Requirements for MPLS Over a Composite Link
draft-ietf-rtgwg-cl-requirement-05

RTGWG                                                 C. Villamizar, Ed.
Internet-Draft                                                OCCNC, LLC
Intended status: Informational                           D. McDysan, Ed.
Expires: August 2, 2012                                          S. Ning
                                                                A. Malis
                                                                 Verizon
                                                                 L. Yong
                                                              Huawei USA
                                                        January 30, 2012

              Requirements for MPLS Over a Composite Link
                   draft-ietf-rtgwg-cl-requirement-05

Abstract

   There is often a need to provide large aggregates of bandwidth that
   are best provided using parallel links between routers or MPLS LSR.
   In core networks there is often no alternative since the aggregate
   capacities of core networks today far exceed the capacity of a single
   physical link or single packet processing element.

   The presence of parallel links, with each link potentially comprised
   of multiple layers has resulted in additional requirements.  Certain
   services may benefit from being restricted to a subset of the
   component links or a specific component link, where component link
   characteristics, such as latency, differ.  Certain services require
   that an LSP be treated as atomic and avoid reordering.  Other
   services will continue to require only that reordering not occur
   within a microflow as is current practice.

   Current practice related to multipath is described briefly in an
   appendix.

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
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   This Internet-Draft will expire on August 2, 2012.

Copyright Notice

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  Assumptions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Network Operator Functional Requirements . . . . . . . . . . .  5
     4.1.  Availability, Stability and Transient Response . . . . . .  5
     4.2.  Component Links Provided by Lower Layer Networks . . . . .  6
     4.3.  Parallel Component Links with Different Characteristics  .  7
   5.  Derived Requirements . . . . . . . . . . . . . . . . . . . . .  9
   6.  Management Requirements  . . . . . . . . . . . . . . . . . . . 10
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
     10.2. Informative References . . . . . . . . . . . . . . . . . . 12
     10.3. Appendix References  . . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Existing Network Operator Practices and Protocol
                Usage . . . . . . . . . . . . . . . . . . . . . . . . 14
   Appendix B.  Existing Multipath Standards and Techniques . . . . . 14
   Appendix C.  ITU-T G.800 Composite Link Definitions and
                Terminology . . . . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15

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1.  Introduction

   The purpose of this document is to describe why network operators
   require certain functions in order to solve certain business problems
   (Section 2).  The intent is to first describe why things need to be
   done in terms of functional requirements that are as independent as
   possible of protocol specifications (Section 4).  For certain
   functional requirements this document describes a set of derived
   protocol requirements (Section 5).  Three appendices provide
   supporting details as a summary of existing/prior operator approaches
   (Appendix A), a summary of implementation techniques and relevant
   protocol standards (Appendix B), and a summary of G.800 terminology
   used to define a composite link (Appendix C).

1.1.  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 [RFC2119].

2.  Assumptions

   The services supported include L3VPN RFC 4364 [RFC4364], RFC 4797
   [RFC4797]L2VPN RFC 4664 [RFC4664] (VPWS, VPLS (RFC 4761 [RFC4761],
   RFC 4762 [RFC4762]) and VPMS VPMS Framework
   [I-D.ietf-l2vpn-vpms-frmwk-requirements]), Internet traffic
   encapsulated by at least one MPLS label, and dynamically signaled
   MPLS or MPLS-TP LSPs and pseudowires.  The MPLS LSPs supporting these
   services may be pt-pt, pt-mpt, or mpt-mpt.

   The locations in a network where these requirements apply are a Label
   Edge Router (LER) or a Label Switch Router (LSR) as defined in RFC
   3031 [RFC3031].

   The IP DSCP cannot be used for flow identification since L3VPN
   requires Diffserv transparency (see RFC 4031 5.5.2 [RFC4031]), and in
   general network operators do not rely on the DSCP of Internet
   packets.

3.  Definitions

   ITU-T G.800 Based Composite and Component Link Definitions:
       Section 6.9.2 of ITU-T-G.800 [ITU-T.G.800] defines composite and
       component links as summarized in Appendix C.  The following
       definitions for composite and component links are derived from
       and intended to be consistent with the cited ITU-T G.800

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       terminology.

       Composite Link:  A composite link is a logical link composed of a
           set of parallel point-to-point component links, where all
           links in the set share the same endpoints.  A composite link
           may itself be a component of another composite link, but only
           a strict hierarchy of links is allowed.

       Component Link:  A point-to-point physical or logical link that
           preserves ordering in the steady state.  A component link may
           have transient out of order events, but such events must not
           exceed the network's specific NPO.  Examples of a physical
           link are: Lambda, Ethernet PHY, and OTN.  Examples of a
           logical link are: MPLS LSP, Ethernet VLAN, and MPLS-TP LSP.

   Flow:  A sequence of packets that must be transferred in order on one
       component link.

   Flow identification:  The label stack and other information that
       uniquely identifies a flow.  Other information in flow
       identification may include an IP header, PW control word,
       Ethernet MAC address, etc.  Note that an LSP may contain one or
       more Flows or an LSP may be equivalent to a Flow.  Flow
       identification is used to locally select a component link, or a
       path through the network toward the destination.

   Network Performance Objective (NPO):  Numerical values for
       performance measures, principally availability, latency, and
       delay variation.  See Appendix A for more details.

4.  Network Operator Functional Requirements

   The Functional Requirements in this section are grouped in
   subsections starting with the highest priority.

4.1.  Availability, Stability and Transient Response

   Limiting the period of unavailability in response to failures or
   transient events is extremely important as well as maintaining
   stability.  The transient period between some service disrupting
   event and the convergence of the routing and/or signaling protocols
   MUST occur within a time frame specified by NPO values.  Appendix A
   provides references and a summary of service types requiring a range
   of restoration times.

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   FR#1  The solution SHALL provide a means to summarize some routing
         advertisements regarding the characteristics of a composite
         link such that the routing protocol converges within the
         timeframe needed to meet the network performance objective.  A
         composite link CAN be announced in conjunction with detailed
         parameters about its component links, such as bandwidth and
         latency.  The composite link SHALL behave as a single IGP
         adjacency.

   FR#2  The solution SHALL ensure that all possible restoration
         operations happen within the timeframe needed to meet the NPO.
         The solution may need to specify a means for aggregating
         signaling to meet this requirement.

   FR#3  The solution SHALL provide a mechanism to select a path for a
         flow across a network that contains a number of paths comprised
         of pairs of nodes connected by composite links in such a way as
         to automatically distribute the load over the network nodes
         connected by composite links while meeting all of the other
         mandatory requirements stated above.  The solution SHOULD work
         in a manner similar to that of current networks without any
         composite link protocol enhancements when the characteristics
         of the individual component links are advertised.

   FR#4  If extensions to existing protocols are specified and/or new
         protocols are defined, then the solution SHOULD provide a means
         for a network operator to migrate an existing deployment in a
         minimally disruptive manner.

   FR#5  Any automatic LSP routing and/or load balancing solutions MUST
         not oscillate such that performance observed by users changes
         such that an NPO is violated.  Since oscillation may cause
         reordering, there MUST be means to control the frequency of
         changing the component link over which a flow is placed.

   FR#6  Management and diagnostic protocols MUST be able to operate
         over composite links.

4.2.  Component Links Provided by Lower Layer Networks

   Case 3 as defined in [ITU-T.G.800] involves a component link
   supporting an MPLS layer network over another lower layer network
   (e.g., circuit switched or another MPLS network (e.g., MPLS-TP)).
   The lower layer network may change the latency (and/or other
   performance parameters) seen by the MPLS layer network.  Network
   Operators have NPOs of which some components are based on performance
   parameters.  Currently, there is no protocol for the lower layer
   network to inform the higher layer network of a change in a

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   performance parameter.  Communication of the latency performance
   parameter is a very important requirement.  Communication of other
   performance parameters (e.g., delay variation) is desirable.

   FR#7   In order to support network NPOs and provide acceptable user
          experience, the solution SHALL specify a protocol means to
          allow a lower layer server network to communicate latency to
          the higher layer client network.

   FR#8   The precision of latency reporting SHOULD be at least 10% of
          the one way latencies for latency of 1 ms or more.

   FR#9   The solution SHALL provide a means to limit the latency on a
          per LSP basis between nodes within a network to meet an NPO
          target when the path between these nodes contains one or more
          pairs of nodes connected via a composite link.

          The NPOs differ across the services, and some services have
          different NPOs for different QoS classes, for example, one QoS
          class may have a much larger latency bound than another.
          Overload can occur which would violate an NPO parameter (e.g.,
          loss) and some remedy to handle this case for a composite link
          is required.

   FR#10  If the total demand offered by traffic flows exceeds the
          capacity of the composite link, the solution SHOULD define a
          means to cause the LSPs for some traffic flows to move to some
          other point in the network that is not congested.  These
          "preempted LSPs" may not be restored if there is no
          uncongested path in the network.

4.3.  Parallel Component Links with Different Characteristics

   Corresponding to Case 1 of [ITU-T.G.800], as one means to provide
   high availability, network operators deploy a topology in the MPLS
   network using lower layer networks that have a certain degree of
   diversity at the lower layer(s).  Many techniques have been developed
   to balance the distribution of flows across component links that
   connect the same pair of nodes.  When the path for a flow can be
   chosen from a set of candidate nodes connected via composite links,
   other techniques have been developed.

   FR#11  The solution SHALL measure traffic on a labeled traffic flow
          and dynamically select the component link on which to place
          this flow in order to balance the load so that no component
          link in the composite link between a pair of nodes is
          overloaded.

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   FR#12  When a traffic flow is moved from one component link to
          another in the same composite link between a set of nodes (or
          sites), it MUST be done so in a minimally disruptive manner.

          When a flow is moved from a current link to a target link with
          different latency, reordering can occur if the target link
          latency is less than that of the current or clumping can occur
          if target link latency is greater than that of the current.
          Therefore, some flows (e.g., timing distribution, PW circuit
          emulation) are quite sensitive to these effects, which may be
          specified in an NPO or are needed to meet a user experience
          objective (e.g. jitter buffer under/overrun).

   FR#13  The solution SHALL provide a means to identify flows whose
          rearrangement frequency needs to be bounded by a configured
          value.

   FR#14  The solution SHALL provide a means that communicates whether
          the flows within an LSP can be split across multiple component
          links.  The solution SHOULD provide a means to indicate the
          flow identification field(s) which can be used along the flow
          path which can be used to perform this function.

   FR#15  The solution SHALL provide a means to indicate that a traffic
          flow shall select a component link with the minimum latency
          value.

   FR#16  The solution SHALL provide a means to indicate that a traffic
          flow shall select a component link with a maximum acceptable
          latency value as specified by protocol.

   FR#17  The solution SHALL provide a means to indicate that a traffic
          flow shall select a component link with a maximum acceptable
          delay variation value as specified by protocol.

   FR#18  The solution SHALL provide a means local to a node that
          automatically distributes flows across the component links in
          the composite link such that NPOs are met.

   FR#19  The solution SHALL provide a means to distribute flows from a
          single LSP across multiple component links to handle at least
          the case where the traffic carried in an LSP exceeds that of
          any component link in the composite link.  As defined in
          section 3, a flow is a sequence of packets that must be
          transferred on one component link.

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   FR#20  The solution SHOULD support the use case where a composite
          link itself is a component link for a higher order composite
          link.  For example, a composite link comprised of MPLS-TP bi-
          directional tunnels viewed as logical links could then be used
          as a component link in yet another composite link that
          connects MPLS routers.

   FR#21  The solution MUST support an optional means for LSP signaling
          to bind an LSP to a particular component link within a
          composite link.  If this option is not exercised, then an LSP
          that is bound to a composite link may be bound to any
          component link matching all other signaled requirements, and
          different directions of a bidirectional LSP can be bound to
          different component links.

   FR#22  The solution MUST support a means to indicate that both
          directions of co-routed bidirectional LSP MUST be bound to the
          same component link.

5.  Derived Requirements

   This section takes the next step and derives high-level requirements
   on protocol specification from the functional requirements.

   DR#1  The solution SHOULD attempt to extend existing protocols
         wherever possible, developing a new protocol only if this adds
         a significant set of capabilities.

   DR#2  A solution SHOULD extend LDP capabilities to meet functional
         requirements (without using TE methods as decided in
         [RFC3468]).

   DR#3  Coexistence of LDP and RSVP-TE signaled LSPs MUST be supported
         on a composite link.  Other functional requirements should be
         supported as independently of signaling protocol as possible.

   DR#4  When the nodes connected via a composite link are in the same
         MPLS network topology, the solution MAY define extensions to
         the IGP.

   DR#5  When the nodes are connected via a composite link are in
         different MPLS network topologies, the solution SHALL NOT rely
         on extensions to the IGP.

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   DR#6  The Solution SHOULD support composite link IGP advertisement
         that results in convergence time better than that of
         advertising the individual component links.  The solution SHALL
         be designed so that it represents the range of capabilities of
         the individual component links such that functional
         requirements are met, and also minimizes the frequency of
         advertisement updates which may cause IGP convergence to occur.

         Examples of advertisement update triggering events to be
         considered include: LSP establishment/release, changes in
         component link characteristics (e.g., latency, up/down state),
         and/or bandwidth utilization.

   DR#7  When a worst case failure scenario occurs, the number of
         RSVP-TE LSPs to be resignaled will cause a period of
         unavailability as perceived by users.  The resignaling time of
         the solution MUST meet the NPO objective for the duration of
         unavailability.  The resignaling time of the solution MUST not
         increase significantly as compared with current methods.

6.  Management Requirements

   MR#1  Management Plane MUST support polling of the status and
         configuration of a composite link and its individual composite
         link and support notification of status change.

   MR#2  Management Plane MUST be able to activate or de-activate any
         component link in a composite link in order to facilitate
         operation maintenance tasks.  The routers at each end of a
         composite link MUST redistribute traffic to move traffic from a
         de-activated link to other component links based on the traffic
         flow TE criteria.

   MR#3  Management Plane MUST be able to configure a LSP over a
         composite link and be able to select a component link for the
         LSP.

   MR#4  Management Plane MUST be able to trace which component link a
         LSP is assigned to and monitor individual component link and
         composite link performance.

   MR#5  Management Plane MUST be able to verify connectivity over each
         individual component link within a composite link.

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   MR#6  Management Plane SHOULD provide the means for an operator to
         initiate an optimization process.

7.  Acknowledgements

   Frederic Jounay of France Telecom and Yuji Kamite of NTT
   Communications Corporation co-authored a version of this document.

   A rewrite of this document occurred after the IETF77 meeting.
   Dimitri Papadimitriou, Lou Berger, Tony Li, the WG chairs John Scuder
   and Alex Zinin, and others provided valuable guidance prior to and at
   the IETF77 RTGWG meeting.

   Tony Li and John Drake have made numerous valuable comments on the
   RTGWG mailing list that are reflected in versions following the
   IETF77 meeting.

8.  IANA Considerations

   This memo includes no request to IANA.

9.  Security Considerations

   This document specifies a set of requirements.  The requirements
   themselves do not pose a security threat.  If these requirements are
   met using MPLS signaling as commonly practiced today with
   authenticated but unencrypted OSPF-TE, ISIS-TE, and RSVP-TE or LDP,
   then the requirement to provide additional information in this
   communication presents additional information that could conceivably
   be gathered in a man-in-the-middle confidentiality breach.  Such an
   attack would require a capability to monitor this signaling either
   through a provider breach or access to provider physical transmission
   infrastructure.  A provider breach already poses a threat of numerous
   tpes of attacks which are of far more serious consequence.  Encrption
   of the signaling can prevent or render more difficult any
   confidentiality breach that otherwise might occur by means of access
   to provider physical transmission infrastructure.

10.  References

10.1.  Normative References

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

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10.2.  Informative References

   [I-D.ietf-l2vpn-vpms-frmwk-requirements]
              Kamite, Y., JOUNAY, F., Niven-Jenkins, B., Brungard, D.,
              and L. Jin, "Framework and Requirements for Virtual
              Private Multicast Service (VPMS)",
              draft-ietf-l2vpn-vpms-frmwk-requirements-03 (work in
              progress), July 2010.

   [ITU-T.G.800]
              ITU-T, "Unified functional architecture of transport
              networks", 2007, <http://www.itu.int/rec/T-REC-G/
              recommendation.asp?parent=T-REC-G.800>.

   [RFC2702]  Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
              McManus, "Requirements for Traffic Engineering Over MPLS",
              RFC 2702, September 1999.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031, January 2001.

   [RFC3468]  Andersson, L. and G. Swallow, "The Multiprotocol Label
              Switching (MPLS) Working Group decision on MPLS signaling
              protocols", RFC 3468, February 2003.

   [RFC3809]  Nagarajan, A., "Generic Requirements for Provider
              Provisioned Virtual Private Networks (PPVPN)", RFC 3809,
              June 2004.

   [RFC4031]  Carugi, M. and D. McDysan, "Service Requirements for Layer
              3 Provider Provisioned Virtual Private Networks (PPVPNs)",
              RFC 4031, April 2005.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006.

   [RFC4664]  Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual
              Private Networks (L2VPNs)", RFC 4664, September 2006.

   [RFC4665]  Augustyn, W. and Y. Serbest, "Service Requirements for
              Layer 2 Provider-Provisioned Virtual Private Networks",
              RFC 4665, September 2006.

   [RFC4761]  Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
              (VPLS) Using BGP for Auto-Discovery and Signaling",
              RFC 4761, January 2007.

   [RFC4762]  Lasserre, M. and V. Kompella, "Virtual Private LAN Service

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              (VPLS) Using Label Distribution Protocol (LDP) Signaling",
              RFC 4762, January 2007.

   [RFC4797]  Rekhter, Y., Bonica, R., and E. Rosen, "Use of Provider
              Edge to Provider Edge (PE-PE) Generic Routing
              Encapsulation (GRE) or IP in BGP/MPLS IP Virtual Private
              Networks", RFC 4797, January 2007.

   [RFC5254]  Bitar, N., Bocci, M., and L. Martini, "Requirements for
              Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3)",
              RFC 5254, October 2008.

10.3.  Appendix 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 PSN", draft-ietf-pwe3-fat-pw-03 (work in
              progress), January 2010.

   [RFC1717]  Sklower, K., Lloyd, B., McGregor, G., and D. Carr, "The
              PPP Multilink Protocol (MP)", RFC 1717, November 1994.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, December 1998.

   [RFC2615]  Malis, A. and W. Simpson, "PPP over SONET/SDH", RFC 2615,
              June 1999.

   [RFC2991]  Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
              Multicast Next-Hop Selection", RFC 2991, November 2000.

   [RFC2992]  Hopps, C., "Analysis of an Equal-Cost Multi-Path
              Algorithm", RFC 2992, November 2000.

   [RFC3260]  Grossman, D., "New Terminology and Clarifications for
              Diffserv", RFC 3260, April 2002.

   [RFC4201]  Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling
              in MPLS Traffic Engineering (TE)", RFC 4201, October 2005.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

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   [RFC4928]  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
              Cost Multipath Treatment in MPLS Networks", BCP 128,
              RFC 4928, June 2007.

Appendix A.  Existing Network Operator Practices and Protocol Usage

   The network operator practices appendix has been moved to a separate
   document.  When that document has an XML I-D tag the references to
   this appendix will be changed to that document and this appendix will
   be deleted.

Appendix B.  Existing Multipath Standards and Techniques

   The multipath standards and techniques appendix has been moved to a
   separate document.  When that document has an XML I-D tag the
   references to this appendix will be changed to that document and this
   appendix will be deleted.

Appendix C.  ITU-T G.800 Composite Link Definitions and Terminology

   Composite Link:
       Section 6.9.2 of ITU-T-G.800 [ITU-T.G.800] defines composite link
       in terms of three cases, of which the following two are relevant
       (the one describing inverse (TDM) multiplexing does not apply).
       Note that these case definitions are taken verbatim from section
       6.9, "Layer Relationships".

       Case 1:  "Multiple parallel links between the same subnetworks
           can be bundled together into a single composite link.  Each
           component of the composite link is independent in the sense
           that each component link is supported by a separate server
           layer trail.  The composite link conveys communication
           information using different server layer trails thus the
           sequence of symbols crossing this link may not be preserved.
           This is illustrated in Figure 14."

       Case 3:  "A link can also be constructed by a concatenation of
           component links and configured channel forwarding
           relationships.  The forwarding relationships must have a 1:1
           correspondence to the link connections that will be provided
           by the client link.  In this case, it is not possible to
           fully infer the status of the link by observing the server
           layer trails visible at the ends of the link.  This is
           illustrated in Figure 16."

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   Subnetwork:  A set of one or more nodes (i.e., LER or LSR) and links.
       As a special case it can represent a site comprised of multiple
       nodes.

   Forwarding Relationship:  Configured forwarding between ports on a
       subnetwork.  It may be connectionless (e.g., IP, not considered
       in this draft), or connection oriented (e.g., MPLS signaled or
       configured).

   Component Link:  A topolological relationship between subnetworks
       (i.e., a connection between nodes), which may be a wavelength,
       circuit, virtual circuit or an MPLS LSP.

Authors' Addresses

   Curtis Villamizar (editor)
   OCCNC, LLC

   Email: curtis@occnc.com

   Dave McDysan (editor)
   Verizon
   22001 Loudoun County PKWY
   Ashburn, VA  20147

   Email: dave.mcdysan@verizon.com

   So Ning
   Verizon
   2400 N. Glenville Ave.
   Richardson, TX  75082

   Phone: +1 972-729-7905
   Email: ning.so@verizonbusiness.com

   Andrew Malis
   Verizon
   117 West St.
   Waltham, MA  02451

   Phone: +1 781-466-2362
   Email: andrew.g.malis@verizon.com

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   Lucy Yong
   Huawei USA
   1700 Alma Dr. Suite 500
   Plano, TX  75075

   Phone: +1 469-229-5387
   Email: lucyyong@huawei.com

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