    Network Working Group                                           T. Koren
    Request for Comments: 3544                                 Cisco Systems
    Obsoletes: 2509                                                S. Casner
    Category: Standards Track                                  Packet Design
                                                                  C. Bormann
                                                     Universitaet Bremen TZI
                                                                   July 2003

                         IP Header Compression over PPP

    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 (2003).  All Rights Reserved.

    Abstract

       This document describes an option for negotiating the use of header
       compression on IP datagrams transmitted over the Point-to-Point
       Protocol (RFC 1661).  It defines extensions to the PPP Control
       Protocols for IPv4 and IPv6 (RFC 1332, RFC 2472).  Header compression
       may be applied to IPv4 and IPv6 datagrams in combination with TCP,
       UDP and RTP transport protocols as specified in RFC 2507, RFC 2508
       and RFC 3545.

    1.  Introduction

       The IP Header Compression (IPHC) defined in [RFC2507] may be used for
       compression of both IPv4 and IPv6 datagrams or packets encapsulated
       with multiple IP headers.  IPHC is also capable of compressing both
       TCP and UDP transport protocol headers.  The IP/UDP/RTP header
       compression defined in [RFC2508] and [RFC3545] fits within the
       framework defined by IPHC so that it may also be applied to both IPv4
       and IPv6 packets.

    Koren, et al.               Standards Track                     [Page 1]

    RFC 3544             IP Header Compression over PPP            July 2003

       In order to establish compression of IP datagrams sent over a PPP
       link each end of the link must agree on a set of configuration
       parameters for the compression.  The process of negotiating link
       parameters for network layer protocols is handled in PPP by a family
       of network control protocols (NCPs).  Since there are separate NCPs
       for IPv4 and IPv6, this document defines configuration options to be
       used in both NCPs to negotiate parameters for the compression scheme.

       This document obsoletes RFC 2509, adding two new suboptions to the IP
       header compression configuration option.  One suboption negotiates
       usage of Enhanced RTP-Compression (specified in [RFC3545]), and the
       other suboption negotiates header compression for only TCP or only
       non-TCP packets.

       IPHC relies on the link layer's ability to indicate the types of
       datagrams carried in the link layer frames.  In this document nine
       new types for the PPP Data Link Layer Protocol Field are defined
       along with their meaning.

       In general, header compression schemes that use delta encoding of
       compressed packets require that the lower layer does not reorder
       packets between compressor and decompressor.  IPHC uses delta
       encoding of compressed packets for TCP and RTP.  The IPHC
       specification [RFC2507] includes methods that allow link layers that
       may reorder packets to be used with IPHC.  Since PPP does not reorder
       packets these mechanisms are disabled by default.  When using
       reordering mechanisms such as multiclass multilink PPP [RFC2686],
       care must be taken so that packets that share the same compression
       context are not reordered.

    2.  Configuration Option

       This document specifies a new compression protocol value for the IPCP
       IP-Compression-Protocol option as specified in [RFC1332].  The new
       value and the associated option format are described in section 2.1.

       The option format is structured to allow future extensions to the
       IPHC scheme.

       NOTE: The specification of link and network layer parameter
          negotiation for PPP [RFC1661], [RFC1331], [RFC1332] does not
          prohibit multiple instances of one configuration option but states
          that the specification of a configuration option must explicitly
          allow multiple instances.  [RFC3241] updates RFC 1332 by
          explicitly allowing the sending of multiple instances of the IP-
          Compression-Protocol configuration option, each with a different
          value for IP-Compression-Protocol.  Each type of compression
          protocol may independently establish its own parameters.

    Koren, et al.               Standards Track                     [Page 2]

    RFC 3544             IP Header Compression over PPP            July 2003

       NOTE: [RFC1332] is not explicit about whether the option
          negotiates the capabilities of the receiver or of the sender.  In
          keeping with current practice, we assume that the option describes
          the capabilities of the decompressor (receiving side) of the peer
          that sends the Config-Req.

    2.1.  Configuration Option Format

       Both the network control protocol for IPv4, IPCP [RFC1332] and the
       IPv6 NCP, IPV6CP [RFC2472] may be used to negotiate IP Header
       Compression parameters for their respective protocols.  The format of
       the configuration option is the same for both IPCP and IPV6CP.

       Description

          This NCP configuration option is used to negotiate parameters for
          IP Header Compression.  Successful negotiation of parameters
          enables the use of Protocol Identifiers FULL_HEADER,
          COMPRESSED_TCP, COMPRESSED_TCP_NODELTA, COMPRESSED_NON_TCP and
          CONTEXT_STATE as specified in [RFC2507].  The option format is
          summarized below.  The fields are transmitted from left to right.

           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
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |     Type      |    Length     |    IP-Compression-Protocol    |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |           TCP_SPACE           |         NON_TCP_SPACE         |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |         F_MAX_PERIOD          |          F_MAX_TIME           |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |           MAX_HEADER          |          suboptions...
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type
          2

       Length
          >= 14

       The length may be increased if the presence of additional
       parameters is indicated by additional suboptions.

       IP-Compression-Protocol
          0061 (hex)

    Koren, et al.               Standards Track                     [Page 3]

    RFC 3544             IP Header Compression over PPP            July 2003

       TCP_SPACE
          The TCP_SPACE field is two octets and indicates the maximum value
          of a context identifier in the space of context identifiers
          allocated for TCP.

             Suggested value: 15

          TCP_SPACE must be at least 0 and at most 255 (the value 0 implies
          having one context).

       NON_TCP_SPACE
          The NON_TCP_SPACE field is two octets and indicates the maximum
          value of a context identifier in the space of context identifiers
          allocated for non-TCP.  These context identifiers are carried in
          COMPRESSED_NON_TCP, COMPRESSED_UDP and COMPRESSED_RTP packet
          headers.

             Suggested value: 15

          NON_TCP_SPACE must be at least 0 and at most 65535 (the value 0
          implies having one context).

       F_MAX_PERIOD
          Maximum interval between full headers.  No more than F_MAX_PERIOD
          COMPRESSED_NON_TCP headers may be sent between FULL_HEADER
          headers.

             Suggested value: 256

          A value of zero implies infinity, i.e. there is no limit to the
          number of consecutive COMPRESSED_NON_TCP headers.

       F_MAX_TIME
          Maximum time interval between full headers.  COMPRESSED_NON_TCP
          headers may not be sent more than F_MAX_TIME seconds after sending
          the last FULL_HEADER header.

             Suggested value: 5 seconds

          A value of zero implies infinity.

       MAX_HEADER
          The largest header size in octets that may be compressed.

             Suggested value: 168 octets

    Koren, et al.               Standards Track                     [Page 4]

    RFC 3544             IP Header Compression over PPP            July 2003

          The value of MAX_HEADER should be large enough so that at least
          the outer network layer header can be compressed.  To increase
          compression efficiency MAX_HEADER should be set to a value large
          enough to cover common combinations of network and transport layer
          headers.

       suboptions
          The suboptions field consists of zero or more suboptions.  Each
          suboption consists of a type field, a length field and zero or
          more parameter octets, as defined by the suboption type.  The
          value of the length field indicates the length of the suboption in
          its entirety, including the lengths of the type and length fields.

           0                   1                   2
           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |     Type      |    Length     |  Parameters...
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    2.2.  RTP-Compression Suboption

       The RTP-Compression suboption is included in the NCP IP-Compression-
       Protocol option for IPHC if IP/UDP/RTP compression is to be enabled.

       Inclusion of the RTP-Compression suboption enables use of additional
       Protocol Identifiers COMPRESSED_RTP and COMPRESSED_UDP along with
       additional forms of CONTEXT_STATE as specified in [RFC2508].

       Description

          Enable use of Protocol Identifiers COMPRESSED_RTP, COMPRESSED_UDP
          and CONTEXT_STATE as specified in [RFC2508].

              0                   1
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |     Type      |    Length     |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Type
             1

          Length
             2

    Koren, et al.               Standards Track                     [Page 5]

    RFC 3544             IP Header Compression over PPP            July 2003

    2.3.  Enhanced RTP-Compression Suboption

       To use the enhanced RTP header compression defined in [RFC3545], a
       new sub-option 2 is added.  Sub-option 2 is negotiated instead of,
       not in addition to, sub-option 1.

       Description

          Enable use of Protocol Identifiers COMPRESSED_RTP and
          CONTEXT_STATE as specified in [RFC2508].  In addition, enable use
          of [RFC3545] compliant compression including the use of Protocol
          Identifier COMPRESSED_UDP with additional flags and use of the C
          flag with the FULL_HEADER Protocol Identifier to indicate use of
          HDRCKSUM with COMPRESSED_RTP and COMPRESSED_UDP packets.

              0                   1
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |     Type      |    Length     |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Type
             2

          Length
             2

    2.4.  Negotiating header compression for only TCP or only non-TCP
       packets

       In RFC 2509 it was not possible to negotiate only TCP header
       compression or only non-TCP header compression because a value of 0
       in the TCP_SPACE or the NON_TCP_SPACE fields actually means that 1
       context is negotiated.

       A new suboption 3 is added to allow specifying that the number of
       contexts for TCP_SPACE or NON_TCP_SPACE is zero, disabling use of the
       corresponding compression.

    Koren, et al.               Standards Track                     [Page 6]

    RFC 3544             IP Header Compression over PPP            July 2003

       Description

       Enable header compression for only TCP or only non-TCP packets.

           0                   1                   2
           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |     Type      |    Length     |   Parameter   |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Type
             3

          Length
             3

          Parameter

          The parameter is 1 byte with one of the following values:

          1 = the number of contexts for TCP_SPACE is 0
          2 = the number of contexts for NON_TCP_SPACE is 0

       This suboption overrides the values that were previously assigned to
       TCP_SPACE and NON_TCP_SPACE in the IP Header Compression option.

       If suboption 3 is included multiple times with parameter 1 and 2,
       compression is disabled for all packets.

    3.  Multiple Network Control Protocols

       The IPHC protocol is able to compress both IPv6 and IPv4 datagrams.
       Both IPCP and IPV6CP are able to negotiate option parameter values
       for IPHC.  These values apply to the compression of packets where the
       outer header is an IPv4 header and an IPv6 header, respectively.

    3.1.  Sharing Context Identifier Space

       For the compression and decompression of IPv4 and IPv6 datagram
       headers the context identifier space is shared.  While the parameter
       values are independently negotiated, sharing the context identifier
       spaces becomes more complex when the parameter values differ.  Since
       the compressed packets share context identifier space, the
       compression engine must allocate context identifiers out of a common
       pool; for compressed packets, the decompressor has to examine the
       context state to determine what parameters to use for decompression.

    Koren, et al.               Standards Track                     [Page 7]

    RFC 3544             IP Header Compression over PPP            July 2003

       Context identifier spaces are not shared between TCP and non-
       TCP/UDP/RTP.  Doing so would require additional mechanisms to ensure
       that no error can occur when switching from using a context
       identifier for TCP to non-TCP.

    4.  Demultiplexing of Datagrams

       The IPHC specification [RFC2507] defines four header formats for
       different types of compressed headers.  They are compressed TCP,
       compressed TCP with no delta encoding, compressed non-TCP with 8 bit
       CID and compressed non-TCP with 16 bit CID.  The two non-TCP formats
       may be distinguished by their contents so both may use the same
       link-level identifier.  A fifth header format, the full header is
       distinct from a regular header in that it carries additional
       information to establish shared context between the compressor and
       decompressor.

       The specification of IP/UDP/RTP Header Compression [RFC2508] defines
       four additional formats of compressed headers.  They are for
       compressed UDP and compressed RTP (on top of UDP), both with either
       8- or 16-bit CIDs.  In addition, there is an explicit error message
       from the decompressor to the compressor.

       The link layer must be able to indicate these header formats with
       distinct values.  Nine PPP Data Link Layer Protocol Field values are
       specified below.

       FULL_HEADER
          The frame contains a full header as specified in [RFC2508] Section
          3.3.1.  This is the same as the FULL_HEADER specified in [RFC2507]
          Section 5.3.
             Value: 0061 (hex)

       COMPRESSED_TCP
          The frame contains a datagram with a compressed header with the
          format as specified in [RFC2507] Section 6a.
             Value: 0063 (hex)

       COMPRESSED_TCP_NODELTA
          The frame contains a datagram with a compressed header with the
          format as specified in [RFC2507] Section 6b.
             Value: 2063 (hex)

       COMPRESSED_NON_TCP
          The frame contains a datagram with a compressed header with the
          format as specified in either Section 6c or Section 6d of
          [RFC2507].
             Value: 0065 (hex)

    Koren, et al.               Standards Track                     [Page 8]

    RFC 3544             IP Header Compression over PPP            July 2003

       COMPRESSED_RTP_8
          The frame contains a datagram with a compressed header with the
          format as specified in [RFC2508] Section 3.3.2, using 8-bit CIDs.
             Value: 0069 (hex)

       COMPRESSED_RTP_16
          The frame contains a datagram with a compressed header with the
          format as specified in [RFC2508] Section 3.3.2, using 16-bit CIDs.
             Value: 2069 (hex)

       COMPRESSED_UDP_8
          The frame contains a datagram with a compressed header with the
          format as specified in [RFC2508] Section 3.3.3 or as specified in
          [RFC3545] Section 2.1, using 8-bit CIDs.
             Value: 0067 (hex)

       COMPRESSED_UDP_16
          The frame contains a datagram with a compressed header with the
          format as specified in [RFC2508] Section 3.3.3 or as specified in
          [RFC3545] Section 2.1, using 16-bit CIDs.
             Value: 2067 (hex)

       CONTEXT_STATE
          The frame is a link-level message sent from the decompressor to
          the compressor as specified in [RFC2508] Section 3.3.5.
             Value: 2065 (hex)

    5.  Changes from RFC 2509

       Two new suboptions are specified.  See Sections 2.3 and 2.4.

    6.  References

    6.1.  Normative References

       [RFC1144]  Jacobson, V., "Compressing TCP/IP Headers for low-speed
                  serial links", RFC 1144, February 1990.

       [RFC1332]  McGregor, G., "The PPP Internet Protocol Control Protocol
                  (IPCP)", RFC 1332, May 1992.

       [RFC2472]  Haskin, D. and E. Allen, "IP Version 6 over PPP", RFC
                  2472, December 1998.

       [RFC2507]  Degermark, M., Nordgren, B. and S. Pink, "Header
                  Compression for IP", RFC 2507, February 1999.

    Koren, et al.               Standards Track                     [Page 9]

    RFC 3544             IP Header Compression over PPP            July 2003

       [RFC2508]  Casner, S. and V. Jacobson, "Compressing IP/UDP/RTP
                  Headers for Low-Speed Serial Links", RFC 2508, February
                  1999.

       [RFC3241]  Bormann, C., "Robust Header Compression (ROHC) over PPP",
                  RFC 3241, April 2002.

       [RFC3545]  Koren, T., Casner, S., Geevarghese, J., Thompson, B. and
                  P. Ruddy, "Enhanced Compressed RTP (CRTP) for Links with
                  High Delay, Packet Loss and Reordering", RFC 3545, July
                  2003.

    6.2.  Informative References

       [RFC1661]  Simpson, W., Ed., "The Point-To-Point Protocol (PPP)", STD
                  51, RFC 1661, July 1994.

       [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
                  IANA Considerations Section in RFCs", BCP 26, RFC 2434,
                  October 1998.

       [RFC2686]  Bormann, C., "The Multi-Class Extension to Multi-Link
                  PPP", RFC 2686, September 1999.

       [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R. and V.
                  Jacobson, "RTP: A Transport Protocol for Real-Time
                  Applications", RFC 3550, July 2003.

    7.  IANA Considerations

       This document does not require any additional allocations from
       existing namespaces in the IANA Point-to-Point Protocol Field
       Assignments registry.  However, there are three namespaces that were
       defined by RFC 1332, RFC 2472, and RFC 2509 but not created in the
       registry.  Those three namespaces, described below, have been added
       to the PPP registry.  This document specifies two additional
       allocations in the third one.

       Section 3.2 of RFC 1332 specifies an IP-Compression-Protocol
       Configuration Option for the PPP IP Control Protocol and defines one
       value for the IP-Compression-Protocol type field in that option.  An
       IANA registry has been created to allocate additional values for that
       type field.  As stated in RFC 1332, the values for the IP-
       Compression-Protocol type field are always the same as the (primary)
       PPP DLL Protocol Number assigned to packets of the particular
       compression protocol.  Assignment of additional IP-Compression-
       Protocol type values is through the IETF consensus procedure as
       specified in [RFC2434].

    Koren, et al.               Standards Track                    [Page 10]

    RFC 3544             IP Header Compression over PPP            July 2003

       Section 4.2 of RFC 2472 specifies an IPv6-Compression-Protocol
       Configuration Option for the PPP IPv6 Control Protocol and defines
       one value for the IPv6-Compression-Protocol type field in that
       option.  An IANA registry has been created to allocate additional
       values for that type field.  The IPv6-Compression-Protocol
       Configuration Option has the same structure as the IP-Compression-
       Protocol Configuration Option defined in RFC 1332, but the set of
       values defined for the type field may be different.  As stated in RFC
       2472, the values for the IPv6-Compression-Protocol type field are
       always the same as the (primary) PPP DLL Protocol Number assigned to
       packets of the particular compression protocol.  Assignment of
       additional IPv6-Compression-Protocol type values is through the IETF
       consensus procedure as specified in [RFC2434].

       Section 2.1 of RFC 2509 specifies an additional type value to be
       registered for both the IP-Compression-Protocol Configuration Option
       and the IPv6-Compression-Protocol Configuration Option to indicate
       use of the "IP Header Compression" protocol.  The specification of
       that type value is repeated in Section 2.1 of this document which
       obsoletes RFC 2509.  In conjunction with the additional type value,
       the format for the variable-length option is specified.  The format
       includes a suboption field that may contain one or more suboptions.
       Each suboption begins with a suboption type value.  An IANA registry
       has been created for the suboption type values; and is titled, "IP
       Header Compression Configuration Option Suboption Types".

       Section 2.2 of RFC 2509 (and this document) defines one suboption
       type.  Sections 2.3 and 2.4 of this document define two additional
       suboption types.  It is expected that the number of additional
       suboptions that will need to be defined is small.  Therefore, anyone
       wishing to define new suboptions is required to produce a revision of
       this document to be vetted through the normal Internet Standards
       process, as specified in [RFC2434].

       RFC 2509 also defines nine PPP Data Link Layer Protocol Field values
       which are already listed in the IANA registry of Point-to-Point
       Protocol Field Assignments.  Section 4 of this document repeats the
       specification of those values without change.

    8.  Security Considerations

       Negotiation of the option defined here imposes no additional security
       considerations beyond those that otherwise apply to PPP [RFC1661].

       The use of header compression can, in rare cases, cause the
       misdelivery of packets.  If necessary, confidentiality of packet
       contents should be assured by encryption.

    Koren, et al.               Standards Track                    [Page 11]

    RFC 3544             IP Header Compression over PPP            July 2003

       Encryption applied at the IP layer (e.g., using IPSEC mechanisms)
       precludes header compression of the encrypted headers, though
       compression of the outer IP header and authentication/security
       headers is still possible as described in [RFC2507].  For RTP
       packets, full header compression is possible if the RTP payload is
       encrypted by itself without encrypting the UDP or RTP headers, as
       described in [RFC3550].  This method is appropriate when the UDP and
       RTP header information need not be kept confidential.

    9.  Intellectual Property Rights Notice

       The IETF takes no position regarding the validity or scope of any
       intellectual property 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; neither does it represent that it
       has made any effort to identify any such rights.  Information on the
       IETF's procedures with respect to rights in standards-track and
       standards-related documentation can be found in BCP-11.  Copies of
       claims of rights made available for publication 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 implementors or users of this specification can
       be obtained from the IETF Secretariat.

       The IETF invites any interested party to bring to its attention any
       copyrights, patents or patent applications, or other proprietary
       rights which may cover technology that may be required to practice
       this standard.  Please address the information to the IETF Executive
       Director.

    Koren, et al.               Standards Track                    [Page 12]

    RFC 3544             IP Header Compression over PPP            July 2003

    10.  Acknowledgements

       Mathias Engan was the primary author of RFC 2509, of which this
       document is a revision.

    11.  Authors' Addresses

       Tmima Koren
       Cisco Systems, Inc.
       170 West Tasman Drive
       San Jose, CA 95134-1706
       United States

       EMail: tmima@cisco.com

       Stephen L. Casner
       Packet Design
       3400 Hillview Avenue, Building 3
       Palo Alto, CA 94304
       United States

       EMail: casner@packetdesign.com

       Carsten Bormann
       Universitaet Bremen FB3 TZI
       Postfach 330440
       D-28334 Bremen, GERMANY

       Phone: +49.421.218-7024
       Fax: +49.421.218-7000
       EMail: cabo@tzi.org

    Koren, et al.               Standards Track                    [Page 13]

    RFC 3544             IP Header Compression over PPP            July 2003

    12.  Full Copyright Statement

       Copyright (C) The Internet Society (2003).  All Rights Reserved.

       This document and translations of it may be copied and furnished to
       others, and derivative works that comment on or otherwise explain it
       or assist in its implementation may be prepared, copied, published
       and distributed, in whole or in part, without restriction of any
       kind, provided that the above copyright notice and this paragraph are
       included on all such copies and derivative works.  However, this
       document itself may not be modified in any way, such as by removing
       the copyright notice or references to the Internet Society or other
       Internet organizations, except as needed for the purpose of
       developing Internet standards in which case the procedures for
       copyrights defined in the Internet Standards process must be
       followed, or as required to translate it into languages other than
       English.

       The limited permissions granted above are perpetual and will not be
       revoked by the Internet Society or its successors or assignees.

       This document and the information contained herein is provided on an
       "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
       TASK FORCE DISCLAIMS 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.

    Acknowledgement

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

    Koren, et al.               Standards Track                    [Page 14]