Betts
   ZTE

   Email: malcolm.betts@zte.com.cn

   Qilei Wang
   ZTE

   Email: wang.qilei@zte.com.cn

   John Drake
   Juniper Networks

   Email: jdrake@juniper.net

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