draft-ietf-idr-ext-opt-param-11.txt   draft-ietf-idr-ext-opt-param-12.txt 
Internet Engineering Task Force E. Chen Internet Engineering Task Force E. Chen
Internet-Draft Palo Alto Networks Internet-Draft Palo Alto Networks
Updates: 4271 (if approved) J. Scudder Updates: 4271 (if approved) J. Scudder
Intended status: Standards Track Juniper Networks Intended status: Standards Track Juniper Networks
Expires: September 24, 2021 March 23, 2021 Expires: October 23, 2021 April 21, 2021
Extended Optional Parameters Length for BGP OPEN Message Extended Optional Parameters Length for BGP OPEN Message
draft-ietf-idr-ext-opt-param-11 draft-ietf-idr-ext-opt-param-12
Abstract Abstract
The Optional Parameters in the BGP OPEN message as defined in the 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 base BGP specification are limited to 255 octets due to a one-octet
length field. BGP Capabilities are carried in this field and may length field. BGP Capabilities are carried in this field and may
foreseeably exceed 255 octets in the future, leading to concern about foreseeably exceed 255 octets in the future, leading to concern about
this limitation. this limitation.
This document updates RFC 4271 by extending, in a backward-compatible This document updates RFC 4271 by extending, in a backward-compatible
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 24, 2021. This Internet-Draft will expire on October 23, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Optional Parameters in the BGP OPEN message is also extended. Optional Parameters in the BGP OPEN message is also extended.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Protocol Extensions 2. Update to RFC 4271
This document reserves Optional Parameter Type code 255 as the This document reserves Optional Parameter Type code 255 as the
"Extended Length" type code. "Extended Length" type code.
In the event that the length of Optional Parameters in the BGP OPEN In the event that the length of Optional Parameters in the BGP OPEN
message does not exceed 255, the encodings of the base BGP message does not exceed 255, the encodings of the base BGP
specification [RFC4271] MUST be used without alteration. (However, specification [RFC4271] MUST be used without alteration. (However,
an implementation MUST accept an OPEN message that uses the encoding an implementation MUST accept an OPEN message that uses the encoding
of this specification even if the length of Optional Parameters is of this specification even if the length of Optional Parameters is
255 or less.) 255 or less.)
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| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Extended Parameters Format Figure 2: Extended Parameters Format
The rules for encoding Optional Parameters are unchanged with respect The rules for encoding Optional Parameters are unchanged with respect
to those given in [RFC4271] other than the extension of the Parameter to those given in [RFC4271] other than the extension of the Parameter
Length field to be a two-octet unsigned integer. Length field to be a two-octet unsigned integer.
In parsing an OPEN message, if the one-octet "Optional Parameters In parsing an OPEN message, if the one-octet "Optional Parameters
Length" field is non-zero, a BGP speaker MUST use the value of the Length" field (labeled "Non-Ext OP Len." in Figure 1) is non-zero, a
octet following the one-octet "Optional Parameters Length" field to BGP speaker MUST use the value of the octet following the one-octet
determine both the encoding of the Optional Parameters length and the "Optional Parameters Length" field (labeled "Non-Ext OP Type" in
size of the "Parameter Length" field of individual Optional Figure 1) to determine both the encoding of the Optional Parameters
Parameters. If the value of this field is 255, then the encoding length and the size of the "Parameter Length" field of individual
described above is used for the Optional Parameters length. Optional Parameters. If the value of the "Non-Ext OP Type" field is
Otherwise the encoding defined in [RFC4271] is used. 255, then the encoding described above is used for the Optional
Parameters length. Otherwise the encoding defined in [RFC4271] is
used.
3. Errors 3. Backward Compatibility
If a BGP speaker supporting this specification (a "new speaker") is If a BGP speaker supporting this specification (a "new speaker") is
peering with one which does not (an "old speaker") no peering with one which does not (an "old speaker") no
interoperability issues arise unless the new speaker needs to encode interoperability issues arise unless the new speaker needs to encode
Optional Parameters whose length exceeds 255. In that case, it will Optional Parameters whose length exceeds 255. In that case, it will
transmit an OPEN message which the old speaker will interpret as transmit an OPEN message which the old speaker will interpret as
containing an Optional Parameter with type code 255. Since by containing an Optional Parameter with type code 255. Since by
definition the old speaker will not recognize that type code, the old definition the old speaker will not recognize that type code, the old
speaker is expected to close the connection with a NOTIFICATION with speaker is expected to close the connection with a NOTIFICATION with
an Error Code of OPEN Message Error and an Error Subcode of an Error Code of OPEN Message Error and an Error Subcode of
Unsupported Optional Parameters, according to Section 6.2 of Unsupported Optional Parameters, according to Section 6.2 of
[RFC4271]. [RFC4271].
Although the Optional Parameter Type code 255 is used in this Although the Optional Parameter Type code 255 is used in this
specification as the indication that the extended encoding is in use, specification as the indication that the extended encoding is in use,
it is not a bonafide Optional Parameter Type in the usual sense, and 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 as an MUST NOT be used other than as described above. If encountered in
actual Optional Parameter Type code, it MUST be treated as an any position other than the first Optional Parameter Type, it MUST be
unrecognized Optional Parameter and handled according to [RFC4271] treated as an unrecognized Optional Parameter and handled according
Section 6.2. to [RFC4271] Section 6.2.
It is not considered an error to receive an OPEN message whose It is not considered an error to receive an OPEN message whose
Extended Optional Parameters Length value is less than or equal to Extended Optional Parameters Length value is less than or equal to
255. It is not considered a fatal error to receive an OPEN message 255. It is not considered a fatal error to receive an OPEN message
whose (non-extended) Optional Parameters Length value is not 255, and whose (non-extended) Optional Parameters Length value is not 255, and
whose first Optional Parameter type code is 255 -- in this case the whose first Optional Parameter type code is 255 -- in this case the
encoding of this specification MUST be used for decoding the message. encoding of this specification MUST be used for decoding the message.
A warning MAY be logged.
4. IANA Considerations 4. IANA Considerations
IANA is requested to designate type code 255 in the BGP OPEN Optional IANA is requested to designate type code 255 in the BGP OPEN Optional
Parameter Types registry as the Extended Length type code. Parameter Types registry as the Extended Length type code.
5. Security Considerations 5. Security Considerations
This extension to BGP does not change the underlying security or This extension to BGP does not change the underlying security or
confidentiality issues inherent in the existing BGP [RFC4272]. confidentiality issues inherent in the existing BGP [RFC4272].
6. Acknowledgements 6. Acknowledgements
The authors would like to thank Yakov Rekhter and Srihari Sangli for The authors would like to thank Yakov Rekhter and Srihari Sangli for
discussing various options to enlarge the Optional Parameters field. discussing various options to enlarge the Optional Parameters field.
We would also like to thank Matthew Bocci, Bruno Decraene, John We would also like to thank Matthew Bocci, Bruno Decraene, John
Heasley, Jakob Heitz, Pradosh Mohapatra, Keyur Patel and Hannes Heasley, Jakob Heitz, Christer Holmberg, Pradosh Mohapatra, Keyur
Gredler for their valuable comments. Patel and Hannes Gredler for their valuable comments.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
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