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rfc:rfc4591

Network Working Group M. Townsley Request for Comments: 4591 G. Wilkie Category: Standards Track S. Booth

                                                             S. Bryant
                                                         Cisco Systems
                                                                J. Lau
                                                             July 2006
   Frame Relay over Layer 2 Tunneling Protocol Version 3 (L2TPv3)

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 (2006).

Abstract

 The Layer 2 Tunneling Protocol, Version 3, (L2TPv3) defines a
 protocol for tunneling a variety of data link protocols over IP
 networks.  This document describes the specifics of how to tunnel
 Frame Relay over L2TPv3, including frame encapsulation, virtual-
 circuit creation and deletion, and status change notification.

Townsley, et al. Standards Track [Page 1] RFC 4591 Frame Relay over L2TPv3 July 2006

Table of Contents

 1. Introduction ....................................................2
    1.1. Abbreviations ..............................................3
    1.2. Specification of Requirements ..............................3
 2. Control Connection Establishment ................................3
 3. PVC Status Notification and Session Establishment ...............3
    3.1. L2TPv3 Session Establishment ...............................4
    3.2. L2TPv3 Session Teardown ....................................5
    3.3. L2TPv3 Session Maintenance .................................5
    3.4. Use of the Circuit Status AVP for Frame Relay ..............6
    3.5. Frame Relay Header Length AVP ..............................7
 4. Encapsulation ...................................................7
    4.1. Data Packet Encapsulation ..................................7
    4.2. Data Packet Sequencing .....................................9
    4.3. MTU Considerations .........................................9
 5. Applicability Statement ........................................10
 6. Security Considerations ........................................10
 7. IANA Considerations ............................................11
    7.1. Pseudowire Type ...........................................11
    7.2. Result Code AVP Values ....................................11
    7.3. Control Message Attribute Value Pairs (AVPs) ..............11
 8. Acknowledgements ...............................................11
 9. References .....................................................12
    9.1. Normative References ......................................12
    9.2. Informative References ....................................12

1. Introduction

 [RFC3931] defines a base protocol for Layer 2 Tunneling over IP
 networks.  This document defines the specifics necessary for
 tunneling Frame Relay over L2TPv3.  Such emulated circuits are
 referred to as Frame Relay Pseudowires (FRPWs).
 Protocol specifics defined in this document for L2TPv3 FRPWs
 operating in a "virtual circuit-to-virtual circuit" mode include
 those necessary for frame encapsulation, PVC creation and deletion,
 and status change notification.  Frame Relay traffic may also be
 transported in a "port-to-port" or "interface-to-interface" fashion
 using High-Level Data Link Control (HDLC) Pseudowires as defined in
 [RFC4349].  Support for Switched Virtual Circuits (SVCs) and
 Switched/Soft Permanent Virtual Circuits (SPVCs) are outside the
 scope of this document.
 The reader is expected to be very familiar with the terminology and
 protocol constructs defined in [RFC3931].

Townsley, et al. Standards Track [Page 2] RFC 4591 Frame Relay over L2TPv3 July 2006

1.1. Abbreviations

 FR    Frame Relay
 FRPW  Frame Relay Pseudowire
 LCCE  L2TP Control Connection Endpoint (See [RFC3931])
 PVC   Permanent virtual circuit
 PW    Pseudowire
 VC    Virtual circuit

1.2. Specification of Requirements

 In this document, several words are used to signify the requirements
 of the specification.  These words are often capitalized.  The key
 words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
 "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document
 are to be interpreted as described in [RFC2119].

2. Control Connection Establishment

 In order to tunnel a Frame Relay circuit over IP using L2TPv3, an
 L2TPv3 Control Connection MUST first be established as described in
 [RFC3931].  The L2TPv3 SCCRQ Control Message and corresponding SCCRP
 Control Message MUST include the Frame Relay Data Link Connection
 Identifier (DLCI) PW Type of 0x0001 (see IANA Considerations), in the
 Pseudowire Capabilities List, as defined in Section 5.4.3 of
 [RFC3931].  This identifies the control connection as able to
 establish L2TP sessions to support Frame Relay Pseudowires (FRPWs).
 An LCCE MUST be able to identify itself uniquely in the SCCRQ and
 SCCRP messages via a globally unique value.  By default, this is
 advertised via the structured Router ID Attribute Value Pairs (AVP)
 [RFC3931], though the unstructured Hostname AVP [RFC3931] MAY be used
 to identify LCCEs as well.

3. PVC Status Notification and Session Establishment

 This section specifies how the status of a PVC is reported between
 two LCCEs.  This includes what should happen when a PVC is created,
 deleted or when it changes state between ACTIVE and INACTIVE.  When
 emulating a Frame Relay service, if the procedures for PVC status
 management defined in [Q933] Annex A are being used between an LCCE
 and the attached Remote System, an LCCE MUST participate in them (see
 Section 3.3).

Townsley, et al. Standards Track [Page 3] RFC 4591 Frame Relay over L2TPv3 July 2006

3.1. L2TPv3 Session Establishment

 PVC creation (provisioning) results in establishment of an L2TP
 session via the standard three-way handshake described in Section
 3.4.1 of [RFC3931].  An LCCE MAY initiate the session immediately
 upon PVC creation or wait until the PVC state transitions to ACTIVE
 before attempting to establish a session for the PVC.  Waiting until
 the PVC transitions to ACTIVE may be preferred, as it delays
 allocation of L2TP resources until it is absolutely necessary.
 The Pseudowire Type AVP defined in Section 5.4.4 of [RFC3931],
 Attribute Type 68, MUST be present in the Incoming-Call-Request
 (ICRQ) messages and MUST include the Frame Relay DLCI PW Type of
 0x0001 for FRPWs.
 The Circuit Status AVP (see Section 3.4) MUST be present in the ICRQ
 and Incoming-Call-Reply (ICRP) messages and MAY be present in the Set
 Link Info (SLI) message for FRPWs.
 The Frame Relay Header Length AVP (see Section 3.5) MAY be present in
 the ICRQ and ICRP messages.
 The following is an example of the L2TP messages exchanged for an
 FRPW that is initiated after a new PVC is provisioned and becomes
 ACTIVE.
       LCCE (LAC) A                     LCCE (LAC) B
    ------------------               ------------------
    FR PVC Provisioned
                                     FR PVC Provisioned
    FR PVC ACTIVE
                 ICRQ (status = 0x03) ---->
                                     FR PVC ACTIVE
                 <---- ICRP (status = 0x03)
    L2TP session established,
    OK to send data into tunnel
                     ICCN ----->
                                  L2TP session established,
                                  OK to send data into tunnel
 In the example above, an ICRQ is sent after the PVC is created and
 becomes ACTIVE.  The Circuit Status AVP indicates that this PVC is
 ACTIVE and New (0x03).  The Remote End ID AVP [RFC3931] MUST be

Townsley, et al. Standards Track [Page 4] RFC 4591 Frame Relay over L2TPv3 July 2006

 present in the ICRQ in order to identify the PVC (together with the
 identity of the LCCE itself, as defined in Section 2) to associate
 the L2TP session with.  The Remote End ID AVP, defined in [RFC3931],
 is of opaque form and variable length, though one MUST at a minimum
 support use of an unstructured four-octet value that is known to both
 LCCEs (either by direct configuration, or some other means).  The
 exact method of how this value is configured, retrieved, discovered,
 or otherwise determined at each LCCE is outside the scope of this
 document.
 As with the ICRQ, the ICRP is sent only after the FR PVC transitions
 to ACTIVE as well.  If LCCE B had not been provisioned for the PVC
 identified in the ICRQ, a Call-Disconnect-Notify (CDN) would have
 been immediately returned indicating that the circuit was not
 provisioned or available at this LCCE.  LCCE A SHOULD then exhibit a
 periodic retry mechanism.  If so, the period and maximum number of
 retries MUST be configurable.
 An Implementation MAY send an ICRQ or ICRP before a PVC is ACTIVE, as
 long as the Circuit Status AVP reflects that the PVC is INACTIVE and
 an SLI is sent when the PVC becomes ACTIVE (see Section 3.3).
 The Incoming-Call-Connected (ICCN) is the final stage in the session
 establishment, confirming the receipt of the ICRP with acceptable
 parameters to allow bidirectional traffic.

3.2. L2TPv3 Session Teardown

 In the event that a PVC is deleted (unprovisioned) at either LCCE,
 the associated L2TP session MUST be torn down via the CDN message
 defined in Section 3.4.3 of [RFC3931].
 General Result Codes regarding L2TP session establishment are defined
 in [RFC3931].  Additional Frame Relay result codes are defined as
 follows:
    17: FR PVC was deleted permanently (no longer provisioned) 18: FR
    PVC has been INACTIVE for an extended period of time 19:
    Mismatched FR Header Length

3.3. L2TPv3 Session Maintenance

 FRPW over L2TP makes use of the SLI control message defined in
 [RFC3931] to signal Frame Relay link status notifications between
 LCCEs.  This includes ACTIVE or INACTIVE notifications of the VC, and
 any other parameters that may need to be shared between the tunnel
 endpoints or LCCEs in order to provide proper PW emulation.  The SLI
 message is a single message that is sent over the L2TP control

Townsley, et al. Standards Track [Page 5] RFC 4591 Frame Relay over L2TPv3 July 2006

 channel signalling the state change.  Since the message is delivered
 reliably, there is no additional response or action required of the
 PW subsystem to ensure that the state change notification was
 received by the tunnel peer.
 The SLI message MUST be sent any time there is a circuit status
 change that may be reported by any values identified in the Circuit
 Status AVP.  The only exceptions to this are the initial ICRQ, ICRP,
 and CDN messages, which establish and tear down the L2TP session
 itself when the PVC is created or deleted.  The SLI message may be
 sent from either LCCE at any time after the first ICRQ is sent (and
 perhaps before an ICRP is received, requiring that the peer to
 perform a reverse Session ID lookup).
 An LCCE participating in the procedures for PVC status management
 defined in [Q933], Annex A, MUST transmit an SLI message including
 the Circuit Status AVP (see Section 3.4) when it detects a change in
 the status for a particular local FR PVC (i.e., when it detects a
 service-affecting condition or the clearing of such a condition).  An
 LCCE receiving an SLI message indicating a change in the status of a
 particular FRPW SHOULD generate corresponding updates for the FR PVC
 towards the Remote System, as defined in [Q933], Annex A.
 All sessions established by a given control connection utilize the
 L2TP Hello facility, defined in Section 4.4 of [RFC3931], for session
 keepalive.  This gives all sessions basic dead peer and path
 detection between LCCEs.

3.4. Use of the Circuit Status AVP for Frame Relay

 Frame Relay circuit status is reported via the Circuit Status AVP
 defined in [RFC3931], Attribute Type 71.  For reference, this AVP is
 shown below:
  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Reserved        |N|A|
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The Value is a 16-bit mask with the two least significant bits
 defined and the remaining bits reserved for future use.  Reserved
 bits MUST be set to 0 by the sender and ignored by the receiver.
 The N (New) bit indicates whether the Circuit Status indication is
 for a new FR PVC (1) or an existing FR PVC (0).

Townsley, et al. Standards Track [Page 6] RFC 4591 Frame Relay over L2TPv3 July 2006

 The A (Active) bit indicates whether the FR PVC is ACTIVE (1) or
 INACTIVE (0).

3.5. Frame Relay Header Length AVP

 The "Frame Relay Header Length AVP", Attribute type 85, indicates the
 number of bytes in the Frame Relay header.  The two peer LCCEs MUST
 agree on the length of the Frame Relay header.
 This AVP is exchanged during session negotiation (in ICRQ, ICRP).  If
 the other LCCE supports a different Frame Relay header length, the
 associated L2TP session MUST be torn down via CDN message with result
 code 19 (see Section 3.2).
 If the Frame Relay Header Length AVP is not signalled, it MUST be
 assumed that the peer uses a 2-byte Frame Relay header.
 The Attribute Value field for this AVP has the following format:
 Frame Relay Header Length (ICRQ, ICRP)
     0                   1
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Frame Relay Header Length   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The Frame Relay Header Length Type is a 2-octet unsigned integer with
 the following values defined in this document:
    2: Two-octet Frame Relay Header 4: Four-octet Frame Relay Header
 This AVP MAY be hidden (the H bit MAY be 0 or 1).  The M bit for this
 AVP MAY be set to 0 but MAY vary (see Section 5.2 of [RFC3931]).  The
 length (before hiding) of this AVP is 8.

4. Encapsulation

4.1. Data Packet Encapsulation

 The FR PDU is transported in its entirety, excluding the opening and
 closing High Level Data Link Control (HDLC) flags and the frame check
 sequence (FCS).  Bit stuffing is undone.  The L2TPv3 Session Header
 is that as defined in [RFC3931].  If sequencing or other features
 require presence of an L2-Specific Sublayer, the Default format
 defined in Section 4.6 of [RFC3931] MUST be used.

Townsley, et al. Standards Track [Page 7] RFC 4591 Frame Relay over L2TPv3 July 2006

 The FR header is defined in [Q922]; however, the notation used
 differs from that used in IETF specifications.  For reference, the FR
 header (referred to as Address Field in [Q922]) in IETF notation is
  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | hi dlci   |C|0|lo dlci|F|B|D|1|
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Two-octet FR Header
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | hi dlci   |C|0| dlci  |F|B|D|0|   dlci      |0| dlci_lo   |0|1|
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Four-octet FR  Header
 C/R (bit 6) FR frame C/R (command/response) bit [Q922].
 F - FECN (bit 12):  FR FECN (Forward Explicit Congestion
 Notification) bit [Q922].
 B - BECN (bit 13):
 FR BECN (Backward Explicit Congestion Notification) bit [Q922].
 D - DE (bit 14) FR DE bit indicates the discard eligibility [Q922].
 Usage of the C/R, FECN, BECN, and DE bits is as specified in [Q922].
 The C/R bit is conveyed transparently.  Its value MUST NOT be changed
 by the LCCE.
 The FECN bit MAY be set by the LCCE to notify the receiving end-user
 that the frames it receives have encountered congestion.  The end-
 user may use this indication for destination-controlled transmit rate
 adjustment.  The bit must never be cleared by the LCCE.  If the LCCE
 does not support FECN, it shall pass the bit unchanged.
 The BECN bit MAY be set by the LCCE to notify the receiving end-user
 that the frames it transmits may encounter congestion.  The end-user
 may use this indication to adjust its transmit rate.  The bit must
 never be cleared by the LCCE.  If the LCCE does not support BECN, it
 shall pass the bit unchanged.

Townsley, et al. Standards Track [Page 8] RFC 4591 Frame Relay over L2TPv3 July 2006

 The DE bit MAY be set by a policing function on the LCCE to indicate
 that this frame SHOULD be discarded in preference to other frames in
 a congestion situation.  The bit must never be cleared by the LCCE.
 If the LCCE does not support DE, it shall pass the bit unchanged.
 The encapsulation of Frame Relay frames with the two-octet FR Header
 is REQUIRED.  The encapsulation of Frame Relay frames with the four-
 octet FR Header is OPTIONAL.  The encapsulation of Frame Relay frames
 with the three-octet FR Header is outside the scope of this document.

4.2. Data Packet Sequencing

 Data Packet Sequencing MAY be enabled for FRPWs.  The sequencing
 mechanisms described in [RFC3931] MUST be used for signalling
 sequencing support.  FRPW over L2TP MUST request the presence of the
 L2TPv3 Default L2-Specific Sublayer when sequencing is enabled and
 MAY request its presence at all times.
 If the FRPW is known to be carrying data that does not require packet
 order be strictly maintained (such as IP), then packet sequencing for
 the FRPW SHOULD NOT be enabled.

4.3. MTU Considerations

 With L2TPv3 as the tunneling protocol, the packet resulted from the
 encapsulation is N bytes longer than Frame Relay frame without the
 opening and closing HDLC flags or FCS.  The value of N depends on the
 following fields:
    L2TP Session Header:
    Flags, Ver, Res       4 octets (L2TPv3 over UDP only)
    Session ID            4 octets
    Cookie Size           0, 4, or 8 octets
    L2-Specific Sublayer  0 or 4 octets (i.e., with sequencing)
 Thus, the range for N in octets is:
    N = 4 - 16   L2TPv3 data messages are over IP
    N = 16 - 28  L2TPv3 data messages are over UDP
    (N does not include the IP header)
 The MTU and fragmentation implications resulting from this are
 discussed in Section 4.1.4 of [RFC3931].

Townsley, et al. Standards Track [Page 9] RFC 4591 Frame Relay over L2TPv3 July 2006

5. Applicability Statement

 The Frame Relay PW emulation described in this document allows a
 service provider to offer a Frame Relay PVC-based service across an
 IP packet-switched network (PSN).  A Frame Relay port-based service
 can be offered using [RFC4349].
 The FRPW emulation has the following characteristics in relationship
 to the native service:
 o There is a one-to-one mapping between a Frame Relay PVC and an
   FRPW, supporting bi-directional transport of variable length
   frames.  The Frame Relay frame is transported in its entirety,
   including the DLCI and the C/R, FECN, BECN, and DE bits, but
   excluding the opening and closing flags and the FCS.  The egress
   LCCE re-writes the DLCI and regenerates the FCS.
 o Two- and four-octet address fields are supported.  The length is
   negotiated between LCCEs during session establishment (see Section
   3.5).
 o The availability or unavailability of the PVC is signalled between
   LCCEs using the Circuit Status AVP (see Section 3.4).  Loss of
   connectivity between LCCEs can be detected by the L2TPv3 keepalive
   mechanism (see Section 4.4 in [RFC3931]).  These indications can be
   used to determine the PVC status to be signalled through [Q933]
   procedures at the Frame Relay interface.
 o The maximum frame size that can be supported is limited by the PSN
   MTU, unless fragmentation and reassembly is used (see Section 4.1.4
   of [RFC3931]).
 o Sequencing may be enabled on the FRPW to ensure that frames are
   delivered in order (see Section 4.2).
 o Quality of Service characteristics, such as throughput (CIR),
   committed burst size (bc), excess burst size (be), and priority,
   can be provided by leveraging Quality of Service features of the
   LCCEs and the underlying PSN.

6. Security Considerations

 Frame Relay over L2TPv3 is subject to the security considerations
 defined in [RFC3931].  There are no additional considerations
 specific to carrying Frame Relay that are not present for carrying
 other data link types.

Townsley, et al. Standards Track [Page 10] RFC 4591 Frame Relay over L2TPv3 July 2006

7. IANA Considerations

7.1. Pseudowire Type

 The following value for the Frame Relay DLCI PW Type (see Pseudowire
 Capabilities List, as defined in 5.4.3 of [RFC3931], and L2TPv3
 Pseudowire Types in 10.6 of [RFC3931]) is allocated by the IANA
 (number space already created as part of publication of [RFC3931]):
    L2TPv3 Pseudowire Types
    -----------------------
    0x0001: Frame Relay DLCI Pseudowire Type

7.2. Result Code AVP Values

 This number space is managed by IANA as described in Section 2.3 of
 [RFC3438].  Three new L2TP Result Codes for the CDN message appear in
 Section 3.2.  The following is a summary:
    Result Code AVP (Attribute Type 1) Values
    -----------------------------------------
    17: PVC was deleted permanently (no longer provisioned)
    18: PVC has been INACTIVE for an extended period of time
    19: Mismatched FR Header Length

7.3. Control Message Attribute Value Pairs (AVPs)

 This number space is managed by IANA as described in Section 2.2 of
 [RFC3438].  An additional AVP Attribute, specified in Section 3.5,
 was allocated for this specification:
    Control Message Attribute Value Pairs
    -------------------------------------
    85: Frame Relay Header Length

8. Acknowledgements

 The first Frame Relay over L2TP document, "Frame Relay Service Type
 for L2TP", was published in February of 2001, by Nishit Vasavada, Jim
 Boyle, Chris Garner, Serge Maskalik, and Vijay Gill.  This document
 is substantially different, but the basic concept of carrying Frame
 Relay over L2TP is the same.

Townsley, et al. Standards Track [Page 11] RFC 4591 Frame Relay over L2TPv3 July 2006

 Thanks to Lloyd Wood for a razor-sharp review.
 Carlos Pignataro helped with review and editing of the document.
 During IETF Last Call, Mark Lewis provided thorough review and
 comments.

9. References

9.1. Normative References

 [RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
           Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC4349] Pignataro, C. and M. Townsley, "High-Level Data Link
           Control (HDLC) Frames over Layer 2 Tunneling Protocol,
           Version 3 (L2TPv3)", RFC 4349, February 2006.

9.2. Informative References

 [RFC3438] Townsley, W., "Layer Two Tunneling Protocol (L2TP) Internet
           Assigned Numbers Authority (IANA) Considerations Update",
           BCP 68, RFC 3438, December 2002.
 [Q922]    ITU-T Recommendation Q.922, "ISDN Data Link Layer
           Specification for Frame Mode Bearer Services", ITU, Geneva,
           1992.
 [Q933]    ITU-T Recommendation Q.933, "Signalling specifications for
           frame mode switched and permanent virtual connection
           control and status monitoring", ITU, Geneva, 2003.

Townsley, et al. Standards Track [Page 12] RFC 4591 Frame Relay over L2TPv3 July 2006

Authors' Addresses

 W. Mark Townsley
 Cisco Systems
 7025 Kit Creek Road
 PO Box 14987
 Research Triangle Park, NC 27709
 EMail: mark@townsley.net
 George Wilkie
 Cisco Systems
 96 Commercial Street
 Edinburgh, EH6 6LX
 United Kingdom
 EMail: gwilkie@cisco.com
 Skip Booth
 Cisco Systems
 7025 Kit Creek Road
 PO Box 14987
 Research Triangle Park, NC 27709
 EMail: ebooth@cisco.com
 Stewart Bryant
 Cisco Systems
 250 Longwater Ave
 Green Park
 Reading RG2 6GB
 United Kingdom
 EMail: stbryant@cisco.com
 Jed Lau
 EMail: jedlau@gmail.com

Townsley, et al. Standards Track [Page 13] RFC 4591 Frame Relay over L2TPv3 July 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 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.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Townsley, et al. Standards Track [Page 14]

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