Secure Inter-Domain Routing (SIDR)                             G. Huston
Internet-Draft                                             G. Michaelson
Intended status: Informational                                     APNIC
Expires: April 9, February 5, 2010                                 August 4, 2009                                   October 6, 2008

 Validation of Route Origination in BGP using the Resource Certificate
                                  PKI
                 draft-ietf-sidr-roa-validation-01.txt
                 draft-ietf-sidr-roa-validation-02.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she

   This Internet-Draft is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, submitted to IETF in accordance full conformance with Section 6 the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on April 9, 2009. February 5, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   This document defines an application of the Resource Public Key
   Infrastructure to validate the origination of routes advertised in
   the Border Gateway Protocol.  The proposed application is intended to
   fit within the requirements for adding security to inter-domain
   routing, including the ability to support incremental and piecemeal
   deployment, and does not require any changes to the specification of
   BGP.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Validation Outcomes of a BGP Route Object . . . . . . . . . . . 3
     2.1.  Decoupled
   3.  Applying Validation . . . . . . . . . . . . . Outcomes to BGP Route Selection . . . . . . 4
     2.2.  Linked Validation  . . .
   4.  Further Considerations  . . . . . . . . . . . . . . . . .  6
   3.  Applying Validation Outcomes to BGP Route Selection . . . 5
   5.  Security Considerations . .  6
     3.1.  Validation Outcomes and Rejection of BGP Route Objects . .  9
   4.  Further Considerations . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . .  9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . 7
   7.  Changes -01 to -02  . 10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
   7. 7
   8.  Normative References  . . . . . . . . . . . . . . . . . . . . . 11 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 13 8

1.  Introduction

   This document defines an application of the Resource Public Key
   Infrastructure (RPKI) to validate the origination of routes
   advertised in the Border Gateway Protocol (BGP) [RFC4271].

   The RPKI is based on Resource Certificates.  Resource Certificates
   are X.509 certificates that conform to the PKIX profile [RFC5280],
   and to the extensions for IP addresses and AS identifiers [RFC3779].
   A Resource Certificate describes an action by an issuer that binds a
   list of IP address blocks and Autonomous System (AS) numbers to the
   Subject of a certificate, identified by the unique association of the
   Subject's private key with the public key contained in the Resource
   Certificate.  The PKI is structured such that each current Resource
   Certificate matches a current resource allocation or assignment.
   This is described in [I-D.ietf-sidr-arch].

   Route Origin Authorizations (ROAs) are digitally signed objects that
   bind an address to an AS number, signed by the address holder.  A ROA
   provides a means of verifying that an IP address block holder has
   authorized an AS to originate route objects in the inter-domain
   routing environment for that address block.  ROAs are described in
   [I-D.ietf-sidr-roa-format].

   Bogon Origin Attestations (BOAs) are digitally signed objects that
   describe a collection of address prefixes and AS numbers that are not
   authorised by the right-of-use holder to be advertised in the inter-
   domain routing system [I-D.ietf-sidr-boa].

   This document describes how ROA and BOA validation outcomes can be
   used in the BGP route selection process, and how the proposed
   application of  ROAs and BOAs are intended to fit within the
   requirements for adding security to inter-domain routing
   [ID.ietf-rpsec-bgpsecrec], routing, including
   the ability to support incremental and piecemeal deployment.

   This document describes the semantic interpretation of a valid ROA,
   with particular reference to application in BGP relating to the
   origination of route objects.  The document does not describe any
   application of a ROA to validation of the AS Path.

   This proposed application does not require any changes to the
   specification of BGP protocol elements.  The application may be used
   as part of BGP's local route selection algorithm [RFC4271].

2.  Validation Outcomes of a BGP Route Object

   A BGP Route Object "Route Object" is an address prefix and a set of attributes.
   In terms of ROA and BOA validation of the Route Object the prefix value and the
   origin AS attribute are used in the validation operation.

   If the route object is an aggregate and the AS Path contains an AS
   Set, then the origin AS is considered to be the AS described as the
   AGGREGATOR [RFC4271] of the route object.

   ROA validation is described in [I-D.ietf-sidr-roa-format], and the
   outcome of the validation operation is that the ROA is valid in the
   context of the RPKI, or validation has failed.

   BOA validation is described in [I-D.ietf-sidr-boa], and the outcome
   of the validation operation

   It is assumed here that the BOA is valid in the context
   of the RPKI, or validation has failed.

   There appears to be two means of matching a route object to a ROA:
   decoupled and linked.

2.1.  Decoupled Validation

   The decoupled approach is where the ROAs are managed and distributed
   independently of the operation of the routing protocol BGP itself, and a local BGP speaker
   has access to a local cache of the complete set of ROAs and the RPKI
   data set when performing a validation operation.

   In this case the

   A BGP route object does not refer to a specific ROA. ROA that should be
   used by a Relying Party (RP) to validate the origination information
   contained in the route object, nor does it refer to the set of
   certificates that the RP should use to validate the ROA's digital
   signature.  The relying party RP needs to match a route object to one or more
   candidate valid ROAs and BOAs in order to determine the appropriate local
   actions to perform on the route object.

   The relying party selects

   To validate a route object the set of RP would undertake the following
   steps:

   1.  Select all valid ROAs where that include a ROAIPAddress value that
       either matches, or is a covering aggregate of, the address prefix
       in the route object either exactly matches an ROAIPAddress (matching
   both the address prefix value and object.
   2.  If the prefix length), or where set of candidate ROAs is empty the
   route object spans a block validation process
       stops with an outcome of addresses "unknown".
   3.  If any ROA has an asID value that is included in matches the span
   described by originating AS in
       the ROA's address prefix value and length route object, and where either the route object's address prefix length is less than
       precisely matches an address in the ROA's prefix length and
   greater then ROA, or equal to the ROA's corresponding maxLength attribute.

   The following outcomes are possible using the defined ROA validation
   procedure for each ROA in this set:

   Exact Match:
      A valid ROA exists, where the route object's
       address prefix in the route object
      exactly matches is a more specific prefix listed in of the ROA, or address in the
       ROA contains a
      covering aggregate and the prefix length of the route object value is
      smaller less than or equal to the ROA's associated
       ROAIPAddress's maxLength attribute,
      and value, then the origin AS in validation process stops
       with an outcome of "valid".
   4.  Otherwise, the route object matches the origin AS listed
      in the ROA.

   Covering Match:
      A valid ROA exists, where an address prefix in the ROA is a
      covering aggregate of the prefix in the route object, and the
      prefix length of the route object is greater than the ROA's
      associated maxLength attribute, and the origin AS in the route
      object matches the AS listed in the ROA.

   Exact Mismatch:
      A valid ROA exists where the address prefix in the route object
      exactly matches a prefix listed in the ROA, or the ROA contains a
      covering aggregate and the prefix length of the route object is
      smaller than or equal to the ROA's associated maxLength attribute,
      and the origin AS of the route object does not match the AS listed
      in the ROA.

   Covering Mismatch:
      A valid ROA exists where an address prefix in the ROA is a
      covering aggregate of the prefix in the route object, the prefix
      length of the route object is greater than the ROA's associated
      maxLength attribute, and the origin AS of the route object does
      not match the AS listed in the ROA.

   No ROA:
      There are no Exact Matches, Covering Matches, no Exact Mismatches
      or Covering Mismatches in the RPKI repository.

   The ROA to be used for the validation function is selected from the
   set of ROAs in the order given above.  In other words an Exact Match
   is preferred over a Covering Match, which, in turn, is preferred over
   an Exact Mismatch which is preferred over a Covering Mismatch.

   The set of BOAs that are used for the validation function are
   composed of the set of valid BOAs where the origin AS of the route
   object matches an AS described in a BOA, or where an address prefix
   in a valid BOA that is an exact match or a covering aggregate of the
   route object.  In the case that the validation outcome using ROAs is
   one of Exact Mismatch, Covering Mismatch or No ROA, then the
   validation outcome of the BOA changes the overall validation result
   to "Bogon".

   Bogon:
      A valid BOA exists where an address prefix in the BOA is a an
      exact match for the prefix in the route object, or is a covering
      aggregate of the prefix in the route object, or an AS in the BOA
      matches the originating AS in the BOA.  In addition, there is no
      valid ROA that is an Exact Match or a Covering Match with the
      route object.

2.2.  Linked Validation

   The linked approach requires the route object to reference a ROA
   either by inclusion of the ROA as an attribute of the route object,
   or inclusion of a identity field in an attribute of the route object
   as a means of identifying a particular ROA.

   If the ROA can be located is valid within the context of the RPKI
   then the route object can be compared against the ROA, as per the
   previous section, giving one of five possible results: Exact Match,
   Covering Match, Exact Mismatch, Covering Mismatch, and No Match,
   which is defined as:

   No Match:
      The valid ROA does not comtain any address prefix that exactly
      matches the address prefix in the route object, or is a covering
      aggregate of the address prefix in the route object.

   In the case of a Mismatch or a No Match condition, the relying party
   should check for the presence of valid BOAs where the origin AS of
   the route object matches an AS described in a BOA, or where an
   address prefix in a valid BOA that is an exact match or a covering
   aggregate of the route object.  If a valid BOA can be found that
   matches either of these conditions that the overall route object
   validation of a route object with a linked ROA is changed to "Bogon".

3.  Applying Validation Outcomes to BGP Route Selection

   Within the framework of the abstract model of BGP operation, a
   received prefix announcement from a peer is compared to all
   announcements for this prefix received from other peers and a route
   selection procedure is used to select the "best" route object from
   this candidate set which is then used locally by placing it in the
   loc-RIB, and is announced to peers as the local "best" route.

   It is proposed here that the validation outcome be used as part of
   the determination of the local degree of preference as defined in
   section 9.1.1 of the BGP specification [RFC4271].

   In the case of partial deployment of ROAs there are a very limited
   set of circumstances where the outcome of ROA validation can be used
   as grounds to reject all consideration of the route object as an
   invalid advertisement.  While the presence of a valid ROA that
   matches the advertisement is a strong indication that an
   advertisement matches the authority provided by the prefix holder to
   advertise the prefix into the routing system, the absence of a ROA or
   the invalidity of a covering ROA does not provide a conclusive
   indication that the advertisement has been undertaken without the
   address holder's permission, unless the object is described in a BOA.

   In the case of a partial deployment scenario of RPKI route
   attestation objects, where some address prefixes and AS numbers are
   described in ROAs or BOAs and others are not, then the relative
   ranking of validation outcomes from the highest (most preferred) to
   the lowest (least preferred) degree of preference are proposed to be
   as specified int he following list.  The exact values to apply to a
   Local Preference setting are left as a matter of local policy and
   local configuration.

   1.  Exact Match

       The prefix has been allocated and is routeable, and that the
       prefix right-of-use holder has authorized the originating AS to
       originate precisely this announcement.

   2.  Covering Match

       This is slightly less preferred because it is possible that the
       address holder of the aggregate has allocated the prefix in
       question to a different party.  It is also possible that the
       originating AS outcome is using more specific advertisements as part of a
       traffic engineering scenario. "invalid".

3.  No ROA

       In the case of partial deployment of ROAs, the absence of
       validation credentials is a neutral outcome, in that there is no
       grounds to increase or decrease the relative degree of preference
       for the route object.

   4.  Covering Mismatch

       A Covering Mismatch is considered  Applying Validation Outcomes to be less preferable than a
       neutral position in that the address holder of a covering
       aggregate has indicated an originating AS that is not BGP Route Selection

   Within the
       originating AS framework of this announcement.  On the other hand it may be the case that this prefix has been validly allocated to another
       party who has not generated abstract model of BGP operation, a ROA for this prefix even through
       the announcement is valid.

   5.  Exact Mismatch

       Here the exact match
   received prefix holder has validly provided an
       authority for origination by an AS that is not the AS that is
       originating this announcement.  This would appear to be a bogus announcement by inference.

   6.  No Match

       Here the route object has referenced from a ROA that peer is not valid, or
       does not include an address prefix that matcehs the route object,
       or the referenced ROA could not be located.  This could be an
       attempt compared to create a false route object and use an invalid ROA.

   7.  Bogon

       Here the right-of-use holder of the AS or address prefix has
       explicitly tagged the address prefix or the AS as a "bogon".
       This implies that the announcement has been made without the
       appropriate authority, and the local preference of the route
       object should be ranked at a level commensurate with rejecting
       the route object.

   In the case of comprehensive deployment of RPKI route attestion
   objects the absence of a specific ROA origination authority for the
   route object should render it as an unusable all
   announcements for routing.  In this
   case the local preference setting for the route object is as follows:

   1.  Exact Match

       The prefix has been allocated and is routeable, received from other peers and that the
       prefix right-of-use holder has authorized the originating AS to
       originate precisely this announcement.

   2.  Covering Match, No ROA, Covering Mismatch, Exact Mismatch, No
       Match

       The local preference of the route object should be ranked at a
       level of least preferred, due route
   selection procedure is used to select the constraints noted in the
       following section.

   3.  Bogon

       Here the right-of-use holder of the AS or address prefix has
       explicitly tagged the address prefix or the AS as a "bogon".
       This implies that the announcement has been made without "best" route object from
   this candidate set, which is then used locally by installing it in
   the
       appropriate authority, loc-RIB [RFC4271], and is announced to peers as the local preference of "best"
   route.

   It is proposed here that the route
       object should ROA validation outcome of "unknown",
   "valid" or "invalid" be ranked at a level commensurate with rejecting used as part of the route object.

3.1.  Validation Outcomes and Rejection determination of BGP Route Objects

   In the case
   local degree of comprehensive deployment preference as defined in section 9.1.1 of ROAs, the use BGP
   specification [RFC4271].

   The proposed addition to the local degree of a
   validation outcome other than an Exact Match as sufficient grounds preference is "valid" is
   to
   reject be preferred over "unknown" over "invalid".

   It is a matter of local BGP selection policy in setting whether
   "invalid" route object objects are discarded from further consideration in
   the route selection process, however the following consideration
   should be undertaken with care. taken into account in such a situation.

   The consideration here is one of potential circularity of dependence.
   If the authoritative publication point of the repository of ROAs or
   any certificates used in relation to an address prefix is stored at a
   location that lies within the address prefix described in a ROA, then
   the repository can only be accessed once a route for the prefix has
   been accepted by the local routing domain.  It is also noted that the
   propagation time of RPKI objects may be different to the propagation
   time of route objects in BGP, and that route objects may be received
   before the relying party's local repository cache picks up the
   associated ROAs and recognises them as valid within the RPKI.

   For these reasons it is proposed that, even in the case of
   comprehensive deployment of ROAs, a missing ROA or a mismatch advised that local policy settings should not be
   result in "unknown" validation outcomes being considered as
   sufficient grounds to reject a route
   advertisement outright.  Alternate approaches object outright from
   consideration as a local "best" route.

   A local policy setting may be considered such that "invalid"
   validation outcomes would be sufficient grounds to reject the route
   object.  However, due to the considerations of circular dependence
   and differing propagation times as noted above, a local policy
   setting may be considered that would involve the use of a local timer
   to accept the route as feasible for an interim period of time until
   there is an acceptable level of assurance that all reasonable efforts
   to local obtain a valid ROA for the object have been undertaken.

4.  Further Considerations

   This document provides a description of how ROAs and BOAs could be
   used by a BGP speaker.

   It is noted that the proposed procedure requires no changes to the
   operation of BGP.

   It is also noted that the decoupled and linked approach are not
   mutually exclusive, and the same procedure can be applied to route
   objects that contain an explicit pointer to the associated ROA and
   route objects where the local BGP speaker has to create a set of
   candidate ROAs that could be applied to used by a route object.
   BGP speaker.

   It is noted that the proposed procedure requires no changes to the
   operation of BGP.  However, there are a number of considerations
   about this approach to origination validation that are relevant to
   the operation of a BGP speaker that are not specified here.

   These considerations include:

   o  It is not specified when validation of an advertised prefix should
      be performed by a BGP speaker.  Is  It is considered to be a matter of
      local policy whether it is considered to be strictly necessary required to perform validation
      at a point prior to loading the object into the Adj-RIB-In structure,
      structure [RFC4271], or once the object has been loaded into Adj-
      RIB-In, or at a later time that is determined by a local
      configuration setting.  It is also not specified whether
      origination validation should be performed each time a route
      object is updated by a peer even when the origin AS has not
      altered.

   o  The lifetime of a validation outcome is not specified here.  This
      specifically refers to the time period during which the original
      validation outcome can be still applied, and at the time when expiration of
      which the routing object should be revalidated. re-tested for validity.  It is
      a matter of local policy setting as to whether a validation
      outcome be regarded as valid until the route object is withdrawn
      or further updated, or whether validation of a route object should
      occur at more frequent
      intervals?

   o  It is a matter of local policy as to whther there are
      circumstances that would allow a route object to be removed from
      further consideration in route selection upon a validation
      failure, similar to the actions of Route Flap Damping. intervals.

   o  It is a matter of local configuration as to whther whether ROA validation
      is performed on a per-AS basis rather than a per-BGP speaker, and
      the appropriate BGP mechanisms to support such a per-AS iBGP route de-coupled framework of
      validation service of ROAs and the loading of outcomes into BGP speakers
      are not considered here.

5.  Security Considerations

   This approach to orgination validation does not allow for
   'deterministic' validation

   This approach to origination validation uses a model of positive
   security, where information that cannot be validated within the RPKI
   framework is intended to interpreted by a RP as invalid.

   However, the considerations of accommodating environments of partial
   adoption, where only a subset of valid route objects have associated
   ROAs within the structure of the RPKI imply some modification to the
   model of positive security.  Here it is assumed that once an address
   prefix is described in a ROA, then this ROA "protects" all address
   prefixes that are more specific than that described in the ROA.
   Thus, any more specific address prefix and originating AS combination
   of a valid ROA, that does not have a matching valid ROA is considered
   to be "invalid".

   The match condition of a route object against a single ROA is
   summarized in the following table:

   Prefix      match AS   mismatch AS
              +---------+-------------+
   Covering   | unknown | unknown     |
   Aggregate  |         |             |
              +---------+-------------+
   match ROA  | valid   | invalid     |
   prefix     |         |             |
              +---------+-------------+
   More       | invalid | invalid     |
   Specific   |         |             |
   than ROA   +---------+-------------+

   In an environment of a collection of ROAs, a route object is
   considered "valid" if any ROA provides a "valid" outcome, and
   "invalid" if one or more ROAs provide an "invalid" outcome and no
   ROAs provide a "valid" outcome.  The "unknown" outcome occurs when no
   ROA produces a "valid" or an "invalid" outcome.

6.  IANA Considerations

   [There are no IANA considerations in terms this document.]

7.  Changes -01 to -02

   Following WG review of the ability of a BGP speker to
   accept or reject an advertised route object outright, given that
   there remains some issues means of potential circularity specification of dependence and
   time lags between denial in
   routing authorizations in the propagation context of information in the routing
   system RPKI at IETF 74 and propagation IETF
   75, it appears that there is no general WG support for the use of information an
   explicit denial object (termed a 'BOA').  The alternative approach,
   explored in the RPKI.

   There are also issues previous iterations of the most appropirate this draft, used a more restricted
   interpretation of a ROA that yielded only "valid" or "unknown"
   outcomes (by using "unknown" where validation "invalid" is used in this revision
   of the authenticity of document).  To allow for "invalid" outcomes the route object has
   not been possible in draft used the context of partial adoption of
   BOA to undertake the RPKI, role of a 'disavow' constraint, where a route
   object was considered to be "invalid" if it was the absense subject of validation information does a
   valid BOA and was not necessarily
   constitute sufficient grounds considered to interpret the route object as an
   invalidly originated object. be "valid" by any valid ROA.  The consequence of these considerations is that while
   reasons advanced to support the use dropping of ROAs
   can increase the confidence in BOA was the validity increased
   complexity of origination RP systems through the use of a second object in route
   objects that match
   validation, a valid ROA, ROAs cannot perform potentially confusing mismatch in the interpretation
   scope between the ROA and the opposite,
   namely BOA, where the rejection ROA's scope was limited
   to set of route objects that cannot be validated by
   ROAs.  To assist prefixes described in the case of rejecting some forms ROA, while the BOA's scope
   included all possible more specifics of route objects
   that cannot be explicitly validated, the prefixes listed in the
   BOA, and the ability to reconstruct the semantic equivalent of a BOA has been
   through the use of a ROA that used as a means restricted-use AS as its asID.
   Accordingly, this draft has been revised to remove all references to
   the use of an explicit rejection denial object and uses the implicit semantics
   of certain classes route objects.  The
   implication is that publishers denial in the RPKI should publish both ROAs
   and BOAs a ROA object.

   There appears to be no WG interest in order consideration of validation in
   a "linked" model, where a ROA is bound to provide the greatest level of information route object that
   will allow relying parties it is
   intended to make appropriate choices in terms validate.  Accordingly this section of
   route preference selection.

6.  IANA Considerations

   [There are no IANA considerations in the text has also
   been dropped from this document.]

7. version.

8.  Normative References

   [I-D.ietf-sidr-arch]
              Lepinski, M., Kent, S., M. and R. Barnes, S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch (work in
              progress), February 2008.

   [I-D.ietf-sidr-boa]
              Huston, G., Manderson, T., and G. Michaelson, "Profile for
              Bogon Origin Attestations (BOAs)", draft-ietf-sidr-bogons
              (work in progress), August 2008. July 2009.

   [I-D.ietf-sidr-roa-format]
              Lepinski, M., Kent, S., and D. Kong, "An Infrastructure to
              Support Secure Internet Routing",
              draft-ietf-sidr-roa-format (work in progress), July 2008.

   [ID.ietf-rpsec-bgpsecrec]
              Christian, B. and T. Tauber, "BGP Security Requirements",
              draft-ietf-sidr-roa-format (work in progress),
              November 2007. 2009.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 2004.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

Authors' Addresses

   Geoff Huston
   Asia Pacific Network Information Centre

   Email: gih@apnic.net

   George Michaelson
   Asia Pacific Network Information Centre

   Email: ggm@apnic.net

Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   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, THE IETF TRUST 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 in BCP 78 and BCP 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 at
   http://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.