One document matched: draft-raggarwa-rsvpte-pw-00.txt


Network Working Group                             Rahul Aggarwal
Internet Draft                                    Kireeti Kompella
Expiration Date: December 2004                    Arthi Ayyangar
                                                  Juniper Networks
                                                  Dimitri Papadimitriou
                                                  Alcatel
                                                  Peter Busschbach
                                                  Lucent

           Setup and Maintenance of Pseudowires using RSVP-TE
                    draft-raggarwa-rsvpte-pw-00.txt


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Abstract

   This document describes procedures for using Resource Reservation
   Protocol-Traffic Engineering (RSVP-TE) for signaling Pseudowires
   (PWs). One motivation is the signaling of PW QoS. The other is the
   setup of a multi-hop PW, for example, to span multiple domains.
   RSVP-TE provides mechanisms for QoS signaling and these can be
   leveraged for signaling PW QoS. It also provides the ability to
   signal bi-directional MPLS Label Switched Paths (LSP) with explicit
   routes. This can be used for signaling multi-hop PWs that require
   explicit routing. RSVP-TE also provides the ability to establish non-
   adjacent or targeted signaling sessions.


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 RFC-2119 [KEYWORDS].


1. Terminology

   Single-hop PW: A PW that comprises only two PW demultiplexor
   allocation nodes.

   Multi-hop PW: A PW that comprises more than two PW demultiplexor
   allocation nodes.


2. Introduction

   A PW is a mechanism that carries the essential elements of an
   emulated service from one PE to another over a PSN [PW-ARCH]. A point
   to point PW is bi-directional. A "PW header", consisting of a (PW)
   demultiplexor field is prepended to the encapsulated PDU. The
   resulting parcket is then transmitted to the remote endpoint of the
   PW over one or more "PSN tunnels"; this may require an additional
   header to be prepended to the packet. When the packet arrives at the
   remote endpoint of the PW, the PW demultiplexor is what enables the
   receiver to identify the particular PW on which the packet has
   arrived.

   In the case that it is not desirable to establish a single PSN tunnel
   between the two endpoints of a PW or the PW needs to be explicitly
   routed across multiple hops for QoS provisioning or administrative
   reasons, a multi-hop PW is needed. In this case each PW hop uses a
   separate PSN tunnel. The PW demultiplexor may have to be changed at



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   each hop.  An example scenario where a multi-hop PW is needed is one
   that spans multiple domains, where edge-to-edge PSNs may not be
   possible for scaling or administrative reasons. Each domain may have
   a different PSN technology.

   [LDP-PW] describes procedures for using the Label Distribution
   Protocol [LDP] for the setup and maintenance of single-hop PWs. The
   PW demultiplexor field is a MPLS label, and PW demultiplexor
   signaling performs label exchange between two PEs.

   If one wants to signal multi-hop, explicitly routed PWs and/or PWs
   with QoS characteristics, new mechanisms are required.  The protocol
   architecture of RSVP-TE is an appropriate fit for these applications
   (as well as basic demultiplexor exchange).  This is because RSVP-TE
   has the mechanisms for signaling QoS and for explicit routing. RSVP-
   TE extensions described in [RFC3473] also provide mechanisms to setup
   bi-directional LSPs. It also has mechanisms that can be used for PW
   identification, setup and maintenance.

   Multi-hop PWs traverse multiple PSN tunnels and the PSN tunnels may
   be setup using Generalized MPLS (GMPLS) signaling [RFC3473]. Hence
   another useful applicability scope of the proposed approach is PWs
   over MPLS PSNs supporting GMPLS RSVP-TE [RFC 3473] as well as other
   switching technologies within the scope of GMPLS.

   This document describes procedures for using RSVP-TE for PW signaling
   motivated by the goals mentioned in the previous paragraph. This
   document assumes familiarity with [RFC3209] and [RFC3473].


3. Motivation

   This section describes the motivations behind this document.

3.1. PW QoS

   A PW is a mechanism that carries the essential elements of an
   emulated service from one PE to another over a PSN [PW-ARCH]. The
   emulated service is offered by a SP to a customer over an attachment
   circuit (AC). Hence a PW can also be considered as a mechanism that
   is used to inter-connect two ACs over a PSN. A Service Level
   Agreement (SLA) is often associated with such an emulated service.
   Packet loss and delay bounds in a given time interval are examples of
   a SLA that a SP may provide to a customer. Such a SLS translates into
   QoS, for example bandwidth, that is associated with the PW. Providing
   this QoS on the PW requires the following:
      a) Assigning QoS parameters to each AC in conformance with the
   SLA. These QoS parameters get associated with the PW that is used to



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   carry traffic from the AC.
      b) Policing on the AC on both the PEs based on the QoS parameters
      c) Call admission control (CAC) of the PW into the PSN tunnel
   which is used to transmit the PW packets. This assumes that the PSN
   tunnel can be signaled with QoS. To achieve this RSVP-TE can be used
   as the PSN tunnel signaling protocol.

   The procedures described above require that the two ends of a PW be
   associated with the same QoS parameters. In current PW deployments
   this is achieved using configuration. However it is desirable to
   signal this QoS information from one end of the PW to another. This
   is beneficial for PW operation and management.  This is also
   desirable for multi-hop PWs described in the next section. It should
   also be possible to change the QoS characteristics of a PW without
   any packet loss on the PW.

3.2. Multi-Hop PWs

   A PW by default inter-connects the ACs between two PEs that exchange
   the PW demultiplexor. These two PEs are the PW demultiplexor
   allocation nodes.  This document uses the term multi-hop PW to refer
   to a PW that comprises more than two PW demultiplexor allocation
   nodes. One way to conceptualize this is as multiple PWs that are
   stitched together and are still part of the same end to end PW.

   A multi-hop PW is needed when it is not desirable to establish a
   single PSN tunnel between the two endpoints of a PW or the PW needs
   to be explicitly routed across multiple hops for QoS provisioning or
   administrative reasons.  The PW demultiplexor allocation nodes along
   a multi-hop PW need to be explicitly specified. This requires a PW
   explicit route.

   A practical application of a multi-hop PWs is the setup of a PW
   across multiple domains. For instance across multiple IGP domains or
   ASs or domains with different PSN technologies.

   Consider an inter-AS PW that is set up by PE1 in AS1 to PE2 in AS2.
   It may be desirable to control the exit point of this PW in AS1 and
   select the entry point of the PW in AS2. Traffic accounting per PW is
   one motivation for this.  Another motivation is to avoid setting up a
   full mesh of end-to-end PWs between ASs. The inter-AS PW may be
   explicitly routed through ASBR1 in AS1, which is PE1's next-hop to
   reach PE2. ASBR1 in turn may explicitly route the PW through ASBR2
   which is its next-hop to reach PE2. ASBR2 will complete the PW
   signaling. In this case there is one signaling protcol adjacency to
   signal the PW between PE1 and ASBR1; one between ASBR1 and ASBR2; and
   one between ASBR2 and PE2. PE1, ASBR1, ASBR2 and PE2 are PW
   demultiplexor allocation points.



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3.3. PW Redundancy

   It may be desirable to backup one PW with another. For instance a CE
   may be dual homed to a PE using two different ACs. One AC is the
   primary while the other is the backup. Both these ACs are attached to
   the same remote AC. The remote PE can setup a PW for each of the two
   local ACs. One of these PWs is the primary PW while the other is the
   backup PW. The backup PW is setup apriori and is in standby mode
   incase the primary PW fails. The primary and backup PWs may also be
   multi-hop PWs and may be signaled with QoS.  The multi-hop primary
   and backup PWs may be routed over different PW demultiplexor
   allocation points. If they pass through the same PW demultiplexor
   points QoS double booking must be avoided between these two PWs as
   only one of them is active at a given time.


4. Motivation for using RSVP-TE

   This section describes why RSVP-TE is an appropriate fit for
   addressing the motivations described in section 3.

   RSVP-TE is used to setup explicitly routed Label Switched Paths
   (LSPs).  Multiple LSPs may belong to the same tunnel. A LSP is
   identified using a SESSION object and a SENDER_TEMPLATE object. The
   SESSION object carries a tunnel identifier (TUNNEL_ID) to identify a
   tunnel. It also carries the tunnel destination. The SENDER_TEMPLATE
   carries the source of the tunnel and a LSP_ID to identify a specific
   LSP. An ingress LSR is defined as the LSR that originates the LSP. An
   egress LSR is defined as the endpoint of the LSP.  LSP setup consists
   of signaling in the forward and the reverse direction.  The ingress
   LSR originates a Path message to the egress LSR and the egress LSR
   responds with a Resv message. The LSP is successfully established
   when the ingress LSR receives the Resv message.

   [RFC3209] defines the setup of unidirectional LSPs. [RFC3473] extends
   this to bidirectional LSPs. Hence a Path message sent by the ingress
   LSR can be used to signal a bidirectional LSP.

   RSVP signaling messages can be exchanged between adjacent or non-
   adjacent nodes [LSP-HIER].

   The specific building blocks of RSVP-TE that make it an appropriate
   fit for solving the problems addressed by this document are discussed
   below.  In the following discussion a LSP refers to a bidirectional
   LSP.






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4.1. QoS Signaling

   RSVP-TE is designed to setup LSPs that are signaled with QoS
   Parameters. The Path message carries the QoS specification that is
   requested by the ingress LSR in the SENDER_TSPEC object. The
   SENDER_TSPEC object carries the traffic specification generated by
   RSVP session sender i.e the ingress LSR.  The SENDER_TSPEC object is
   forwarded unchanged and delivered to both transit and egress LSRs.
   The FLOWSPEC object carries reservation request information generated
   by receivers i.e. the QoS desired by egress LSRs. The information
   content of the FLOWSPEC object flows upstream towards the ingress
   LSR. Each transit LSR uses the FLOWSPEC object for CAC and to setup
   the LSP QoS in hardware in the direction from the ingress LSR to the
   egress LSR and also in the reverse direction.

   This mechanism can be used for signaling PW QoS.

4.2. Explicit Routing

   As discussed in section 3 the primary requirement of signaling multi-
   hop PWs is the specification of an explicit route. RSVP-TE allows a
   LSP to be setup using an EXPLICIT_ROUTE_OBJECT (ERO). An ERO contains
   a sequence of hops that the LSP must be routed through. The semantics
   allow an intermediate hop to insert hops in the ERO.

4.3. Sharing QoS Resources between LSPs

   RSVP-TE allows multiple LSPs to belong to the same tunnel. These LSPs
   can be signaled such that they share QoS resources with each other
   between common hops. This can be used for PW redundancy. A backup PW
   can be setup to share QoS resources with the primary PW between
   common hops. It can also be used for modifying the QoS of a PW using
   RSVP-TE make-before-break [RFC3209].

4.4. Bidirectional Label Allocation

   RSVP-TE [RFC3209] sets up unidirectional LSPs and provides the
   mechanism to signal the downstream label in the Resv message.
   [RFC3473] extends this to signal bidirectional LSPs allowing the
   upstream label to be carried in the Path message. A PW is
   bidirectional and RSVP-TE bidirectional label allocation mechanisms
   will be used for PW label exchange with a single signaling session.









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4.5. LSP Hierarchy

   [RFC3209] has the notion of LSP hierarchy. A LSP can be advertised as
   a Forwarding Adjacency (FA) to rest of the domain, allowing other
   nodes in the domain to use the FA LSP as a link for computing traffic
   engineered paths for other LSPs [LSP-HIER]. One or more LSPs (inner
   LSPs) can be carried over the FA LSP (outer LSP). When RSVP-TE is
   used for PW signaling and PSN tunnels are also setup using RSVP-TE,
   the PSN tunnels may be advertised as FA LSPs.  If this is the case
   the multi-hop PW origination point can use the FA LSPs to traffic
   engineer the path of the multi-hop PW, which is the inner LSP.


5. Design Overview

   This section gives an overview of how RSVP-TE can be used for
   addressing the motivations described in section 3.

5.1. Mapping RSVP-TE LSPs to PWs

   This document maps a PW to a bidirectional LSP. A PW is identified by
   the SESSION object, SENDER_TEMPLATE object and a new PW TLV that is
   carried in a new SENDER_TSPEC C-Type. The PW TLV is discussed in
   section 6.1. Mapping a PW to a LSP allows the use of QoS signaling,
   explicit and record routing, resource sharing as well as as any other
   RSVP capability that can be mapped to an LSP

5.2. Non-Adjacent Signaling

   Non-adjacent signaling between PW demultiplexor allocation points is
   used for signaling PWs with RSVP-TE. This allows RSVP-TE signaling
   messages to be exchanged between hops that are not directly adjacent.

5.3. Single-Hop PW Label Signaling

   This document proposes that RSVP-TE can also be used for signaling
   single-hop PW demultiplexors. This is done using bidirectional label
   allocation mechanisms. It is conceivable that a different protocol
   can be used for signaling single-hop PW demultiplexors when RSVP-TE
   is used for multi-hop PW signaling or PW QoS signaling. LDP [LDP-PW]
   can be used for this purpose. This may be useful if a network has
   currently deployed LDP for single-hop PW setup with or without QoS
   and wishes to setup multi-hop PWs.  In that case a PW association is
   needed between LDP and RSVP-TE. This is for further study.







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5.4. Single Sided Signaling

   RSVP-TE PW sessions are originated by one end of the PW. The other
   end of the PW completes the signaling by responding to this request.
   This follows the single sided signaling concept that has been
   proposed earlier in [LDP-PW]. In this model both the PW ends do not
   initiate asynchronous signaling messages. It is only one end that
   initiates the PW setup.


6. Procedures

6.1. RSVP-TE PW Identification

   A LSP is mapped to a PW. A PW is identified by the SESSION object,
   the SENDER_TEMPLATE object and a new PSEUDOWIRE TLV (PW TLV) included
   as part of a new SENDER_TSPEC/FLOWSPEC object. Details of the
   SENDER_TSPEC/FLOWSPEC object encoding carried in the Path and Resv
   message, respectively, will be specified in the next revision. The PW
   TLV  identifies the individual PW. It also allows the receiver of the
   RSVP-TE Path message to realize that the signaled session is being
   used to setup a PW. This identifier can either be a 32 bit number or
   it can have generalized semantics. A different TLV type is used for
   both these cases. The generalized PW TLV will be specified in the
   next revision. The encoding when the PW TLV contains a 32 bit number
   follows.


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      TLV Type = TBD             |  Length                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          PW ID                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The PW type, presence of the control word and any other PW specific
   parameters are signaled in the TSPEC. Details will be specified in
   the next revision.

6.2. Single-Hop PW Setup

   This document proposes the use of RSVP-TE for exchanging single-hop
   PW labels when RSVP-TE is used for addressing the motivations
   described in Section 3. This is accomplished by using bidirectional
   label allocation mechanisms. The PW is signaled as a bidirectional
   LSP by the local PE using a non-adjacent i.e. targeted Path message.



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   The remote PE can associate PW semantics with the LSP based on the PW
   parameters carried in the SENDER_TSPEC object including the PW TLV.
   The remote PE adds a route that is used to map traffic from the AC
   into the PW.  The inner label of the route's next-hop is the PW label
   (i.e. the upstream label) received from the PE that signaled the PW.
   When a Path message containing an upstream_PW label is received by
   the remote PE, the latter first verifies that the upstream label is
   acceptable. If the label is not acceptable, the receiver MUST issue a
   PathErr message with a "Routing problem/Unacceptable PW label value"
   indication. The remote PE also adds a MPLS route for the received PW
   label with the AC as the next-hop. The remote PE then generates a
   Resv message and sends it to the local PE along with a PW label (i.e.
   the downstream label). The local PE completes the PW setup by adding
   the local AC route and the MPLS PW label route. Contention resolution
   for bi-directional LSPs follows rules specified in Section 3.2 of
   [RFC3473].

   The SENDER_TSPEC object that carries the traffic specification
   generated by the RSVP session sender MUST be delivered unchanged to
   the egress PE. The FLOWSPEC object that carries reservation request
   information generated by receivers. The information content of the
   FLOWSPEC object flows upstream towards ingress PE. For a particular
   sender PE, for a single-hop PW, the contents of the FLOWSPEC object
   received in a Resv message SHOULD be identical (or lower, for the QoS
   parameters, see Section 6.3) to the contents of the SENDER_TSPEC
   object sent in the corresponding Path message. If the objects do not
   match, a ResvErr message with a "Traffic Control Error/Bad Flowspec
   value" error SHOULD be generated.

   When a bidirectional LSP is torn down, both upstream and downstream
   labels are invalidated and it is no longer valid to send data using
   the associated labels.

   The outer label can be the transport LSP label when using MPLS
   tunnels. It can also be any other PSN tunnel encapsulation: eg. IP or
   GRE.

   Refresh reduction [RFC2961] can be used to reduce the refresh and
   processing overhead of RSVP-TE control messages.

6.3. Single-Hop PW QoS Signaling

   A RSVP-TE LSP is established for the PW between the two PEs using
   non-adjacent signaling. This is a bidirectional LSP. This LSP is
   signaled with the QoS parameters desired by the local PE for the PW.
   These parameters are carried in the SENDER_TSPEC object in the Path
   Message and in the FLOWSPEC object in the Resv message.




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   The SENDER_TSPEC object MUST be delivered unchanged to the egress PE.
   This object also includes the PW TLV used to identify the PW.

   The egress PE MUST verify that the incoming SENDER_TSPEC QoS
   parameters can be supported for the requested LSP. If the requested
   value(s) can not be supported, the egress PE MUST generate a PathErr
   message with a "Traffic Control Error/Service unsupported" indication
   (see [RFC2205]).

   The remote PE responds with a Resv message that contains in the
   FLOWSPEC object the QoS parameters desired by the remote PE. This
   value is either the same as the QoS requested in the SENDER_TSPEC or
   lower. Both the local and the remote PE use the FLOWSPEC for
   administering PW QoS. If the objects do not match the PW TLV or the
   QoS requested parameters are larger, a ResvErr message with a
   "Traffic Control Error/Bad Flowspec value" error SHOULD be generated.

   QoS signaling mechanisms in RSVP-TE are fairly mature. They have been
   defined for various QoS service models. Also RSVP-TE [RFC3209] and
   various extensions to it [RFC3473] describe mechanisms for signaling
   QoS for different media such as ATM, Frame Relay, optical interfaces
   etc. Based on the AC being inter-connected, the PW LSP is signaled
   with an appropriate SENDER_TSPEC/FLOWSPEC object.

   RSVP-TE make-before-break procedures can be used to modify PW QoS
   without impacting PW traffic.

6.4. Multi-Hop PW Signaling

   A multi-hop PW that requires explicit routing is signaled using a
   RSVP-TE bidirectional LSP with a PW TLV in the SENDER_TSPEC object
   and an explicit route encoded in the EXPLICIT_ROUTE object. The
   ingress LSR sends a Path message with the destination address being
   the multi-hop PW end point. The explicit route specifies the hops
   that the PW must be routed through. Intermediate nodes may insert
   hops in the explicit route as the ingress LSR may specify the
   explicit route partially. PW labels that are used to send data in the
   direction from the egress LSR to the ingress LSR are allocated by
   each PW demultiplexor allocation hop and propagated in the Path
   message. The SENDER_TSPEC object is propagated unchanged to the
   multi-hop PW endpoint which uses the PW TLV to identify the PW. The
   egress of the multi-hop PW responds with a Resv message. This message
   contains the FLOWSPEC object, which is used to administer the QoS at
   each intermediate node as the Resv message is propagated to the
   ingress LSR. PW labels that are used to send data in the direction
   from the ingress LSR to the egress LSR are allocated by each PW
   demultiplexor allocation hop and propagated in the Resv message.




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   In addition to the processing of the SENDER_TSPEC and FLOWSPEC object
   described in Section 6.3 at the ingress and egress LSR, here,
   intermediate PW demultiplexors MUST verify that the node itself and
   the interfaces on which the LSP will be established can support the
   requested QoS parameters. If the requested value(s) can not be
   supported, the receiver node MUST generate a PathErr message with a
   "Traffic Control Error/Service unsupported" indication (see
   [RFC2205]).

6.5. Redundant PWs

   A local PE can signal a redundant PW using the same SESSION object as
   the primary PW and by varying the LSP-ID in the SENDER_TEMPLATE
   object. This allows intermediate hops to share QoS between the two.
   In the case of failure of the primary PW the local PE can try to
   switch traffic to the backup PW.

   Note that the procedures described in this document allow a CE to be
   dual homed to the same PE. Procedures for dual homing a CE to
   different PEs will be described in the next revision.


7. Security Considerations

   Security considerations from [RFC3209] and [RFC3473] apply to this
   document.


8. IANA Considerations

   TBD


9. Acknowledgments

   Thanks to Chaitanya Kodeboyina and Sasha Vainshtein for discussing
   the ideas presented here.














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10. References

10.1. Normative References

   [RFC3209]  Awduche, D., et al, "RSVP-TE: Extensions to RSVP for LSP
              tunnels", RFC 3209, December 2001.

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

   [RFC2210]  Wroclawski, J., "The Use of RSVP with IETF
              Integrated Services", RFC 2210, September 1997.

   [LSP-HIER] K. Kompella, Y. Rekhter, "LSP Hierarchy with Generalized
              MPLS TE", draft-ietf-mpls-lsp-hierarchy-08.txt

   [RFC2961]  Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi,
              F. and S. Molendini, "RSVP Refresh Overhead
              Reduction Extensions", RFC 2961, April 2001.

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

   [PW-ARCH]  "PWE3 Architecture" Bryant, et al.,
              draft-ietf-pwe3-arch-07.txt, March 2003.

10.2. Informative References


   [LSP-Ping] K. Kompella et. al., "Detecting MPLS Data Plane Failures",
              draft-ietf-mpls-lsp-ping-03.txt


   [VCCV]     T. Nadeau, R. Aggarwal, "Pseudo Wire (PW) Virtual Circuit
              Connection Verification ((VCCV)",
              draft-ietf-pwe3-vccv-03.txt

   [LDP]      Andersson, L., et al, "LDP Specification", RFC 3036

   [LDP-PW]   L. Martini et. al.,"Pseudowire Setup and Maintenance
              using LDP",
              draft-ietf-pwe3-control-protocol-08.txt

   [MPLS-ST]  "MPLS Label Stack Encoding", E. Rosen, Y. Rekhter,
              D. Tappan, G. Fedorkow, D. Farinacci, T. Li, A. Conta.
              RFC3032




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Author Information


   Rahul Aggarwal
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089
   Email: rahul@juniper.net

   Kireeti Kompella
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089
   Email: kireeti@juniper.net

   Arthi Ayyangar
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089
   Email: arthi@juniper.net

   Dimitri Papadimitriou
   Alcatel
   Francis Wellesplein 1,
   B-2018 Antwerpen, Belgium
   Phone: +32 3 240-8491
   Email: Dimitri.Papadimitriou@alcatel.be

   Peter Busschbach
   Lucent Technologies
   67 Whippany Road
   Whippany, NJ 07981
   email: busschbach@lucent.com



11. Intellectual Property

   The IETF takes no position regarding the validity or scope of any
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   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any



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Internet Draft       draft-raggarwa-rsvpte-pw-00.txt           June 2004


   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
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   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
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12. Full Copyright Statement

   Copyright (C) The Internet Society (2004). This document is subject
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   This document and the information contained herein is provided on an
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13. Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.




















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