Internet-Draft One Administrative Domain July 2024
Uttaro, et al. Expires 9 January 2025 [Page]
Workgroup:
Inter-Domain Routing
Internet-Draft:
draft-uttaro-idr-bgp-oad-04
Published:
Intended Status:
Standards Track
Expires:
Authors:
J. Uttaro
Individual Contributor
A. Retana
Futurewei Technologies, Inc.
P. Mohapatra
Google
K. Patel
Arrcus, Inc.
B. Wen
Comcast

One Administrative Domain using BGP

Abstract

This document defines a new External BGP (EBGP) peering type known as EBGP-OAD, which is used between two EBGP peers that belong to One Administrative Domain (OAD).

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 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 9 January 2025.

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Table of Contents

1. Introduction

At each EBGP boundary, BGP path attributes are modified as per [RFC4271], which includes stripping any attributes not allowed over an EBGP session. An example is the LOCAL_PREF attribute.

Some networks span more than one autonomous system and require more flexibility in the propagation of path attributes. It is worth noting that these multi-AS networks have a common or single administrative entity. These networks are said to belong to One Administrative Domain (OAD). It is desirable to have the ability to carry any attribute across EBGP peerings when the peers belong to an OAD.

This document defines a new EBGP peering type known as EBGP-OAD, which is used between two EBGP peers that belong to an OAD. This document also defines rules for route announcement and processing for EBGP-OAD peers.

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

2. Discussion

Networks have traditionally been demarcated by an autonomous system/BGP border, which correlates to an administrative boundary. This paradigm no longer serves the needs of network designers or customers due to the decoupling of the Interior Gateway Protocol (IGP) from BGP, BGP-free core in the underlay (e.g., using BGP labeled unicast [RFC8277]), the use of BGP to facilitate multiple service overlays (e.g., L2VPN, L3VPN, etc.) spanning multiple regions and AS domains, and the instantiation of customer sites on multiple content service providers (CSPs).

For example, sites in a BGP/MPLS VPN [RFC4364] may be distributed across different AS domains. In some cases, the administrator of the VPN may prefer that some attributes are propagated to all their sites to influence the BGP decision process.

3. Operation

[RFC4271] defines two types of BGP peerings used during a BGP protocol session. As part of the extensions defined in this document, EBGP peering is divided into two types:

  1. EBGP as defined in [RFC4271].
  2. EBGP-OAD as defined below.

The EBGP-OAD session is a BGP connection between peers in different Autonomous Systems that belong to an OAD. By default, the EBGP-OAD speakers follow the EBGP route advertisement, route processing, path attribute announcement, and processing rules as defined in [RFC4271].

EBGP-OAD peers handle receiving optional transitive attributes as specified in [RFC4271]. Unrecognized non-transitive optional attributes MUST be quietly ignored and not passed along to other BGP peers.

Unless explicitly specifed, EBGP-OAD speakers are allowed to announce and receive any attribute over an EBGP-OAD session. Receiving any attribute over an EBGP-OAD session MUST NOT result in an error. For example, the ORIGINATOR_ID (Section 3.9) and the CLUSTER_LIST (Section 3.10) are not allowed over EBGP-OAD sessions.

EBGP-OAD sessions MUST comply with the behavior specified in [RFC8212]. Furthermore, the propagation of attributes not allowed over EBGP sessions (see Table 1) MUST be explicitly allowed by an Export Policy, and their reception SHOULD be explicitly allowed by an Import Policy.

An EBGP-OAD speaker MUST support four-octet AS numbers and advertise the "support for four-octet AS number capability" [RFC6793].

This section addresses all path attributes defined at the time of this writing that are not marked as "deprecated" in the "BGP Path Attributes" registry [IANA-BGP-ATTRS]. The following subsections specify the behavior for each path attribute as related to an EBGP-OAD session. Table 1 summarizes the behavior for all session types.

Documents specifying new path attributes MUST indicate whether they are allowed for each session type: IBGP, EBGP, and EBGP-OAD.

3.1. ORIGIN

The ORIGIN attribute is a well-known mandatory BGP path attribute [RFC4271] that MUST be present in UPDATE messages sent over EBGP-OAD sessions. Its origination and value MUST comply with the specification in [RFC4271].

3.2. AS_PATH

The AS_PATH attribute is a well-known mandatory BGP path attribute [RFC4271]. It SHOULD be present in UPDATE messages sent over EBGP-OAD sessions unless it has been replaced by the BGPsec_PATH attribute [RFC8205]. The origination and modification of the AS_PATH attribute MUST comply with the EBGP-related specification in [RFC4271].

3.3. NEXT_HOP

The NEXT_HOP attribute is a well-known mandatory BGP path attribute [RFC4271] that SHOULD be present in UPDATE messages sent over EBGP-OAD sessions [RFC4760]. The origination and modification of the NEXT_HOP attribute MUST comply with the EBGP-related specification in [RFC4271].

It is reasonable for members of an OAD to share a common reachability domain. In such a case, the NEXT_HOP attribute MAY be left unchanged.

3.4. MULTI_EXIT_DISC

The MULTI_EXIT_DISC attribute is an optional non-transitive BGP path attribute [RFC4271] that MAY be present in UPDATE messages sent over EBGP-OAD sessions, even if it has been received from a neighboring AS. Otherwise, the use of the MULTI_EXIT_DISC attribute MUST comply with the specification in [RFC4271].

The determination of the neighboring AS for the purpose of BGP Route Selection [RFC4271] MAY ignore the ASNs of other members of the OAD. If so, all the members of the OAD SHOULD be configured to use the same criteria. Failure to do so may result in inconsistent forwarding between members of the OAD. Care should also be taken to avoid the creation of persistent route oscillations, similar to the Type II Churn described in [RFC3345]. [RFC7964] provides solutions and recommendations to address this issue.

3.5. LOCAL_PREF

The LOCAL_PREF attribute is a well-known BGP path attribute [RFC4271] that MAY be present in UPDATE messages sent over EBGP-OAD sessions. The use of the LOCAL_PREF attribute MUST comply with the specification in [RFC4271].

3.6. ATOMIC_AGGREGATE

The ATOMIC_AGGREGATE attribute is a well-known discretionary BGP path attribute [RFC4271] that MAY be present in UPDATE messages sent over EBGP-OAD sessions. The use of the ATOMIC_AGGREGATE attribute MUST comply with the specification in [RFC4271].

3.7. AGGREGATOR

The AGGREGATOR attribute is an optional transitive BGP path attribute [RFC4271] that MAY be present in UPDATE messages sent over EBGP-OAD sessions. The use of the AGGREGATOR attribute MUST comply with the specification in [RFC4271].

3.8. COMMUNITIES

The COMMUNITIES attribute is an optional transitive BGP path attribute [RFC1997] that MAY be present in UPDATE messages sent over EBGP-OAD sessions. The advertisement semantics MUST comply with the specification in [RFC1997].

Routes with a COMMUNITIES attribute containing the well-known NO_EXPORT community [RFC1997] SHOULD NOT be advertised across an EBGP-OAD session unless allowed by explicit policy configuration. If allowed, all the members of the OAD SHOULD be configured to use the same criteria. Failure to do so may result in inconsistent forwarding between members of the OAD.

Routes with a COMMUNITIES attribute containing the well-known NO_EXPORT_SUBCONFED community [RFC1997] MUST NOT be advertised across an EBGP-OAD session.

3.9. ORIGINATOR_ID

The ORIGINATOR_ID attribute is an optional non-transitive BGP path attribute [RFC4456] that MUST NOT be advertised over an EBGP-OAD session. If received from an EBGP-OAD neighbor, it SHALL be discarded using the "attribute discard" approach [RFC7606]. An implementation MAY log an error message for further analysis.

3.10. CLUSTER_LIST

The CLUSTER_LIST attribute is an optional non-transitive BGP path attribute [RFC4456] that MUST NOT be advertised over an EBGP-OAD session. If received from an EBGP-OAD neighbor, it SHALL be discarded using the "attribute discard" approach [RFC7606]. An implementation MAY log an error message for further analysis.

3.11. MP_REACH_NLRI

The MP_REACH_NLRI attribute is an optional non-transitive BGP path attribute [RFC4760] that MAY be advertised over an EBGP-OAD session. The use of the MP_REACH_NLRI attribute MUST comply with the EBGP-related specification in [RFC4760].

It is reasonable for members of an OAD to share a common reachability domain. In such a case, the Next Hop in the MP_REACH_NLRI attribute MAY be left unchanged.

3.12. MP_UNREACH_NLRI

The MP_UNREACH_NLRI attribute is an optional non-transitive BGP path attribute [RFC4760] that MAY be advertised over an EBGP-OAD session. The use of the MP_UNREACH_NLRI attribute MUST comply with the specification in [RFC4760].

3.13. EXTENDED COMMUNITIES

The EXTENDED COMMUNITIES attribute is a transitive optional BGP path attribute [RFC4360] that MAY be advertised over an EBGP-OAD session.

Extended communities which are non-transitive across an AS boundary MAY be advertised over an EBGP-OAD session if allowed by explicit policy configuration. If allowed, all the members of the OAD SHOULD be configured to use the same criteria. For example, the Origin Validation State Extended Community, defined as non-transitive in [RFC8097], can be advertised to peers in the same OAD.

3.14. AS4_PATH

The AS4_PATH attribute is an optional transitive BGP path attribute [RFC6793] that MAY be advertised over an EBGP-OAD session. The use of the AS4_PATH attribute MUST comply with the specification in [RFC6793].

3.15. AS4_AGGREGATOR

The AS4_AGGREGATOR attribute is an optional transitive BGP path attribute [RFC6793] that MAY be advertised over an EBGP-OAD session. The use of the AS4_AGGREGATOR attribute MUST comply with the specification in [RFC6793].

3.16. PMSI_TUNNEL

The PMSI_TUNNEL attribute is an optional transitive BGP path attribute [RFC6514] that MAY be advertised over an EBGP-OAD session. The use of the PMSI_TUNNEL attribute MUST comply with the EBGP-related specification in [RFC6514].

3.17. Tunnel Encapsulation

The Tunnel Encapsulation attribute is an optional transitive BGP path attribute [RFC9012] that MAY be advertised over an EBGP-OAD session. The use of the Tunnel Encapsulation attribute MUST comply with the EBGP-related specification in [RFC9012].

3.18. Traffic Engineering

The Traffic Engineering attribute is an optional non-transitive BGP path attribute [RFC5543] that MAY be advertised over an EBGP-OAD session. The use of the Traffic Engineering attribute MUST comply with the specification in [RFC5543].

3.19. IPv6 Address Specific Extended Community

The IPv6 Address Specific Extended Community attribute is an optional transitive BGP path attribute [RFC5701] that MAY be advertised over an EBGP-OAD session.

Extended communities which are non-transitive across Autonomous Systems MAY be advertised over an EBGP-OAD session if allowed by explicit policy configuration. If allowed, all the members of the OAD SHOULD be configured to use the same criteria.

3.20. AIGP

The AIGP attribute is an optional non-transitive BGP path attribute [RFC7311] that MAY be advertised over an EBGP-OAD session. The default value of AIGP_SESSION [RFC7311] MUST be "disabled" and it MAY be "enabled" by explicit policy configuration. The use of the AIGP attribute MUST comply with the specification in [RFC7311].

3.21. PE Distinguisher Labels

The PE Distinguisher Labels attribute is an optional transitive BGP path attribute [RFC6514] that MAY be advertised over an EBGP-OAD session. The use of the PE Distinguisher Labels attribute MUST comply with the specification in [RFC6513] and [RFC6514].

3.22. BGP-LS Attribute

The BGP Link-State (BGP-LS) attribute is an optional non-transitive BGP path attribute [RFC9552] that MAY be advertised over an EBGP-OAD session. The use of the BGP-LS Attribute MUST comply with the specification in [RFC9552].

3.23. LARGE_COMMUNITY

The LARGE_COMMUNITY attribute is an optional transitive BGP path attribute [RFC8092] that MAY be advertised over an EBGP-OAD session. The use of the LARGE_COMMUNITY attribute MUST comply with the specification in [RFC8092].

3.24. BGPsec_PATH

The BGPsec_PATH attribute is an optional non-transitive BGP path attribute [RFC8205] that MAY be advertised over an EBGP-OAD session. The use of the BGPsec_PATH attribute MUST comply with the specification in [RFC8205].

3.25. BGP Community Container

The BGP Community Container attribute is an optional transitive BGP path attribute [WIDE] that MAY be advertised over an EBGP-OAD session.

In particular, communities with the T bit [WIDE] not set MAY be advertised over an EBGP-OAD session if allowed by explicit policy configuration. Communities with the T bit set MUST be advertised over an EBGP-OAD session. Communities with the C bit [WIDE] not set MUST NOT be advertised over an EBGP-OAD session. Communities with the C bit set MAY be advertised over an EBGP-OAD session if allowed by explicit policy configuration. In all cases, all the members of the OAD SHOULD be configured to use the same criteria.

3.26. Only to Customer

The Only to Customer (OTC) attribute is an optional transitive BGP path attribute [RFC9234] that MAY be advertised over an EBGP-OAD session. However, the BGP Role negotiation and OTC Attribute-based procedures specified in [RFC9234] are NOT RECOMMENDED to be used between peers using an EBGP-OAD session. If received, the OTC attribute MUST be preserved unchanged. The use and negotiation of BGP Roles between EBGP-OAD peers is outside the scope of this document.

3.27. D-PATH

The Domain Path (D-PATH) attribute is an optional transitive BGP path attribute [IPVPN] that MAY be advertised over an EBGP-OAD session. The use of the D-PATH attribute MUST comply with the specification in [IPVPN].

3.28. SFP

The Service Function Path (SFP) attribute is an optional transitive BGP path attribute [RFC9015] that MAY be advertised over an EBGP-OAD session. The use of the SFP attribute MUST comply with the specification in [RFC9015].

3.29. BFD Discriminator

The BFD Discriminator attribute is an optional transitive BGP path attribute [RFC9026] that MAY be advertised over an EBGP-OAD session. The use of the BFD Discriminator attribute MUST comply with the specification in [RFC9026].

3.30. BGP Router Capabilities

The BGP Router Capabilities attribute (RCA) is an optional transitive BGP path attribute [ENTROPY] that MAY be advertised over an EBGP-OAD session. The use of the RCA attribute MUST comply with the specification in [ENTROPY].

3.31. BGP Prefix-SID

The BGP Prefix-SID attribute is an optional transitive BGP path attribute [RFC8669] that MAY be advertised over an EBGP-OAD session. The use of the BGP Prefix-SID attribute MUST comply with the specification in [RFC8669].

3.32. ATTR_SET

The ATTR_SET attribute is an optional transitive BGP path attribute [RFC6368] that MAY be advertised over an EBGP-OAD session. The use of the ATTR_SET attribute MUST comply with the specification in [RFC6368].

3.33. Summary Table

Table 1: Path Attribute Behavior
Path Attribute EBGP IBGP EBGP-OAD Reference
ORIGIN Mandatory Mandatory Mandatory Section 3.1
AS_PATH Optional Optional Optional Section 3.2
NEXT_HOP Optional Optional Optional Section 3.3
MULTI_EXIT_DISC Optional Optional Optional Section 3.4
LOCAL_PREF Not allowed Mandatory Optional Section 3.5
ATOMIC_AGGREGATE Optional Optional Optional Section 3.6
AGGREGATOR Optional Optional Optional Section 3.7
COMMUNITIES Optional Optional Optional Section 3.8
ORIGINATOR_ID Not Allowed Optional Not allowed Section 3.9
CLUSTER_LIST Not Allowed Optional Not allowed Section 3.10
MP_REACH_NLRI Optional Optional Optional Section 3.11
MP_UNREACH_NLRI Optional Optional Optional Section 3.12
EXTENDED COMMUNITIES Optional Optional Optional Section 3.13
AS4_PATH Optional Optional Optional Section 3.14
AS4_AGGREGATOR Optional Optional Optional Section 3.15
PMSI_TUNNEL Optional Optional Optional Section 3.16
Tunnel Encapsulation Optional Optional Optional Section 3.17
Traffic Engineering Not Allowed Optional Optional Section 3.18
IPv6 Address Specific Extended Community Optional Optional Optional Section 3.19
AIGP Optional Optional Optional Section 3.20
PE Distinguisher Labels Optional Optional Optional Section 3.21
BGP-LS Attribute Not Allowed Optional Optional Section 3.22
LARGE_COMMUNITY Optional Optional Optional Section 3.23
BGPsec_PATH Optional Optional Optional Section 3.24
BGP Community Container Optional Optional Optional Section 3.25
Only to Customer Optional Optional Optional Section 3.26
D-PATH Optional Optional Optional Section 3.27
SFP Optional Optional Optional Section 3.28
BFD Discriminator Optional Optional Optional Section 3.29
BGP Router Capabilities Optional Optional Optional Section 3.30
BGP Prefix-SID Optional Optional Optional Section 3.31
ATTR_SET Optional Optional Optional Section 3.32

4. Changes to the Decision Process

Section 9 of [RFC4271] describes the BGP Decision Process to select routes for local forwarding and subsequent advertisement. Section 9.1.2.2 of [RFC4271] describes tie breaking procedures in cases where a BGP speaker has several routes to the same destination. This document modifies step d) as follows:

d)
If at least one of the candidate routes was received via EBGP, remove from consideration all routes that were received via EBGP-OAD and IBGP. If at least one of the candidate routes was received via EBGP-OAD, remove from consideration all routes that were received via IBGP.

The algorithm defined in [RFC5004] to avoid unnecessary path transitions between external paths MUST be used when the routes considered were received via EBGP-OAD.

5. Deployment and Operational Considerations

For the Import and Export Policies to behave as expected, both EBGP-OADGP speakers must be configured with the same session type. If only one BGP speaker is configured that way, and the other uses an EBGP session, the result is that some path attributes may be ignored and others will be discarded.

The default BGP peering type for a session that is across autonomous systems SHOULD be EBGP. A BGP implementation SHOULD provide a configuration-time option to enable the EBGP-OAD session type. The session type may be changed once the BGP connection has been established.

If multiple peerings exist between autonomous systems that belong to an OAD, all SHOULD be configured consistently. Improper configuration may result in inconsistent or unexpected forwarding. The inconsistent use of EBGP-OAD sessions is out of scope of this document.

BGP Confederations [RFC5065] provide similar behavior, on a session by session basis, as what is specified in this document. The use of confederations with an EBGP-OAD peering is out of scope of this document.

6. IANA Considerations

IANA is requested to update the BGP Path Attributes registry as shown in Table 2. Also, IANA is requested to add [this document] as a reference in the registry.

Table 2: BGP Path Attributes
Value Code EBGP IBGP EBGP-OAD Reference
1 ORIGIN Mandatory Mandatory Mandatory [RFC4271]
2 AS_PATH Optional Optional Optional [RFC4271] [RFC8205]
3 NEXT_HOP Optional Optional Optional [RFC4271] [RFC4760]
4 MULTI_EXIT_DISC Optional Optional Optional [RFC4271]
5 LOCAL_PREF Not allowed Mandatory Optional [RFC4271]
6 ATOMIC_AGGREGATE Optional Optional Optional [RFC4271]
7 AGGREGATOR Optional Optional Optional [RFC4271]
8 COMMUNITIES Optional Optional Optional [RFC1997]
9 ORIGINATOR_ID Not Allowed Optional Not allowed [RFC4456]
10 CLUSTER_LIST Not Allowed Optional Not allowed [RFC4456]
14 MP_REACH_NLRI Optional Optional Optional [RFC4760]
15 MP_UNREACH_NLRI Optional Optional Optional [RFC4760]
16 EXTENDED COMMUNITIES Optional Optional Optional [RFC4360]
17 AS4_PATH Optional Optional Optional [RFC6793]
18 AS4_AGGREGATOR Optional Optional Optional [RFC6793]
22 PMSI_TUNNEL Optional Optional Optional [RFC6514]
23 Tunnel Encapsulation Optional Optional Optional [RFC9012]
24 Traffic Engineering Not Allowed Optional Optional [RFC5543]
25 IPv6 Address Specific Extended Community Optional Optional Optional [RFC5701]
26 AIGP Optional Optional Optional [RFC7311]
27 PE Distinguisher Labels Optional Optional Optional [RFC6514]
29 BGP-LS Attribute Not Allowed Optional Optional [RFC9552]
32 LARGE_COMMUNITY Optional Optional Optional [RFC8092]
33 BGPsec_PATH Optional Optional Optional [RFC8205]
34 BGP Community Container Optional Optional Optional [WIDE]
35 Only to Customer Optional Optional Optional [RFC9234]
36 D-PATH Optional Optional Optional [IPVPN]
37 SFP Optional Optional Optional [RFC9015]
38 BFD Discriminator Optional Optional Optional [RFC9026]
39 BGP Router Capabilities Optional Optional Optional [ENTROPY]
40 BGP Prefix-SID Optional Optional Optional [RFC8669]
128 ATTR_SET Optional Optional Optional [RFC6368]

Table 2 only includes the path attributes referenced in this document. Any Reserved, Deprecated, or Unassigned values should contain empty IBGP, EBGP, and EBGP-OAD columns.

7. Security Considerations

EBGP-OAD peering does not change the underlying security issues inherent in the existing BGP protocol, such as those described in [RFC4271] and [RFC4272]. Any security considerations related to existing path attributes apply to EBGP-OAD sessions.

All BGP attributes may now be propagated to another autonomous system. However, it is expected that the new session type will only be enabled when peering with a router that also belongs to the OAD. If misconfigured, the impact is minimal due to the fact that both [RFC4271] and [RFC7606] define mechanisms to deal with unexpected path attributes. Also, the use of the Import and Export Policy mechanisms speficied in [RFC8212] are REQUIRED.

8. References

8.1. Normative References

[ENTROPY]
Decraene, B., Scudder, J., Henderickx, W., Kompella, K., Mohanty, M., Uttaro, J., and B. Wen, "BGP Next Hop Dependent Capabilities Attribute", Work in Progress, Internet-Draft, draft-ietf-idr-entropy-label-14, , <https://datatracker.ietf.org/doc/html/draft-ietf-idr-entropy-label-14>.
[WIDE]
Raszuk, R., Haas, J., Lange, A., Decraene, B., Amante, S., and P. Jakma, "BGP Community Container Attribute", Work in Progress, Internet-Draft, draft-ietf-idr-wide-bgp-communities-11, , <https://datatracker.ietf.org/doc/html/draft-ietf-idr-wide-bgp-communities-11>.
[IPVPN]
Rabadan, J., Sajassi, A., Rosen, E. C., Drake, J., Lin, W., Uttaro, J., and A. Simpson, "EVPN Interworking with IPVPN", Work in Progress, Internet-Draft, draft-ietf-bess-evpn-ipvpn-interworking-11, , <https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-ipvpn-interworking-11>.
[RFC1997]
Chandra, R., Traina, P., and T. Li, "BGP Communities Attribute", RFC 1997, DOI 10.17487/RFC1997, , <https://www.rfc-editor.org/info/rfc1997>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC4271]
Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, , <https://www.rfc-editor.org/info/rfc4271>.
[RFC4360]
Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, , <https://www.rfc-editor.org/info/rfc4360>.
[RFC4456]
Bates, T., Chen, E., and R. Chandra, "BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)", RFC 4456, DOI 10.17487/RFC4456, , <https://www.rfc-editor.org/info/rfc4456>.
[RFC5004]
Chen, E. and S. Sangli, "Avoid BGP Best Path Transitions from One External to Another", RFC 5004, DOI 10.17487/RFC5004, , <https://www.rfc-editor.org/info/rfc5004>.
[RFC5065]
Traina, P., McPherson, D., and J. Scudder, "Autonomous System Confederations for BGP", RFC 5065, DOI 10.17487/RFC5065, , <https://www.rfc-editor.org/info/rfc5065>.
[RFC5543]
Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP Traffic Engineering Attribute", RFC 5543, DOI 10.17487/RFC5543, , <https://www.rfc-editor.org/info/rfc5543>.
[RFC5701]
Rekhter, Y., "IPv6 Address Specific BGP Extended Community Attribute", RFC 5701, DOI 10.17487/RFC5701, , <https://www.rfc-editor.org/info/rfc5701>.
[RFC6368]
Marques, P., Raszuk, R., Patel, K., Kumaki, K., and T. Yamagata, "Internal BGP as the Provider/Customer Edge Protocol for BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 6368, DOI 10.17487/RFC6368, , <https://www.rfc-editor.org/info/rfc6368>.
[RFC6513]
Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, , <https://www.rfc-editor.org/info/rfc6513>.
[RFC6514]
Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs", RFC 6514, DOI 10.17487/RFC6514, , <https://www.rfc-editor.org/info/rfc6514>.
[RFC6793]
Vohra, Q. and E. Chen, "BGP Support for Four-Octet Autonomous System (AS) Number Space", RFC 6793, DOI 10.17487/RFC6793, , <https://www.rfc-editor.org/info/rfc6793>.
[RFC7311]
Mohapatra, P., Fernando, R., Rosen, E., and J. Uttaro, "The Accumulated IGP Metric Attribute for BGP", RFC 7311, DOI 10.17487/RFC7311, , <https://www.rfc-editor.org/info/rfc7311>.
[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, , <https://www.rfc-editor.org/info/rfc7606>.
[RFC8092]
Heitz, J., Ed., Snijders, J., Ed., Patel, K., Bagdonas, I., and N. Hilliard, "BGP Large Communities Attribute", RFC 8092, DOI 10.17487/RFC8092, , <https://www.rfc-editor.org/info/rfc8092>.
[RFC8205]
Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol Specification", RFC 8205, DOI 10.17487/RFC8205, , <https://www.rfc-editor.org/info/rfc8205>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RFC8212]
Mauch, J., Snijders, J., and G. Hankins, "Default External BGP (EBGP) Route Propagation Behavior without Policies", RFC 8212, DOI 10.17487/RFC8212, , <https://www.rfc-editor.org/info/rfc8212>.
[RFC8669]
Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah, A., and H. Gredler, "Segment Routing Prefix Segment Identifier Extensions for BGP", RFC 8669, DOI 10.17487/RFC8669, , <https://www.rfc-editor.org/info/rfc8669>.
[RFC9012]
Patel, K., Van de Velde, G., Sangli, S., and J. Scudder, "The BGP Tunnel Encapsulation Attribute", RFC 9012, DOI 10.17487/RFC9012, , <https://www.rfc-editor.org/info/rfc9012>.
[RFC9015]
Farrel, A., Drake, J., Rosen, E., Uttaro, J., and L. Jalil, "BGP Control Plane for the Network Service Header in Service Function Chaining", RFC 9015, DOI 10.17487/RFC9015, , <https://www.rfc-editor.org/info/rfc9015>.
[RFC9026]
Morin, T., Ed., Kebler, R., Ed., and G. Mirsky, Ed., "Multicast VPN Fast Upstream Failover", RFC 9026, DOI 10.17487/RFC9026, , <https://www.rfc-editor.org/info/rfc9026>.
[RFC9234]
Azimov, A., Bogomazov, E., Bush, R., Patel, K., and K. Sriram, "Route Leak Prevention and Detection Using Roles in UPDATE and OPEN Messages", RFC 9234, DOI 10.17487/RFC9234, , <https://www.rfc-editor.org/info/rfc9234>.
[RFC9552]
Talaulikar, K., Ed., "Distribution of Link-State and Traffic Engineering Information Using BGP", RFC 9552, DOI 10.17487/RFC9552, , <https://www.rfc-editor.org/info/rfc9552>.

8.2. Informative References

[RFC3345]
McPherson, D., Gill, V., Walton, D., and A. Retana, "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", RFC 3345, DOI 10.17487/RFC3345, , <https://www.rfc-editor.org/info/rfc3345>.
[RFC4272]
Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 4272, DOI 10.17487/RFC4272, , <https://www.rfc-editor.org/info/rfc4272>.
[RFC4364]
Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, , <https://www.rfc-editor.org/info/rfc4364>.
[RFC4760]
Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, , <https://www.rfc-editor.org/info/rfc4760>.
[RFC7964]
Walton, D., Retana, A., Chen, E., and J. Scudder, "Solutions for BGP Persistent Route Oscillation", RFC 7964, DOI 10.17487/RFC7964, , <https://www.rfc-editor.org/info/rfc7964>.
[RFC8097]
Mohapatra, P., Patel, K., Scudder, J., Ward, D., and R. Bush, "BGP Prefix Origin Validation State Extended Community", RFC 8097, DOI 10.17487/RFC8097, , <https://www.rfc-editor.org/info/rfc8097>.
[RFC8277]
Rosen, E., "Using BGP to Bind MPLS Labels to Address Prefixes", RFC 8277, DOI 10.17487/RFC8277, , <https://www.rfc-editor.org/info/rfc8277>.
[IANA-BGP-ATTRS]
IANA, "BGP Path Attributes", <http://www.iana.org/assignments/bgp-parameters>.

Acknowledgements

The authors would like to thank everyone who has commented on this work, including (in alphabetical order) Donatas Abraitis, Randy Bush, Gert Doering, Jeff Haas, Jakob Heitz, Nick Hilliard, Igor Malyushkin, Gyan Mishra, Robert Raszuk, John Scudder, and Shyam Sethuram.

Contributors

The following people have made significant contributions to the content of this document.

Avinash Lingala
AT&T
Dhananjaya Rao
Cisco Systems
Srihari Sangli
Juniper Networks

Authors' Addresses

Jim Uttaro
Individual Contributor
Alvaro Retana
Futurewei Technologies, Inc.
Pradosh Mohapatra
Google
Keyur Patel
Arrcus, Inc.
Bin Wen
Comcast