wdiff rfc9072xml2.original.xml rfc9072.xml

<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [ encoding="UTF-8"?>

<!-- One method to get references from the online citation libraries.
     There has to be one entity for each item to be referenced.
     An alternate method (rfc include) is described in the references. [CS] updated by Chris 05/05/21 -->

<!ENTITY RFC2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">
<!ENTITY RFC4271 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4271.xml">
<!ENTITY RFC4272 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4272.xml">
<!ENTITY RFC5492 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5492.xml">
<!ENTITY RFC8174 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.8174.xml">
<!ENTITY I-D.narten-iana-considerations-rfc2434bis

<!DOCTYPE rfc SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.narten-iana-considerations-rfc2434bis.xml">
]>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc strict="yes" ?>
<?rfc toc="no"?>
<?rfc tocdepth="4"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes" ?>
<?rfc compact="yes" ?>
<?rfc subcompact="no" ?> "rfc2629-xhtml.ent">

<rfc category="std" xmlns:xi="http://www.w3.org/2001/XInclude" docName="draft-ietf-idr-ext-opt-param-13" number="9072" ipr="trust200902"
 updates="4271"> updates="4271" obsoletes="" submissionType="IETF" category="std" consensus="true" xml:lang="en" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3">

  <!-- xml2rfc v2v3 conversion 3.7.0 -->
  <front>
    <title abbrev="Extended Optional Parameters Length">Extended
      Optional Parameters Length for BGP OPEN Message</title>
      <seriesInfo name="RFC" value="9072"/>
    <author fullname="Enke Chen" initials="E.C." initials="E." surname="Chen">
      <organization>Palo Alto Networks</organization>
      <address>
        <email>enchen@paloaltonetworks.com</email>
      </address>
    </author>
    <author fullname="John Scudder" initials="J.S." initials="J." surname="Scudder">
      <organization>Juniper Networks</organization>
      <address>
        <email>jgs@juniper.net</email>
      </address>
    </author>

    <date/>
    <date year="2021" month="June" />
    <area>General</area>
    <workgroup>IDR</workgroup>
    <keyword>IDR</keyword>
    <keyword>BGP</keyword>
    <abstract>
      <t>
The Optional Parameters in the BGP OPEN message as defined in the base
BGP specification are limited to 255 octets due to a one-octet length
field.

BGP Capabilities capabilities are carried in this field and may foreseeably
exceed 255 octets in the future, leading to concern concerns about this
limitation.
      </t>
      <t>
This document updates RFC 4271 by extending, in a backward-compatible manner, the length of the Optional Parameters in the a BGP OPEN. OPEN message. The Parameter Length field of individual Optional Parameters is also extended.
      </t>
    </abstract>
  </front>
  <middle>
    <section title="Introduction"> numbered="true" toc="default">
      <name>Introduction</name>
      <t>
The Optional Parameters Length field in the BGP OPEN message is defined
in <xref target="RFC4271">the target="RFC4271" format="default">the base BGP specification</xref> as one
octet, thus limiting the Optional Parameters field in the OPEN message
to 255 octets.  Since BGP Capabilities capabilities <xref target="RFC5492"></xref> target="RFC5492" format="default"/> are
carried in the Optional Parameters field, and new BGP capabilities
continue to be introduced, the limitation is a concern for BGP
development.
      </t>
      <t>
This document updates <xref target="RFC4271"/> target="RFC4271" format="default"/> by extending, in a
backward-compatible manner, extending the length of the Optional Parameters in BGP
OPEN.
OPEN in a
backward-compatible manner. This is done by using Optional Parameter Type type code 255 as a
distinguished value, that which indicates an extended Optional Parameters
Length field follows and that the parsing of the BGP OPEN should be
modified according to these procedures.  In this case case, the Parameter Length
field of the individual Optional Parameters in the BGP OPEN message is
also extended.
      </t>
      <section title="Requirements Language">
        <t>The numbered="true" toc="default">
        <name>Requirements Language</name>
        <t>
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
        NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
        "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
    NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as
    described in BCP 14 BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
    when, and only when, they appear in all capitals, as shown here.</t> here.
        </t>
      </section>
    </section>
    <section anchor="protocol_extensions" title="Update numbered="true" toc="default">
      <name>Update to RFC 4271"> 4271</name>
      <t>
This document reserves Optional Parameter Type type code 255 as the "Extended
Length" type code.
Length".
      </t>
      <t>
In the event that the length of the Optional Parameters in the BGP OPEN
message does not exceed 255, the encodings of <xref target="RFC4271">the target="RFC4271" format="default">the
base BGP specification</xref> SHOULD <bcp14>SHOULD</bcp14> be used without alteration.
Configuration MAY <bcp14>MAY</bcp14> override this to force the extended format to be used
in all cases; this might be used, for example example, to test that a peer
supports this specification. (In any case, an implementation MUST <bcp14>MUST</bcp14> accept
an OPEN message that uses the encoding of this specification even if the
length of the Optional Parameters is 255 or less.)
      </t>
      <t>
However, if the length of the Optional Parameters in the BGP OPEN message
does exceed 255, the OPEN message MUST <bcp14>MUST</bcp14> be encoded according to the
procedure below.
      </t>

      <figure title="Extended anchor="open_fmt">
        <name>Extended Encoding OPEN Format" anchor="open_fmt">
        <artwork><![CDATA[ Format</name>
        <artwork name="" type="" align="left" alt=""><![CDATA[
        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
       +-+-+-+-+-+-+-+-+
       |    Version    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     My Autonomous System      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           Hold Time           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         BGP Identifier                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Non-Ext OP Len.|Non-Ext OP Type|  Extended Opt. Parm. Length   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |             Optional Parameters (variable)                    |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ]]></artwork>
      </figure>
      <t>
The Non-Extended Optional Parameters Length field (Non-Ext OP Len)
SHOULD Len.)
<bcp14>SHOULD</bcp14> be set to 255 on transmission and and, in any event MUST NOT event, <bcp14>MUST NOT</bcp14> be set to
0, and MUST
0; it <bcp14>MUST</bcp14> be ignored on receipt once the use of the extended format is
determined positively by inspection of the Non-Extended Optional
Parameters Type (Non-Ext OP Type) field.
      </t>
      <t>
The subsequent one-octet field (that (which would be the first Optional
Parameter Type field in the non-extended format, format and is called "Non-Ext
OP Type" in the figure above) MUST <xref target="open_fmt" format="none">figure above</xref>) <bcp14>MUST</bcp14> be set to 255 on transmission. On
receipt, a value of 255 for this field is the indication that the
extended format is in use.
      </t>
      <t>
In this extended encoding, the subsequent two-octet field, termed
the Extended "Extended Optional Parameters Length field, field", is an unsigned
integer indicating the total length of the Optional Parameters field
in octets.  If the value of this field is zero, no Optional
Parameters are present.
      </t>
      <t>
Likewise, in that situation situation, the Optional Parameters encoding is modified
to be the following:
      </t>
      <figure title="Extended Parameters Format" anchor="parm_fmt">
        <artwork><![CDATA[
        <name>Extended Parameters Format</name>
        <artwork name="" type="" align="left" alt=""><![CDATA[
     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 4
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Parm. Type   |        Parameter Length       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~            Parameter Value (variable)         ~
    |                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ]]></artwork>
      </figure>
      <t>
The rules for encoding Optional Parameters are unchanged with respect
to those given in <xref target="RFC4271"/> other than the extension
of target="RFC4271" format="default"/>, except that the Parameter Length field is extended to be a two-octet unsigned integer.
      </t>
      <t>
In parsing an OPEN message, if the one-octet "Optional Optional Parameters
Length"
Length field (labeled "Non-Ext OP Len." in <xref
target="open_fmt"/>) target="open_fmt" format="default"/>) is non-zero, a BGP speaker
MUST
<bcp14>MUST</bcp14> use the value of the octet following the one-octet "Optional Optional
Parameters Length" Length field (labeled "Non-Ext OP Type" in <xref
target="open_fmt"/>) target="open_fmt" format="default"/>) to determine both the encoding of the Optional
Parameters length and the size of the "Parameter Length" Parameter Length field of
individual Optional Parameters.  If the value of the "Non-Ext OP Type"
field is 255, then the encoding described above is used for the Optional
Parameters length. Otherwise Otherwise, the encoding defined in <xref
target="RFC4271"></xref> target="RFC4271" format="default"/> is used.
      </t>
    </section>
    <section title="Backward Compatibility"> numbered="true" toc="default">
      <name>Backward Compatibility</name>
      <t>
If a BGP speaker supporting this specification (a "new speaker") is
peering with one which that does not (an "old speaker") speaker"), no interoperability
issues arise unless the new speaker needs to encode Optional Parameters
whose length exceeds 255.  In that case, it will transmit an OPEN
message which that the old speaker will interpret as containing an Optional
Parameter with type code 255.  Since by definition the old speaker will
not recognize that type code, code by definition, the old speaker is expected to close
the connection with a NOTIFICATION with an Error Code error code of OPEN "OPEN Message
Error
Error" and an Error Subcode error subcode of Unsupported "Unsupported Optional Parameters, Parameters", according
to Section 6.2 of <xref target="RFC4271"></xref>. target="RFC4271" sectionFormat="of" section="6.2"/>.
      </t>
      <t>
Although the Optional Parameter Type type code 255 is used in this
specification as the indication that the extended encoding is in use, it
is not a bona fide Optional Parameter type code in the usual sense and <bcp14>MUST
NOT</bcp14> be used other than as described above.

<!--[rfced] Please clarify if "Optional Parameter Type" (2 instances in
Section 3) refers to the "Non-Parameter Type field", as described in
Section 2. If so, should "Optional Parameter Type" be updated as
"Non Ext OP Type"?

Original (Section 2):
   The subsequent one-octet field (which would be the first Optional
   Parameter Type field in the non-extended format and is called "Non-
   Ext OP Type" in the figure above) MUST be set to 255 on transmission.

Original (Section 3):
   Although the Optional Parameter Type Code 255 is used in this
   specification as the indication that the extended encoding is in use,
   it is not a bona fide Optional Parameter Type in the usual sense, and
   MUST NOT be used other than as described above.

   If encountered in any position other than the first Optional Parameter
   Type, it MUST be treated as an unrecognized Optional Parameter and
   handled according to
<xref target="RFC4271"/> [RFC4271], Section 6.2.

Perhaps:
   Although the Optional Parameter type code 255 is used in this
   specification as the indication that the extended encoding is in use,
   it is not a bona fide Non-Ext OP Type in the usual sense and
   MUST NOT be used other than as described above.

   If encountered in any position other than the first Non-Ext OP Type,
   it MUST be treated as an unrecognized Optional Parameter and handled
   according to [RFC4271], Section 6.2.
-->

If encountered other than as the Non-Ext OP Type, it <bcp14>MUST</bcp14> be
treated as an unrecognized Optional Parameter and handled according to
<xref target="RFC4271" sectionFormat="comma" section="6.2"/>.
      </t>
      <t>
It is not considered an error to receive an OPEN message whose Extended
Optional Parameters Length value is less than or equal to 255. It is not
considered a fatal error to receive an OPEN message whose (non-extended)
Optional Parameters Length value is not 255, 255 and whose first Optional
Parameter type code is 255 -- in this case case, the encoding of this
specification MUST <bcp14>MUST</bcp14> be used for decoding the message.
      </t>
    </section>
    <section title="IANA Considerations"> numbered="true" toc="default">
      <name>IANA Considerations</name>
      <t>
IANA is requested to designate has assigned value 255 as the Extended Length type code 255 in the BGP "BGP OPEN Optional
Parameter Types registry as the Extended Length type code. Types" registry.
      </t>
    </section>
    <section title="Security Considerations"> numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>
This extension to BGP does not change the underlying security or
confidentiality issues
inherent in the existing BGP <xref target="RFC4272"/>. target="RFC4272" format="default"/>.
      </t>
    </section>
  </middle>
  <back>
    <references>
      <name>References</name>
      <references>
        <name>Normative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4271.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
      </references>
      <references>
        <name>Informative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5492.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4272.xml"/>
      </references>
    </references>
    <section title="Acknowledgements"> numbered="false" toc="default">
      <name>Acknowledgements</name>
      <t>
The authors would like to thank Yakov Rekhter <contact fullname="Yakov Rekhter"/> and Srihari Sangli <contact fullname="Srihari Sangli"/> for
discussing various options to enlarge the Optional Parameters field. We
would also like to thank Matthew Bocci, Bruno Decraene, John Heasley,
Jakob Heitz, Christer Holmberg, Pradosh Mohapatra, Keyur Patel <contact fullname="Matthew Bocci"/>, <contact fullname="Bruno Decraene"/>, <contact fullname="John Heasley"/>,
<contact fullname="Jakob Heitz"/>, <contact fullname="Christer Holmberg"/>, <contact fullname="Pradosh Mohapatra"/>, <contact fullname="Keyur Patel"/>, and Hannes Gredler <contact fullname="Hannes Gredler"/> for their
valuable comments.
      </t>
    </section>
  </middle>

  <back>
    <references title="Normative References">
      &RFC2119;
      &RFC4271;
      &RFC8174;
    </references>

    <references title="Informative References">
      &RFC5492;
      &RFC4272;
    </references>
  </back>
</rfc>