--- 1/draft-ietf-grow-large-communities-usage-02.txt 2017-03-12 03:13:09.086783393 -0700 +++ 2/draft-ietf-grow-large-communities-usage-03.txt 2017-03-12 03:13:09.118784160 -0700 @@ -1,482 +1,543 @@ Global Routing Operations J. Snijders Internet-Draft J. Heasley Intended status: Informational NTT -Expires: August 20, 2017 M. Schmidt +Expires: September 13, 2017 M. Schmidt i3D.net - February 16, 2017 + March 12, 2017 Usage of BGP Large Communities - draft-ietf-grow-large-communities-usage-02 + draft-ietf-grow-large-communities-usage-03 Abstract Examples and inspiration for operators for the use of BGP Large Communities. -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 [RFC2119]. - Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 http://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 August 20, 2017. + This Internet-Draft will expire on September 13, 2017. Copyright Notice Copyright (c) 2017 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 (http://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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 - 2. The Generic Design Pattern . . . . . . . . . . . . . . . . . 3 - 2.1. Informational Communities . . . . . . . . . . . . . . . . 3 + 2. The Design Overview . . . . . . . . . . . . . . . . . . . . . 2 + 2.1. Informational Communities . . . . . . . . . . . . . . . . 4 2.2. Action Communities . . . . . . . . . . . . . . . . . . . 4 - 3. Examples of Informational Communities . . . . . . . . . . . . 4 - 3.1. Location . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3.1.1. An ISO 3166-1 numeric function . . . . . . . . . . . 4 - 3.1.2. An UNSD region function . . . . . . . . . . . . . . . 5 - 3.2. Relation . . . . . . . . . . . . . . . . . . . . . . . . 5 + 3. Examples of Informational Communities . . . . . . . . . . . . 5 + 3.1. Location . . . . . . . . . . . . . . . . . . . . . . . . 5 + 3.1.1. An ISO 3166-1 numeric function . . . . . . . . . . . 5 + 3.1.2. A UN M.49 Region function . . . . . . . . . . . . . . 5 + 3.2. Relation Function . . . . . . . . . . . . . . . . . . . . 6 3.3. Combining Informational Communities . . . . . . . . . . . 6 - 4. Examples of Action Communities . . . . . . . . . . . . . . . 6 - 4.1. Selective NO_EXPORT . . . . . . . . . . . . . . . . . . . 6 - 4.1.1. Peer ASN Based Selective NO_EXPORT . . . . . . . . . 6 + 4. Examples of Action Communities . . . . . . . . . . . . . . . 7 + 4.1. Selective NO_EXPORT . . . . . . . . . . . . . . . . . . . 7 + 4.1.1. ASN Based Selective NO_EXPORT . . . . . . . . . . . . 7 4.1.2. Location Based Selective NO_EXPORT . . . . . . . . . 7 - 4.2. Selective AS_PATH Prepending . . . . . . . . . . . . . . 7 - 4.2.1. Peer ASN Based Selective AS_PATH Prepending . . . . . 7 - 4.2.2. Location Based Selective AS_PATH Prepending . . . . . 8 - 4.3. Location based manipulation of LOCAL_PREF . . . . . . . . 8 - 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 - 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 10 - 8.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 + 4.2. 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 + 4.3. Manipulation of the LOCAL_PREF attribute . . . . . . . . 9 + 4.3.1. Global 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 + 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 + 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 + 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 + 8.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 12 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction BGP Large Communities [RFC8092] provide a mechanism to signal opaque - information between Autonomous Systems. This document presents a set - of examples of how Large BGP Communities could be employed by an - operator to achieve various goals. This document draws from - experience in Operational Communities such as NANOG [1] and NLNOG - [2]. + information between Autonomous Systems. This document presents + examples of how operators might utilise BGP Large Communities to + achieve various goals. This document draws from experience of + operational communities such as NANOG [1] and NLNOG [2]. - The opaque nature of BGP Large Communities allows for rapid - deployment of new features or changes to the product. Operators are - encouraged to publicly publish and maintain documentation of the - purpose of each Large BGP Community, both informational and action, - that they support or are visible in looking glasses. +2. The Design Overview -2. The Generic Design Pattern + BGP Large Communities are composed of three 4-octet fields. The + first is the Global Administrator (GA) field, whose value is the + Autonomous System Number (ASN) of the Autonomous System (AS) that has + defined the meaning of the remaining two 4-octet fields, known as + "Local Data Part 1" and "Local Data Part 2". This document describes + an approach where the "Local Data Part 1" field contains a function + identifier and the "Local Data Part 2" contains a parameter value. - BGP Large Communities are composed of a 4-octet Global Administrator - field followed by two 4-octet Local Data fields. Large BGP - Communities are compose three 4-octet fields. The first is the - Global Administrator field, whose value is the ASN of AS that has - defined the meaning of the remaining two 4-octet fields, the Local - Data fields. This document describes an approach defining these - fields as "ASN:Function:Parameter"-approach to fill the three fields. + Using the canonical notation the above can be summarized as + "ASN:Function:Parameter". - In deployments of both BGP Communities [RFC1997] and BGP Large - Communities, two categories of Communities exist: + +----------------------+---------------+ + | RFC 8092 | this document | + +----------------------+---------------+ + | Global Administrator | ASN | + | Local Data Part 1 | Function | + | Local Data Part 2 | Parameter | + +----------------------+---------------+ + + A mapping table on the usage of fields in BGP Large Communities + between [RFC8092] and this document. + + Table 1: Field mapping + + In contemporary deployments of both BGP Communities [RFC1997] and BGP + Large Communities, the function of a community can be divided into + two categories: o Informational Communities o Action Communities - For each, ideas are provided regarding the contents of each of the - three fields in BGP Large Communities. - Throughout the document a topology of four Autonomous Systems is used to illustrate the usage of Communities in the following configuration: AS 65551 | ^ | AS 64497 / \ ^ \ / ^ AS 64498 \ | | `<->- AS 64499 - AS 64497 obtains transit services from AS 65551, a 32-bit ASN. AS - 64497 provides transit services to both AS 64498 and AS 64499. AS - 64498 and AS 64499 maintain a peering relationship in which they only - exchange their customer routes. + 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 + AS 64499. AS 64498 and AS 64499 maintain a peering relationship in + which they only exchange their customer routes. + + The opaque nature of BGP Large Communities allows for rapid + deployment of new features or changes to products. Operators are + encouraged to publicly publish and maintain documentation of the + purpose of each BGP Large Community, both informational and action, + that they support or are visible in BGP RIBs. 2.1. Informational Communities - Informational Communites are labels for attributes such as origin of - the route announcement, the relation with the EBGP neighbor or for - instance the intended propagation audience. Informational - Communities also assist in network operations such as debugging. + Informational Communities are labels for attributes such as the + origin of the route announcement, the nature of the relation with an + EBGP neighbor or the intended propagation audience. Informational + Communities can also assist in providing valuable information for + day-to-day network operations such as debugging or capacity planning. - The Global Administrator field is set to the ASN which is marking the + The Global Administrator field is set to the ASN which labels the routes with the Informational Communities. For example, AS 64497 - might add a community with the GA 64497 to a route learned from an - iBGP or eBGP peer that means that the route was learned from or - originated by a device in the Netherlands. + 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 + a certain geographical region. - In general the intended audience of Informational Communities are + In general, the intended audiences of Informational Communities are downstream networks and the Global Administrator itself, but any Autonomous System could benefit from receiving these communities. 2.2. Action Communities - Action Communities are attached to routes to request non-default - behaviour in this, a conferation or an external AS. Action - Communities could be used to change the route's propagation - characteristics, the LOCAL_PREFENCE or the number of AS_PATH prepends - to add when exporting or importing a route. + Action Communities are added as a label to request non-default + treatment of a route within an AS. The operator of that AS defines + routing policy which, based upon the communities, adjusts route + attributes such as its propagation characteristics, the LOCAL_PREF + (local preference), the next-hop, or the number of AS_PATH prepends + to be added upon reception or propagation. - The Global Administrator field is set to the ASN which is expected to - perform the action. For instance, AS 64499 might add a Large - Community with the GA 64497 to signal AS 64497 to perform an action - upon that route. + The Global Administrator field is set to the ASN which has defined + the functionality of that BGP Large Community and is therefore the + ASN that is expected to perform the action. For instance, AS 64499 + might label a route with a BGP Large Community containing GA 64497 to + request that AS 64497 perform a pre-defined action upon that route. - In general the intended audience of Action Communities is an upstream - provider, but realistically could be any AS willing to act upon it. + In general, the intended audience of Action Communities are transit + providers taking action on behalf of a customer or the Global + Administrator itself, but any AS could take action if they chose and + any AS could add an action community with the GA of a non-adjacent + ASN. However, note that an Action Community could also be + informational. Its presence is an indicator that the GA may have + performed the action and that an AS in the AS_PATH requested it. 3. Examples of Informational Communities 3.1. Location - AS 64497 can inform its downstream networks about the geographical - entity where AS 64497 learned a route by marking the route with BGP - Large Communities following one or a combination of the following - schemes. + An AS, AS 64497 in these examples, may inform other networks about + the geographical region where AS 64497 imported a route by labeling + it with BGP Large Communities following one of the following schemes + or a combination thereof. 3.1.1. An ISO 3166-1 numeric function - AS 64497 could assign a value of 1 to the first Local Data field to - designate the function of the second Local Data field as ISO-3166-1 - numeric country identifiers. + 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 + country identifier. - +---------------------+-------------------------------------------+ + +---------------------+---------------------------------------------+ | BGP Large Community | Description | - +---------------------+-------------------------------------------+ - | 64497:1:528 | Route learned in Netherlands | + +---------------------+---------------------------------------------+ + | 64497:1:528 | Route learned in the Netherlands | | 64497:1:392 | Route learned in Japan | - | 64497:1:840 | Route learned in United States of America | - +---------------------+-------------------------------------------+ + | 64497:1:840 | Route learned in the United States of | + | | America | + +---------------------+---------------------------------------------+ - Example documentation for AS 64497 using Informational Communities - describing the origin of routes using ISO 3166-1 numeric identifiers. + Example documentation for Informational Communities deployed by AS + 64497 to describe the location where a route was imported using ISO + 3166-1 numeric identifiers. - Table 1: Information: ISO 3166-1 + Table 2: Information: ISO 3166-1 -3.1.2. An UNSD region function +3.1.2. A UN M.49 Region function - AS 64497 could assign a value of 2 to the first Local Data field to - designate the function of the parameter in the second Local Data - field as an identifier for the macro geographical (continental) - regions, geographical sub-regions, or selected economic and other - groupings following a set of published identifiers by the United - Nations Statistics Division [3]. + 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 + by the United Nations Statistics Division (UNSD) [4] for macro + geographical (continental) regions, geographical sub-regions, or + selected economic and other groupings. +---------------------+-------------------------------+ | BGP Large Community | Description | +---------------------+-------------------------------+ | 64497:2:2 | Route learned in Africa | | 64497:2:9 | Route learned in Oceania | | 64497:2:145 | Route learned in Western Asia | | 64497:2:150 | Route learned in Europe | +---------------------+-------------------------------+ - Example documentation for AS 64497 using Informational Communities - describing the origin of routes using numeric identifiers provided by - the UN Statistics Division. + Example documentation for Informational Communities deployed by AS + 64497 to describe the location where a route was imported using M.49 + numeric codes published by the United Nations Statistics Division. - Table 2: Information: Regions + Table 3: Information: UNSD Regions -3.2. Relation +3.2. Relation Function - AS 64497 could assign a value of 3 to the first Local Data field to - designate that the second Local Data field contains an identifier - showing the relation with the EBGP neighbor from whom the route was - received. + An AS, AS 64497 in this example, could assign a value of 3 to the + Function field to designate the content of the Parameter field as a + number indicating whether the route originated inside its own network + or was learned externally, and if learned externally, it might + simultaneously characterize the nature of the relation with that + specific EBGP neighbor. - +---------------------+-----------------------------------------+ + +---------------------+---------------------------------------+ | BGP Large Community | Description | - +---------------------+-----------------------------------------+ - | 64497:3:1 | Route learned from a customer | - | 64497:3:2 | Route learned from a peering partner | - | 64497:3:3 | Route learned from an upstream provider | - +---------------------+-----------------------------------------+ + +---------------------+---------------------------------------+ + | 64497:3:1 | Route originated internally | + | 64497:3:2 | Route learned from a customer | + | 64497:3:3 | Route learned from a peering partner | + | 64497:3:4 | Route learned from a transit provider | + +---------------------+---------------------------------------+ - Example documentation for AS 64497 using Informational Communities - describing the relation with the ASN from which the route was - received. + Example documentation for Informational Communities deployed by AS + 64497 to describe the relation to the ASN from which the route was + learned. - Table 3: Information: Relation + Table 4: Information: Relation 3.3. Combining Informational Communities - Multiple Informational Communities can be tagged on a route, for - example: a route learned in the Netherlands from a customer can - contain both 64497:1:528 and 64497:2:150 and 64497:3:1. + A route may be labeled with multiple Informational Communities. For + example, a route learned in the Netherlands from a customer might be + labeled with communities 64497:1:528, 64497:2:150 and 64497:3:2 at + the same time. 4. Examples of Action Communities 4.1. Selective NO_EXPORT - As part of the commercial agreement between AS 64497 and AS 64498, AS - 64497 might offer AS 64498 certain BGP Traffic Engineering features - such as selectively not export routes learned from 64498 to certain - EBGP neighbors of AS 64497. + As part of an agreement, often a commercial transit agreement, + between AS 64497 and AS 64498, AS 64497 might expose BGP traffic + engineering functions to AS 64498. One such BGP traffic engineering + function could be selective NO_EXPORT, which is the selective + filtering of a route learned from one AS, AS 64498, to certain EBGP + neighbors of the GA, AS 64497. -4.1.1. Peer ASN Based Selective NO_EXPORT +4.1.1. ASN Based Selective NO_EXPORT - AS 64497 might assign function identifier 4 to allow preventing - propagation of routes to the ASN listed in the second Local Data - field. + AS 64497 could assign a value of 4 to the Function field to designate + the content of the Parameter field as a neighboring ASN to which a + route should not be propagated. +---------------------+---------------------------------+ | BGP Large Community | Description | +---------------------+---------------------------------+ - | 64497:4:2914 | Do not export route to AS 2914 | - | 64497:4:7018 | Do not export route to AS 7018 | + | 64497:4:64498 | Do not export route to AS 64498 | + | 64497:4:64499 | Do not export route to AS 64499 | | 64497:4:65551 | Do not export route to AS 65551 | +---------------------+---------------------------------+ - Example documentation for AS 64497 offering Action Communities to - limit propagation of routes based on the Peer ASN described in the - third field. + Example documentation for Action Communities deployed by AS 64497 to + expose a BGP traffic engineering function which selectively prevents + the propagation of routes to the neighboring ASN specified in the + Parameter field. - Table 4: Action: Peer ASN NO_EXPORT + Table 5: Action: ASN NO_EXPORT 4.1.2. Location Based Selective NO_EXPORT - AS 64497 might assign function identifier 5 to allow its customers to - request selectively not exporting routes on EBGP sessions within a - certain geographical area. This example follows the ISO 3166-1 - numeric encoding. + 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 + identifier within which a labeled route is not propagated to EBGP + neighbors. However this might not prevent one of those EBGP + neighbors from learning that route in another country and thereby + making it available in the country specified by the BGP Large + Community. - +------------------+------------------------------------------------+ + +-----------------+-------------------------------------------------+ | BGP Large | Description | | Community | | - +------------------+------------------------------------------------+ + +-----------------+-------------------------------------------------+ | 64497:5:528 | Do not export to EBGP neighbors in the | | | Netherlands | | 64497:5:392 | Do not export to EBGP neighbors in Japan | - | 64497:5:840 | Do not export to EBGP neighbors in United | + | 64497:5:840 | Do not export to EBGP neighbors in the United | | | States of America | - +------------------+------------------------------------------------+ + +-----------------+-------------------------------------------------+ - Example documentation for AS 64497 offering Action Communities to - trigger NO_EXPORT on routes only when propagating the route to a - certain geographical region. + Example documentation for Action Communities deployed by AS 64497 to + expose a BGP traffic engineering function which selectively prevents + the propagation of routes to all EBGP neighbors in the geographical + region specified in the Parameter field. - Table 5: Action: NO_EXPORT in Region + Table 6: Action: NO_EXPORT in Region 4.2. Selective AS_PATH Prepending - As part of the commercial agreement between AS 64497 and AS 64498, AS - 64497 might offer AS 64498 certain BGP Traffic Engineering features - such as selectively prepending the AS_PATH with 64497's ASN to - certain EBGP neighbors of AS 64497. + 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 + traffic engineering function could be selective prepending of the + AS_PATH with AS 64497 to certain certain EBGP neighbors of AS 64497. -4.2.1. Peer ASN Based Selective AS_PATH Prepending +4.2.1. ASN Based Selective AS_PATH Prepending - AS 64497 might assign function identifier 6 to allow prepending the - AS_PATH on propagation of routes to the ASN listed in the second - Local Data field. + 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 + prepending of the AS_PATH with AS 64497 is requested upon propagation + of the route. Additional AS_PATH Prepending functions might also be + defined to support multiples of prepending, that is two, three or + more prepends of AS 64497. +---------------------+------------------------------------------+ | BGP Large Community | Description | +---------------------+------------------------------------------+ - | 64497:6:2914 | Prepend 64497 once on export to AS 2914 | - | 64497:6:7018 | Prepend 64497 once on export to AS 7018 | + | 64497:6:64498 | Prepend 64497 once on export to AS 64498 | + | 64497:6:64499 | Prepend 64497 once on export to AS 64499 | | 64497:6:65551 | Prepend 64497 once on export to AS 65551 | +---------------------+------------------------------------------+ - Example documentation for AS 64497 offering Action Communities to - trigger prepending of the AS_PATH only when propagating the route to - a certain Peer ASN. + Example documentation for Action Communities deployed by AS 64497 to + expose a BGP traffic engineering function which selectively prepends + the AS_PATH with AS 64497 when propagating the route to the specified + EBGP neighbor. - Table 6: Action: Prepend to Peer ASN + Table 7: Action: Prepend to ASN 4.2.2. Location Based Selective AS_PATH Prepending - AS 64497 might assign function identifier 7 to allow prepending of - the AS_PATH on propagation of routes to on any EBGP neighbor's - interconnection in the geographical entity listed in the second Local - Data field. This example follows the ISO 3166-1 numeric regions - codes in the Local Data 2 field. + 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 + 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 + region. +------------------+------------------------------------------------+ | BGP Large | Description | | Community | | +------------------+------------------------------------------------+ | 64497:7:528 | Prepend once to EBGP neighbors in the | | | Netherlands | | 64497:7:392 | Prepend once to EBGP neighbors in Japan | | 64497:7:840 | Prepend once to EBGP neighbors in United | | | States of America | +------------------+------------------------------------------------+ - Example documentation for AS 64497 offering Action Communities to - trigger prepending of the AS_PATH only when propagating the route to - a certain geographical region. + Example documentation for Action Communities deployed by AS 64497 to + expose a BGP traffic engineering function which selectively prepends + the AS_PATH with AS 64497 when propagating the route to all EBGP + neighbors in the geographical region specified in the Parameter + field. - Table 7: Action: Prepend in Region + Table 8: Action: Prepend in Region -4.3. Location based manipulation of LOCAL_PREF +4.3. Manipulation of the LOCAL_PREF attribute - In some cases, it can be desirable for an autonomous system to allow - adjacent Autonomous Systems to directly influence the degree of - preference associated with a route, usually expressed within the - LOCAL_PREF attribute. + 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 + traffic engineering function might allow AS 64498 to manipulate the + value of the LOCAL_PREF attribute of routes learned from AS 64498 + within AS 64497, even though the LOCAL_PREF attribute is non- + transitive and therefore is not propagated to EBGP neighbors. - Furthermore, in the case of large networks spanning significant - geography, it is often also useful to be able to extend this - capability and scope its effect to a geographic region. This is a - more powerful mechanism than AS_PATH prepending, but since degree of - preference determines BGP route selection and thus onward - advertisement, it can also be self-limiting in its scope. + The LOCAL_PREF value of routes are locally significant within each + Autonomous System and therefore are impossible to list in this + document. Instead, the typical LOCAL_PREF values could be classified + as a hierarchy and a BGP Large Community function exposed allowing an + EBGP neighbor to affect the LOCAL_PREF value within the specified GA. + The following non-exhaustive list defines the classes of routes in + the order of descending LOCAL_PREF value and assigns a function + identifier which could be used in the Function field of a BGP Large + Community. - Since the LOCAL_PREF attribute which influences degree of preference - is locally significant within each autonomous system, it is not - usually practical or useful to compare LOCAL_PREF attribute values - between autonomous systems. Instead it can be useful to classify the - major types of route likely to exist within an autonomous system's - routing hierarchy and provide an ability to set one's route to that - preference: + +----------+--------------------------------------------------------+ + | Function | Preference Class | + +----------+--------------------------------------------------------+ + | 8 | Normal customer route. | + | 9 | Backup customer route. | + | 10 | Peering route. | + | 11 | Upstream transit route. | + | 12 | Fallback route, to be installed if no other path is | + | | available. | + +----------+--------------------------------------------------------+ - o A qualified customer route. Usually the highest preference. + Table 9: Action: Preference Function Identifiers - o A peer, or network-share, route. A co-operating network provider - engaged in a partnership for customer coverage ("peering"). +4.3.1. Global Manipulation of LOCAL_PREF - o A last resort, or backup route. + AS 64497 could place one of the previously defined Preference + Function Identifiers in the Function field and set the value 0 in the + Parameter field to designate that the LOCAL_PREF associated with that + function identifier should be applied for that route throughout the + whole Autonomous System. - It is entirely possible that some providers may have more classes of - route preference but it is possible to codify both the route - preference class and the regional scope within the Local Data fields - of the Large Community attribute. + +---------------------+---------------------------------------------+ + | BGP Large Community | Description | + +---------------------+---------------------------------------------+ + | 64497:9:0 | Assign LOCAL_PREF for a customer backup | + | | route | + | 64497:10:0 | Assign LOCAL_PREF for a peering route | + | 64497:12:0 | Assign LOCAL_PREF for a fallback route | + +---------------------+---------------------------------------------+ - For example, AS64497 might establish the following function - identifiers to set route preference class, which could allow pairing - with a location or peer-based operand to determine scope. + Example documentation for Action Communities deployed by AS 64497 to + expose a BGP traffic engineering function which allows a BGP neighbor + to globally manipulate the LOCAL_PREF attribute for the route within + AS 64497. - +----------+-----------------------------------------------+ - | Function | Preference Class | - +----------+-----------------------------------------------+ - | 10 | Qualified customer route. Highest preference. | - | 15 | Peering partner. Median preference. | - | 19 | Route of last resort. Lowest preference. | - +----------+-----------------------------------------------+ + Table 10: Action: Global LOCAL_PREF Manipulation - Table 8: Action: Preference Function Identifiers +4.3.2. Location Based Manipulation of LOCAL_PREF - Once established, these route preference setting functions can be - linked with a scoping operand such as per-peer or per-location based - identifiers in order to provide AS64497's customers with a - comprehensive and rich toolset to influence route preference. + AS 64497 could place one of the previously defined Preference + Function Identifiers in the Function field and use an ISO 3166-1 + numeric country identifier in the Parameter field to designate the + geographical region within which the non-default LOCAL_PREF + associated with that function identifier should be applied to the + route. The value of the LOCAL_PREF attribute should not deviate from + the default for that route class in any region not specified by one + or more of these Action Communities. - +--------------------+----------------------------------------------+ + +--------------+----------------------------------------------------+ | BGP Large | Description | | Community | | - +--------------------+----------------------------------------------+ - | 64497:15:528 | Set as peer route in Netherlands | - | 64497:19:840 | Set as backup route in United States of | - | | America | - +--------------------+----------------------------------------------+ + +--------------+----------------------------------------------------+ + | 64497:9:528 | Assign LOCAL_PREF for a customer backup route on | + | | BGP speakers in the Netherlands | + | 64497:10:392 | Assign LOCAL_PREF for a peering route on BGP | + | | speakers in Japan | + | 64497:12:840 | Assign LOCAL_PREF for a fallback route on BGP | + | | speakers in United States of America | + +--------------+----------------------------------------------------+ - Table 9: Action: Regional Preference Communities + Example documentation for Action Communities deployed by AS 64497 to + expose a BGP traffic engineering function which allows a BGP neighbor + to selectively manipulate the LOCAL_PREF attribute within AS 64497 in + the geographical region specified in the Parameter field. - Since the degree of preference influences BGP best path selection - (which in turn influences onward route propagation) Operators should - take special care with a traffic engineering tool such as location - based local preference influence (BGP Wedgies [RFC4264]). + Table 11: Action: Regional LOCAL_PREF Manipulation + +4.3.3. Note of Caution for LOCAL_PREF Functions + + The LOCAL_PREF attribute strongly influences the BGP Decision + Process, which in turn affects the scope of route propagation. + Therefore, Operators should take special care when using Action + Communities that decrease the LOCAL_PREF value, and therefore the + degree of preference, to a value below that of another route class. + Some of the unintended BGP states that might arise as a result of + these traffic engineering decisions are described as "BGP Wedgies" in + [RFC4264]. 5. Security Considerations Network operators should note the recommendations in Section 11 of BGP Operations and Security [RFC7454]. 6. IANA Considerations None. -7. Acknowledgements +7. Acknowledgments The authors would like to gratefully acknowledge the insightful - comments, contributions, critique and support from John Heasley, Adam - Chappell, Jonathan Stewart, and Will Hargrave. + comments, contributions, critique and support from Adam Chappell, + Jonathan Stewart, and Will Hargrave. 8. References 8.1. Normative References [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996, . - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, - DOI 10.17487/RFC2119, March 1997, - . - [RFC4264] Griffin, T. and G. Huston, "BGP Wedgies", RFC 4264, DOI 10.17487/RFC4264, November 2005, . [RFC7454] Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454, February 2015, . [RFC8092] Heitz, J., Ed., Snijders, J., Ed., Patel, K., Bagdonas, I., and N. Hilliard, "BGP Large Communities Attribute", RFC 8092, DOI 10.17487/RFC8092, February 2017, . 8.2. URIs [1] http://nanog.net [2] http://nlnog.net - [3] http://unstats.un.org/unsd/methods/m49/m49regin.htm + [3] https://www.iso.org/iso-3166-country-codes.html + + [4] https://unstats.un.org/unsd/methodology/m49/ Authors' Addresses Job Snijders NTT Communications Theodorus Majofskistraat 100 Amsterdam 1065 SZ The Netherlands Email: job@ntt.net @@ -473,25 +534,24 @@ Authors' Addresses Job Snijders NTT Communications Theodorus Majofskistraat 100 Amsterdam 1065 SZ The Netherlands Email: job@ntt.net - John Heasley NTT Communications - 12160 NW Coleman Drive - Portland, OR 97229 + 1111 NW 53rd Drive + Portland, OR 97210 United States of America Email: heas@shrubbery.net Martijn Schmidt i3D.net Rivium 1e Straat 1 Capelle aan den IJssel 2909 LE NL