draft-ietf-idr-ext-opt-param-04.txt   draft-ietf-idr-ext-opt-param-05.txt 
Internet Engineering Task Force E. Chen Internet Engineering Task Force E. Chen
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Standards Track J. Scudder Updates: 4271 (if approved) J. Scudder
Expires: September 15, 2016 Juniper Networks Intended status: Standards Track Juniper Networks
March 14, 2016 Expires: December 30, 2016 June 28, 2016
Extended Optional Parameters Length for BGP OPEN Message Extended Optional Parameters Length for BGP OPEN Message
draft-ietf-idr-ext-opt-param-04 draft-ietf-idr-ext-opt-param-05
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.
In this document we extend the BGP OPEN length field in a backward- In this document we update RFC 4271 by extending the BGP OPEN length
compatible manner. The Parameter Length field of individual Optional field in a backward-compatible manner. The Parameter Length field of
Parameters is similarly extended. individual Optional Parameters is similarly extended.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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
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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 15, 2016. This Internet-Draft will expire on December 30, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://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
skipping to change at page 2, line 19 skipping to change at page 2, line 19
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. As BGP Capabilities [RFC5492] are carried in the Optional octets. As 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 becoming a concern for BGP development. the limitation is becoming a concern for BGP development.
In this document we extend the BGP OPEN length field in a backward- In this document we update [RFC4271] by extending the BGP OPEN length
compatible manner. The Parameter Length field of individual Optional field in a backward-compatible manner. The Parameter Length field of
Parameters is similarly extended. This is done by using Optional individual Optional Parameters is similarly extended. This is done
Parameters Length of 255 combined with Optional Parameter Type 255 as by using Optional Parameters Length of 255 combined with Optional
a distinguished value pair, which indicates that an extended Optional Parameter Type 255 as a distinguished value pair, which indicates
Parameters Length field follows. In this case the Parameter Length that an extended Optional Parameters Length field follows. In this
field of the Optional Parameters in the BGP OPEN message is also case the Parameter Length field of the Optional Parameters in the BGP
extended. 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Protocol Extensions 2. Protocol Extensions
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. specification [RFC4271] MUST be used without alteration.
However, if the length of Optional Parameters is greater than 255, However, if the length of Optional Parameters is greater than 255, an
four octets are used for the length field. Each of the first two extended encoding is used. The (non-extended) length field is set to
octets is set to 255, and the remaining two octets carry the actual 255, as is the subsequent octet that in the non-extended format would
length. In addition, the "Parameter Length" field of each Optional be the first Optional Parameter Type. The subsequent two octets
Parameter is enlarged to two octets. Other than the larger sizes of carry the actual length. In addition, the "Parameter Length" field
the given fields, there is no change to the BGP OPEN message defined of each Optional Parameter is enlarged to two octets. Other than the
in [RFC4271]. larger sizes of the given fields, there is no change to the BGP OPEN
message defined in [RFC4271].
When receiving an OPEN, a BGP speaker determines the extended
encoding is in use if the first Optional Parameter Type field is 255.
In this case, the BGP speaker MUST ignore the non-extended Optional
Parameters Length field, and must instead rely on the Extended
Optional Parameters Length field.
Accordingly, when the length of Optional Parameters in the BGP OPEN Accordingly, when the length of Optional Parameters in the BGP OPEN
message is greater than 255, the OPEN message format is modified to message is greater than 255, the OPEN message format is modified as
be the following: follows, repurposing the Optional Parameters Length field as well as
the first Optional Parameter Type field to indicate the use of the
extended format:
0 1 2 3 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 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF | 0xFF | Extended Opt. Parm. Length | |Non-Ext OP Len.|Non-Ext OP Type| Extended Opt. Parm. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Optional Parameters (variable) | | Optional Parameters (variable) |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The non-extended Optional Parameters Length field MUST be set to 255
on transmission, and MUST be ignored on receipt once the use of the
extended format is determined.
The subsequent one-octet field, that in the non-extended format would
be the first Optional Parameter Type field, MUST 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.
In this extended encoding, the subsequent two-octet field, termed the
Extended Optional Parameters Length 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 (this would never be expected to happen with the extended
encoding, however).
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) ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The rules for encoding Optional Parameters are unchanged with respect
to those given in [RFC4271] other than the extension of the Parameter
Length field to be a two-octet unsigned integer.
In parsing an OPEN message, a BGP speaker MUST use the value of the In parsing an OPEN message, a BGP speaker MUST use the value of the
one-octet "Optional Parameters Length" field and the value of the one-octet "Optional Parameters Length" field and the value of the
octet following it to determine the encoding of the Optional octet following it to determine the encoding of the Optional
Parameters length, as well as the size of the "Parameter Length" Parameters length, as well as the size of the "Parameter Length"
field of the Optional Parameters. If both values are 255, then the field of the Optional Parameters. If both values are 255, then the
four-octet encoding described above is used for the Optional four-octet 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.
This encoding is chosen for backward compatibility reasons -- a BGP This encoding is chosen for backward compatibility reasons -- a BGP
skipping to change at page 4, line 32 skipping to change at page 5, line 11
impossible that the old speaker might detect some other error first, impossible that the old speaker might detect some other error first,
such as a length error, depending on the details of the such as a length error, depending on the details of the
implementation. In no case would the peering be expected to implementation. In no case would the peering be expected to
establish successfully; the only question is which NOTIFICATION would establish successfully; the only question is which NOTIFICATION would
be generated. be generated.
We note that in any case, such a peering could not succeed, since by We note that in any case, such a peering could not succeed, since by
definition the extended length encoding would not be used by the new definition the extended length encoding would not be used by the new
speaker unless the basic encoding was insufficient. speaker unless the basic encoding was insufficient.
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 bonafide Optional Parameter Type in the usual sense, and
MUST NOT be used other than as described above. If encountered as an
actual Optional Parameter Type code, it MUST be treated as an
unrecognized Optional Parameter and handled according to [RFC4271]
Section 6.2.
4. IANA Considerations 4. IANA Considerations
IANA is requested to designate BGP OPEN Optional Parameter Type code IANA is requested to designate BGP OPEN Optional Parameter Type code
255 as the Extended Length type code. 255 as the Extended Length type code.
5. Security Considerations 5. Security Considerations
This extension to BGP does not change the underlying security issues. This extension to BGP does not change the underlying security 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 Pradosh Mohapatra, Keyur Patel and Hannes We would also like to thank Matthew Bocci, Jakob Heitz, Pradosh
Gredler for their valuable comments. Mohapatra, Keyur 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,
<http://www.rfc-editor.org/info/rfc2119>. <http://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,
<http://www.rfc-editor.org/info/rfc4271>. <http://www.rfc-editor.org/info/rfc4271>.
7.2. Informative References 7.2. Informative References
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006,
<http://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, <http://www.rfc-editor.org/info/rfc5492>. 2009, <http://www.rfc-editor.org/info/rfc5492>.
Authors' Addresses Authors' Addresses
Enke Chen Enke Chen
Cisco Systems Cisco Systems
Email: enkechen@cisco.com Email: enkechen@cisco.com
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