Registered Wide BGP Community Values

According to RFC 1997 as well as to IANA's Well-Known BGP Communities registry today the following BGP communities are defined to have global significance: 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 Attribute type 8 as defined in RFC 1997 to distribute non Autonomous System specific Well-Known BGP Communities. For the same reason the described registry does not intend to obsolete BGP Extended Community Attribute and any already defined and deployed extended communities. The new registry is to be used primarly for new community definitions in particular those which require to carry various new parameters or which should be propagated with a controled scope and radius.

It has been requested numerous times to have a globally unified way to express some particular Autonomous System based routing policies. When defining a new way to encode bgp communities we have an opportunity to define set of new registered routing policies and route markings which could be passed within and between Autonomous Systems resulting in their common interpretation. This document will request IANA to define and maintain a new registry for pre-defined Wide BGP Community values. The allocation policy is on a first come first served basis. It is recommended that an implementation supports by an explicit enabling defined below Registered Wide BGP Communities. Depending on the BGP implementation support it is recommended that an implementation would support Registered Wide BGP Communities without breaking static or dynamic peer/update groups. However it needs to be pointed out that support of all Registered Wide BGP Communities is not mandatory. It will be perfectly valid for any BGP implementation to support only subset of Wide BGP Communities. It is strongly advised that each Autonomous System does an inbound verification of received Wide BGP Communities from all of its EBGP peers before accepting them and propagating within their own domain. The document does not mandate nor enforces that given registered type value of Wide BGP Community would be of transitive or non-transitive type. It is for the operator to determine the propagation AS radius required for such community when appending it to routing information. However the document will provide a transitivity radius recommendation to defined communities. The following Wide BGP Communities have global significance and their execution should be uniformly implemented by any BGP speaker supporting given set of Wide BGP Communities. The defined below value of the community should be interpreted as registered value only if "R" - registered bit is set in the community Type 1 container as described in [draft-ietf-idr-wide-bgp-communities] Otherwise the value is local and it's actions is locally defined by the operator.

The below set of communities will be defined to be carried in Wide BGP Community Type 1, with the container type values (Community Registered Value) as per .

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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0001 |R C 0 0 0 0 0 0| Hop Count | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Registered Community Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source AS Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Context AS Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Wide Community Target(s) TLV (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Wide Community Exclude Target(s) TLV (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Wide Community Parameter(s) TLV (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Description format: TYPE: 0x0001 (constant for this registry) FLAGS "F": R - Registered bit (Set to 1 for registered values) C - Confederation bit (Set when applicable) HOP COUNT "H": Defines domain or sub-domain propagation radius LENGTH "L": Length of the Container Type 1 in octets REGISTERED COMMUNITY VALUE "R": Value of the community in registry SOURCE AS "S": Originator AS of Wide BGP Community CONTEXT AS "C": For registered communities carries predefined meaning or otherwise should be set to 0x00000000 TARGET TLV "T": Set of atoms containing targets for execution EXCLUDE TARGET TLV "E": Set of atoms containing excluded targets for execution PARAMETER TLV "P": Set of atoms containing optional parameters for execution

BLACKHOLE Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - All transit traffic to destinations for which advertised routes carry such community value should be dropped. It is recommended that specified Autonomous System number should be eligible and verified by BGP Origin Validation functionality to advertise given BGP destinations.

SOURCE FILTER Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - All transit traffic which source addresses have been tagged by such Wide BGP Community should be dropped.

SOURCE DO RPF Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - All transit traffic which source addresses have been tagged by such Wide BGP Community should be subject to Reverse Path Forwarding check when crossing Autonomous System boundaries. Source Autonomous System number specified in the body of this community should directly indicate the peering interfaces on which such RPF check should be performed.

HIGH PRIORITY PREFIX Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = 0x00 T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - BGP prefixes carrying such Wide BGP Community should be advertised to restarting peers before other prefixes received by given BGP speaker.

ATTACK TARGET Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - The ATTACK_TARGET Registered Wide BGP Community indicates that BGP prefixes carrying such community are receiving unusual amount of unwanted traffic most likely due to some form of network attack. Network devices capable of analyzing and mitigating such attacks can use such community as a hint on what destinations to focus the most.

NO ADVERTISE TO AS Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (Peer_AS) L = 25 octets E = none R = IANA assigned P = none DESCRIPTION - All routes received which carry such Wide BGP Community containing this value MUST NOT be advertised to BGP peer which Autonomous System number has been listed in the TARGET TLV field of this community. Semantically specifying the reserved Autonomous System value of 0xFFFFFFFF (ANY AS) would be an equivalent of using NO_ADVERTISE Well-Known Standard BGP Community Attribute.

ADVERTISE TO AS Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (Peer_AS) L = 25 octets E = none R = IANA assigned P = none DESCRIPTION - All routes received carrying such Wide BGP Community containing this value MUST ONLY be advertised to BGP peers which Autonomous System number is specified in the TARGET TLV field of this community. Semantically specifying the reserved Autonomous System value of 0xFFFFFFFF (ANY AS) would be an equivalent of advertisement to all neighbors. Post execution this community MUST be removed.

ADVERTISE AND SET NO EXPORT Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (Peer_AS) L = 25 octets E = none R = IANA assigned P = none DESCRIPTION - All routes received carrying such Wide BGP Community containing this value MUST be advertised to BGP peer which Autonomous System number is specified in the TARGET TLV field of this community with NO_EXPORT Standard BGP Community attached. Semantically specifying in TARGET TLV the reserved Autonomous System value of 0xFFFFFFFF (ANY AS) would be an equivalent of advertisement to all neighbors with NO_EXPORT community being set. Post execution this community MUST be removed.

FROM PEER Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = 0x00 T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System may attach this community to routes received from their EBGP peers to later, when advertising them outside the domain, apply or relax local policies only on such group of destinations.

FROM CUSTOMER Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = 0x00 T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System may attach this community to routes received from their customers to later, when advertising them outside the domain, apply or relax local policies only on such group of destinations.

INTERNAL Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = 0x00 T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System may attach this community to routes originated in their own domain to later, when advertising them outside the domain, apply or relax local policies only on such group of destinations.

FROM UPSTREAM Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = 0x00 T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System may attach this community to routes received from their EBGP upstream peers to later, when advertising them outside the domain, apply or relax local policies only on such group of destinations.

FROM IX Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = 0x00 T = none L = 18 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System may attach this community to routes received from their EBGP peering sessions with the Internet Exchange peers or with Route Server to later, when advertising them outside the domain, apply or relax local policies only on such group of destinations.

LEARNED FROM AS Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = 0x00 T = Type_1 (Peer_AS) L = 25 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System may attach this community to routes received from their EBGP peer by explicitly tagging them with their peer's Autonomous System number as a value of the TARGET TLV field. If the AS number is a two octet number first two octest will be filled with zero. It is possible to use this to also carry private AS number of customers.

PATH HINT Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (AS#) L = 25 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System receiving such Wide BGP Community value should prefer for BGP prefixes received with such community (for example by increasing value of local preference on ingress), a BGP path which traverses Autonomous System number which has been specified in the TARGET TLV field of this community. Post execution this community SHOULD be kept.

NEGATIVE PATH HINT Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (AS#) L = 25 octets E = none R = IANA assigned P = none DESCRIPTION - Autonomous System receiving such Wide BGP Community value should prefer for BGP prefixes received with such community (for example by increasing value of local preference on ingress), a BGP path which DOES NOT traverses Autonomous System number which has been specified in the TARGET TLV field of this community. Post execution this community SHOULD be kept.

PREPEND N TIMES BY AS Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (AS#) L = 29 octets E = none R = IANA assigned P = Type_4 (0xAA) DESCRIPTION - The Autonomous System specified in the TARGET TLV field of such community should prepend N times (encoded as 0xAA) its own Autonomous System number when advertising routes tagged with this community to peers. Number of requested AS prepends is provided in the PARAMETERS TLV field value. Post execution this community MUST be removed.

PREPEND N TIMES TO AS Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (AS#) L = 29 octets E = none R = IANA assigned P = Type_4 (0xAA) DESCRIPTION - The Autonomous System advertising routes externally should prepend N times (encoded as 0xAA) its own Autonomous System number when advertising routes tagged with this community to peer which AS number is defined by TARGET TLV field. Number of requested AS prepends is provided in the PARAMETERS TLV field. Post execution this community MUST be removed.

REPLACE BY Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = Type_1 (AS#) L = 25 octets E = none R = IANA assigned P = none DESCRIPTION - All routes marked with such community advertised by an Autonomous System to all of its external peers should have any occurrence of an Autonomous System number specified in the TARGET TLV field replaced with advertising domain's local Autonomous System number. Post execution this community MUST be removed.

LOCAL PREFERENCE Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = none L = 22 octets E = none R = IANA assigned P = Type_4 (ABBBBBBB) SEMANTICS of PARAMETERS TLV 1 octet 1st bit indicates: 0-increment, 1-decrement 7 bits - value of local preference value 1..127 DESCRIPTION - Autonomous System may suggest to its EBGP neighbor the following adjustments to the value of local preference as specified by given domain's local policy. The values of requested increment or decrement of local preference value is carried in the PARAMETERS TLV field. Post execution this community MUST be removed.

AS_PATH TTL MAX RADIUS Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = none L = 22 octets E = none R = IANA assigned P = Type_4 (0xAA) max AS_PATH radius DESCRIPTION - Autonomous System may suggest to drop advertised prefix by any transit network if its AS_PATH attribute length would be equal or greater to encoded value both inbound or outbound of EBGP session. The value of max AS_PATH length allowed is specified in the PARAMETERS TLV field of the community. Post comparison this community MUST be kept.

GEOGRAPHIC LOCATION WHERE BGP ROUTE IS INTRODUCED TO AS Type: 0x0001 S = src AS # F = 0x80 C = 0x00000000 H = Operator's defined T = none L = 26 octets E = none R = IANA assigned P = Type_8 (5 UTF-8 characters) DESCRIPTION - Autonomous Systems may attach this community to routes received from EBGP neighbors or introduced to BGP by other routing protocols to identify the geographic location where the route was introduced to the AS. The "right-most" two octets of PARAMETERS TLV correspond to an ISO3166-1 alpha-2 country identifier, while the "left-most" three octets may express a more specific geographic location, such as a city or IXP encoded in 3 octets. Example:

Wide BGP Community describing route learnt by the AS at London, GB HOP COUNT - operator defined LENGTH - 26 PARAMETERS - 3 octets locality string + 2 octets country id.

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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0001 | 0x80 | 0xFF | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x001A | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IANA assigned | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x000000AS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x00000000 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x08 | 0x0008 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | "L" | "O" | "N" | "G" | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | "B" | +-+-+-+-+-+-+-+-+