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rfc:rfc4023

Network Working Group T. Worster Request for Comments: 4023 Motorola, Inc. Category: Standards Track Y. Rekhter

                                                Juniper Networks, Inc.
                                                         E. Rosen, Ed.
                                                   Cisco Systems, Inc.
                                                            March 2005
  Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2005).

Abstract

 Various applications of MPLS make use of label stacks with multiple
 entries.  In some cases, it is possible to replace the top label of
 the stack with an IP-based encapsulation, thereby enabling the
 application to run over networks that do not have MPLS enabled in
 their core routers.  This document specifies two IP-based
 encapsulations: MPLS-in-IP and MPLS-in-GRE (Generic Routing
 Encapsulation).  Each of these is applicable in some circumstances.

Worster, et al. Standards Track [Page 1] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

Table of Contents

 1.  Motivation  ..................................................  2
 2.  Specification of Requirements  ...............................  3
 3.  Encapsulation in IP  .........................................  3
 4.  Encapsulation in GRE  ........................................  4
 5.  Common Procedures  ...........................................  5
     5.1.  Preventing Fragmentation and Reassembly  ...............  5
     5.2.  TTL or Hop Limit  ......................................  6
     5.3.  Differentiated Services  ...............................  7
 6.  Applicability  ...............................................  7
 7.  IANA Considerations  .........................................  8
 8.  Security Considerations  .....................................  8
     8.1.  Securing the Tunnel with IPsec .........................  8
     8.2.  In the Absence of IPsec  ............................... 10
 9.  Acknowledgements ............................................. 11
 10. Normative References  ........................................ 11
 11. Informative References  ...................................... 12
 Authors' Addresses ............................................... 13
 Full Copyright Statement ......................................... 14

1. Motivation

 In many applications of MPLS, packets traversing an MPLS backbone
 carry label stacks with more than one label.  As described in section
 3.15 of [RFC3031], each label represents a Label Switched Path (LSP).
 For each LSP, there is a Label Switching Router (LSR) that is the
 "LSP Ingress", and an LSR that is the "LSP Egress".  If LSRs A and B
 are the Ingress and Egress, respectively, of the LSP corresponding to
 a packet's top label, then A and B are adjacent LSRs on the LSP
 corresponding to the packet's second label (i.e., the label
 immediately beneath the top label).
 The purpose (or one of the purposes) of the top label is to get the
 packet delivered from A to B, so that B can further process the
 packet based on the second label.  In this sense, the top label
 serves as an encapsulation header for the rest of the packet.  In
 some cases, other sorts of encapsulation headers can replace the top
 label without loss of functionality.  For example, an IP header or a
 Generic Routing Encapsulation (GRE) header could replace the top
 label.  As the encapsulated packet would still be an MPLS packet, the
 result is an MPLS-in-IP or MPLS-in-GRE encapsulation.
 With these encapsulations, it is possible for two LSRs that are
 adjacent on an LSP to be separated by an IP network, even if that IP
 network does not provide MPLS.

Worster, et al. Standards Track [Page 2] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 To use either of these encapsulations, the encapsulating LSR must
 know
  1. the IP address of the decapsulating LSR, and
  1. that the decapsulating LSR actually supports the particular

encapsulation.

 This knowledge may be conveyed to the encapsulating LSR by manual
 configuration, or by means of some discovery protocol.  In
 particular, if the tunnel is being used to support a particular
 application and that application has a setup or discovery protocol,
 then the application's protocol may convey this knowledge.  The means
 of conveying this knowledge is outside the scope of the this
 document.

2. Specification of Requirements

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

3. Encapsulation in IP

 MPLS-in-IP messages have the following format:
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           |                                     |
           |             IP Header               |
           |                                     |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           |                                     |
           |          MPLS Label Stack           |
           |                                     |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           |                                     |
           |            Message Body             |
           |                                     |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       IP Header
           This field contains an IPv4 or an IPv6 datagram header
           as defined in [RFC791] or [RFC2460], respectively.  The
           source and destination addresses are set to addresses
           of the encapsulating and decapsulating LSRs, respectively.

Worster, et al. Standards Track [Page 3] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

       MPLS Label Stack
           This field contains an MPLS Label Stack as defined in
           [RFC3032].
       Message Body
           This field contains one MPLS message body.
 The IPv4 Protocol Number field or the IPv6 Next Header field is set
 to 137, indicating an MPLS unicast packet.  (The use of the MPLS-in-
 IP encapsulation for MPLS multicast packets is not supported by this
 specification.)
 Following the IP header is an MPLS packet, as specified in [RFC3032].
 This encapsulation causes MPLS packets to be sent through "IP
 tunnels".  When the tunnel's receive endpoint receives a packet, it
 decapsulates the MPLS packet by removing the IP header.  The packet
 is then processed as a received MPLS packet whose "incoming label"
 [RFC3031] is the topmost label of the decapsulated packet.

4. Encapsulation in GRE

 The MPLS-in-GRE encapsulation encapsulates an MPLS packet in GRE
 [RFC2784].  The packet then consists of an IP header (either IPv4 or
 IPv6), followed by a GRE header, followed by an MPLS label stack as
 specified in [RFC3032].  The protocol type field in the GRE header
 MUST be set to the Ethertype value for MPLS Unicast (0x8847) or
 Multicast (0x8848).
 This encapsulation causes MPLS packets to be sent through "GRE
 tunnels".  When the tunnel's receive endpoint receives a packet, it
 decapsulates the MPLS packet by removing the IP and the GRE headers.
 The packet is then processed as a received MPLS packet whose
 "incoming label" [RFC3031] is the topmost label of the decapsulated
 packet.
 [RFC2784] specifies an optional GRE checksum, and [RFC2890] specifies
 optional GRE key and sequence number fields.  These optional fields
 are not very useful for the MPLS-in-GRE encapsulation.  The sequence
 number and checksum fields are not needed, as there are no
 corresponding fields in the native MPLS packets being tunneled.  The
 GRE key field is not needed for demultiplexing, as the top MPLS label
 of the encapsulated packet is used for that purpose.  The GRE key
 field is sometimes considered a security feature, functioning as a
 32-bit cleartext password, but this is an extremely weak form of
 security.  In order (a) to facilitate high-speed implementations of
 the encapsulation/decapsulation procedures and (b) to ensure
 interoperability, we require that all implementations be able to
 operate correctly without these optional fields.

Worster, et al. Standards Track [Page 4] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 More precisely, an implementation of an MPLS-in-GRE decapsulator MUST
 be able to process packets correctly without these optional fields.
 It MAY be able to process packets correctly with these optional
 fields.
 An implementation of an MPLS-in-GRE encapsulator MUST be able to
 generate packets without these optional fields.  It MAY have the
 capability to generate packets with these fields, but the default
 state MUST be that packets are generated without these fields.  The
 encapsulator MUST NOT include any of these optional fields unless it
 is known that the decapsulator can process them correctly.  Methods
 for conveying this knowledge are outside the scope of this
 specification.

5. Common Procedures

 Certain procedures are common to both the MPLS-in-IP and the MPLS-
 in-GRE encapsulations.  In the following, the encapsulator, whose
 address appears in the IP source address field of the encapsulating
 IP header, is known as the "tunnel head".  The decapsulator, whose
 address appears in the IP destination address field of the
 decapsulating IP header, is known as the "tunnel tail".
 If IPv6 is being used (for either MPLS-in-IPv6 or MPLS-in-GRE-in-
 IPv6), the procedures of [RFC2473] are generally applicable.

5.1. Preventing Fragmentation and Reassembly

 If an MPLS-in-IP or MPLS-in-GRE packet were fragmented (due to
 "ordinary" IP fragmentation), the tunnel tail would have to
 reassemble it before the contained MPLS packet could be decapsulated.
 When the tunnel tail is a router, this is likely to be undesirable;
 the tunnel tail may not have the ability or the resources to perform
 reassembly at the necessary level of performance.
 Whether fragmentation of the tunneled packets is allowed MUST be
 configurable at the tunnel head.  The default value MUST be that
 packets are not fragmented.  The default value would only be changed
 if it were known that the tunnel tail could perform the reassembly
 function adequately.
 THE PROCEDURES SPECIFIED IN THE REMAINDER OF THIS SECTION ONLY APPLY
 IF PACKETS ARE NOT TO BE FRAGMENTED.
 Obviously, if packets are not to be fragmented, the tunnel head MUST
 NOT fragment a packet before encapsulating it.

Worster, et al. Standards Track [Page 5] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 If IPv4 is used, then the tunnel MUST set the DF bit.  This prevents
 intermediate nodes in the tunnel from performing fragmentation.  (If
 IPv6 is used, intermediate nodes do not perform fragmentation in any
 event.)
 The tunnel head SHOULD perform Path MTU Discovery ([RFC1191] for
 IPv4, or [RFC1981] for IPv6).
 The tunnel head MUST maintain a "Tunnel MTU" for each tunnel; this is
 the minimum of (a) an administratively configured value, and, if
 known, (b) the discovered Path MTU value minus the encapsulation
 overhead.
 If the tunnel head receives, for encapsulation, an MPLS packet whose
 size exceeds the Tunnel MTU, that packet MUST be discarded.  However,
 silently dropping such packets may cause significant operational
 problems; the originator of the packets will notice that his data is
 not getting through, but he may not realize that large packets are
 causing packet loss.  He may therefore continue sending packets that
 are discarded.  Path MTU discovery can help (if the tunnel head sends
 back ICMP errors), but frequently there is insufficient information
 available at the tunnel head to identify the originating sender
 properly.  To minimize problems, it is advised that MTUs be
 engineered to be large enough in practice to avoid fragmentation.
 In some cases, the tunnel head receives, for encapsulation, an IP
 packet, which it first encapsulates in MPLS and then encapsulates in
 MPLS-in-IP or MPLS-in-GRE.  If the source of the IP packet is
 reachable from the tunnel head, and if the result of encapsulating
 the packet in MPLS would be a packet whose size exceeds the Tunnel
 MTU, then the value that the tunnel head SHOULD use for fragmentation
 and PMTU discovery outside the tunnel is the Tunnel MTU value minus
 the size of the MPLS encapsulation.  (That is, the Tunnel MTU value
 minus the size of the MPLS encapsulation is the MTU that is to be
 reported in ICMP messages.)  The packet will have to be discarded,
 but the tunnel head should send the IP source of the discarded packet
 the proper ICMP error message as specified in [RFC1191] or [RFC1981].

5.2. TTL or Hop Limit

 The tunnel head MAY place the TTL from the MPLS label stack into the
 TTL field of the encapsulating IPv4 header or the Hop Limit field of
 the encapsulating IPv6 header.  The tunnel tail MAY place the TTL
 from the encapsulating IPv4 header or the Hop Limit from the
 encapsulating IPv6 header into the TTL field of the MPLS header, but
 only if this does not increase the TTL value in the MPLS header.

Worster, et al. Standards Track [Page 6] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 Whether such modifications are made, and the details of how they are
 made, will depend on the configuration of the tunnel tail and the
 tunnel head.

5.3. Differentiated Services

 The procedures specified in this document enable an LSP to be sent
 through an IP or GRE tunnel.  [RFC2983] details a number of
 considerations and procedures that have to be applied to support the
 Differentiated Services Architecture properly in the presence of IP-
 in-IP tunnels.  These considerations and procedures also apply in the
 presence of MPLS-in-IP or MPLS-in-GRE tunnels.
 Accordingly, when a tunnel head is about to send an MPLS packet into
 an MPLS-in-IP or MPLS-in-GRE tunnel, the setting of the DS field of
 the encapsulating IPv4 or IPv6 header MAY be determined (at least
 partially) by the "Behavior Aggregate" of the MPLS packet.
 Procedures for determining the Behavior Aggregate of an MPLS packet
 are specified in [RFC3270].
 Similarly, at the tunnel tail, the DS field of the encapsulating IPv4
 or IPv6 header MAY be used to determine the Behavior Aggregate of the
 encapsulated MPLS packet. [RFC3270] specifies the relation between
 the Behavior Aggregate and the subsequent disposition of the packet.

6. Applicability

 The MPLS-in-IP encapsulation is the more efficient, and it would
 generally be regarded as preferable, other things being equal.  There
 are, however, some situations in which the MPLS-in-GRE encapsulation
 may be used:
  1. Two routers are "adjacent" over a GRE tunnel that exists for

some reason that is outside the scope of this document, and

       those two routers have to send MPLS packets over that
       adjacency.  As all packets sent over this adjacency must have a
       GRE encapsulation, the MPLS-in-GRE encapsulation is more
       efficient than the alternative, that would be an MPLS-in-IP
       encapsulation which is then encapsulated in GRE.
  1. Implementation considerations may dictate the use of MPLS-in-

GRE. For example, some hardware device might only be able to

       handle GRE encapsulations in its fastpath.

Worster, et al. Standards Track [Page 7] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

7. IANA Considerations

 The IANA has allocated IP Protocol Number 137 for MPLS-in-IP
 encapsulation, as described in section 3.  No future IANA actions
 will be required.  The MPLS-in-GRE encapsulation does not require any
 IANA action.

8. Security Considerations

 The main security problem faced when IP or GRE tunnels are used is
 the possibility that the tunnel's receive endpoint will get a packet
 that appears to be from the tunnel, but that was not actually put
 into the tunnel by the tunnel's transmit endpoint.  (The specified
 encapsulations do not by themselves enable the decapsulator to
 authenticate the encapsulator.)  A second problem is the possibility
 that the packet will be altered between the time it enters the tunnel
 and the time it leaves. (The specified encapsulations do not by
 themselves assure the decapsulator of the packet's integrity.)  A
 third problem is the possibility that the packet's contents will be
 seen while the packet is in transit through the tunnel.  (The
 specification encapsulations do not ensure privacy.)  How significant
 these issues are in practice depends on the security requirements of
 the applications whose traffic is being sent through the tunnel.  For
 example, lack of privacy for tunneled packets is not a significant
 issue if the applications generating the packets do not require
 privacy.
 Because of the different potential security requirements, deployment
 scenarios, and performance considerations of different applications
 using the described encapsulation mechanism, this specification
 defines IPsec support as OPTIONAL.  Basic implementation requirements
 if IPsec is implemented are described in section 8.1.  If IPsec is
 not implemented, additional mechanisms may have to be implemented and
 deployed.  Those are discussed in section 8.2.

8.1. Securing the Tunnel with IPsec

 All of these security issues can be avoided if the MPLS-in-IP or
 MPLS-in-GRE tunnels are secured with IPsec.  Implementation
 requirements defined in this section apply if IPsec is implemented.
 When IPsec is used, the tunnel head and the tunnel tail should be
 treated as the endpoints of a Security Association.  For this
 purpose, a single IP address of the tunnel head will be used as the
 source IP address, and a single IP address of the tunnel tail will be
 used as the destination IP address.  The means by which each node
 knows the proper address of the other is outside the scope of this
 document.  If a control protocol is used to set up the tunnels (e.g.,

Worster, et al. Standards Track [Page 8] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 to inform one tunnel endpoint of the IP address of the other), the
 control protocol MUST have an authentication mechanism, and this MUST
 be used when the tunnel is set up.  If the tunnel is set up
 automatically as the result of, for example, information distributed
 by BGP, then the use of BGP's MD5-based authentication mechanism is
 satisfactory.
 The MPLS-in-IP or MPLS-in-GRE encapsulated packets should be viewed
 as originating at the tunnel head and as being destined for the
 tunnel tail; IPsec transport mode SHOULD thus be used.
 The IP header of the MPLS-in-IP packet becomes the outer IP header of
 the resulting packet when the tunnel head uses IPsec transport mode
 to secure the MPLS-in-IP packet.  This is followed by an IPsec
 header, followed by the MPLS label stack.  The IPsec header has to
 set the payload type to MPLS by using the IP protocol number
 specified in section 3.  If IPsec transport mode is applied on a
 MPLS-in-GRE packet, the GRE header follows the IPsec header.
 At the tunnel tail, IPsec outbound processing recovers the contained
 MPLS-in-IP/GRE packet.  The tunnel tail then strips off the
 encapsulating IP/GRE header to recover the MPLS packet, which is then
 forwarded according to its label stack.
 Note that the tunnel tail and the tunnel head are LSP adjacencies,
 which means that the topmost label of any packet sent through the
 tunnel must be one that was distributed by the tunnel tail to the
 tunnel head.  The tunnel tail MUST know precisely which labels it has
 distributed to the tunnel heads of IPsec-secured tunnels.  Labels in
 this set MUST NOT be distributed by the tunnel tail to any LSP
 adjacencies other than those that are tunnel heads of IPsec-secured
 tunnels.  If an MPLS packet is received without an IPsec
 encapsulation, and if its topmost label is in this set, then the
 packet MUST be discarded.
 An IPsec-secured MPLS-in-IP or MPLS-in-GRE tunnel MUST provide
 authentication and integrity.  (Note that the authentication and
 integrity will apply to the entire MPLS packet, including the MPLS
 label stack.)  Thus, the implementation MUST support ESP will null
 encryption.  ESP with encryption MAY be supported if a source
 requires confidentiality.  If ESP is used, the tunnel tail MUST check
 that the source IP address of any packet received on a given SA is
 the one expected.
 Key distribution may be done either manually or automatically by
 means of IKE [RFC2409].  Manual keying MUST be supported.  If
 automatic keying is implemented, IKE in main mode with preshared keys

Worster, et al. Standards Track [Page 9] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 MUST be supported.  A particular application may escalate this
 requirement and request implementation of automatic keying.
 Manual key distribution is much simpler, but also less scalable, than
 automatic key distribution.  Therefore, which method of key
 distribution is appropriate for a particular tunnel has to be
 carefully considered by the administrator (or pair of administrators)
 responsible for the tunnel endpoints.  If replay protection is
 regarded as necessary for a particular tunnel, automatic key
 distribution should be configured.
 If the MPLS-in-IP encapsulation is being used, the selectors
 associated with the SA would be the source and destination addresses
 mentioned above, plus the IP protocol number specified in section 3.
 If it is desired to secure multiple MPLS-in-IP tunnels between a
 given pair of nodes separately, each tunnel must have unique pair of
 IP addresses.
 If the MPLS-in-GRE encapsulation is being used, the selectors
 associated with the SA would be the source and destination addresses
 mentioned above, and the IP protocol number representing GRE (47).
 If it is desired to secure multiple MPLS-in-GRE tunnels between a
 given pair of nodes separately, each tunnel must have unique pair of
 IP addresses.

8.2. In the Absence of IPsec

 If the tunnels are not secured with IPsec, then some other method
 should be used to ensure that packets are decapsulated and forwarded
 by the tunnel tail only if those packets were encapsulated by the
 tunnel head.  If the tunnel lies entirely within a single
 administrative domain, address filtering at the boundaries can be
 used to ensure that no packet with the IP source address of a tunnel
 endpoint or with the IP destination address of a tunnel endpoint can
 enter the domain from outside.
 However, when the tunnel head and the tunnel tail are not in the same
 administrative domain, this may become difficult, and filtering based
 on the destination address can even become impossible if the packets
 must traverse the public Internet.
 Sometimes only source address filtering (but not destination address
 filtering) is done at the boundaries of an administrative domain.  If
 this is the case, the filtering does not provide effective protection
 at all unless the decapsulator of an MPLS-in-IP or MPLS-in-GRE
 validates the IP source address of the packet.  This document does
 not require that the decapsulator validate the IP source address of
 the tunneled packets, but it should be understood that failure to do

Worster, et al. Standards Track [Page 10] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 so presupposes that there is effective destination-based (or a
 combination of source-based and destination-based) filtering at the
 boundaries.

9. Acknowledgements

 This specification combines prior work on encapsulating MPLS in IP,
 by Tom Worster, Paul Doolan, Yasuhiro Katsube, Tom K. Johnson, Andrew
 G. Malis, and Rick Wilder, with prior work on encapsulating MPLS in
 GRE, by Yakov Rekhter, Daniel Tappan, and Eric Rosen.  The current
 authors wish to thank all these authors for their contribution.
 Many people have made valuable comments and corrections, including
 Rahul Aggarwal, Scott Bradner, Alex Conta, Mark Duffy, Francois Le
 Feucheur, Allison Mankin, Thomas Narten, Pekka Savola, and Alex
 Zinin.

10. Normative References

 [RFC791]  Postel, J., "Internet Protocol", STD 5, RFC 791, September
           1981.
 [RFC792]  Postel, J., "Internet Control Message Protocol", STD 5, RFC
           792, September 1981.
 [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
           November 1990.
 [RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
           for IP version 6", RFC 1981, August 1996.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
           (IPv6) Specification", RFC 2460, December 1998.
 [RFC2463] Conta, A. and S. Deering, "Internet Control Message
           Protocol (ICMPv6) for the Internet Protocol Version 6
           (IPv6) Specification", RFC 2463, December 1998.
 [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6
           Specification", RFC 2473, December 1998.
 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina,
           "Generic Routing Encapsulation (GRE)", RFC 2784, March
           2000.

Worster, et al. Standards Track [Page 11] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
           Label Switching Architecture", RFC 3031, January 2001.
 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
           Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
           Encoding", RFC 3032, January 2001.

11. Informative References

 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
           Internet Protocol", RFC 2401, November 1998.
 [RFC2402] Kent, S. and R. Atkinson, "IP Authentication Header", RFC
           2402, November 1998.
 [RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security
           Payload (ESP)", RFC 2406, November 1998.
 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
           (IKE)", RFC 2409, November 1998.
 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
           and W. Weiss, "An Architecture for Differentiated Service",
           RFC 2475, December 1998.
 [RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
           RFC 2890, September 2000.
 [RFC2983] Black, D., "Differentiated Services and Tunnels", RFC 2983,
           October 2000.
 [RFC3260] Grossman, D., "New Terminology and Clarifications for
           Diffserv", RFC 3260, April 2002.
 [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
           P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
           Protocol Label Switching (MPLS) Support of Differentiated
           Services", RFC 3270, May 2002.

Worster, et al. Standards Track [Page 12] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

Authors' Addresses

 Tom Worster
 Motorola, Inc.
 120 Turnpike Road
 Southborough, MA 01772
 EMail: tom.worster@motorola.com
 Yakov Rekhter
 Juniper Networks, Inc.
 1194 N. Mathilda Ave.
 Sunnyvale, CA 94089
 EMail: yakov@juniper.net
 Eric Rosen
 Cisco Systems, Inc.
 1414 Massachusetts Avenue
 Boxborough, MA 01719
 EMail: erosen@cisco.com

Worster, et al. Standards Track [Page 13] RFC 4023 Encapsulating MPLS in IP or GRE March 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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Acknowledgement

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

Worster, et al. Standards Track [Page 14]

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