BGP Community Container Attribute
draft-ietf-idr-wide-bgp-communities-06
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
|
|
|---|---|---|---|
| Authors | Robert Raszuk , Jeffrey Haas , Andrew Lange, Bruno Decraene , Shane Amante , Paul Jakma | ||
| Last updated | 2022-04-29 (Latest revision 2022-01-10) | ||
| Replaces | draft-raszuk-wide-bgp-communities | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
OPSDIR Early review
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Has issues
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Keyur Patel | ||
| Shepherd write-up | Show Last changed 2022-04-29 | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
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| Responsible AD | (None) | ||
| Send notices to | shares@ndzh.com, keyur@arrcus.com |
draft-ietf-idr-wide-bgp-communities-06
IDR Working Group R. Raszuk, Ed.
Internet-Draft Bloomberg LP
Intended status: Standards Track J. Haas, Ed.
Expires: 14 July 2022 Juniper Networks
A. Lange, Ed.
Nokia
B. Decraene, Ed.
Orange
S. Amante
Apple, Inc.
P. Jakma
Hewlett Packard Enterprise
10 January 2022
BGP Community Container Attribute
draft-ietf-idr-wide-bgp-communities-06
Abstract
Route tagging plays an important role in external BGP [RFC4271]
relations, in communicating various routing policies between peers.
It is also a very common best practice among operators to propagate
various additional information about routes intra-domain. The most
common tool used today to attach various information about routes is
through the use of BGP communities [RFC1997].
This document defines a new encoding which will enhance and simplify
what can be accomplished today with the use of BGP communities. The
most important addition this specification makes over currently
defined BGP communities is the ability to specify, carry as well as
use for execution an operator's defined set of parameters. It also
provides an extensible platform for any new community encoding needs
in the future.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 July 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Summary . . . . . . . . . . . . . . . . . . . . . . 4
2.1. BGP Community Container Common Header . . . . . . . . . . 4
2.2. Community Containers . . . . . . . . . . . . . . . . . . 5
2.2.1. Type 1: BGP Wide Community . . . . . . . . . . . . . 5
2.3. BGP Community Container Atoms . . . . . . . . . . . . . . 5
3. BGP Community Container Attribute . . . . . . . . . . . . . . 5
3.1. BGP Community Container Attribute Common Header . . . . . 6
4. BGP Community Container, Type 1: BGP Wide Community . . . . . 7
4.1. Community Value . . . . . . . . . . . . . . . . . . . . . 8
4.2. Source AS Number . . . . . . . . . . . . . . . . . . . . 8
4.3. Context AS Number . . . . . . . . . . . . . . . . . . . . 8
4.4. BGP Wide Community TLVs . . . . . . . . . . . . . . . . . 8
4.4.1. Sub-Type 1, BGP Wide Community Target(s) TLV . . . . 9
4.4.2. Sub-Type 2, BGP Wide Community Exclude Target(s)
TLV . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4.3. Sub-Type 3, BGP Wide Community Parameter(s) TLV . . . 10
4.4.4. Usage . . . . . . . . . . . . . . . . . . . . . . . . 11
5. BGP Community Container Atoms . . . . . . . . . . . . . . . . 11
5.1. Atom Type 1, The Autonomous System Number List . . . . . 12
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5.2. Atom Types 2 and 3, The IPv4 and IPv6 Prefix Lists . . . 12
5.3. Atom Type 4, The Integer32 List . . . . . . . . . . . . . 13
5.4. Atom Type 5, The IEEE Floating Point Number List . . . . 13
5.5. Atom Type 6, The Neighbor Class List . . . . . . . . . . 13
5.6. Atom Type 7, The User-defined Class List . . . . . . . . 14
5.7. Atom Type 8, the UTF-8 String . . . . . . . . . . . . . . 14
6. Well Known Standard BGP Communities . . . . . . . . . . . . . 14
7. Operational Considerations . . . . . . . . . . . . . . . . . 15
8. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. General Error Handling for BGP Community Containers . . . 15
8.2. BGP Wide Community Container Error Handling . . . . . . . 15
9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1. Example Type 1 Wide Community Definition . . . . . . . . 16
9.2. Example Type 1 BGP Wide Community Encoding . . . . . . . 16
10. Security considerations . . . . . . . . . . . . . . . . . . . 17
10.1. BGP Community Container Security Considerations . . . . 18
10.2. BGP Wide Community Security Considerations . . . . . . . 18
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
11.1. BGP Community Container Attribute . . . . . . . . . . . 18
11.2. BGP Community Container Atoms Types . . . . . . . . . . 18
11.3. BGP Community Container Neighbor Class List Atom
Types . . . . . . . . . . . . . . . . . . . . . . . . . 19
11.4. BGP Community Container Types . . . . . . . . . . . . . 19
11.5. Registered Type 1 BGP Wide Communities Community
Types . . . . . . . . . . . . . . . . . . . . . . . . . 20
11.6. Registered Type 1 BGP Wide Community Optional
Sub-Types . . . . . . . . . . . . . . . . . . . . . . . 20
12. Change History . . . . . . . . . . . . . . . . . . . . . . . 21
12.1. Working Group draft . . . . . . . . . . . . . . . . . . 21
12.2. Individual draft . . . . . . . . . . . . . . . . . . . . 22
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
15.1. Normative References . . . . . . . . . . . . . . . . . . 24
15.2. Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
RFC 1997 [RFC1997] defines the BGP Community Attribute. This
attribute is used as a tool to carry additional information in BGP
routes which may help to automate peering administration. The BGP
Communities Attribute consists of a set of one or more four-octet
values, where each specifies a different community. Except for two
reserved ranges, the encoding of community values mandates that the
first two octets are to contain the Autonomous System number, with
the next two octets containing some locally defined value.
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Since the introduction of [RFC1997], numerous additional mechanisms
have been introduced to provide BGP Community-like functionality.
Each of these mechanisms introduce a new syntax, typically covered by
its encoding with the BGP Path Attribute that defines it, and a
semantic space.
The authors believe that defining a new BGP Path Attribute, with the
ability to contain locally defined parameters will enhance the
current level of network policies, as well as simplify BGP policy
management. The proposed encoding will also facilitate the delivery
of new network services without a need to define a new BGP extension
each time.
When defining any new type of tool there is always a unique
opportunity to specify a subset of well recognized behaviors. Lists
of the current most commonly used BGP communities, as well as
provision for a new registry for future definitions will be contained
in a separate document.
2. Protocol Summary
This specification defines a new BGP Path Attribute, the BGP
Community Container. It carries a series of BGP Community Container
types, each prefaced with the BGP Community Container Common Header.
This specification also defines the BGP Wide Community Container.
2.1. BGP Community Container Common Header
The BGP Community Container Common Header permits Community-like
attributes to be grouped under a single BGP Path Attribute. This
provides hierarchy for future Community-like features. It permits
implementations without knowledge of a specific Community Container's
format to address that Community Container by its code point. It
also permits common enforcement of the Community Container's
transitivity across AS boundaries without need for the implementation
to understand a specific Container's implementation.
The BGP Community Container Common Header is defined in Section 3.1
and contains following encoding:
Container Type:
Container Type 1, BGP Wide Community is defined in this document.
Flags:
Flags control common behavior including the transitivity of the
Container.
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Length:
Length of the Container contents.
2.2. Community Containers
This document defines one Community Container with the following
encoding:
2.2.1. Type 1: BGP Wide Community
The container type 1 "BGP Wide Community TLVs" is defined in
Section 4.
Community Value:
This section defines the action that an operator wishes a router
to take.
Source AS:
This is the AS originating the community.
Context AS:
AS that defines and provides the semantics to interpret this
Community.
Target(s):
This is an optional list that encodes where the community's
action should be taken.
Exclude Target(s):
This is an optional list that encodes where the community's
actions should not be taken.
Parameters:
This is an optional list of Atoms that encodes additional
information that the community's action needs to execute
properly.
2.3. BGP Community Container Atoms
Atoms provide data types that can be used to encode contents of BGP
Community Containers. They are in the format of TLVs and are defined
later in this document in Section 5.
3. BGP Community Container Attribute
This document defines a new BGP Path Attribute, the BGP Community
Container. The attribute type code is TBD.
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The BGP Community Container attribute is an optional, transitive BGP
attribute, and may be present only once in the BGP UPDATE message.
The attribute contains a set of typed containers. Any given
container type may appear multiple times, unless that container
type's definition specifies otherwise.
3.1. BGP Community Container Attribute Common Header
Containers always start with the following common header:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Flags |C|T| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Common container header
This document defines container type 1. See the Section 11 for
information on additional type registration policies.
+======+=======+===================================================+
| Bit | Value | Meaning |
+======+=======+===================================================+
| T | 0 | Not Transitive across administrative boundary. |
+------+-------+---------------------------------------------------+
| | 1 | Transitive across AS and administrative boundary. |
+------+-------+---------------------------------------------------+
| C | 0 | Not transitive across confederation boundaries. |
+------+-------+---------------------------------------------------+
| | 1 | Transitive across confederation boundaries. |
+------+-------+---------------------------------------------------+
| 3..7 | - | RESERVED - MUST be zero when originated and |
| | | SHOULD be ignored upon receipt. |
+------+-------+---------------------------------------------------+
Table 1: Flags
Flags are defined globally and apply to all container types.
Bit 0 (T bit) Transitivity bit:
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When not set (value 0), the community in the container is
transitive across AS boundaries, but not across an administrative
boundary.
When set (value 1), the community in the container is transitive
across all ASes. An administrative boundary, in this sense, is an
arbitrary set of connected ASes, possibly under control of a
single entity. How such an administrative boundary is determined
is out of scope of this document.
Bit 1 (C bit) Confederation bit:
The confederation bit is used to manage the propagation scope of a
given BGP Wide Community across confederation boundaries.
When not set (value 0) community is not transitive across
confederation sub-AS boundary. When set (value of 1) indicates
that community in a given container is transitive across
confederation boundary.
The Reserved field MUST be set to zero when originated and SHOULD be
ignored upon receipt.
The Length field represents the total length of a given container's
contents in octets.
4. BGP Community Container, Type 1: BGP Wide Community
The Type 1 BGP Community Container, the BGP Wide Community, is of
variable size (but minimum length 12). It is composed of a fixed
12-octets - containing the Community Value, the Source AS Number, and
the Context AS Number - followed by optional TLVs:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I| Community Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Context AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| TLVs (optional) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Type 1, BGP Wide Community
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4.1. Community Value
Community Value: 4 octets
The Community Value indicates what set of actions a router is
requested to take upon reception of a route containing this
community. The semantics of this value depend on whether this is a
private/local community or IANA registered.
When the high order bit of the Community Value field - I - is set,
the value is IANA Registered and has a well defined meaning with
underlying semantics. See the documentation for each Registered BGP
Wide Community for its semantics and validation requirements.
When the high order bit of the Community Value field is clear, the
value is Locally defined and has semantics solely within the control
of the AS defining that community. The Context AS Number provides
the namespace in which this Community Value is interpreted. It is
that AS's responsibility to provide the semantics and validation
requirements for that BGP Wide Community.
See Section 11.5 for code point space partitioning.
4.2. Source AS Number
Source Autonomous System Number: 4 octets
The Autonomous System number indicates the AS originating this BGP
Wide Community.
4.3. Context AS Number
Context Autonomous System Number: 4 octets
This identifies the AS that provides the semantics to interpret this
Community.
4.4. BGP Wide Community TLVs
Optional type 1 container TLVs are encoded in the following format:
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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
+-+-+-+-+-+-+-+-+
| Sub-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Type 1 Container TLVs
Sub-Type:
The sub-type of the BGP Wide Community TLV. A given Sub-Type
MUST NOT appear more than once.
Length:
Length of the "Value" field in octets.
Value:
Specific to the underlying Sub-Type.
4.4.1. Sub-Type 1, BGP Wide Community Target(s) TLV
The value field of the Wide Community Target(s) TLV (Sub-Type 1) is a
series of Atom TLVs. The semantics of any given Atom TLV MUST be
part of the definition of a given Wide Community.
BGP Wide Community Targets define the matching criteria for the
community. A given wide community may have a number of targets that
it applies to. The semantics of these targets will vary on a per
community basis. Depending on the definition of the community,
targets may be optional.
Wide Community Targets consist of a series of Atoms that have "match
any" semantics. Thus, if any given target matches per the semantics
of that Atom for the community, the community is considered to match
and the action defined by the community should be executed.
When no Target(s) TLV is specified, it is considered "match all".
If the semantics of a given Atom is undefined for the community in
question, this Atom MUST be ignored.
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When no targets are required by the definition of a given Wide
Community, the Wide Community Target(s) TLV SHOULD NOT be encoded in
the community. Implementations MUST be prepared to accept a Wide
Community Target(s) TLV with an empty value field.
4.4.2. Sub-Type 2, BGP Wide Community Exclude Target(s) TLV
The BGP Wide Community Exclude Target(s) TLV (Sub-Type 2) contains a
list of a Atoms.
Wide Community Exclude Targets define criteria by which the community
is considered to NOT match. Depending on the semantics of the BGP
Wide Community, Exclude Target(s) may be optional.
The semantic of the BGP Wide Community Exclude Target(s) is to match
all specified Target(s) with the exception of those listed in this
TLV.
The value field of the BGP Wide Community Exclude Target(s) TLV is a
series of BGP Wide Community Atom TLVs. The semantics of any given
Atom TLV MUST be part of the definition of a given Wide Community.
If the semantics of a given Atom is undefined for the community in
question, this Atom MUST be ignored.
If the BGP Wide Community Target(s) TLV and the BGP Wide Community
Exclude Target(s) TLV have conflicting semantics, priority MUST be
given to the Wide Community Exclude Target(s) TLV.
When no exclude targets are required by the definition of a given BGP
Wide Community, the BGP Wide Community Exclude Target(s) TLV SHOULD
NOT be encoded in the community. Implementations MUST be prepared to
accept a BGP Wide Community Exclude Target(s) TLV with an empty value
field.
4.4.3. Sub-Type 3, BGP Wide Community Parameter(s) TLV
The BGP Wide Community Parameter(s) TLV (Sub-Type 3) contains a list
of a Atoms.
A given BGP Wide Community may have parameters that are used as
inputs for executing actions defined for that community. These
parameters, and any constraints implied by the parameters, MUST be
defined by the wide community definition. Parameters consist of an
ordered set of Atom sub-TLVs. The semantics of any specific
positional instance of an Atom MUST be defined by the wide community.
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Care must be taken when using Atoms with list semantics. If the
desired behavior is a single or limited number of instances of that
type, this should be documented as part of the use case of that BGP
Wide Community.
If it is the case that a parameter for a given community is of an
unexpected type or length, the BGP Wide Community MUST be ignored.
If it is the case that there are too many or two few parameters for a
given community, the BGP Wide Community MUST be ignored.
When no parameters are required by the definition of a given Wide
Community, the Wide Community Parameters TLV SHOULD NOT be encoded in
the community. Implementations MUST be prepared to accept a Wide
Community Parameter TLV with an empty value field.
4.4.4. Usage
The detailed interpretation of the targets or parameters SHALL be
provided when describing given community type in a separate document
or when locally defined by an operator.
5. BGP Community Container Atoms
Some types of BGP Community Contaners, for example BGP Wide
Communities, will act on and hence need to encode some distinct Atoms
of data. Use of Atoms is solely subject to definition of the
specific BGP Container type. Atoms are encoded as TLVs, where each
TLV has the following format:
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
+-+-+-+-+-+-+-+-+
| Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Atoms TLVs
The Type field contains a value of 1-254. The values 0 and 255 are
reserved for future use. The TLV types are to be assigned and
maintained by IANA registry; see Section 11.2.
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The Length represents the length of the "Value" field in octets.
The Value field contains the TLV value.
Supported format of the TLVs can be:
Type 1: Autonomous System Number List.
Type 2: IPv4 Prefix (1 octet prefix length + prefix) List.
Type 3: IPv6 Prefix (1 octet prefix length + prefix) List.
Type 4: Integer32 List.
Type 5: IEEE Floating Point Number List.
Type 6: Neighbor Class List.
Type 7: User-defined Class List.
Type 8: UTF-8 String.
The semantics of a given Atom will depend upon the context in which
it is used, as defined by the containing wide community.
In the following sections defining the different Atoms, validation
rules for the Length of the Atom will be presented. If the Length of
the Atom does not match the rules for that Atom, it SHALL be
considered malformed. (See Section 8.)
In general, Atoms of List type have the semantics of sets. Duplicate
entries SHOULD NOT be present and MAY be removed by BGP Speaker
propagating the Lists. The presence of duplicate entries have no
additional semantics.
5.1. Atom Type 1, The Autonomous System Number List
This Atom represents a list of Autonomous System numbers, each 4
octets in size. When encoding two octet ASes, the first two octets
of this four octet value MUST be filled with zeros. The minimum
Length of this Atom is 4 octets. The Length MUST be a multiple of 4.
Two special values are reserved for the Autonomous System Atoms:
0x00000000 - to indicate "No Autonomous Systems".
0xFFFFFFFF - to indicate "All Autonomous Systems".
5.2. Atom Types 2 and 3, The IPv4 and IPv6 Prefix Lists
This Atom represents a list of IPv4 or IPv6 prefixes. IPv4 and IPv6
Prefix Atom values are encoded in the same format used by BGP NLRI in
Section 4.3 of [RFC4271].
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+---------------------------+
| Prefix Length (1 octet) |
+---------------------------+
| Prefix (variable) |
+---------------------------+
Figure 5: IP prefix atoms
The Prefix Length for IPv4 prefixes MUST be in the range of 0..32.
The Prefix Length for IPv6 prefixes MUST be in the range of 0..128.
The Length field must be able to accommodate the list of prefixes
according to the encoding rules. If the Length cannot fully
accommodate the required number of octets to encode the Prefix Length
and the Prefix, the Atom is considered malformed.
5.3. Atom Type 4, The Integer32 List
This Atom represents a list of four-octet Integers. These Integers
are stored in network byte order.
The minimum Length of the Integer32 list Atom is 4 octets. The
Length MUST be a multiple of 4.
5.4. Atom Type 5, The IEEE Floating Point Number List
This Atom represents a list of floating point numbers. Floating
point numbers are a fixed Length of 4 octets and are stored in
[IEEE.754.1985] format.
The minimum Length of the Floating Point Number list Atom is 4
octets. The Length MUST be a multiple of 4.
5.5. Atom Type 6, The Neighbor Class List
The Neighbor Class list Atom represents a list of Neighbor classes,
each 4 octets in size. Neighbor class currently can contain three
values:
Peer (1):
This class is typically applied to sessions where a transit-free
relationship exists between two providers.
Customer (2):
This class is typically applied to sessions where the remote end
of the session is operated by a customer.
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Upstream (3):
This class is typically applied to sessions where the remote end
of the session is operated by a network from which you receive
transit routes.
The minimum Length of the Neighbor Class list Atom is 4 octets. The
Length MUST be a multiple of 4.
5.6. Atom Type 7, The User-defined Class List
The User-defined Class list Atom represents a list of user-defined
class, each 4 octets in size. The exact property definition is up to
the semantics of the defining Autonomous System. The semantics
governing a given User-defined Class list are defined by the Context
AS Number and the Community Value.
Examples of User-defined Class properties include geography (East,
West), continent (North America, Asia, Europe), etc. Similar to the
[RFC1997] BGP Communities, it is necessary that the Context AS
provide a registry of the value and the semantics of a given
community.
The minimum Length of the User-defined Class list Atom is 4 octets.
The Length of this Atom MUST be a multiple of 4.
5.7. Atom Type 8, the UTF-8 String
The UTF-8 String Atom represents an arbitrary Unicode string in UTF-8
[RFC3629] format. The Length is required to be of sufficient size to
carry the UTF-8 string in the Value field.
Implementations MUST be prepared for truncated/improperly formed
UTF-8 strings. When detecting such a string, the implementation
should remove trailing octets of a multi-octet sequence in order to
have a well-formed string.
Implementations MUST be prepared to receive empty (zero-Length) UTF-8
String Atoms as they may be used as Parameters.
6. Well Known Standard BGP Communities
According to RFC 1997, as well as IANA's Well-Known BGP Communities
registry, the following BGP communities are defined to have global
significance:
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0xFFFF0000 planned-shut [draft-francois-bgp-gshut]
0xFFFFFF01 NO_EXPORT [RFC1997]
0xFFFFFF02 NO_ADVERTISE [RFC1997]
0xFFFFFF03 NO_EXPORT_SUBCONFED [RFC1997]
0xFFFFFF04 NOPEER [RFC3765]
This document recommends for simplicity as well as for avoidance of
backward compatibility issues the continued use of BGP Standard
Community Path Attribute, type 8, as defined in RFC 1997 to
distribute non-Autonomous System specific Well-Known BGP Communities.
For the same reason, this document does not intend to obsolete the
currently defined and deployed BGP Extended Communities.
7. Operational Considerations
Having multiple ways to propagate locally assigned BGP Communities -
via the use of Standard, Extended or Large BGP Communities versus the
use of BGP Wide Communities - may seem to potentially cause problems
when considering propagation of conflicting actions. However, even
at present, an operator may append such Communities with conflicting
information. It is therefore recommended that any implementation, in
supporting both standard and BGP Wide Communities, allow for their
easy inbound and outbound processing. The actual execution of all
communities should be treated as a union and, if supported by an
implementation, their execution permissions are to be a local
configuration matter.
8. Error Handling
8.1. General Error Handling for BGP Community Containers
[RFC7606] "treat as withdraw" behavior is expected for any malformed
Community Containers or malformation of their contents.
Each Community Container type may have additional validation rules,
including permitted length of Atoms. Failure to conform to those
additional rules MUST also be treated as a malformed Community
Container.
8.2. BGP Wide Community Container Error Handling
If any Atom in a BGP Wide Community container's Exclude Targets TLV
is unrecognized, that Wide Community MUST NOT be considered a match
and no actions for that community should be processed. While the
Targets TLV is meant to be inclusive, the Exclude Targets TLV is
meant to be proscriptive of applying the action.
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9. Example
9.1. Example Type 1 Wide Community Definition
An operator of an AS 64496, wishes to locally define a Wide Community
with the semantics of permitting AS_PATH prepending with targets that
include AS numbers of peer ASes and peers who have been marked with a
set of enumerated city locations. AS 64496 has selected Community
Value 1 to represent this functionality.
AS 64496 has established a registered set of values to use for its
User-defined Class:
100 - Amsterdam
101 - New York
102 - San Francisco
103 - Tokyo
104 - Moscow
Target semantics:
The Autonomous System Number list Atom refers to the target peer
AS Numbers.
The User-defined Class for AS 64496 has been defined elsewhere and
the values 100..104 may be used for this locally defined Wide
Community.
The Targets TLV MUST contain at least one entry.
The Exclude Targets TLV MAY contain entries of the above supported
Atoms.
The semantics of all other Atoms are undefined for this community.
Parameter semantics:
The parameter TLV shall consist of exactly one Integer32 Atom
value that is constrained to have a value of 2..8.
9.2. Example Type 1 BGP Wide Community Encoding
AS_PATH prepend 4 TIMES TO AS 2424, AS 8888, to peers marked as
Amsterdam (100) or to peers marked Moscow (104), but not to peers in
New York (101).
The T Flag (transitive) is set to prevent propagation of this
community.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (1, Wide) | Flags |0|1| Reserved(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length: 53 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community: LOCAL PREPEND ACTION CATEGORY 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source AS 64496 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Context AS 64496 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target TLV (1)| Length: 18 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASN List (1) | Length: 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target ASN# 2424 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target ASN# 8888 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| User List(7) | Length: 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Amsterdam (100) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Moscow (104) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ExcTargetTLV(2)| Length: 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| User List(7) | Length: 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New York (101) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Param TLV (3) | Length: 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Integer32 (4) | Length: 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prepend # 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Example 1
10. Security considerations
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10.1. BGP Community Container Security Considerations
Transitive BGP Community Container communities could unintentionally
spread far from their origin. If a router receives many routes from
multiple sources on the Internet with different communities, it could
cause significant memory usage. To prevent excessive memory usage,
routers should be configured to strip unexpected communities from
received routes.
All the security considerations for BGP Communities [RFC1997] or BGP
Extended Communities [RFC4360] apply to BGP Community Containers.
10.2. BGP Wide Community Security Considerations
For BGP Wide Communities, the Community Value the Source AS may
provide sufficient context to strip unwanted or unexpected
communities.
Given the flexibility and power offered by BGP Wide communities, it
is important to consider the additional possibilities allowed by
their definition. In particular, for locally defined BGP Wide
Communities, it may be wise to restrict the range of parameters. For
registered BGP Wide Communities, the security considerations of the
document defining them MUST address issues specific to those newly
defined Communities.
11. IANA Considerations
11.1. BGP Community Container Attribute
This document defines a new BGP Path Attribute called BGP Community
Container Attribute. For this new type IANA is requested to allocate
a new value in the corresponding registry:
Registry Name: BGP Path Attributes
This document makes the following assignments for the optional,
transitive BGP Community Container Attribute:
Name Type Value
---- ----------
BGP Community Container Attribute TBD
11.2. BGP Community Container Atoms Types
This document requests IANA to define and maintain a new registry
named: "BGP Community Container Atom Types". The pool of 0x00-0xFF
has been defined for its allocations.
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Registration procedures:
0x00: Reserved.
0x01-0x08: Defined in this document.
0x09-0xFE: IETF Consensus.
0xFF: Reserved.
This document makes the following assignments for the BGP Community
Container Atom Type values registry:
Name Type Value
---- ----------
Autonomous System Number List 0x01
IPv4 Prefix list 0x02
IPv6 Prefix list 0x03
Integer32 list 0x04
IEEE Floating Point Number list 0x05
Neighbor Class list 0x06
User-defined Class list 0x07
UTF-8 string 0x08
11.3. BGP Community Container Neighbor Class List Atom Types
This document requests IANA to define and maintain a new registry
named: "BGP Community Container Neighbor Class List Atom Types". The
pool of 0x00000000-0xFFFFFFFF has been defined for its allocations.
Registration procedures:
0x00000000 : Reserved.
0x00000001-0x00000003 : Defined in this document.
0x00000004-0xFFFFFFFE : IETF Consensus.
0xFFFFFFFF : Reserved.
This document makes the following assignments for the BGP Community
Container Neighbor Class List Atom Types registry:
Name Type Value
---- ----------
Peer 1
Customer 2
Upstream 3
11.4. BGP Community Container Types
This document requests IANA to define and maintain a new registry
named: "BGP Community Container Types".
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The pool of: 0x0000..0xFFFF has been defined for its allocations.
Registration procedures:
0x0000 : Reserved.
0x0001 : BGP Wide Community (defined in this
document).
0x0002-0x0004 : Reserved.
0x0005-0x00FF : IETF Consensus.
0x0100-0xFF00 : First Come, First Served.
0xFF01-0xFFFE : Experimental.
0xFFFF : Reserved.
11.5. Registered Type 1 BGP Wide Communities Community Types
This document requests IANA to define and maintain a new registry
named: "Registered Type 1 BGP Wide Community Community Types". The
pool of 0x00000000..0xFFFFFFFF has been defined for its allocation.
Registration procedures:
0x00000000 : Reserved.
0x00000001-0x7FFFFFFF : Available for private/local use.
0x80000000 : Reserved.
0x80000001-0xFFFFFEFF : First Come, First Served for
registered use.
0xFFFFFF00-0xFFFFFFFE : Experimental.
0xFFFFFFFF : Reserved.
11.6. Registered Type 1 BGP Wide Community Optional Sub-Types
This document requests IANA to define and maintain a new registry
named: "Registered Type 1 BGP Wide Community Optional Sub-Types".
The pool of 0x00..0xFF has been defined for its allocation.
Registration procedures:
0 : Reserved.
1..3 : Defined in this document.
4..254 : IETF Consensus.
255 : Reserved.
This document makes the following assignments for the Registered Type
1 BGP Wide Community Optional Sub-Types registry:
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Name Type Value
---- ----------
Targets 1
Exclude Targets 2
Parameters 3
12. Change History
12.1. Working Group draft
Changes from -03 to -04:
Many editorial changes.
Restored the structure of the common header to accommodate prior
implementations from Huawei. However, do not keep the Hop count
per prior IDR and author discussion.
Adopt the name BGP Community Container for the general feature and
common header after discussion on IDR regarding Large BGP
Communities. Wide communities now specifically refer to the Type
1 container.
Updated the Common Container Header's definition of Length to only
cover the length of the contents, and not the header.
Hide the Type 2 (4:4), Type 3 (Nx4), Type 4 (16+Nx4) containers
for now.
Outstanding issues addresses and section removed.
Type 1 container renamed from "Wide community" to "Wide community
TLVs".
Rename Integer Atom to Integer32.
Example changed, following previous specification change.
Changes from -02 to -03:
Many editorial change.
Introduction of new type of containers: Type 2 (4:4), Type 3
(Nx4), Type 4 (16+Nx4)
Common container header: Type length changed from 2-octets to 1
octet, "Hop Count" removed, "Context AS number" moved from type 1
to the generic header.
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Remove community "AS-4 List Generic Wide BGP Community"
Changes from -00 to -02: no change
00: no change
12.2. Individual draft
Changes from -03 via -04 to -05:
Update the Introduction.
Substantial re-work of Atom types removing proposed Group
container and moving Atoms to be lists.
Added the Exclude Targets TLV to the Wide Community container.
Added a section on error handling.
Updated the example.
Changes from -02 to -03:
Removed C and R named bit fields originally from -00.
Rename Target AS field to Context AS.
Make Integer Atom a fixed 4 octets in length.
Add Neighbor Class Atom
Rename TTL to Hop Count
Changes from -01 to -02:
The Type field has been expanded to 2 octets.
The Length field has been moved to the common header.
Changed format to use TLVs.
Added Atom TLV to define well defined syntactic items.
Added TLVs to distinguish targets from parameters.
Various editorial changes to language.
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13. Contributors
The following people contributed significantly to the content of the
document:
Shintaro Kojima
OTEMACHI 1st. SQUARE EAST TOWER, 3F
1-5-1, Otemachi,
Chiyoda-ku, Tokyo 100-0004
Japan
Email: koji@mfeed.ad.jp
Juan Alcaide
Cisco Systems
Research Triangle Park, NC
United States
Email: jalcaide@cisco.com
Burjiz Pithawala
Cisco Systems
170 West Tasman Dr
San Jose, CA
United States
Email: bpithaw@cisco.com
Saku Ytti
TDC Oy
Mechelininkatu 1a
00094 TDC
Finland
Email: ytti@tdc.net
14. Acknowledgments
This document owes draft-lange-flexible-bgp-communities a debt for
the inspiration of many features contained herein.
The authors would like to thank Enke Chen, Pedro Marques, Alton Lo,
Igor Gashinsky and Job Snijders for their valuable input.
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15. References
15.1. Normative References
[IEEE.754.1985]
Institute of Electrical and Electronics Engineers,
"Standard for Binary Floating-Point Arithmetic",
IEEE Standard 754, August 1985.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
Patel, "Revised Error Handling for BGP UPDATE Messages",
RFC 7606, DOI 10.17487/RFC7606, August 2015,
<https://www.rfc-editor.org/info/rfc7606>.
15.2. Informative References
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
<https://www.rfc-editor.org/info/rfc1997>.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
February 2006, <https://www.rfc-editor.org/info/rfc4360>.
Authors' Addresses
Robert Raszuk (editor)
Bloomberg LP
731 Lexington Ave
New York City, NY 10022
United States of America
Email: robert@raszuk.net
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Jeffrey Haas (editor)
Juniper Networks
1194 N.Mathilda Ave
Sunnyvale, CA 94089
United States of America
Email: jhaas@juniper.net
Andrew Lange (editor)
Nokia
777 E. Middlefield Road
Mountain View, CA 94043
United States of America
Email: andrew.lange@nokia.com
Bruno Decraene (editor)
Orange
Email: bruno.decraene@orange.com
Shane Amante
Apple, Inc.
1 Infinite Loop
Cupertino, CA 95014
United States of America
Email: amante@apple.com
Paul Jakma
Hewlett Packard Enterprise
CSA02, Erskine Ferry Road
Bishopton
Email: paul.jakma@hpe.com
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