--- 1/draft-ietf-idr-bgp-open-policy-15.txt 2021-08-10 09:13:19.713643031 -0700 +++ 2/draft-ietf-idr-bgp-open-policy-16.txt 2021-08-10 09:13:19.741643726 -0700 @@ -1,42 +1,43 @@ Network Working Group A. Azimov Internet-Draft Qrator Labs & Yandex Intended status: Standards Track E. Bogomazov -Expires: July 20, 2021 Qrator Labs +Expires: February 11, 2022 Qrator Labs R. Bush Internet Initiative Japan & Arrcus, Inc. K. Patel Arrcus K. Sriram USA NIST - January 16, 2021 + August 10, 2021 - Route Leak Prevention using Roles in Update and Open messages - draft-ietf-idr-bgp-open-policy-15 + Route Leak Prevention and Detection using Roles in UPDATE and OPEN + Messages + draft-ietf-idr-bgp-open-policy-16 Abstract - Route leaks are the propagation of BGP prefixes which violate - assumptions of BGP topology relationships; e.g. passing a route + Route leaks are the propagation of BGP prefixes that violate + assumptions of BGP topology relationships, e.g., passing a route learned from one lateral peer to another lateral peer or a transit - provider, passing a route learned from one transit provider to + provider and passing a route learned from one transit provider to another transit provider or a lateral peer. Existing approaches to leak prevention rely on marking routes by operator configuration, with no check that the configuration corresponds to that of the eBGP neighbor, or enforcement that the two eBGP speakers agree on the - relationship. This document enhances BGP OPEN to establish agreement - of the (peer, customer, provider, Route Server, Route Server client) - relationship of two neighboring eBGP speakers to enforce appropriate - configuration on both sides. Propagated routes are then marked with - an Only to Customer (OTC) attribute according to the agreed - relationship, allowing both prevention and detection of route leaks. + relationship. This document enhances the BGP OPEN message to + establish an agreement of the relationship on each eBGP session + between autonomous systems in order to enforce appropriate + configuration on both sides. Propagated routes are then marked + according to the agreed relationship, allowing both prevention and + detection of route leaks. 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. Status of This Memo @@ -47,412 +48,476 @@ 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 July 20, 2021. + This Internet-Draft will expire on February 11, 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Peering Relationships . . . . . . . . . . . . . . . . . . . . 3 + 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Peering Relationships . . . . . . . . . . . . . . . . . . . . 4 3. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 4. BGP Role Capability . . . . . . . . . . . . . . . . . . . . . 5 - 5. Role correctness . . . . . . . . . . . . . . . . . . . . . . 5 - 5.1. Strict mode . . . . . . . . . . . . . . . . . . . . . . . 6 - 6. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 6 - 7. Enforcement . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 8. Additional Considerations . . . . . . . . . . . . . . . . . . 7 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 - 10. Security Considerations . . . . . . . . . . . . . . . . . . . 8 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 9 - 11.2. Informative References . . . . . . . . . . . . . . . . . 9 - Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10 - Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 + 3.1. BGP Role Capability . . . . . . . . . . . . . . . . . . . 5 + 3.2. Role Correctness . . . . . . . . . . . . . . . . . . . . 5 + 4. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 6 + 5. Additional Considerations . . . . . . . . . . . . . . . . . . 8 + 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 10 + 8.2. Informative References . . . . . . . . . . . . . . . . . 11 + Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11 + Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 11 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction A BGP route leak occurs when a route is learned from a transit provider or lateral peer and then announced to another provider or - lateral peer. See [RFC7908]. These are usually the result of + lateral peer [RFC7908]. These are usually the result of misconfigured or absent BGP route filtering or lack of coordination - between two eBGP speakers. + between autonomous systems (ASes). - The mechanism proposed in - [I-D.ietf-grow-route-leak-detection-mitigation] uses large- - communities to perform detection and mitigation of route leaks. - While signaling using communities is easy to implement and deploy - quickly, it normally relies on operator-maintained policy - configuration, which is vulnerable to misconfiguration [Streibelt]. - The community signal can also be stripped at the ISP boundaries. + Existing approaches to leak prevention rely on marking routes by + operator configuration, with no check that the configuration + corresponds to that of the eBGP neighbor, or enforcement that the two + eBGP speakers agree on the relationship. This document enhances the + BGP OPEN message to establish an agreement of the relationship on + each eBGP session between autonomous systems in order to enforce + appropriate configuration on both sides. Propagated routes are then + marked according to the agreed relationship, allowing both prevention + and detection of route leaks. - This document provides configuration automation using 'BGP roles', - which are negotiated using a new BGP Capability Code in OPEN message - (see Section 4 in [RFC5492]). Either or both BGP speakers MAY be - configured to require that this capability be agreed for the BGP OPEN - to succeed. + This document provides configuration automation using BGP Roles, + which are negotiated using a BGP Role Capability in the OPEN message + [RFC5492]. An eBGP speaker may require the use of this capability + and confirmation of BGP Role with a neighbor for the BGP OPEN to + succeed. - A new optional, transitive BGP Path Attribute Only to Customer (OTC) - is specified that SHOULD be automatically configured using BGP roles. - This attribute prevents networks from creating leaks, and detects - leaks created by third parties. + An optional, transitive BGP Path Attribute, called Only to Customer + (OTC), is specified in Section 4. It prevents ASes from creating + leaks, and detects leaks created by the ASes in the middle of an AS + path. The main focus/applicability is the Internet (IPv4 and IPv6 + unicast route advertisements). - In the rest of this document, we use the term "peer" to refer to - "lateral peer" for simplicity. +1.1. Terminology -2. Peering Relationships + In the rest of this document, the term "Peer" is used to refer to a + "lateral peer" for simplicity. Also, the terms Provider and Customer + are used to refer to a transit provider and a transit customer, + respectively. Further, the terms RS and RS-Client are used to refer + to a Route Server and its client, respectively. - Despite the use of terms such as "customer", "peer", etc. in this - document, these are not necessarily business relationships based on - payment agreements. These terms are used to represent restrictions - on BGP route propagation, sometimes known as the Gao-Rexford model - [Gao]. The following is a list of various roles in eBGP peering and - the corresponding rules for route propagation: + The terms "local AS" and "remote AS" are used to refer to the two + ends of an eBGP session. The "local AS" is the AS where the protocol + action being described is to be performed, and "remote AS" is the AS + at the other end of the eBGP session in consideration. - Provider: MAY send to a customer all available prefixes. + The use of the term "route is ineligible" in this document has the + same meaning as in [RFC4271], i.e., "route is ineligible to be + installed in Loc-RIB and will be excluded from the next phase of + route selection." - Customer: MAY send to a provider prefixes which the sender - originates and prefixes learned from any of their customers. A - customer MUST NOT send to a provider prefixes learned from its - peers, from other providers, or from Route Servers. +2. Peering Relationships - Route Server (RS): MAY send to an Route Server client (RS-client) - all available prefixes. + The terms defined and used in this document (see below) do not + necessarily represent business relationships based on payment + agreements. These terms are used to represent restrictions on BGP + route propagation, sometimes known as the Gao-Rexford model [Gao]. + The following is a list of BGP Roles for eBGP peering and the + corresponding rules for route propagation: - RS-client: MAY send to an RS prefixes which the sender originates - and prefixes learned from its customers. An RS-client MUST NOT - send to an RS prefixes learned from its peers or providers, or - from another RS. + Provider: MAY propagate any available route to a Customer. - Peer: MAY send to a peer prefixes which the sender originates and - prefixes learned from its customers. A peer MUST NOT send to a - peer prefixes learned from other peers, from its providers, or - from RS(s). + Customer: MAY propagate any route learned from a Customer, or + locally originated, to a Provider. All other routes MUST NOT be + propagated. - Of course, any BGP speaker may apply policy to reduce what is - announced, and a recipient may apply policy to reduce the set of - routes they accept. Violation of the above rules may result in route - leaks and MUST NOT be allowed. Automatic enforcement of these rules - should significantly reduce route leaks that may otherwise occur due - to manual configuration mistakes. While enforcing the above rules - will address most BGP peering scenarios, their configuration is not - part of BGP itself; therefore, configuration of ingress and egress - prefix filters is still strongly advised. + Route Server (RS): MAY propagate any available route to a Route + Server Client (RS-Client). -3. BGP Role + RS-Client: MAY propagate any route learned from a Customer, or + locally originated, to an RS. All other routes MUST NOT be + propagated. - BGP Role is a new configuration option that is configured on a per- - session basis. BGP Roles reflect the agreement between two BGP - speakers about their relationship. One of the Roles described below - SHOULD be configured on each eBGP session between ISPs that carry - IPv4 and(or) IPv6 unicast prefixes. + Peer: MAY propagate any route learned from a Customer, or locally + originated, to a Peer. All other routes MUST NOT be propagated. - Allowed Role values for eBGP sessions between ISPs are: + A BGP speaker may apply policy to reduce what is announced, and a + recipient may apply policy to reduce the set of routes they accept. + Violation of the above rules may result in route leaks. Automatic + enforcement of these rules should significantly reduce route leaks + that may otherwise occur due to manual configuration mistakes. - o Provider - sender is a transit provider to neighbor; +3. BGP Role - o Customer - sender is a transit customer of neighbor; + The BGP Role characterizes the relationship between the eBGP speakers + forming a session. BGP Role is configured on a per-session basis. + An eBGP speaker SHOULD configure the BGP Role locally based on the + local AS's knowledge of its Role. The only exception is when the + eBGP connection is complex (see Section 5). BGP Roles are mutually + confirmed using the BGP Role Capability (described in Section 3.1) on + each eBGP session between autonomous systems (ASes). One of the + Roles described below SHOULD be configured at the local AS for each + eBGP session with a neighbor (remote AS) (see definitions in + Section 1.1). - o RS - sender is a Route Server, usually at an Internet exchange - point (IX); + Allowed Roles for eBGP sessions are: - o RS-client - sender is client of an RS; + o Provider - the local AS is a transit Provider of the remote AS; + o Customer - the local AS is a transit Customer of the remote AS; - o Peer - sender and neighbor are peers. + o RS - the local AS is a Route Server (usually at an Internet + exchange point) and the remote AS is its RS-Client; - Since BGP Role reflects the relationship between two BGP speakers, it - could also be used for other purposes besides route leak mitigation. + o RS-Client - the local AS is a client of an RS and the RS is the + remote AS; -4. BGP Role Capability + o Peer - the local and remote ASes are Peers (i.e., have a lateral + peering relationship). - The TLV (type, length, value) of the BGP Role capability are: +3.1. BGP Role Capability - o Type - ; + The BGP Role Capability is defined as follows: - o Length - 1 (byte); + o Code - 9 + + o Length - 1 (octet) o Value - integer corresponding to speaker's BGP Role (see Table 1). - +-------+---------------------+ - | Value | Role name | - +-------+---------------------+ - | 0 | Sender is Provider | - | 1 | Sender is RS | - | 2 | Sender is RS-client | - | 3 | Sender is Customer | - | 4 | Sender is Peer | - +-------+---------------------+ + +-------+------------------------------+ + | Value | Role name (for the local AS) | + +-------+------------------------------+ + | 0 | Provider | + | 1 | RS | + | 2 | RS-Client | + | 3 | Customer | + | 4 | Peer (Lateral Peer) | + | 5-255 | Unassigned | + +-------+------------------------------+ Table 1: Predefined BGP Role Values -5. Role correctness + If BGP Role is locally configured, the eBGP speaker MUST advertise + BGP Role Capability in the BGP OPEN message. An eBGP speaker MUST + NOT advertise multiple versions of the BGP Role Capability. - Section 3 described how BGP Role encodes the relationship between two - eBGP speakers. But the mere presence of BGP Role doesn't - automatically guarantee role agreement between two BGP peers. +3.2. Role Correctness - To enforce correctness, the BGP Role check is applied with a set of - constraints on how speakers' BGP Roles MUST correspond. Of course, - each speaker MUST announce and accept the BGP Role capability in the - BGP OPEN message exchange. + Section 3.1 described how BGP Role encodes the relationship on each + eBGP session between autonomous systems (ASes). - If a speaker receives a BGP Role capability, it MUST check the value - of the received capability (i.e., the sender's role) with its own BGP - Role. The allowed pairings are as follows: + The mere receipt of BGP Role Capability does not automatically + guarantee the Role agreement between two eBGP neighbors. If the BGP + Role Capability is advertised, and one is also received from the + peer, the roles MUST correspond to the relationships in Table 2. If + the roles do not correspond, the BGP speaker MUST reject the + connection using the Role Mismatch Notification (code 2, subcode 8). - +---------------+-----------------+ - | Sender's Role | Receiver's Role | - +---------------+-----------------+ + +---------------+----------------+ + | Local AS Role | Remote AS Role | + +---------------+----------------+ | Provider | Customer | | Customer | Provider | - | RS | RS-client | - | RS-client | RS | + | RS | RS-Client | + | RS-Client | RS | | Peer | Peer | - +---------------+-----------------+ + +---------------+----------------+ Table 2: Allowed Pairs of Role Capabilities - If the role of the receiving speaker for the eBGP session in - consideration is included in Table 1 and the observed Role pair is - not in the above table, then the receiving speaker MUST reject the - eBGP connection, send a Role Mismatch Notification (code 2, subcode - ), and also send a Connection Rejected Notification [RFC4486] - (Notification with error code 6, subcode 5). + If the BGP Role Capability is sent, but one is not received, then the + connection MAY be rejected using the Role Mismatch Notification (code + 2, subcode 8); this mode of operation is called the "strict mode". + For backward compatibility, if the BGP speaker does not receive the + capability from its peer, it SHOULD ignore the absence of BGP Role + Capability and proceed with session establishment; this SHOULD be the + default non-strict mode of operation. In this case, the locally + configured BGP Role is used for the procedures described in + Section 4. -5.1. Strict mode + If an eBGP speaker receives multiple but identical BGP Role + Capabilities with the same value in each, then the speaker MUST + consider it to be a single BGP Role Capability and proceed [RFC5492]. + If multiple BGP Role Capabilities are received and not all of them + have the same value, then the BGP speaker MUST reject the connection + using the Role Mismatch Notification (code 2, subcode 8). - A new BGP configuration option "strict mode" is defined with values - of true or false. If set to true, then the speaker MUST refuse to - establish a BGP session with a neighbor which does not announce the - BGP Role capability in the OPEN message. If a speaker rejects a - connection, it MUST send a send a Role Mismatch Notification (code 2, - subcode ), and also send a Connection Rejected Notification - [RFC4486] (Notification with error code 6, subcode 5). By default, - strict mode SHOULD be set to false for backward compatibility with - BGP speakers that do not yet support this mechanism. + The BGP Role value for the local AS is used in the route leak + prevention and detection procedures described in Section 4. -6. BGP Only to Customer (OTC) Attribute +4. BGP Only to Customer (OTC) Attribute - Newly defined here, the Only to Customer (OTC) is an optional, 4 - bytes long, transitive BGP Path attribute with the Type Code . - The purpose of this attribute is to guarantee that once a route is - sent to customer, peer, or RS-client, it will subsequently go only to - customers. The value of OTC is an AS number determined by policy as - described below. The semantics and usage of the OTC attribute are - made clear by the ingress and egress policies described below. + The Only to Customer (OTC) Attribute is an optional transitive path + attribute with Attribute Type Code 35 and a length of 4 octets. The + purpose of this attribute is to guarantee that once a route is sent + to a Customer, Peer, or RS-Client, it will subsequently go only to + Customers. The attribute value is an AS number determined by the + policy described below. - The following ingress policy applies to the OTC attribute: + The following ingress policy applies to the processing of the OTC + Attribute: - 1. If a route with OTC attribute is received from a Customer or RS- - client, then it is a route leak and MUST be rejected. + 1. If a route with the OTC Attribute is received from a Customer or + RS-Client, then it is a route leak and MUST be considered + ineligible (see Section 1.1). - 2. If a route with OTC attribute is received from a Peer and its - value is not equal to the sending neighbor's Autonomous System - (AS) number, then it is a route leak and MUST be rejected. + 2. If a route with the OTC Attribute is received from a Peer and at + least one of the OTC Attributes has a value that is not equal to + the remote (i.e., Peer's) AS number, then it is a route leak and + MUST be considered ineligible. - 3. If a route is received from a Provider, Peer, or RS and the OTC - attribute is not present, then it MUST be added with value equal - to the sending neighbor's AS number. + 3. If a route is received from a Provider, Peer, or RS, and the OTC + Attribute is not present, then it MUST be added with a value + equal to the AS number of the remote AS. - The egress policy MUST be: + The following egress policy applies to the processing of the OTC + Attribute: - 1. A route with the OTC attribute set MUST NOT be sent to Providers, - Peers, or RS(s). + 1. If a route is to be advertised to a Customer, Peer, or RS-Client + (when the sender is an RS), and the OTC Attribute is not present, + then an OTC Attribute MUST be added with a value equal to the AS + number of the local AS. - 2. If route is sent to a Customer or Peer, or an RS-client (when the - sender is an RS) and the OTC attribute is not present, then it - MUST be added with value equal to AS number of the sender. + 2. If a route already contains the OTC Attribute, it MUST NOT be + propagated to Providers, Peers, or RS(s). - Once the OTC attribute has been set, it MUST be preserved unchanged. + The described policies provide both leak prevention for the local AS + and leak detection and mitigation multiple hops away. In the case of + prevention at the local AS, the presence of an OTC Attribute + indicates to the egress router that the route was learned from a + Peer, Provider, or RS, and it can be advertised only to the + customers. The same OTC Attribute which is set locally also provides + a way to detect route leaks by an AS multiple hops away if a route is + received from a Customer, Peer, or RS-Client. -7. Enforcement + The OTC Attribute may be set by the egress policy of remote AS or by + the ingress policy of local AS. In both scenarios, the OTC value + will be the same. This makes the scheme more robust and benefits + early adopters. - Having the relationship unequivocally agreed between the two peers in - BGP OPEN is critical; BGP implementations MUST enforce the - relationship/role establishment rules (see Section 5) in order to - ameliorate operator policy configuration errors (if any). + If an eBGP speaker receives an UPDATE with an OTC Attribute with a + length different from 4 octets, then the UPDATE SHALL be considered + malformed. If malformed, the UPDATE message SHALL be handled using + the approach of "treat-as-withdraw" [RFC7606]. - Similarly, the application of that relationship on prefix propagation - using OTC MUST be enforced by the BGP implementations, and not - exposed to user misconfiguration. + Once the OTC Attribute has been set, it MUST be preserved unchanged. - As opposed to communities, BGP attributes may not be generally - modified or stripped by the operator; BGP router implementations - enforce such treatment. This is the desired property for the OTC - marking. Hence, this document specifies OTC as an attribute. + Correct implementation of the procedures specified in this document + is not expected to result in the presence of multiple OTC Attributes + in an UPDATE. However, if an eBGP speaker receives multiple OTC + Attributes with a route, then the only difference in the processing + is in Step 2 of the ingress policy. -8. Additional Considerations + The described ingress and egress policies are applicable only for + unicast IPv4 and IPv6 address families and MUST not affect other + address families by default. The operator MUST NOT have the ability + to modify the policies defined in this section. + +5. Additional Considerations There are peering relationships that are 'complex', i.e., both - parties are intentionally sending prefixes received from each other - to their non-transit peers and/or transit providers. If multiple BGP - peerings can segregate the 'complex' parts of the relationship, the - complex peering roles can be segregated into different normal BGP - sessions, and BGP Roles MUST be used on each of the resulting normal - (non-complex) BGP sessions. + parties intentionally advertise prefixes received from each other to + their Peers and/or transit Providers. If multiple eBGP sessions can + segregate the 'complex' parts of the relationship, then the complex + peering roles can be segregated into different normal eBGP sessions, + and BGP Roles MUST be used on each of the resulting normal (non- + complex) eBGP sessions. - No Roles SHOULD be configured on a 'complex' BGP session (assuming it - is not segregated) and in that case, OTC MUST be set by configuration - on a per-prefix basis. However, there are no built-in measures to - check correctness of OTC use if BGP Role is not configured. + No Roles SHOULD be configured on a 'complex' eBGP session (assuming + it is not segregated) and in that case, the OTC Attribute processing + MUST be done relying on configuration on a per-prefix basis. Also, + in this case, the per-prefix peering configuration MUST follow the + same definitions of peering relations as described in Section 2. + However, in this case, there are no built-in measures to check + correctness of the per-prefix peering configuration. - The incorrect setting of BGP Roles and/or OTC attributes may affect - prefix propagation. Further, this document doesn't specify any - special handling of incorrect/private ASNs in OTC attribute; such + The incorrect setting of BGP Roles and/or OTC Attributes may affect + prefix propagation. Further, this document does not specify any + special handling of incorrect AS numbers in the OTC Attribute. Such errors should not happen with proper configuration. - As the BGP Role reflects the peering relationship between neighbors, - it might have other uses beyond the route leak solution discussed so - far. For example, BGP Role might affect route priority, or be used - to distinguish borders of a network if a network consists of multiple - ASs. Though such uses may be worthwhile, they are not the goal of - this document. Note that such uses would require local policy - control. +6. IANA Considerations - The use of BGP Roles are specified for unicast IPv4 and IPv6 address - families. While BGP roles can be configured on other address - families its applicability for these cases is out of scope of this - document. + IANA has registered a new BGP Capability described in Section 3.1 in + the "Capability Codes" registry's "IETF Review" range [RFC5492]. The + description for the new capability is "BGP Role". IANA has assigned + the value 9 [to be removed upon publication: + https://www.iana.org/assignments/capability-codes/capability- + codes.xhtml]. This document is the reference for the new capability. - As BGP role configuration results in automatic creation of inbound/ - outbound filters, existence of roles should be treated as existence - of Import and Export policy [RFC8212]. + The BGP Role capability includes a Value field, for which IANA is + requested to create and maintain a new sub-registry called "BGP Role + Value" in the Capability Codes registry. Assignments consist of a + Value and a corresponding Role name. Initially, this registry is to + be populated with the data contained in Table 1 found in Section 3.1. + Future assignments may be made by the "IETF Review" policy as defined + in [RFC8126]. The registry is as shown in Table 3. -9. IANA Considerations + +-------+--------------------------------+---------------+ + | Value | Role name (for the local AS) | Reference | + +-------+--------------------------------+---------------+ + | 0 | Provider | This document | + | 1 | RS | This document | + | 2 | RS-Client | This document | + | 3 | Customer | This document | + | 4 | Peer (i.e., Lateral Peer) | This document | + | 5-255 | To be assigned by IETF Review | + +-------+--------------------------------+---------------+ - This document defines a new Capability Codes option [to be removed - upon publication: https://www.iana.org/assignments/capability-codes/ - capability-codes.xhtml ] [RFC5492], named "BGP Role" with an assigned - value . The length of this capability is 1. + Table 3: IANA Registry for BGP Role - The BGP Role capability includes a Value field, for which IANA is - requested to create and maintain a new sub-registry called "BGP Role - Value". Assignments consist of Value and corresponding Role name. - Initially this registry is to be populated with the data contained in - Table 1 found in Section 4. Future assignments may be made by a - Standard Action procedure [RFC8126]. The allocation policy for new - entries up to and including value 127 is "Expert Review" [RFC8126]. - The allocation policy for values 128 through 251 is "First Come First - Served". The values from 252 through 255 are for "Experimental Use". + IANA has registered a new OPEN Message Error subcode named the "Role + Mismatch" (see Section 3.2) in the OPEN Message Error subcodes + registry. IANA has assigned the value 8 [to be removed upon + publication: https://www.iana.org/assignments/bgp-parameters/bgp- + parameters.xhtml#bgp-parameters-6]. This document is the reference + for the new subcode. - This document defines a new subcode, "Role Mismatch" with an assigned - value in the OPEN Message Error subcodes registry [to be - removed upon publication: http://www.iana.org/assignments/bgp- - parameters/bgp-parameters.xhtml#bgp-parameters-6] [RFC4271]. + IANA has also registered a new path attribute named "Only to Customer + (OTC)" (see Section 4) in the "BGP Path Attributes" registry. IANA + has assigned code value 35 [To be removed upon publication: + http://www.iana.org/assignments/bgp-parameters/bgp- + parameters.xhtml#bgp-parameters-2]. This document is the reference + for the new attribute. - This document defines a new optional, transitive BGP Path Attributes - option, named "Only to Customer (OTC)" with an assigned value - [To be removed upon publication: http://www.iana.org/assignments/bgp- - parameters/bgp-parameters.xhtml#bgp-parameters-2] [RFC4271]. The - length of this attribute is four bytes. +7. Security Considerations -10. Security Considerations + The security considerations of BGP (as specified in [RFC4271] and + [RFC4272]) apply. - This document proposes a mechanism for prevention of route leaks that - are the result of BGP policy misconfiguration. + This document proposes a mechanism using BGP Role for the prevention + and detection of route leaks that are the result of BGP policy + misconfiguration. A misconfiguration of the BGP Role may affect + prefix propagation. For example, if a downstream (i.e., towards a + Customer) peering link were misconfigured with a Provider or Peer + role, this will limit the number of prefixes that can be advertised + in this direction. On the other hand if an upstream provider were + misconfigured (by a local AS) with the Customer role, this may result + in propagating routes that are received from other Providers or + Peers. But the BGP Role negotiation and the resulting confirmation + of Roles make such misconfigurations unlikely. - A misconfiguration in OTC setup may affect prefix propagation. But - the automation that is provided by BGP roles should make such - misconfiguration unlikely. + Setting the strict mode of operation for BGP Role negotiation as the + default may result in a situation where the eBGP session will not + come up after a software update. Such an implementation of this + document is strongly discouraged. -11. References + Removing the OTC Attribute or changing its value can limit the + opportunity of route leak detection. Such activity can be done on + purpose as part of a Man in the Middle (MITM) attack. For example, + an AS can remove the OTC Attribute on a received route and then leak + the route to its transit provider. Such malicious activity cannot be + prevented without cryptographically signing the BGP UPDATE [RFC8205] + or out of band detection [I-D.ietf-sidrops-aspa-verification], but + such schemes are beyond the scope of this document. -11.1. Normative References + Adding an OTC Attribute when the route is advertised from Customer to + Provider will limit the propagation of the route. Such a route may + be considered as ineligible by the immediate Provider or its Peers or + upper layer Providers. This kind of OTC Attribute addition is + unlikely to happen on the Provider side because it will limit the + traffic volume towards its Customer. On the Customer side, adding an + OTC Attribute for traffic engineering purposes is also discouraged + because it will limit route propagation in an unpredictable way. + +8. References + +8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006, . - [RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease - Notification Message", RFC 4486, DOI 10.17487/RFC4486, - April 2006, . + [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", + RFC 4272, DOI 10.17487/RFC4272, January 2006, + . [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February 2009, . - [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC - 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, - May 2017, . - -11.2. Informative References - - [Gao] Gao, L. and J. Rexford, "Stable Internet routing without - global coordination", IEEE/ACM Transactions on - Networking, Volume 9, Issue 6, pp 689-692, DOI - 10.1109/90.974523, December 2001, - . - - [I-D.ietf-grow-route-leak-detection-mitigation] - Sriram, K. and A. Azimov, "Methods for Detection and - Mitigation of BGP Route Leaks", draft-ietf-grow-route- - leak-detection-mitigation-04 (work in progress), October - 2020. + [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. + Patel, "Revised Error Handling for BGP UPDATE Messages", + RFC 7606, DOI 10.17487/RFC7606, August 2015, + . [RFC7908] Sriram, K., Montgomery, D., McPherson, D., Osterweil, E., and B. Dickson, "Problem Definition and Classification of BGP Route Leaks", RFC 7908, DOI 10.17487/RFC7908, June 2016, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . - [RFC8212] Mauch, J., Snijders, J., and G. Hankins, "Default External - BGP (EBGP) Route Propagation Behavior without Policies", - RFC 8212, DOI 10.17487/RFC8212, July 2017, - . + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, . - [Streibelt] - Streibelt, F., Lichtblau, F., Beverly, R., Feldmann, A., - Cristel, C., Smaragdakis, G., and R. Bush, "BGP - Communities: Even more Worms in the Routing Can", - . +8.2. Informative References + + [Gao] Gao, L. and J. Rexford, "Stable Internet routing without + global coordination", IEEE/ACM Transactions on + Networking, Volume 9, Issue 6, pp 689-692, DOI + 10.1109/90.974523, December 2001, + . + + [I-D.ietf-sidrops-aspa-verification] + Azimov, A., Bogomazov, E., Bush, R., Patel, K., and J. + Snijders, "Verification of AS_PATH Using the Resource + Certificate Public Key Infrastructure and Autonomous + System Provider Authorization", draft-ietf-sidrops-aspa- + verification-07 (work in progress), February 2021. + + [RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol + Specification", RFC 8205, DOI 10.17487/RFC8205, September + 2017, . Acknowledgements - The authors wish to thank Andrei Robachevsky, Daniel Ginsburg, Jeff - Haas, Ruediger Volk, Pavel Lunin, Gyan Mishra, Ignas Bagdonas, Sue - Hares, and John Scudder for comments, suggestions, and critique. + The authors wish to thank Alvaro Retana, Andrei Robachevsky, Daniel + Ginsburg, Jeff Haas, Ruediger Volk, Pavel Lunin, Gyan Mishra, Ignas + Bagdonas, Sue Hares, and John Scudder for comments, suggestions, and + critique. Contributors - Brian Dickson Independent Email: brian.peter.dickson@gmail.com Doug Montgomery USA National Institute of Standards and Technology Email: dougm@nist.gov Authors' Addresses