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Network Working Group                                        M. TownsleyRequest for Comments: 4591                                     G. WilkieCategory: Standards Track                                       S. Booth                                                               S. Bryant                                                           Cisco Systems                                                                  J. Lau                                                               July 2006Frame 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 2006Table of Contents1. Introduction ....................................................21.1. Abbreviations ..............................................31.2. Specification of Requirements ..............................32. Control Connection Establishment ................................33. PVC Status Notification and Session Establishment ...............33.1. L2TPv3 Session Establishment ...............................43.2. L2TPv3 Session Teardown ....................................53.3. L2TPv3 Session Maintenance .................................53.4. Use of the Circuit Status AVP for Frame Relay ..............63.5. Frame Relay Header Length AVP ..............................74. Encapsulation ...................................................74.1. Data Packet Encapsulation ..................................74.2. Data Packet Sequencing .....................................94.3. MTU Considerations .........................................95. Applicability Statement ........................................106. Security Considerations ........................................107. IANA Considerations ............................................117.1. Pseudowire Type ...........................................117.2. Result Code AVP Values ....................................117.3. Control Message Attribute Value Pairs (AVPs) ..............118. Acknowledgements ...............................................119. References .....................................................129.1. Normative References ......................................129.2. Informative References ....................................121.  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 20061.1.  Abbreviations   FR    Frame Relay   FRPW  Frame Relay Pseudowire   LCCE  L2TP Control Connection Endpoint (See [RFC3931])   PVC   Permanent virtual circuit   PW    Pseudowire   VC    Virtual circuit1.2. 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 inSection 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 (seeSection 3.3).Townsley, et al.            Standards Track                     [Page 3]

RFC 4591                Frame Relay over L2TPv3                July 20063.1.  L2TPv3 Session Establishment   PVC creation (provisioning) results in establishment of an L2TP   session via the standard three-way handshake described inSection3.4.1 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 inSection 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 (seeSection 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 (seeSection 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 beTownsley, 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 inSection 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 (seeSection 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 inSection 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 Length3.3.  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 controlTownsley, 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 (seeSection 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 inSection 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 (seeSection 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 (seeSection 5.2 of [RFC3931]).  The   length (before hiding) of this AVP is 8.4.  Encapsulation4.1.  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 inSection 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 inSection 4.1.4 of [RFC3931].Townsley, et al.            Standards Track                     [Page 9]

RFC 4591                Frame Relay over L2TPv3                July 20065.  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 (seeSection3.5).   o The availability or unavailability of the PVC is signalled between     LCCEs using the Circuit Status AVP (seeSection 3.4).  Loss of     connectivity between LCCEs can be detected by the L2TPv3 keepalive     mechanism (seeSection 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 (seeSection 4.1.4     of [RFC3931]).   o Sequencing may be enabled on the FRPW to ensure that frames are     delivered in order (seeSection 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 20067. IANA Considerations7.1.  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 Type7.2.  Result Code AVP Values   This number space is managed by IANA as described inSection 2.3 of   [RFC3438].  Three new L2TP Result Codes for the CDN message appear inSection 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 Length7.3.  Control Message Attribute Value Pairs (AVPs)   This number space is managed by IANA as described inSection 2.2 of   [RFC3438].  An additional AVP Attribute, specified inSection 3.5,   was allocated for this specification:      Control Message Attribute Value Pairs      -------------------------------------      85: Frame Relay Header Length8.  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.  References9.1.  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 2006Authors' 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.comTownsley, et al.            Standards Track                    [Page 13]

RFC 4591                Frame Relay over L2TPv3                July 2006Full Copyright Statement   Copyright (C) The Internet Society (2006).   This document is subject to the rights, licenses and restrictions   contained inBCP 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.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   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   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is provided by the IETF   Administrative Support Activity (IASA).Townsley, et al.            Standards Track                    [Page 14]