draft-ietf-idr-bgp-ext-communities-00.txt   draft-ietf-idr-bgp-ext-communities-01.txt 
Network Working Group Srihari R. Sangli Network Working Group Srihari R. Sangli
Internet Draft Procket Networks Internet Draft Procket Networks
Expiration Date: January 2002 Expiration Date: February 2002
Daniel Tappan Daniel Tappan
Cisco Systems Cisco Systems
Yakov Rekhter Yakov Rekhter
Juniper Networks Juniper Networks
BGP Extended Communities Attribute BGP Extended Communities Attribute
draft-ietf-idr-bgp-ext-communities-00.txt draft-ietf-idr-bgp-ext-communities-01.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 except that the right to all provisions of Section 10 of RFC2026.
produce derivative works is not granted.
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.
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.''
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The Extended Community Attribute provides two important enhancements The Extended Community Attribute provides two important enhancements
over the existing BGP Community Attribute: over the existing BGP Community Attribute:
- It provides an extended range, ensuring that communities can be - It provides an extended range, ensuring that communities can be
assigned for a plethora of uses, without fear of overlap. assigned for a plethora of uses, without fear of overlap.
- The addition of a Type field provides structure for the - The addition of a Type field provides structure for the
community space. community space.
The addition of structure allows the application of policy based on The addition of structure allows the usage of policy based on the
the application for which the community value will be used. For application for which the community value will be used. For example,
example, one can filter out all communities of a particular type, or one can filter out all communities of a particular type, or allow
allow only certain values for a particular type of community. It also only certain values for a particular type of community. It also
allows one to specify whether a particular community is transitive or allows one to specify whether a particular community is transitive or
non-transitive across Autonomous system boundary. Without structure non-transitive across Autonomous system boundary. Without structure,
this can only be accomplished by explicitly enumerating all community this can only be accomplished by explicitly enumerating all community
values which will be denied or allowed and passed to BGP speakers in values which will be denied or allowed and passed to BGP speakers in
neighboring ASes based on the transitive property. neighboring ASes based on the transitive property.
4. BGP Extended Communities Attribute 4. BGP Extended Communities Attribute
The Extended Communities Attribute is a transitive optional BGP The Extended Communities Attribute is a transitive optional BGP
attribute. The attribute consists of a set of "extended attribute. The attribute consists of a set of "extended
communities". Each extended community is coded as an eight octet communities". Each extended community is coded as an eight octet
value. All routes with the Extended Communities attribute belong to value. All routes with the Extended Communities attribute belong to
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The Extended Communities Attribute has Type Code 16. The Extended Communities Attribute has Type Code 16.
Each Extended Community is encoded as an eight octet quantity, as Each Extended Community is encoded as an eight octet quantity, as
follows: follows:
- Type Field : 1 or 2 octets - Type Field : 1 or 2 octets
- Value Field : Remaining octets - Value Field : Remaining octets
Type Field: Type Field:
Two classes of Type Field are introduced: Regular type and
Extended type.
The size of Type Field for Regular types is 1 octet and the
size of the Type Field for Extended types is 2 octets.
The value of the high-order octet will determine if its a The value of the high-order octet will determine if its a
regular type or extended type. The size of Type Field for regular type or an extended type. The value of the high-order
regular types is 1 octet and the size of the Type Field for octet of the Type Field defined as regular type (or extended
extended types is 2 octets. type) for a extended community MUST NOT be reused as the value
of the high-order octet of the Type Field defined as extended
type (or regular type). In other words, a new extended
community of regular type (extended type) should have unique
(and new) value for the high-order octet (high-order and low-
order octet).
The high-order octet of the Type Field is as shown below: The high-order octet of the Type Field is as shown below:
First bit (MSB) : IANA authority bit First bit (MSB) : IANA authority bit
Value 0 : IANA assignable type Value 0 : IANA assignable type
Value 1 : Vendor-specific types Value 1 : Vendor-specific types
Second bit : Transitive bit Second bit : Transitive bit
Value 0 : The community is Value 0 : The community is
Transitive across ASes Transitive across ASes
Value 1 : The community is Value 1 : The community is
Non-Transitive across ASes Non-Transitive across ASes
Remaining 6 bits : Indicates the structure of the Remaining 6 bits : Indicates the structure of the
community community
For regular types, values of the Type Field 0 through 0x3f
inclusive are assignable by IANA. The values 0x80 through 0xbf
inclusive are vendor-specific.
For extended types, values of the Type Field 0 through 0x3fff
inclusive are assignable by IANA. The values 0x8000 through
0xbfff inclusive are vendor-specific.
Value Field: Value Field:
The encoding of the Value Field is dependent on the "type" of The encoding of the Value Field is dependent on the "type" of
the community as specified by the Type Field. The encoding of the community as specified by the Type Field. The encoding of
the community for the transitive communities should be such the community for the transitive communities should be such
that it is unique globally (i.e. across the Autonomous that it is unique globally (i.e. across the Autonomous
Systems). Systems).
Two extended communities are declared equal only when entire 8 Two extended communities are declared equal only when entire 8
octets are equal. octets are equal.
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This document introduces a few extended types and defines the Value This document introduces a few extended types and defines the Value
Field for those types. Field for those types.
Type 0x00: Type 0x00:
This is an extended type with Type Field comprising of 2 octets This is an extended type with Type Field comprising of 2 octets
and Value Field comprising of 6 octets. and Value Field comprising of 6 octets.
The value of the high-order octet of this extended type is The value of the high-order octet of this extended type is
0x00. The low-order octet of this extended type is used to 0x00. The low-order octet of this extended type is used to
indicate subtypes. indicate sub-types.
The Value Field consists of two subfields: The Value Field consists of two sub-fields:
Global Administrator subfield: 2 octets Global Administrator sub-field: 2 octets
This subfield contains an Autonomous System number This sub-field contains an Autonomous System number
assigned by IANA. assigned by IANA.
Local Administrator subfield: 4 octets Local Administrator sub-field: 4 octets
The organization identified by Autonomous System number The organization identified by Autonomous System number
in the Global Administrator subfield, can encode any in the Global Administrator sub-field, can encode any
information in this subfield. The value and meaning of information in this sub-field. The value and meaning of
the value encoded in this subfield should be defined by the value encoded in this sub-field should be defined by
the subtype of the community. the sub-type of the community.
Type 0x01: Type 0x01:
This is an extended type with Type Field comprising of 2 octets This is an extended type with Type Field comprising of 2 octets
and Value Field comprising of 6 octets. and Value Field comprising of 6 octets.
The value of the high-order octet of this extended type is The value of the high-order octet of this extended type is
0x01. The low-order octet of this extended type is used to 0x01. The low-order octet of this extended type is used to
indicate subtypes. indicate sub-types.
The Value field consists of two subfields. The Value field consists of two sub-fields.
Global Administrator subfield: 4 octets Global Administrator sub-field: 4 octets
This subfield contains an IPv4 address assigned by IANA. This sub-field contains an IPv4 address assigned by IANA.
Local Administrator subfield: 2 octets Local Administrator sub-field: 2 octets
The organization which has been assigned the IPv4 address The organization which has been assigned the IPv4 address
in the Global Administrator subfield, can encode any in the Global Administrator sub-field, can encode any
information in this subfield. The value and meaning of information in this sub-field. The value and meaning of
this value encoded in this subfield should be defined by this value encoded in this sub-field should be defined by
the subtype of the community. the sub-type of the community.
Type 0x02: Type 0x02:
This is an extended type with Type Field comprising of 2 octets This is an extended type with Type Field comprising of 2 octets
and Value Field comprising of 6 octets. and Value Field comprising of 6 octets.
The value of the high-order octet of this extended type is The value of the high-order octet of this extended type is
0x02. The low-order octet of this extended type is used to 0x02. The low-order octet of this extended type is used to
indicate subtypes. indicate sub-types.
The Value Field consists of two subfields. The Value Field consists of two sub-fields.
Global Administrator subfield: 4 octets Global Administrator sub-field: 4 octets
This subfield contains a 4-octets Autonomous System This sub-field contains a 4-octets Autonomous System
number assigned by IANA. number assigned by IANA.
Local Administrator subfield: 2 octets Local Administrator sub-field: 2 octets
The organization identified by Autonomous System number The organization identified by Autonomous System number
in the Global Administrator subfield, can encode any in the Global Administrator sub-field, can encode any
information in this subfield. The value and meaning of information in this sub-field. The value and meaning of
the value encoded in this subfield should be defined by the value encoded in this sub-field should be defined by
the subtype of the community. the sub-type of the community.
6. Route Target Community 6. Route Target Community
The Route Target Community identifies one or more routers that may The Route Target Community identifies one or more routers that may
receive a set of routes (that carry this Community) carried by BGP. receive a set of routes (that carry this Community) carried by BGP.
This is transitive across the Autonomous system boundary. This is transitive across the Autonomous system boundary.
The value of the Type field for the Route Target Community is 0x00 or The value of the Type field for the Route Target Community is 0x00 or
0x01. The value of the low-order octet of the extended type field 0x01. The value of the low-order octet of the extended type field
for this community is 0x02. for this community is 0x02.
When the value of the Type field is 0x00, the value of the Local When the value of the Type field is 0x00, the value of the Local
Administrator subfield in the Value Field MUST be unique within the Administrator sub-field in the Value Field MUST be unique within the
Autonomous system carried in the Global Administrator subfield. Autonomous system carried in the Global Administrator sub-field.
7. Route Origin Community 7. Route Origin Community
The Route Origin Community identifies one or more routers that inject The Route Origin Community identifies one or more routers that inject
a set of routes (that carry this Community) into BGP. This is a set of routes (that carry this Community) into BGP. This is
transitive across the Autonomous system boundary. transitive across the Autonomous system boundary.
The value of the Type field for the Route Origin Community is 0x00 or The value of the Type field for the Route Origin Community is 0x00 or
0x01. The value of the low-order octet of the extended type field 0x01. The value of the low-order octet of the extended type field
for this community is 0x03. for this community is 0x03.
When the value of the Type field is 0x00, the value of the Local When the value of the Type field is 0x00, the value of the Local
Administrator subfield in the Value Field MUST be unique within the Administrator sub-field in the Value Field MUST be unique within the
Autonomous system carried in the Global Administrator subfield. Autonomous system carried in the Global Administrator sub-field.
8. Link Bandwidth Community 8. Link Bandwidth Community
When a router receives a route from a directly connected external When a router receives a route from a directly connected external
neighbor (the external neighbor that is one IP hop away), and neighbor (the external neighbor that is one IP hop away), and
advertises this route (via IBGP) to internal neighbors, as part of advertises this route (via IBGP) to internal neighbors, as part of
this advertisement the router may carry the bandwidth of the link this advertisement the router may carry the bandwidth of the link
that connects the router with the external neighbor. The bandwidth of that connects the router with the external neighbor. The bandwidth of
such a link is carried in the Link Bandwidth Community. The community such a link is carried in the Link Bandwidth Community. The community
is non-transitive across the Autonomous system boundary. is non-transitive across the Autonomous system boundary.
The value of the high-order octet of the extended Type Field is 0x40. The value of the high-order octet of the extended Type Field is 0x40.
The value of the low-order octet of the extended type field for this The value of the low-order octet of the extended type field for this
community is 0x04. community is 0x04.
The value of the Global Administrator subfield in the Value Field The value of the Global Administrator sub-field in the Value Field
MUST represent the Autonomous System of the router that attaches the MUST represent the Autonomous System of the router that attaches the
Link Bandwidth Community. When a router receives a route with the Link Bandwidth Community. When a router receives a route with the
community, the router may check the AS number in the Global community, the router may check the AS number in the Global
Administrator subfield to see if its if its not the local AS and Administrator sub-field to see if its not the local AS and hence
hence ignore the information carried in the Link Bandwidth Community. ignore the information carried in the Link Bandwidth Community.
The bandwidth of the link is expressed as 4 octets in IEEE floating The bandwidth of the link is expressed as 4 octets in IEEE floating
point format, units being bytes per second. It is carried in the point format, units being bytes per second. It is carried in the
Local Administrator subfield of the Value Field. Local Administrator sub-field of the Value Field.
9. Operations 9. Operations
A BGP speaker may use the Extended Communities attribute to control A BGP speaker may use the Extended Communities attribute to control
which routing information it accepts, prefers or distributes to its which routing information it accepts, prefers or distributes to its
peers. peers.
A BGP speaker receiving a route that doesn't have the Extended A BGP speaker receiving a route that doesn't have the Extended
Communities attribute may append this attribute to the route when Communities attribute may append this attribute to the route when
propagating it to its peers. propagating it to its peers.
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community across the Autonomous system boundary. community across the Autonomous system boundary.
A route may carry both the BGP Communities attribute as defined in A route may carry both the BGP Communities attribute as defined in
[RFC1997]), and the Extended BGP Communities attribute. In this case [RFC1997]), and the Extended BGP Communities attribute. In this case
the BGP Communities attribute is handled as specified in [RFC1997], the BGP Communities attribute is handled as specified in [RFC1997],
and the Extended BGP Communities attribute is handled as specified in and the Extended BGP Communities attribute is handled as specified in
this document. this document.
10. IANA Considerations 10. IANA Considerations
The Type Field values 0x00 and 0x01 are assigned in this document. For the high-order octet of the Type Field, values 0x00 through 0x02
Type Field values 2-0x3fff for extended-types (2-0x3f for regular are assigned in this document and are defined as extended types. For
types) are to be assigned by IANA, using the "First Come First the low-order octet of the Type Field, values 0x02 through 0x04 are
Served" policy defined in RFC 2434. Type values 0x8000-0xbfff for assigned in this document.
extended-types (0x80-0xbf for regular-types) are for vendor-specific
types, and values in this range are not to be assigned by IANA. The Type Field values 0x03-0x3f for regular types (0x0300-0x3fff when
expressed as extended types) are to be assigned by IANA, using the
"First Come First Served" policy defined in RFC 2434. The extended
type field values 0x0005-0x00ff, 0x0104-0x01ff and 0x0200-0x02ff are
to be assigned by IANA, using the "First Come First Served" policy
defined in RFC 2434. Type values 0x80-0xbf for regular types
(0x8000-0xbfff when expressed as extended types) are for vendor-
specific types, and values in this range are not to be assigned by
IANA.
11. Security Considerations 11. Security Considerations
This extension to BGP does not change the underlying security issues. This extension to BGP does not change the underlying security issues.
12. Acknowledgements 12. Acknowledgements
The authors would like to thank John Hawkinson, Jeffrey Haas for The authors would like to thank John Hawkinson, Jeffrey Haas for
their feedback. their feedback.
 End of changes. 

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