rfc9072.original   rfc9072.txt 
IDR E. Chen Internet Engineering Task Force (IETF) E. Chen
Internet-Draft Palo Alto Networks Request for Comments: 9072 Palo Alto Networks
Updates: 4271 (if approved) J. Scudder Updates: 4271 J. Scudder
Intended status: Standards Track Juniper Networks Category: Standards Track Juniper Networks
Expires: October 24, 2021 April 22, 2021 ISSN: 2070-1721 June 2021
Extended Optional Parameters Length for BGP OPEN Message Extended Optional Parameters Length for BGP OPEN Message
draft-ietf-idr-ext-opt-param-13
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 concerns
this limitation. about this limitation.
This document updates RFC 4271 by extending, in a backward-compatible This document updates RFC 4271 by extending, in a backward-compatible
manner, the length of the Optional Parameters in the BGP OPEN. The manner, the length of the Optional Parameters in a BGP OPEN message.
Parameter Length field of individual Optional Parameters is also The Parameter Length field of individual Optional Parameters is also
extended. extended.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on October 24, 2021. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9072.
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.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents
1. Introduction
1.1. Requirements Language
2. Update to RFC 4271
3. Backward Compatibility
4. IANA Considerations
5. Security Considerations
6. References
6.1. Normative References
6.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction 1. Introduction
The Optional Parameters Length field in the BGP OPEN message is The Optional Parameters Length field in the BGP OPEN message is
defined in the base BGP specification [RFC4271] as one octet, thus defined in the base BGP specification [RFC4271] as one octet, thus
limiting the Optional Parameters field in the OPEN message to 255 limiting the Optional Parameters field in the OPEN message to 255
octets. Since BGP Capabilities [RFC5492] are carried in the Optional octets. Since BGP capabilities [RFC5492] are carried in the Optional
Parameters field, and new BGP capabilities continue to be introduced, Parameters field, and new BGP capabilities continue to be introduced,
the limitation is a concern for BGP development. the limitation is a concern for BGP development.
This document updates [RFC4271] by extending, in a backward- This document updates [RFC4271] by extending the length of the
compatible manner, the length of the Optional Parameters in BGP OPEN. Optional Parameters in BGP OPEN in a backward-compatible manner.
This is done by using Optional Parameter Type 255 as a distinguished This is done by using Optional Parameter type code 255 as a
value, that indicates an extended Optional Parameters Length field distinguished value, which indicates an extended Optional Parameters
follows and that the parsing of the BGP OPEN should be modified Length field follows and that the parsing of the BGP OPEN should be
according to these procedures. In this case the Parameter Length modified according to these procedures. In this case, the Parameter
field of the individual Optional Parameters in the BGP OPEN message Length field of the individual Optional Parameters in the BGP OPEN
is also extended. 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
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Update to RFC 4271 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".
In the event that the length of Optional Parameters in the BGP OPEN In the event that the length of the Optional Parameters in the BGP
message does not exceed 255, the encodings of the base BGP OPEN message does not exceed 255, the encodings of the base BGP
specification [RFC4271] SHOULD be used without alteration. specification [RFC4271] SHOULD be used without alteration.
Configuration MAY override this to force the extended format to be Configuration MAY override this to force the extended format to be
used in all cases; this might be used, for example to test that a used in all cases; this might be used, for example, to test that a
peer supports this specification. (In any case, an implementation peer supports this specification. (In any case, an implementation
MUST accept an OPEN message that uses the encoding of this MUST accept an OPEN message that uses the encoding of this
specification even if the length of Optional Parameters is 255 or specification even if the length of the Optional Parameters is 255 or
less.) less.)
However, if the length of Optional Parameters in the BGP OPEN message
does exceed 255, the OPEN message MUST be encoded according to the
procedure below.
0 1 2 3 However, if the length of the Optional Parameters in the BGP OPEN
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 message does exceed 255, the OPEN message MUST be encoded according
to the procedure below.
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 | | Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Autonomous System | | My Autonomous System |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hold Time | | Hold Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BGP Identifier | | BGP Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Non-Ext OP Len.|Non-Ext OP Type| Extended Opt. Parm. Length | |Non-Ext OP Len.|Non-Ext OP Type| Extended Opt. Parm. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Optional Parameters (variable) | | Optional Parameters (variable) |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Extended Encoding OPEN Format Figure 1: Extended Encoding OPEN Format
The Non-Extended Optional Parameters Length field (Non-Ext OP Len) The Non-Extended Optional Parameters Length field (Non-Ext OP Len.)
SHOULD be set to 255 on transmission and in any event MUST NOT be set SHOULD be set to 255 on transmission and, in any event, MUST NOT be
to 0, and MUST be ignored on receipt once the use of the extended set to 0; it MUST be ignored on receipt once the use of the extended
format is determined positively by inspection of the Non-Extended format is determined positively by inspection of the Non-Extended
Optional Parameters Type (Non-Ext OP Type) field. Optional Parameters Type (Non-Ext OP Type) field.
The subsequent one-octet field (that would be the first Optional The subsequent one-octet field (which would be the first Optional
Parameter Type field in the non-extended format, and is called "Non- 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. Ext OP Type" in the figure above) MUST be set to 255 on transmission.
On receipt, a value of 255 for this field is the indication that the On receipt, a value of 255 for this field is the indication that the
extended format is in use. extended format is in use.
In this extended encoding, the subsequent two-octet field, termed the In this extended encoding, the subsequent two-octet field, termed the
Extended Optional Parameters Length field, is an unsigned integer "Extended Optional Parameters Length field", is an unsigned integer
indicating the total length of the Optional Parameters field in indicating the total length of the Optional Parameters field in
octets. If the value of this field is zero, no Optional Parameters octets. If the value of this field is zero, no Optional Parameters
are present. are present.
Likewise, in that situation the Optional Parameters encoding is Likewise, in that situation, the Optional Parameters encoding is
modified to be the following: modified to be the following:
0 1 2 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 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 | | Parm. Type | Parameter Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Parameter Value (variable) ~ ~ Parameter Value (variable) ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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], except that the Parameter Length field
Length field to be a two-octet unsigned integer. is extended 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 (labeled "Non-Ext OP Len." in Figure 1) is non-zero, a Length field (labeled "Non-Ext OP Len." in Figure 1) is non-zero, a
BGP speaker MUST use the value of the octet following the one-octet BGP speaker MUST use the value of the octet following the one-octet
"Optional Parameters Length" field (labeled "Non-Ext OP Type" in Optional Parameters Length field (labeled "Non-Ext OP Type" in
Figure 1) to determine both the encoding of the Optional Parameters Figure 1) to determine both the encoding of the Optional Parameters
length and the size of the "Parameter Length" field of individual length and the size of the Parameter Length field of individual
Optional Parameters. If the value of the "Non-Ext OP Type" field is Optional Parameters. If the value of the "Non-Ext OP Type" field is
255, then the encoding described above is used for the Optional 255, then the encoding described above is used for the Optional
Parameters length. Otherwise the encoding defined in [RFC4271] is Parameters length. Otherwise, the encoding defined in [RFC4271] is
used. used.
3. Backward Compatibility 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 that 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 that 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 the old
definition the old speaker will not recognize that type code, the old speaker will not recognize that type code by definition, 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 bona fide Optional Parameter Type in the usual sense, and it is not a bona fide Optional Parameter type code in the usual sense
MUST NOT be used other than as described above. If encountered in and MUST NOT be used other than as described above. If encountered
any position other than the first Optional Parameter Type, it MUST be other than as the Non-Ext OP Type, it MUST be treated as an
treated as an unrecognized Optional Parameter and handled according unrecognized Optional Parameter and handled according to [RFC4271],
to [RFC4271] Section 6.2. 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.
4. IANA Considerations 4. IANA Considerations
IANA is requested to designate type code 255 in the BGP OPEN Optional IANA has assigned value 255 as the Extended Length type code in the
Parameter Types registry as the Extended Length type code. "BGP OPEN Optional Parameter Types" registry.
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. References
The authors would like to thank Yakov Rekhter and 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 and Hannes Gredler for their valuable comments.
7. References
7.1. Normative References 6.1. 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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>. <https://www.rfc-editor.org/info/rfc4271>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References 6.2. Informative References
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006, RFC 4272, DOI 10.17487/RFC4272, January 2006,
<https://www.rfc-editor.org/info/rfc4272>. <https://www.rfc-editor.org/info/rfc4272>.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
2009, <https://www.rfc-editor.org/info/rfc5492>. 2009, <https://www.rfc-editor.org/info/rfc5492>.
Acknowledgements
The authors would like to thank Yakov Rekhter and 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, and Hannes Gredler for their valuable comments.
Authors' Addresses Authors' Addresses
Enke Chen Enke Chen
Palo Alto Networks Palo Alto Networks
Email: enchen@paloaltonetworks.com Email: enchen@paloaltonetworks.com
John Scudder John Scudder
Juniper Networks Juniper Networks
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