draft-ietf-idr-as4bytes-01.txt   draft-ietf-idr-as4bytes-02.txt 
Network Working Group Quaizar Vohra Network Working Group Quaizar Vohra
Internet Draft Juniper Networks Internet Draft Juniper Networks
Expiration Date: August 2001 Enke Chen Expiration Date: October 2001 Enke Chen
Network Working Group Redback Networks, Inc. Network Working Group Redback Networks, Inc.
BGP support for four-octet AS number space BGP support for four-octet AS number space
draft-ietf-idr-as4bytes-01.txt draft-ietf-idr-as4bytes-02.txt
1. Status of this Memo 1. Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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BGP carries the Autonomous System number in the My Autonomous System BGP carries the Autonomous System number in the My Autonomous System
field of the OPEN message, in the AS_PATH attribute of the UPDATE field of the OPEN message, in the AS_PATH attribute of the UPDATE
message, and in the AGGREGATOR attribute of the UPDATE message. BGP message, and in the AGGREGATOR attribute of the UPDATE message. BGP
also carries the Autonomous System number in the BGP Communities also carries the Autonomous System number in the BGP Communities
attribute. attribute.
A NEW BGP speaker uses BGP Capability Advertisements [RFC2842] to A NEW BGP speaker uses BGP Capability Advertisements [RFC2842] to
advertise to its neighbors (either internal or external) that it advertise to its neighbors (either internal or external) that it
supports 4-octets AS number extensions, as specified in this supports 4-octets AS number extensions, as specified in this
document. The BGP Capability code for this capability is [TBD]. document.
The Capability that is used by a BGP speaker to convey to its BGP The Capability that is used by a BGP speaker to convey to its BGP
peer the 4-octets Autonomous System number capability, also carries peer the 4-octets Autonomous System number capability, also carries
the 4-octets Autonomous System number of the speaker in the the 4-octets Autonomous System number of the speaker in the
Capability Value field of the Capability Optional Parameter. The Capability Value field of the Capability Optional Parameter. The
Capability Length field of the Capability is set to 4. Capability Length field of the Capability is set to 4.
NEW BGP speakers carry AS path information expressed in terms of NEW BGP speakers carry AS path information expressed in terms of
4-octets Autonomous Systems numbers by using the existing AS_PATH 4-octets Autonomous Systems numbers by using the existing AS_PATH
attribute, except that each AS number in this attribute is encoded attribute, except that each AS number in this attribute is encoded
not as a 2-octets, but as a 4-octets entity. The same applies to the not as a 2-octets, but as a 4-octets entity. The same applies to the
AGGREGATOR attribute - NEW BGP speakers use the same attribute, AGGREGATOR attribute - NEW BGP speakers use the same attribute,
except that the AS carried in this attribute is encoded as a 4-octets except that the AS carried in this attribute is encoded as a 4-octets
entity. entity.
To preserve AS path information with 4-octets AS numbers across OLD To preserve AS path information with 4-octets AS numbers across OLD
BGP speakers, this document defines a new AS path attribute, called BGP speakers, this document defines a new AS path attribute, called
NEW_AS_PATH. This attribute is optional transitive and contains the NEW_AS_PATH. This attribute is optional transitive and contains the
AS path encoded with 4-octets AS numbers. The NEW_AS_PATH attribute AS path encoded with 4-octets AS numbers. The NEW_AS_PATH attribute
has the same semantics as the AS_PATH attribute, except that it is has the same semantics as the AS_PATH attribute, except that it is
optional transitive, and it carries 4-octets AS numbers. The Type optional transitive, and it carries 4-octets AS numbers.
Code for this attribute is <TBD>
To prevent the possible propagation of confederation path segments To prevent the possible propagation of confederation path segments
outside of a confederation, the path segment types AS_CONFED_SEQUENCE outside of a confederation, the path segment types AS_CONFED_SEQUENCE
and AS_CONFED_SET [RFC3065] are declared invalid for the NEW_AS_PATH and AS_CONFED_SET [RFC3065] are declared invalid for the NEW_AS_PATH
attribute. attribute.
Similarly, this document defines a new aggregator attribute called Similarly, this document defines a new aggregator attribute called
NEW_AGGREGATOR, which is optional transitive. The NEW_AGGREGATOR NEW_AGGREGATOR, which is optional transitive. The NEW_AGGREGATOR
attribute has the same semantics as the AGGREGATOR attribute, except attribute has the same semantics as the AGGREGATOR attribute, except
that it carries 4-octets AS numbers. The Type Code for this attribute that it carries 4-octets AS numbers.
is <TBD>.
Currently assigned 2-octets Autonomous System numbers are converted Currently assigned 2-octets Autonomous System numbers are converted
into 4-octets Autonomous System numbers by setting the high-order 2 into 4-octets Autonomous System numbers by setting the high-order 2
octets of the 4-octets field to zero. Such a 4-octets AS number is octets of the 4-octets field to zero. Such a 4-octets AS number is
said to be mappable to a 2-octets AS number. said to be mappable to a 2-octets AS number.
To represent 4-octets AS numbers (which are not mapped from 2-octets) To represent 4-octets AS numbers (which are not mapped from 2-octets)
as 2-octets AS numbers in the AS path information encoded with as 2-octets AS numbers in the AS path information encoded with
2-octets AS numbers, this document reserves a 2-octets AS number. The 2-octets AS numbers, this document reserves a 2-octets AS number.
value of this AS number is <TBD>. Lets denote this special AS number Lets denote this special AS number as AS_TRANS for ease of
as AS_TRANS for ease of description in the rest of this description in the rest of this specification. This AS number is also
specification. This AS number is also placed in the My Autonomous placed in the My Autonomous System field of the OPEN message
System field of the OPEN message originated by a NEW BGP speaker if originated by a NEW BGP speaker if the speaker doesn't have a
the speaker doesn't have a (globally unique) 2-octets AS number. (globally unique) 2-octets AS number.
4. Operations 4. Operations
4.1. Interaction between NEW BGP speakers 4.1. Interaction between NEW BGP speakers
A BGP speaker that supports 4-octets Autonomous System numbers may A BGP speaker that supports 4-octets Autonomous System numbers may
advertise this to its peers using the BGP Capability Advertisements. advertise this to its peers using the BGP Capability Advertisements.
A BGP speaker that advertises such capability to a particular peer, A BGP speaker that advertises such capability to a particular peer,
and receives from that peer the advertisement of such capability MUST and receives from that peer the advertisement of such capability MUST
encode Autonomous System numbers as 4-octets entities in both the encode Autonomous System numbers as 4-octets entities in both the
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composed of 2-octets AS numbers only. In this case the NEW speaker composed of 2-octets AS numbers only. In this case the NEW speaker
should not send the NEW_AS_PATH attribute. should not send the NEW_AS_PATH attribute.
In the AS_PATH attribute encoded with 2-octets AS numbers, non- In the AS_PATH attribute encoded with 2-octets AS numbers, non-
mappable 4-octets AS numbers are represented by the well known mappable 4-octets AS numbers are represented by the well known
2-octets AS number, AS_TRANS. This will preserve the path length 2-octets AS number, AS_TRANS. This will preserve the path length
property of the AS path information; and will also help in updating property of the AS path information; and will also help in updating
the AS path information received on a NEW BGP speaker from an OLD the AS path information received on a NEW BGP speaker from an OLD
speaker, as explained in the next section. speaker, as explained in the next section.
Except for the case where the AS_PATH attribute contains either The NEW speaker constructs the NEW_AS_PATH attribute from the
AS_CONFED_SEQUENCE or AS_CONFED_SET path segment, the NEW speaker information carried in the AS_PATH attribute. In the case where the
constructs the NEW_AS_PATH attribute from the AS_PATH attribute by AS_PATH attribute contains either AS_CONFED_SEQUENCE or AS_CONFED_SET
taking the attribute length and attribute value from the AS_PATH path segments, the NEW speaker, when constructing the NEW_AS_PATH
attribute and placing them into the attribute length and attribute attribute from the AS_PATH attribute, must exclude such path
value of the NEW_AS_PATH attribute. In the case where the AS_PATH segments. The NEW_AS_PATH attribute will be carried across a series
attribute contains either AS_CONFED_SEQUENCE or AS_CONFED_SET path of OLD BGP speakers without modification and will help preserve the
segments, the NEW speaker, when copying information from the AS_PATH truely 4-octets AS numbers in the AS path information.
attribute into the NEW_AS_PATH attribute, must exclude such path
segments from copying. The NEW_AS_PATH attribute will be carried
across a series of OLD BGP speakers without modification and will
help preserve the truely 4-octets AS numbers in the AS path
information.
Similarly, if the NEW speaker has to send the AGGREGATOR attribute, Similarly, if the NEW speaker has to send the AGGREGATOR attribute,
and if the aggregating Autonomous System's AS number is truely and if the aggregating Autonomous System's AS number is truely
4-octets, the speaker constructs the NEW_AGGREGATOR attributes by 4-octets, the speaker constructs the NEW_AGGREGATOR attributes by
taking the attribute length and attribute value from the AGGREGATOR taking the attribute length and attribute value from the AGGREGATOR
attribute and placing them into the attribute length and attribute attribute and placing them into the attribute length and attribute
value of the NEW_AGGREGATOR attribute, and sets the AS number field value of the NEW_AGGREGATOR attribute, and sets the AS number field
in the existing AGGREGATOR attribute to the reserved AS number, in the existing AGGREGATOR attribute to the reserved AS number,
AS_TRANS. Note that if the AS number is 2-octets only, then the AS_TRANS. Note that if the AS number is 2-octets only, then the
NEW_AGGREGATE attribute should not be sent. NEW_AGGREGATE attribute should not be sent.
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the NEW_AS_PATH attribute are aggregated by an OLD BGP speaker, and the NEW_AS_PATH attribute are aggregated by an OLD BGP speaker, and
the NEW_AS_PATH attribute of at least one of these routes carries at the NEW_AS_PATH attribute of at least one of these routes carries at
least one 4-octets AS number (as oppose to a 2-octets AS number that least one 4-octets AS number (as oppose to a 2-octets AS number that
is encoded in 4 octets). When such aggregation results in creating a is encoded in 4 octets). When such aggregation results in creating a
route that is less specific than any of the component routes, (route route that is less specific than any of the component routes, (route
whose NLRI covers NLRI of all the component routes), loss of the AS whose NLRI covers NLRI of all the component routes), loss of the AS
path information does not create a risk of a routing loop. In all path information does not create a risk of a routing loop. In all
other cases loss of the AS path information does create a risk of a other cases loss of the AS path information does create a risk of a
routing loop. routing loop.
7. Security Considerations 7. IANA Consideration
This document uses a BGP Capability code to indicate that a BGP
speaker supports the 4-octets AS numbers. The Capability code needs
to be assigned by IANA per RFC 2842. Capability Code values 1 through
63 are to be assigned by IANA using the "IETF Consensus" policy
defined in RFC2434.
In addition, this document introduces two new BGP optional transitive
attributes. The first is the NEW_AS_PATH attribute, which preserves
the AS path information with 4-octet AS numbers across old BGP
speakers. The second is the NEW_AGGREGATOR attribute, which is
similar in use to the current AGGREGATOR attribute but it carries
4-octet AS numbers. The Type Codes for these attributes are to be
assigned by IANA.
Finally, this document introduces a reserved 2-octets AS number -
AS_TRANS. The AS number for AS_TRANS are to be assigned by the IANA.
8. Security Considerations
Security issues are not discussed in this document. Security issues are not discussed in this document.
8. Acknowledgments 9. Acknowledgments
The authors would like to thank Yakov Rekhter and Chaitanya The authors would like to thank Yakov Rekhter and Chaitanya
Kodeboyina for the numerous discussions which went into the making of Kodeboyina for the numerous discussions which went into the making of
this draft. this draft.
9. References 10. References
[BGP] Rekhter, Y., Li, T., "Border Gateway Protocol 4", draft-ietf- [BGP] Rekhter, Y., Li, T., "Border Gateway Protocol 4", draft-ietf-
idr-bgp4-12.txt idr-bgp4-12.txt
[EXT-COM] Ramachandra, S., Tappan, D., and Rekter Y. "BGP Extended [EXT-COM] Ramachandra, S., Tappan, D., and Rekter Y. "BGP Extended
Communities Attribute", draft-ramachandra-bgp-ext-communities-02.txt Communities Attribute", draft-ramachandra-bgp-ext-communities-02.txt
[RFC1997] Chandra, R., Traina, P. and T. Li, "BGP Communities [RFC1997] Chandra, R., Traina, P. and T. Li, "BGP Communities
Attribute", RFC 1997, August 1996. Attribute", RFC 1997, August 1996.
[RFC2842] Chandra, R., and Scudder, J., "Capabilities Advertisement [RFC2842] Chandra, R., and Scudder, J., "Capabilities Advertisement
with BGP-4", RFC 2842, May 2000. with BGP-4", RFC 2842, May 2000.
[RFC3065] Traina, P., McPherson, D., Scudder, J., "Autonomous System [RFC3065] Traina, P., McPherson, D., Scudder, J., "Autonomous System
Confederations for BGP", RFC3065, February 2001. Confederations for BGP", RFC3065, February 2001.
10. Author Information 11. Author Information
Quaizar Vohra Quaizar Vohra
Juniper Networks Juniper Networks
1194 N.Mathilda Ave 1194 N.Mathilda Ave
Sunnyvale, CA 94089 Sunnyvale, CA 94089
e-mail: qv@juniper.net e-mail: qv@juniper.net
Enke Chen Enke Chen
Redback Networks, Inc. Redback Networks, Inc.
350 Holger Way 350 Holger Way
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