draft-ietf-grow-large-communities-usage-03.txt   draft-ietf-grow-large-communities-usage-04.txt 
Global Routing Operations J. Snijders Global Routing Operations J. Snijders
Internet-Draft J. Heasley Internet-Draft J. Heasley
Intended status: Informational NTT Intended status: Informational NTT
Expires: September 13, 2017 M. Schmidt Expires: September 14, 2017 M. Schmidt
i3D.net i3D.net
March 12, 2017 March 13, 2017
Usage of BGP Large Communities Use of BGP Large Communities
draft-ietf-grow-large-communities-usage-03 draft-ietf-grow-large-communities-usage-04
Abstract Abstract
Examples and inspiration for operators for the use of BGP Large Examples and inspiration for operators to use BGP Large Communities.
Communities.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 13, 2017. This Internet-Draft will expire on September 14, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 13 skipping to change at page 2, line 13
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Design Overview . . . . . . . . . . . . . . . . . . . . . 2 2. The Design Overview . . . . . . . . . . . . . . . . . . . . . 2
2.1. Informational Communities . . . . . . . . . . . . . . . . 4 2.1. Informational Communities . . . . . . . . . . . . . . . . 4
2.2. Action Communities . . . . . . . . . . . . . . . . . . . 4 2.2. Action Communities . . . . . . . . . . . . . . . . . . . 4
3. Examples of Informational Communities . . . . . . . . . . . . 5 3. Examples of Informational Communities . . . . . . . . . . . . 5
3.1. Location . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Location . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1.1. An ISO 3166-1 numeric function . . . . . . . . . . . 5 3.1.1. An ISO 3166-1 Numeric Function . . . . . . . . . . . 5
3.1.2. A UN M.49 Region function . . . . . . . . . . . . . . 5 3.1.2. A UN M.49 Region Function . . . . . . . . . . . . . . 5
3.2. Relation Function . . . . . . . . . . . . . . . . . . . . 6 3.2. Relation Function . . . . . . . . . . . . . . . . . . . . 6
3.3. Combining Informational Communities . . . . . . . . . . . 6 3.3. Combining Informational Communities . . . . . . . . . . . 6
4. Examples of Action Communities . . . . . . . . . . . . . . . 7 4. Examples of Action Communities . . . . . . . . . . . . . . . 7
4.1. Selective NO_EXPORT . . . . . . . . . . . . . . . . . . . 7 4.1. Selective NO_EXPORT . . . . . . . . . . . . . . . . . . . 7
4.1.1. ASN Based Selective NO_EXPORT . . . . . . . . . . . . 7 4.1.1. ASN Based Selective NO_EXPORT . . . . . . . . . . . . 7
4.1.2. Location Based Selective NO_EXPORT . . . . . . . . . 7 4.1.2. Location Based Selective NO_EXPORT . . . . . . . . . 7
4.2. Selective AS_PATH Prepending . . . . . . . . . . . . . . 8 4.2. Selective AS_PATH Prepending . . . . . . . . . . . . . . 8
4.2.1. ASN Based Selective AS_PATH Prepending . . . . . . . 8 4.2.1. ASN Based Selective AS_PATH Prepending . . . . . . . 8
4.2.2. Location Based Selective AS_PATH Prepending . . . . . 9 4.2.2. Location Based Selective AS_PATH Prepending . . . . . 9
4.3. Manipulation of the LOCAL_PREF attribute . . . . . . . . 9 4.3. Manipulation of the LOCAL_PREF Attribute . . . . . . . . 9
4.3.1. Global Manipulation of LOCAL_PREF . . . . . . . . . . 10 4.3.1. Global Manipulation of LOCAL_PREF . . . . . . . . . . 10
4.3.2. Location Based Manipulation of LOCAL_PREF . . . . . . 10 4.3.2. Location Based Manipulation of LOCAL_PREF . . . . . . 10
4.3.3. Note of Caution for LOCAL_PREF Functions . . . . . . 11 4.3.3. Note of Caution for LOCAL_PREF Functions . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 4.4. Route Server Prefix Distribution Control . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . 13
8.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
BGP Large Communities [RFC8092] provide a mechanism to signal opaque BGP Large Communities [RFC8092] provide a mechanism to signal opaque
information between Autonomous Systems. This document presents information between Autonomous Systems (ASs). This document presents
examples of how operators might utilise BGP Large Communities to examples of how operators might utilize BGP Large Communities to
achieve various goals. This document draws from experience of achieve various goals. This document draws on the experience of
operational communities such as NANOG [1] and NLNOG [2]. operator communities such as NANOG [1] and NLNOG [2].
2. The Design Overview 2. The Design Overview
BGP Large Communities are composed of three 4-octet fields. The BGP Large Communities are composed of three 4-octet fields. The
first is the Global Administrator (GA) field, whose value is the first is the Global Administrator (GA) field, whose value is the
Autonomous System Number (ASN) of the Autonomous System (AS) that has Autonomous System Number (ASN) of the AS that has defined the meaning
defined the meaning of the remaining two 4-octet fields, known as of the remaining two 4-octet fields, known as "Local Data Part 1" and
"Local Data Part 1" and "Local Data Part 2". This document describes "Local Data Part 2". This document describes an approach where the
an approach where the "Local Data Part 1" field contains a function "Local Data Part 1" field contains a function identifier and the
identifier and the "Local Data Part 2" contains a parameter value. "Local Data Part 2" contains a parameter value. Using the canonical
notation this format can be summarized as "ASN:Function:Parameter".
Using the canonical notation the above can be summarized as
"ASN:Function:Parameter".
+----------------------+---------------+ +----------------------+---------------+
| RFC 8092 | this document | | RFC 8092 | this document |
+----------------------+---------------+ +----------------------+---------------+
| Global Administrator | ASN | | Global Administrator | ASN |
| Local Data Part 1 | Function | | Local Data Part 1 | Function |
| Local Data Part 2 | Parameter | | Local Data Part 2 | Parameter |
+----------------------+---------------+ +----------------------+---------------+
A mapping table on the usage of fields in BGP Large Communities A mapping table on the use of fields in BGP Large Communities between
between [RFC8092] and this document. [RFC8092] and this document.
Table 1: Field mapping Table 1: Field Mapping
In contemporary deployments of both BGP Communities [RFC1997] and BGP In contemporary deployments of both BGP Communities [RFC1997] and BGP
Large Communities, the function of a community can be divided into Large Communities, the function of a community can be divided into
two categories: two categories:
o Informational Communities o Informational Communities
o Action Communities o Action Communities
Throughout the document a topology of four Autonomous Systems is used Throughout the document a topology of four ASs is used to illustrate
to illustrate the usage of Communities in the following the use of communities in the following configuration:
configuration:
AS 65551 AS 65551
| |
^ ^
| |
AS 64497 AS 64497
/ \ / \
^ \ ^ \
/ ^ / ^
AS 64498 \ AS 64498 \
| | | |
`<->- AS 64499 `<->- AS 64499
AS 64497 obtains transit services from (is a customer of) AS 65551, a AS 64497 obtains transit services from (is a customer of) AS 65551, a
32-bit ASN. AS 64497 provides transit services to both AS 64498 and 4-octet ASN. AS 64497 provides transit services to both AS 64498 and
AS 64499. AS 64498 and AS 64499 maintain a peering relationship in AS 64499. AS 64498 and AS 64499 maintain a peering relationship in
which they only exchange their customer routes. which they only exchange their customer routes.
The opaque nature of BGP Large Communities allows for rapid The opaque nature of BGP Large Communities allows for rapid
deployment of new features or changes to products. Operators are deployment of new features or changes to their routing policy that
encouraged to publicly publish and maintain documentation of the perform an action. Operators are encouraged to publicly publish and
purpose of each BGP Large Community, both informational and action, maintain documentation on the purpose of each BGP Large Community,
that they support or are visible in BGP RIBs. both informational and action, that they support or are visible in
BGP RIBs.
2.1. Informational Communities 2.1. Informational Communities
Informational Communities are labels for attributes such as the Informational Communities are labels for attributes such as the
origin of the route announcement, the nature of the relation with an origin of the route announcement, the nature of the relation with an
EBGP neighbor or the intended propagation audience. Informational EBGP neighbor or the intended propagation audience. Informational
Communities can also assist in providing valuable information for Communities can also assist in providing valuable information for
day-to-day network operations such as debugging or capacity planning. day-to-day network operations such as debugging or capacity planning.
The Global Administrator field is set to the ASN which labels the The Global Administrator field is set to the ASN which labels the
routes with the Informational Communities. For example, AS 64497 routes with the Informational Communities. For example, AS 64497
might add a community with the GA 64497 to a route accepted from an might add a community with the GA 64497 to a route accepted from an
IBGP or EBGP neighbor as a means of signaling that it was imported in IBGP or EBGP neighbor as a means of signaling that it was imported in
a certain geographical region. a certain geographical region.
In general, the intended audiences of Informational Communities are In general, the intended audiences of Informational Communities are
downstream networks and the Global Administrator itself, but any downstream networks and the Global Administrator itself, but any AS
Autonomous System could benefit from receiving these communities. could benefit from receiving these communities.
2.2. Action Communities 2.2. Action Communities
Action Communities are added as a label to request non-default Action Communities are added as a label to request that a route be
treatment of a route within an AS. The operator of that AS defines treated in a particular way within an AS. The operator of the AS
routing policy which, based upon the communities, adjusts route defines a routing policy that adjusts path attributes based on the
attributes such as its propagation characteristics, the LOCAL_PREF community. For example, the route's propagation characteristics, the
(local preference), the next-hop, or the number of AS_PATH prepends LOCAL_PREF (local preference), the next-hop, or the number of AS_PATH
to be added upon reception or propagation. prepends to be added when it is received or propagated can be
changed.
The Global Administrator field is set to the ASN which has defined The Global Administrator field is set to the ASN which has defined
the functionality of that BGP Large Community and is therefore the the functionality of that BGP Large Community and is the ASN that is
ASN that is expected to perform the action. For instance, AS 64499 expected to perform the action. For example, AS 64499 might label a
might label a route with a BGP Large Community containing GA 64497 to route with a BGP Large Community containing GA 64497 to request that
request that AS 64497 perform a pre-defined action upon that route. AS 64497 perform a pre-defined action on that route.
In general, the intended audience of Action Communities are transit In general, the intended audience of Action Communities are transit
providers taking action on behalf of a customer or the Global providers taking action on behalf of a customer or the Global
Administrator itself, but any AS could take action if they chose and Administrator itself, but any AS could take action if they choose and
any AS could add an action community with the GA of a non-adjacent any AS could add an Action Community with the GA of a non-adjacent
ASN. However, note that an Action Community could also be ASN. However, note that an Action Community could also be
informational. Its presence is an indicator that the GA may have informational. Its presence is an indicator that the GA may have
performed the action and that an AS in the AS_PATH requested it. performed the action and that an AS in the AS_PATH requested it.
Operators are recommended to publish the relative order in which
Action Communities (both BGP Communities and BGP Large Communities)
are processed in their routing policy.
3. Examples of Informational Communities 3. Examples of Informational Communities
3.1. Location 3.1. Location
An AS, AS 64497 in these examples, may inform other networks about An AS, AS 64497 in these examples, may inform other networks about
the geographical region where AS 64497 imported a route by labeling the geographical region where AS 64497 imported a route by labeling
it with BGP Large Communities following one of the following schemes it with BGP Large Communities following one of the following schemes
or a combination thereof. or a combination of them.
3.1.1. An ISO 3166-1 numeric function 3.1.1. An ISO 3166-1 Numeric Function
AS 64497 could assign a value of 1 to the Function field to designate AS 64497 could assign a value of 1 to the Function field to designate
the content of the Parameter field as an ISO-3166-1 [3] numeric the content of the Parameter field as an ISO-3166-1 [3] numeric
country identifier. country identifier.
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
| BGP Large Community | Description | | BGP Large Community | Description |
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
| 64497:1:528 | Route learned in the Netherlands | | 64497:1:528 | Route learned in the Netherlands |
| 64497:1:392 | Route learned in Japan | | 64497:1:392 | Route learned in Japan |
| 64497:1:840 | Route learned in the United States of | | 64497:1:840 | Route learned in the United States of |
| | America | | | America |
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
Example documentation for Informational Communities deployed by AS Example documentation for Informational Communities deployed by AS
64497 to describe the location where a route was imported using ISO 64497 to describe the location where a route was imported using ISO
3166-1 numeric identifiers. 3166-1 numeric identifiers.
Table 2: Information: ISO 3166-1 Table 2: Information: ISO 3166-1
3.1.2. A UN M.49 Region function 3.1.2. A UN M.49 Region Function
AS 64497 could assign a value of 2 to the Function field to designate AS 64497 could assign a value of 2 to the Function field to designate
the content of the Parameter field as the M.49 numeric code published the content of the Parameter field as the M.49 numeric code published
by the United Nations Statistics Division (UNSD) [4] for macro by the United Nations Statistics Division (UNSD) [4] for macro
geographical (continental) regions, geographical sub-regions, or geographical (continental) regions, geographical sub-regions, or
selected economic and other groupings. selected economic and other groupings.
+---------------------+-------------------------------+ +---------------------+-------------------------------+
| BGP Large Community | Description | | BGP Large Community | Description |
+---------------------+-------------------------------+ +---------------------+-------------------------------+
skipping to change at page 7, line 42 skipping to change at page 7, line 42
the propagation of routes to the neighboring ASN specified in the the propagation of routes to the neighboring ASN specified in the
Parameter field. Parameter field.
Table 5: Action: ASN NO_EXPORT Table 5: Action: ASN NO_EXPORT
4.1.2. Location Based Selective NO_EXPORT 4.1.2. Location Based Selective NO_EXPORT
AS 64497 could assign a value of 5 to the Function field to designate AS 64497 could assign a value of 5 to the Function field to designate
the content of the Parameter field as an ISO 3166-1 numeric country the content of the Parameter field as an ISO 3166-1 numeric country
identifier within which a labeled route is not propagated to EBGP identifier within which a labeled route is not propagated to EBGP
neighbors. However this might not prevent one of those EBGP neighbors. However, this might not prevent one of those EBGP
neighbors from learning that route in another country and thereby neighbors from learning that route in another country and making it
making it available in the country specified by the BGP Large available in the country specified by the BGP Large Community.
Community.
+-----------------+-------------------------------------------------+ +-----------------+-------------------------------------------------+
| BGP Large | Description | | BGP Large | Description |
| Community | | | Community | |
+-----------------+-------------------------------------------------+ +-----------------+-------------------------------------------------+
| 64497:5:528 | Do not export to EBGP neighbors in the | | 64497:5:528 | Do not export to EBGP neighbors in the |
| | Netherlands | | | Netherlands |
| 64497:5:392 | Do not export to EBGP neighbors in Japan | | 64497:5:392 | Do not export to EBGP neighbors in Japan |
| 64497:5:840 | Do not export to EBGP neighbors in the United | | 64497:5:840 | Do not export to EBGP neighbors in the United |
| | States of America | | | States of America |
skipping to change at page 8, line 34 skipping to change at page 8, line 34
As part of an agreement between AS 64497 and AS 64498, AS 64497 might As part of an agreement between AS 64497 and AS 64498, AS 64497 might
expose BGP traffic engineering functions to AS 64498. One such BGP expose BGP traffic engineering functions to AS 64498. One such BGP
traffic engineering function could be selective prepending of the traffic engineering function could be selective prepending of the
AS_PATH with AS 64497 to certain certain EBGP neighbors of AS 64497. AS_PATH with AS 64497 to certain certain EBGP neighbors of AS 64497.
4.2.1. ASN Based Selective AS_PATH Prepending 4.2.1. ASN Based Selective AS_PATH Prepending
AS 64497 could assign a value of 6 to the Function field to designate AS 64497 could assign a value of 6 to the Function field to designate
the content of the Parameter field as a neighboring ASN to which the content of the Parameter field as a neighboring ASN to which
prepending of the AS_PATH with AS 64497 is requested upon propagation prepending of the AS_PATH with AS 64497 is requested on propagation
of the route. Additional AS_PATH Prepending functions might also be of the route. Additional AS_PATH prepending functions might also be
defined to support multiples of prepending, that is two, three or defined to support multiples of prepending, that is two, three or
more prepends of AS 64497. more prepends of AS 64497.
+---------------------+------------------------------------------+ +---------------------+------------------------------------------+
| BGP Large Community | Description | | BGP Large Community | Description |
+---------------------+------------------------------------------+ +---------------------+------------------------------------------+
| 64497:6:64498 | Prepend 64497 once on export to AS 64498 | | 64497:6:64498 | Prepend 64497 once on export to AS 64498 |
| 64497:6:64499 | Prepend 64497 once on export to AS 64499 | | 64497:6:64499 | Prepend 64497 once on export to AS 64499 |
| 64497:6:65551 | Prepend 64497 once on export to AS 65551 | | 64497:6:65551 | Prepend 64497 once on export to AS 65551 |
+---------------------+------------------------------------------+ +---------------------+------------------------------------------+
skipping to change at page 9, line 10 skipping to change at page 9, line 10
the AS_PATH with AS 64497 when propagating the route to the specified the AS_PATH with AS 64497 when propagating the route to the specified
EBGP neighbor. EBGP neighbor.
Table 7: Action: Prepend to ASN Table 7: Action: Prepend to ASN
4.2.2. Location Based Selective AS_PATH Prepending 4.2.2. Location Based Selective AS_PATH Prepending
AS 64497 could assign a value of 7 to the Function field to designate AS 64497 could assign a value of 7 to the Function field to designate
the content of the Parameter field as an ISO 3166-1 numeric country the content of the Parameter field as an ISO 3166-1 numeric country
identifier to which the prepending of the AS_PATH with AS 64497 is identifier to which the prepending of the AS_PATH with AS 64497 is
requested upon propagation of the route to all EBGP neighbors in that requested on propagation of the route to all EBGP neighbors in that
region. region.
+------------------+------------------------------------------------+ +------------------+------------------------------------------------+
| BGP Large | Description | | BGP Large | Description |
| Community | | | Community | |
+------------------+------------------------------------------------+ +------------------+------------------------------------------------+
| 64497:7:528 | Prepend once to EBGP neighbors in the | | 64497:7:528 | Prepend once to EBGP neighbors in the |
| | Netherlands | | | Netherlands |
| 64497:7:392 | Prepend once to EBGP neighbors in Japan | | 64497:7:392 | Prepend once to EBGP neighbors in Japan |
| 64497:7:840 | Prepend once to EBGP neighbors in United | | 64497:7:840 | Prepend once to EBGP neighbors in United |
skipping to change at page 9, line 32 skipping to change at page 9, line 32
+------------------+------------------------------------------------+ +------------------+------------------------------------------------+
Example documentation for Action Communities deployed by AS 64497 to Example documentation for Action Communities deployed by AS 64497 to
expose a BGP traffic engineering function which selectively prepends expose a BGP traffic engineering function which selectively prepends
the AS_PATH with AS 64497 when propagating the route to all EBGP the AS_PATH with AS 64497 when propagating the route to all EBGP
neighbors in the geographical region specified in the Parameter neighbors in the geographical region specified in the Parameter
field. field.
Table 8: Action: Prepend in Region Table 8: Action: Prepend in Region
4.3. Manipulation of the LOCAL_PREF attribute 4.3. Manipulation of the LOCAL_PREF Attribute
As part of an agreement between AS 64497 and AS 64498, AS 64497 might As part of an agreement between AS 64497 and AS 64498, AS 64497 might
expose BGP traffic engineering functions to AS 64498. One such BGP expose BGP traffic engineering functions to AS 64498. One such BGP
traffic engineering function might allow AS 64498 to manipulate the traffic engineering function might allow AS 64498 to manipulate the
value of the LOCAL_PREF attribute of routes learned from AS 64498 value of the LOCAL_PREF attribute of routes learned from AS 64498
within AS 64497, even though the LOCAL_PREF attribute is non- within AS 64497, even though the LOCAL_PREF attribute is non-
transitive and therefore is not propagated to EBGP neighbors. transitive and is not propagated to EBGP neighbors.
The LOCAL_PREF value of routes are locally significant within each The LOCAL_PREF value of routes are locally significant within each AS
Autonomous System and therefore are impossible to list in this and are impossible to list in this document. Instead, the typical
document. Instead, the typical LOCAL_PREF values could be classified LOCAL_PREF values could be classified as a hierarchy and a BGP Large
as a hierarchy and a BGP Large Community function exposed allowing an Community function exposed allowing an EBGP neighbor to affect the
EBGP neighbor to affect the LOCAL_PREF value within the specified GA. LOCAL_PREF value within the specified GA. The following example list
The following non-exhaustive list defines the classes of routes in defines the classes of routes in the order of descending LOCAL_PREF
the order of descending LOCAL_PREF value and assigns a function value and assigns a function identifier which could be used in the
identifier which could be used in the Function field of a BGP Large Function field of a BGP Large Community.
Community.
+----------+--------------------------------------------------------+ +----------+--------------------------------------------------------+
| Function | Preference Class | | Function | Preference Class |
+----------+--------------------------------------------------------+ +----------+--------------------------------------------------------+
| 8 | Normal customer route. | | 8 | Normal customer route |
| 9 | Backup customer route. | | 9 | Backup customer route |
| 10 | Peering route. | | 10 | Peering route |
| 11 | Upstream transit route. | | 11 | Upstream transit route |
| 12 | Fallback route, to be installed if no other path is | | 12 | Fallback route, to be installed if no other path is |
| | available. | | | available |
+----------+--------------------------------------------------------+ +----------+--------------------------------------------------------+
Table 9: Action: Preference Function Identifiers Table 9: Action: Preference Function Identifiers
4.3.1. Global Manipulation of LOCAL_PREF 4.3.1. Global Manipulation of LOCAL_PREF
AS 64497 could place one of the previously defined Preference AS 64497 could place one of the previously defined Preference
Function Identifiers in the Function field and set the value 0 in the Function Identifiers in the Function field and set the value 0 in the
Parameter field to designate that the LOCAL_PREF associated with that Parameter field to designate that the LOCAL_PREF associated with that
function identifier should be applied for that route throughout the function identifier should be applied for that route throughout the
whole Autonomous System. whole AS.
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
| BGP Large Community | Description | | BGP Large Community | Description |
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
| 64497:9:0 | Assign LOCAL_PREF for a customer backup | | 64497:9:0 | Assign LOCAL_PREF for a customer backup |
| | route | | | route |
| 64497:10:0 | Assign LOCAL_PREF for a peering route | | 64497:10:0 | Assign LOCAL_PREF for a peering route |
| 64497:12:0 | Assign LOCAL_PREF for a fallback route | | 64497:12:0 | Assign LOCAL_PREF for a fallback route |
+---------------------+---------------------------------------------+ +---------------------+---------------------------------------------+
skipping to change at page 11, line 28 skipping to change at page 11, line 28
expose a BGP traffic engineering function which allows a BGP neighbor expose a BGP traffic engineering function which allows a BGP neighbor
to selectively manipulate the LOCAL_PREF attribute within AS 64497 in to selectively manipulate the LOCAL_PREF attribute within AS 64497 in
the geographical region specified in the Parameter field. the geographical region specified in the Parameter field.
Table 11: Action: Regional LOCAL_PREF Manipulation Table 11: Action: Regional LOCAL_PREF Manipulation
4.3.3. Note of Caution for LOCAL_PREF Functions 4.3.3. Note of Caution for LOCAL_PREF Functions
The LOCAL_PREF attribute strongly influences the BGP Decision The LOCAL_PREF attribute strongly influences the BGP Decision
Process, which in turn affects the scope of route propagation. Process, which in turn affects the scope of route propagation.
Therefore, Operators should take special care when using Action Operators should take special care when using Action Communities that
Communities that decrease the LOCAL_PREF value, and therefore the decrease the LOCAL_PREF value, and the degree of preference, to a
degree of preference, to a value below that of another route class. value below that of another route class. Some of the unintended BGP
Some of the unintended BGP states that might arise as a result of states that might arise as a result of these traffic engineering
these traffic engineering decisions are described as "BGP Wedgies" in decisions are described as "BGP Wedgies" in [RFC4264].
[RFC4264].
4.4. Route Server Prefix Distribution Control
Route Servers [RFC7947] use BGP to broker network reachability
information among their clients. As not all route server clients may
wish to interconnect with each other, the route server operator will
usually implement a mechanism to allow each client to control the
route server's export routing policy, as described in Section 4.6 of
[RFC7948]. One widely-used mechanism is a route server specific
adaption of "ASN Based Selective NO_EXPORT" (Section 4.1.1).
An example BGP Large Communities policy which enables client-
controlled prefix distribution for a route server operating as AS
64497, is outlined as follows:
+-------------------+-----------------------------------------------+
| BGP Large | Description |
| Community | |
+-------------------+-----------------------------------------------+
| 64497:0:peer-as | Explicitly prevent announcement of route to |
| | peer-as |
| 64497:1:peer-as | Explicitly announce route to peer-as |
| 64497:0:0 | Do not announce route to any peers by default |
| 64497:1:0 | Announce route to all peers by default |
+-------------------+-----------------------------------------------+
Table 12: Action: Route Server Prefix Distribution Control
Multiple BGP Large Community values can be used together to implement
fine-grained route distribution control. For example, route server
client AS 64500 might wish to use a route server for interconnecting
to all other clients except AS 64510. In this case, they would label
all their outbound routes to the route server with 64497:1:0 (to
announce to all clients by default) and 64497:1:64510 (to prevent
announcement to AS 64510).
Alternatively, route server client AS 64501 may have a selective
routing policy and may wish to interconnect with only AS 64505 and AS
64506. This could be implemented by announcing routes labeled with
64497:0:0 (blocking all distribution by default) and 64497:1:64505,
64497:1:64506 to instruct the route server to force announcement to
those two ASNs.
5. Security Considerations 5. Security Considerations
Network operators should note the recommendations in Section 11 of Operators should note the recommendations in Section 11 of BGP
BGP Operations and Security [RFC7454]. Operations and Security [RFC7454].
6. IANA Considerations 6. IANA Considerations
None. None.
7. Acknowledgments 7. Acknowledgments
The authors would like to gratefully acknowledge the insightful The authors would like to gratefully acknowledge the insightful
comments, contributions, critique and support from Adam Chappell, comments, contributions, critique and support from Adam Chappell,
Jonathan Stewart, and Will Hargrave. Jonathan Stewart, Greg Hankins, Nick Hilliard, Will Hargrave, and
Randy Bush.
8. References 8. References
8.1. Normative References 8.1. Normative References
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996, Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
<http://www.rfc-editor.org/info/rfc1997>. <http://www.rfc-editor.org/info/rfc1997>.
[RFC4264] Griffin, T. and G. Huston, "BGP Wedgies", RFC 4264,
DOI 10.17487/RFC4264, November 2005,
<http://www.rfc-editor.org/info/rfc4264>.
[RFC7454] Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations [RFC7454] Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454, and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
February 2015, <http://www.rfc-editor.org/info/rfc7454>. February 2015, <http://www.rfc-editor.org/info/rfc7454>.
[RFC8092] Heitz, J., Ed., Snijders, J., Ed., Patel, K., Bagdonas, [RFC8092] Heitz, J., Ed., Snijders, J., Ed., Patel, K., Bagdonas,
I., and N. Hilliard, "BGP Large Communities Attribute", I., and N. Hilliard, "BGP Large Communities Attribute",
RFC 8092, DOI 10.17487/RFC8092, February 2017, RFC 8092, DOI 10.17487/RFC8092, February 2017,
<http://www.rfc-editor.org/info/rfc8092>. <http://www.rfc-editor.org/info/rfc8092>.
8.2. URIs 8.2. Informative References
[1] http://nanog.net [RFC4264] Griffin, T. and G. Huston, "BGP Wedgies", RFC 4264,
DOI 10.17487/RFC4264, November 2005,
<http://www.rfc-editor.org/info/rfc4264>.
[2] http://nlnog.net [RFC7947] Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
"Internet Exchange BGP Route Server", RFC 7947,
DOI 10.17487/RFC7947, September 2016,
<http://www.rfc-editor.org/info/rfc7947>.
[RFC7948] Hilliard, N., Jasinska, E., Raszuk, R., and N. Bakker,
"Internet Exchange BGP Route Server Operations", RFC 7948,
DOI 10.17487/RFC7948, September 2016,
<http://www.rfc-editor.org/info/rfc7948>.
8.3. URIs
[1] https://www.nanog.org
[2] https://nlnog.net
[3] https://www.iso.org/iso-3166-country-codes.html [3] https://www.iso.org/iso-3166-country-codes.html
[4] https://unstats.un.org/unsd/methodology/m49/ [4] https://unstats.un.org/unsd/methodology/m49/
Authors' Addresses Authors' Addresses
Job Snijders Job Snijders
NTT Communications NTT Communications
Theodorus Majofskistraat 100 Theodorus Majofskistraat 100
Amsterdam 1065 SZ Amsterdam 1065 SZ
The Netherlands The Netherlands
Email: job@ntt.net Email: job@ntt.net
John Heasley John Heasley
NTT Communications NTT Communications
1111 NW 53rd Drive 1111 NW 53rd Drive
Portland, OR 97210 Portland, OR 97210
United States of America United States of America
Email: heas@shrubbery.net Email: heas@shrubbery.net
Martijn Schmidt Martijn Schmidt
i3D.net i3D.net
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