draft-ietf-idr-bgp-open-policy-24.txt   rfc9234.txt 
Network Working Group A. Azimov Internet Engineering Task Force (IETF) A. Azimov
Internet-Draft Qrator Labs & Yandex Request for Comments: 9234 Qrator Labs & Yandex
Intended status: Standards Track E. Bogomazov Category: Standards Track E. Bogomazov
Expires: 3 October 2022 Qrator Labs ISSN: 2070-1721 Qrator Labs
R. Bush R. Bush
Internet Initiative Japan & Arrcus, Inc. IIJ & Arrcus
K. Patel K. Patel
Arrcus Arrcus
K. Sriram K. Sriram
USA NIST USA NIST
1 April 2022 May 2022
Route Leak Prevention and Detection using Roles in UPDATE and OPEN Route Leak Prevention and Detection Using Roles in UPDATE and OPEN
Messages Messages
draft-ietf-idr-bgp-open-policy-24
Abstract Abstract
Route leaks are the propagation of BGP prefixes that violate Route leaks are the propagation of BGP prefixes that violate
assumptions of BGP topology relationships, e.g., announcing a route assumptions of BGP topology relationships, e.g., announcing a route
learned from one transit provider to another transit provider or a learned from one transit provider to another transit provider or a
lateral (i.e., non-transit) peer or announcing a route learned from lateral (i.e., non-transit) peer or announcing a route learned from
one lateral peer to another lateral peer or a transit provider. one lateral peer to another lateral peer or a transit provider.
These are usually the result of misconfigured or absent BGP route These are usually the result of misconfigured or absent BGP route
filtering or lack of coordination between autonomous systems (ASes). filtering or lack of coordination between autonomous systems (ASes).
Existing approaches to leak prevention rely on marking routes by Existing approaches to leak prevention rely on marking routes by
operator configuration, with no check that the configuration operator configuration, with no check that the configuration
corresponds to that of the eBGP neighbor, or enforcement that the two corresponds to that of the External BGP (eBGP) neighbor, or
eBGP speakers agree on the peering relationship. This document enforcement of the two eBGP speakers agreeing on the peering
enhances the BGP OPEN message to establish an agreement of the relationship. This document enhances the BGP OPEN message to
peering relationship on each eBGP session between autonomous systems establish an agreement of the peering relationship on each eBGP
in order to enforce appropriate configuration on both sides. session between autonomous systems in order to enforce appropriate
Propagated routes are then marked according to the agreed configuration on both sides. Propagated routes are then marked
relationship, allowing both prevention and detection of route leaks. 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 Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 3 October 2022. Information about the current status of this document, any errata,
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language
2.1. Peering Relationships . . . . . . . . . . . . . . . . . . 4 3. Terminology
3. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Peering Relationships
3.1. BGP Role Capability . . . . . . . . . . . . . . . . . . . 5 4. BGP Role
3.2. Role Correctness . . . . . . . . . . . . . . . . . . . . 6 4.1. BGP Role Capability
4. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 8 4.2. Role Correctness
5. Additional Considerations . . . . . . . . . . . . . . . . . . 10 5. BGP Only to Customer (OTC) Attribute
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. Additional Considerations
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7. IANA Considerations
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. Security Considerations
8.1. Normative References . . . . . . . . . . . . . . . . . . 12 9. References
8.2. Informative References . . . . . . . . . . . . . . . . . 13 9.1. Normative References
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 14 9.2. Informative References
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Contributors
Authors' Addresses
1. Introduction 1. Introduction
Route leaks are the propagation of BGP prefixes that violate Route leaks are the propagation of BGP prefixes that violate
assumptions of BGP topology relationships, e.g., announcing a route assumptions of BGP topology relationships, e.g., announcing a route
learned from one transit provider to another transit provider or a learned from one transit provider to another transit provider or a
lateral (i.e., non-transit) peer or announcing a route learned from lateral (i.e., non-transit) peer or announcing a route learned from
one lateral peer to another lateral peer or a transit provider one lateral peer to another lateral peer or a transit provider
[RFC7908]. These are usually the result of misconfigured or absent [RFC7908]. These are usually the result of misconfigured or absent
BGP route filtering or lack of coordination between autonomous BGP route filtering or lack of coordination between autonomous
systems (ASes). systems (ASes).
Existing approaches to leak prevention rely on marking routes by Existing approaches to leak prevention rely on marking routes by
operator configuration, with no check that the configuration operator configuration, with no check that the configuration
corresponds to that of the eBGP neighbor, or enforcement that the two corresponds to that of the eBGP neighbor, or enforcement of the two
eBGP speakers agree on the relationship. This document enhances the eBGP speakers agreeing on the relationship. This document enhances
BGP OPEN message to establish an agreement of the relationship on the BGP OPEN message to establish an agreement of the relationship on
each eBGP session between autonomous systems in order to enforce each eBGP session between autonomous systems in order to enforce
appropriate configuration on both sides. Propagated routes are then appropriate configuration on both sides. Propagated routes are then
marked according to the agreed relationship, allowing both prevention marked according to the agreed relationship, allowing both prevention
and detection of route leaks. and detection of route leaks.
This document specifies a means of replacing the operator-driven This document specifies a means of replacing the operator-driven
configuration-based method of route leak prevention, described above, configuration-based method of route leak prevention, described above,
with an in-band method for route leak prevention and detection. with an in-band method for route leak prevention and detection.
This method uses a new configuration parameter, BGP Role, which is This method uses a new configuration parameter, BGP Role, which is
negotiated using a BGP Role Capability in the OPEN message [RFC5492]. negotiated using a BGP Role Capability in the OPEN message [RFC5492].
An eBGP speaker may require the use of this capability and An eBGP speaker may require the use of this capability and
confirmation of BGP Role with a neighbor for the BGP OPEN to succeed. confirmation of the BGP Role with a neighbor for the BGP OPEN to
succeed.
An optional, transitive BGP Path Attribute, called Only to Customer An optional, transitive BGP Path Attribute, called "Only to Customer
(OTC), is specified in Section 4. It prevents ASes from creating (OTC)", is specified in Section 5. It prevents ASes from creating
leaks and detects leaks created by the ASes in the middle of an AS 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 path. The main focus/applicability is the Internet (IPv4 and IPv6
unicast route advertisements). unicast route advertisements).
2. Terminology 2. 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.
3. Terminology
The terms "local AS" and "remote AS" are used to refer to the two 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 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 action being described is to be performed, and "remote AS" is the AS
at the other end of the eBGP session in consideration. at the other end of the eBGP session in consideration.
The use of the term "route is ineligible" in this document has the 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 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 installed in Loc-RIB and will be excluded from the next phase of
route selection." route selection."
2.1. Peering Relationships 3.1. Peering Relationships
The terms for peering relationships defined and used in this document The terms for peering relationships defined and used in this document
(see below) do not necessarily represent business relationships based (see below) do not necessarily represent business relationships based
on payment agreements. These terms are used to represent on payment agreements. These terms are used to represent
restrictions on BGP route propagation, sometimes known as the Gao- restrictions on BGP route propagation, sometimes known as the Gao-
Rexford model [Gao]. The terms Provider, Customer, and Peer used Rexford model [GAO-REXFORD]. The terms "Provider", "Customer", and
here are synonymous to the terms "transit provider", "customer", and "Peer" used here are synonymous to the terms "transit provider",
"lateral (i.e., non-transit) peer", respectively, used in [RFC7908]. "customer", and "lateral (i.e., non-transit) peer", respectively,
used in [RFC7908].
The following is a list of BGP Roles for eBGP peering and the The following is a list of BGP Roles for eBGP peering and the
corresponding rules for route propagation: corresponding rules for route propagation:
Provider: MAY propagate any available route to a Customer. Provider: MAY propagate any available route to a Customer.
Customer: MAY propagate any route learned from a Customer, or Customer: MAY propagate any route learned from a Customer, or that
locally originated, to a Provider. All other routes MUST NOT be is locally originated, to a Provider. All other routes MUST NOT
propagated. be propagated.
Route Server (RS): MAY propagate any available route to a Route Route Server (RS): MAY propagate any available route to a Route
Server Client (RS-Client). Server Client (RS-Client).
Route Server Client (RS-Client): MAY propagate any route learned Route Server Client (RS-Client): MAY propagate any route learned
from a Customer, or locally originated, to an RS. All other from a Customer, or that is locally originated, to an RS. All
routes MUST NOT be propagated. other routes MUST NOT be propagated.
Peer: MAY propagate any route learned from a Customer, or locally Peer: MAY propagate any route learned from a Customer, or that is
originated, to a Peer. All other routes MUST NOT be propagated. locally originated, to a Peer. All other routes MUST NOT be
propagated.
If the local AS has one of the above Roles (in the order shown), then If the local AS has one of the above Roles (in the order shown), then
the corresponding peering relationship with the remote AS is the corresponding peering relationship with the remote AS is
Provider-to-Customer, Customer-to-Provider, RS-to-RS-Client, RS- Provider-to-Customer, Customer-to-Provider, RS-to-RS-Client, RS-
Client-to-RS, or Peer-to-Peer (i.e., lateral peers), respectively. Client-to-RS, or Peer-to-Peer (i.e., lateral peers), respectively.
These are called normal peering relationships. These are called normal peering relationships.
If the local AS has more than one peering role with the remote AS If the local AS has more than one peering Role with the remote AS,
such peering relation is called Complex. An example is when the such a peering relation is called "Complex". An example is when the
peering relationship is Provider-to-Customer for some prefixes while peering relationship is Provider-to-Customer for some prefixes while
it is Peer-to-Peer for other prefixes [Gao]. it is Peer-to-Peer for other prefixes [GAO-REXFORD].
A BGP speaker may apply policy to reduce what is announced, and a 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. recipient may apply policy to reduce the set of routes they accept.
Violation of the route propagation rules listed above may result in Violation of the route propagation rules listed above may result in
route leaks [RFC7908]. Automatic enforcement of these rules should route leaks [RFC7908]. Automatic enforcement of these rules should
significantly reduce route leaks that may otherwise occur due to significantly reduce route leaks that may otherwise occur due to
manual configuration mistakes. manual configuration mistakes.
As specified in Section 4, the Only to Customer (OTC) Attribute is As specified in Section 5, the OTC Attribute is used to identify all
used to identify all the routes in the AS that have been received the routes in the AS that have been received from a Peer, a Provider,
from a Peer, Provider, or RS. or an RS.
3. BGP Role 4. BGP Role
The BGP Role characterizes the relationship between the eBGP speakers The BGP Role characterizes the relationship between the eBGP speakers
forming a session. One of the Roles described below SHOULD be forming a session. One of the Roles described below SHOULD be
configured at the local AS for each eBGP session (see definitions in configured at the local AS for each eBGP session (see definitions in
Section 2) based on the local AS's knowledge of its Role. The only Section 3) based on the local AS's knowledge of its Role. The only
exception is when the eBGP connection is Complex (see Section 5). exception is when the eBGP connection is Complex (see Section 6).
BGP Roles are mutually confirmed using the BGP Role Capability BGP Roles are mutually confirmed using the BGP Role Capability
(described in Section 3.1) on each eBGP session. (described in Section 4.1) on each eBGP session.
Allowed Roles for eBGP sessions are: Allowed Roles for eBGP sessions are:
* Provider - the local AS is a transit Provider of the remote AS; Provider: the local AS is a transit provider of the remote AS;
* Customer - the local AS is a transit Customer of the remote AS; Customer: the local AS is a transit customer of the remote AS;
* RS - the local AS is a Route Server (usually at an Internet RS: the local AS is a Route Server (usually at an Internet exchange
exchange point) and the remote AS is its RS-Client; point), and the remote AS is its RS-Client;
* RS-Client - the local AS is a client of an RS and the RS is the RS-Client: the local AS is a client of an RS and the RS is the
remote AS; remote AS; and
* Peer - the local and remote ASes are Peers (i.e., have a lateral Peer: the local and remote ASes are Peers (i.e., have a lateral
peering relationship). peering relationship).
3.1. BGP Role Capability 4.1. BGP Role Capability
The BGP Role Capability is defined as follows: The BGP Role Capability is defined as follows:
* Code - 9 Code: 9
* Length - 1 (octet) Length: 1 (octet)
* Value - integer corresponding to speaker's BGP Role (see Table 1). Value: integer corresponding to the speaker's BGP Role (see Table 1)
+=======+==============================+ +=======+==============================+
| Value | Role name (for the local AS) | | Value | Role name (for the local AS) |
+=======+==============================+ +=======+==============================+
| 0 | Provider | | 0 | Provider |
+-------+------------------------------+ +-------+------------------------------+
| 1 | RS | | 1 | RS |
+-------+------------------------------+ +-------+------------------------------+
| 2 | RS-Client | | 2 | RS-Client |
+-------+------------------------------+ +-------+------------------------------+
| 3 | Customer | | 3 | Customer |
+-------+------------------------------+ +-------+------------------------------+
| 4 | Peer (i.e., Lateral Peer) | | 4 | Peer (i.e., Lateral Peer) |
+-------+------------------------------+ +-------+------------------------------+
| 5-255 | Unassigned | | 5-255 | Unassigned |
+-------+------------------------------+ +-------+------------------------------+
Table 1: Predefined BGP Role Values Table 1: Predefined BGP Role Values
If BGP Role is locally configured, the eBGP speaker MUST advertise If the BGP Role is locally configured, the eBGP speaker MUST
BGP Role Capability in the BGP OPEN message. An eBGP speaker MUST advertise the BGP Role Capability in the BGP OPEN message. An eBGP
NOT advertise multiple versions of the BGP Role Capability. The speaker MUST NOT advertise multiple versions of the BGP Role
error handling when multiple BGP Role Capabilities are received is Capability. The error handling when multiple BGP Role Capabilities
described in Section 3.2. are received is described in Section 4.2.
3.2. Role Correctness 4.2. Role Correctness
Section 3.1 described how BGP Role encodes the relationship on each Section 4.1 describes how the BGP Role encodes the relationship on
eBGP session between autonomous systems (ASes). each eBGP session between ASes.
The mere receipt of BGP Role Capability does not automatically The mere receipt of the BGP Role Capability does not automatically
guarantee the Role agreement between two eBGP neighbors. If the BGP guarantee the Role agreement between two eBGP neighbors. If the BGP
Role Capability is advertised, and one is also received from the Role Capability is advertised, and one is also received from the
peer, the Roles MUST correspond to the relationships in Table 2. If peer, the Roles MUST correspond to the relationships in Table 2. If
the Roles do not correspond, the BGP speaker MUST reject the the Roles do not correspond, the BGP speaker MUST reject the
connection using the Role Mismatch Notification (code 2, subcode connection using the Role Mismatch Notification (code 2, subcode 11).
TBD).
+===============+================+ +===============+================+
| Local AS Role | Remote AS Role | | Local AS Role | Remote AS Role |
+===============+================+ +===============+================+
| Provider | Customer | | Provider | Customer |
+---------------+----------------+ +---------------+----------------+
| Customer | Provider | | Customer | Provider |
+---------------+----------------+ +---------------+----------------+
| RS | RS-Client | | RS | RS-Client |
+---------------+----------------+ +---------------+----------------+
skipping to change at page 7, line 26 skipping to change at line 289
| Peer | Peer | | Peer | Peer |
+---------------+----------------+ +---------------+----------------+
Table 2: Allowed Pairs of Role Table 2: Allowed Pairs of Role
Capabilities Capabilities
For backward compatibility, if the BGP Role Capability is sent but For backward compatibility, if the BGP Role Capability is sent but
one is not received, the BGP Speaker SHOULD ignore the absence of the one is not received, the BGP Speaker SHOULD ignore the absence of the
BGP Role Capability and proceed with session establishment. The BGP Role Capability and proceed with session establishment. The
locally configured BGP Role is used for the procedures described in locally configured BGP Role is used for the procedures described in
Section 4. Section 5.
An operator may choose to apply a "strict mode" in which the receipt An operator may choose to apply a "strict mode" in which the receipt
of a BGP Role Capability from the remote AS is required. When of a BGP Role Capability from the remote AS is required. When
operating in the "strict mode", if the BGP Role Capability is sent, operating in the "strict mode", if the BGP Role Capability is sent
but one is not received, then the connection is rejected using the but one is not received, the connection is rejected using the Role
Role Mismatch Notification (code 2, subcode TBD). See comments in Mismatch Notification (code 2, subcode 11). See comments in
Section 7. Section 8.
If an eBGP speaker receives multiple but identical BGP Role If an eBGP speaker receives multiple but identical BGP Role
Capabilities with the same value in each, then the speaker considers Capabilities with the same value in each, then the speaker considers
them to be a single BGP Role Capability and proceeds [RFC5492]. If them to be a single BGP Role Capability and proceeds [RFC5492]. If
multiple BGP Role Capabilities are received and not all of them have 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 same value, then the BGP speaker MUST reject the connection using
the Role Mismatch Notification (code 2, subcode TBD). the Role Mismatch Notification (code 2, subcode 11).
The BGP Role value for the local AS (in conjunction with the OTC The BGP Role value for the local AS (in conjunction with the OTC
Attribute in the received UPDATE message) is used in the route leak Attribute in the received UPDATE message) is used in the route leak
prevention and detection procedures described in Section 4. prevention and detection procedures described in Section 5.
4. BGP Only to Customer (OTC) Attribute 5. BGP Only to Customer (OTC) Attribute
The Only to Customer (OTC) Attribute is an optional transitive path The OTC Attribute is an optional transitive Path Attribute of the
attribute of the UPDATE message with Attribute Type Code 35 and a UPDATE message with Attribute Type Code 35 and a length of 4 octets.
length of 4 octets. The purpose of this attribute is to enforce that The purpose of this attribute is to enforce that once a route is sent
once a route is sent to a Customer, Peer, or RS-Client (see to a Customer, a Peer, or an RS-Client (see definitions in
definitions in Section 2.1), it will subsequently go only to Section 3.1), it will subsequently go only to the Customers. The
Customers. The attribute value is an AS number (ASN) determined by attribute value is an AS number (ASN) determined by the procedures
the procedures described below. described below.
The following ingress procedure applies to the processing of the OTC The following ingress procedure applies to the processing of the OTC
Attribute on route receipt: Attribute on route receipt:
1. If a route with the OTC Attribute is received from a Customer or 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 an RS-Client, then it is a route leak and MUST be considered
ineligible (see Section 2). ineligible (see Section 3).
2. If a route with the OTC Attribute is received from a Peer (i.e., 2. If a route with the OTC Attribute is received from a Peer (i.e.,
remote AS with a Peer Role) and the Attribute has a value that is remote AS with a Peer Role) and the Attribute has a value that is
not equal to the remote (i.e., Peer's) AS number, then it is a not equal to the remote (i.e., Peer's) AS number, then it is a
route leak and MUST be considered ineligible. route leak and MUST be considered ineligible.
3. If a route is received from a Provider, Peer, or RS, and the OTC 3. If a route is received from a Provider, a Peer, or an RS and the
Attribute is not present, then it MUST be added with a value OTC Attribute is not present, then it MUST be added with a value
equal to the AS number of the remote AS. equal to the AS number of the remote AS.
The following egress procedure applies to the processing of the OTC The following egress procedure applies to the processing of the OTC
Attribute on route advertisement: Attribute on route advertisement:
1. If a route is to be advertised to a Customer, Peer, or RS-Client 1. If a route is to be advertised to a Customer, a Peer, or an RS-
(when the sender is an RS), and the OTC Attribute is not present, Client (when the sender is an RS), and the OTC Attribute is not
then when advertising the route, an OTC Attribute MUST be added present, then when advertising the route, an OTC Attribute MUST
with a value equal to the AS number of the local AS. be added with a value equal to the AS number of the local AS.
2. If a route already contains the OTC Attribute, it MUST NOT be 2. If a route already contains the OTC Attribute, it MUST NOT be
propagated to Providers, Peers, or RS(s). propagated to Providers, Peers, or RSes.
The above-described procedures provide both leak prevention for the The above-described procedures provide both leak prevention for the
local AS and leak detection and mitigation multiple hops away. In local AS and leak detection and mitigation multiple hops away. In
the case of prevention at the local AS, the presence of an OTC the case of prevention at the local AS, the presence of an OTC
Attribute indicates to the egress router that the route was learned 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 from a Peer, a Provider, or an RS, and it can be advertised only to
customers. The same OTC Attribute which is set locally also provides the Customers. The same OTC Attribute that is set locally also
a way to detect route leaks by an AS multiple hops away if a route is provides a way to detect route leaks by an AS multiple hops away if a
received from a Customer, Peer, or RS-Client. For example, if an AS route is received from a Customer, a Peer, or an RS-Client. For
sets the OTC Attribute on a route sent to a Peer and the route is example, if an AS sets the OTC Attribute on a route sent to a Peer
subsequently received by a compliant AS from a Customer, then the and the route is subsequently received by a compliant AS from a
receiving AS detects (based on the presence of the OTC Attribute) Customer, then the receiving AS detects (based on the presence of the
that the route is a leak. OTC Attribute) that the route is a leak.
The OTC Attribute might be set at the egress of the remote AS or at The OTC Attribute might be set at the egress of the remote AS or at
the ingress of the local AS, i.e., if the remote AS is non-compliant the ingress of the local AS, i.e., if the remote AS is non-compliant
with this specification, then the local AS will have to set the OTC with this specification, then the local AS will have to set the OTC
Attribute if it is absent. In both scenarios, the OTC value will be Attribute if it is absent. In both scenarios, the OTC value will be
the same. This makes the scheme more robust and benefits early the same. This makes the scheme more robust and benefits early
adopters. adopters.
The OTC Attribute is considered malformed if the length value is not The OTC Attribute is considered malformed if the length value is not
4. An UPDATE message with a malformed OTC Attribute SHALL be handled 4. An UPDATE message with a malformed OTC Attribute SHALL be handled
using the approach of "treat-as-withdraw" [RFC7606]. using the approach of "treat-as-withdraw" [RFC7606].
The BGP Role negotiation and OTC Attribute based procedures specified The BGP Role negotiation and OTC-Attribute-based procedures specified
in this document are NOT RECOMMENDED to be used between autonomous in this document are NOT RECOMMENDED to be used between autonomous
systems in an AS Confederation [RFC5065]. If an OTC Attribute is systems in an AS Confederation [RFC5065]. If an OTC Attribute is
added on egress from the AS Confederation, its value MUST equal the added on egress from the AS Confederation, its value MUST equal the
AS Confederation Identifier. Also, on egress from the AS AS Confederation Identifier. Also, on egress from the AS
Confederation, an UPDATE MUST NOT contain an OTC Attribute with a Confederation, an UPDATE MUST NOT contain an OTC Attribute with a
value corresponding to any Member-AS Number other than the AS value corresponding to any Member-AS Number other than the AS
Confederation Identifier. Confederation Identifier.
The procedures specified in this document in scenarios that use The procedures specified in this document in scenarios that use
private AS numbers behind an Internet-facing ASN (e.g., a data center private AS numbers behind an Internet-facing ASN (e.g., a data-center
network [RFC7938] or stub customer) may be used, but any details are network [RFC7938] or stub customer) may be used, but any details are
outside the scope of this document. On egress from the Internet- outside the scope of this document. On egress from the Internet-
facing AS, the OTC Attribute MUST NOT contain a value other than the facing AS, the OTC Attribute MUST NOT contain a value other than the
Internet-facing ASN. Internet-facing ASN.
Once the OTC Attribute has been set, it MUST be preserved unchanged Once the OTC Attribute has been set, it MUST be preserved unchanged
(this also applies to an AS Confederation). (this also applies to an AS Confederation).
The described ingress and egress procedures are applicable only for The described ingress and egress procedures are applicable only for
the address families AFI 1 (IPv4) and AFI 2 (IPv6) with SAFI 1 the address families AFI 1 (IPv4) and AFI 2 (IPv6) with SAFI 1
(unicast) in both cases and MUST NOT be applied to other address (unicast) in both cases and MUST NOT be applied to other address
families by default. The operator MUST NOT have the ability to families by default. The operator MUST NOT have the ability to
modify the procedures defined in this section. modify the procedures defined in this section.
5. Additional Considerations 6. Additional Considerations
Roles MUST NOT be configured on an eBGP session with a Complex Roles MUST NOT be configured on an eBGP session with a Complex
peering relationship. If multiple eBGP sessions can segregate the peering relationship. If multiple eBGP sessions can segregate the
Complex peering relationship into eBGP sessions with normal peering Complex peering relationship into eBGP sessions with normal peering
relationships, BGP Roles SHOULD be used on each of the resulting eBGP relationships, BGP Roles SHOULD be used on each of the resulting eBGP
sessions. sessions.
An operator may want to achieve an equivalent outcome by configuring An operator may want to achieve an equivalent outcome by configuring
policies on a per-prefix basis to follow the definitions of peering policies on a per-prefix basis to follow the definitions of peering
relations as described in Section 2.1. However, in this case, there relations as described in Section 3.1. However, in this case, there
are no in-band measures to check the correctness of the per-prefix are no in-band measures to check the correctness of the per-prefix
peering configuration. peering configuration.
The incorrect setting of BGP Roles and/or OTC Attributes may affect The incorrect setting of BGP Roles and/or OTC Attributes may affect
prefix propagation. Further, this document does not specify any prefix propagation. Further, this document does not specify any
special handling of an incorrect AS number in the OTC Attribute. special handling of an incorrect AS number in the OTC Attribute.
In AS migration scenarios [RFC7705], a given router may represent In AS migration scenarios [RFC7705], a given router may represent
itself as any one of several different ASes. This should not be a itself as any one of several different ASes. This should not be a
problem since the egress procedures in Section 4 specify that the OTC problem since the egress procedures in Section 5 specify that the OTC
Attribute is to be attached as part of route transmission. Attribute is to be attached as part of route transmission.
Therefore, a router is expected to set the OTC value equal to the ASN Therefore, a router is expected to set the OTC value equal to the ASN
it is currently representing itself as. it is currently representing itself as.
Section 6 of [RFC7606] documents possible negative impacts of "treat- Section 6 of [RFC7606] documents possible negative impacts of "treat-
as-withdraw" behavior. Such negative impacts may include forwarding as-withdraw" behavior. Such negative impacts may include forwarding
loops or blackholes. It also discusses debugging considerations loops or dropped traffic. It also discusses debugging considerations
related to this behavior. related to this behavior.
6. IANA Considerations 7. IANA Considerations
IANA has registered a new BGP Capability (Section 3.1) in the IANA has registered a new BGP Capability (Section 4.1) in the
"Capability Codes" registry's "IETF Review" range [RFC5492]. The "Capability Codes" registry within the "IETF Review" range [RFC5492].
description for the new capability is "BGP Role". IANA has assigned The description for the new capability is "BGP Role". IANA has
the value 9 [to be removed upon publication: assigned the value 9. This document is the reference for the new
https://www.iana.org/assignments/capability-codes/capability- capability.
codes.xhtml]. This document is the reference for the new capability.
The BGP Role capability includes a Value field, for which IANA is IANA has created and now maintains a new subregistry called "BGP Role
requested to create and maintain a new sub-registry called "BGP Role Value" within the "Capability Codes" registry. Registrations should
Value" in the Capability Codes registry. Assignments consist of a include a value, a role name, and a reference to the defining
Value and a corresponding Role name. Initially, this registry is to document. IANA has registered the values in Table 3. Future
be populated with the data contained in Table 1 found in Section 3.1. assignments may be made by the "IETF Review" policy as defined in
Future assignments may be made by the "IETF Review" policy as defined [RFC8126].
in [RFC8126]. The registry is as shown in Table 3.
+=======+===============================+===============+ +=======+===============================+===============+
| Value | Role name (for the local AS) | Reference | | Value | Role name (for the local AS) | Reference |
+=======+===============================+===============+ +=======+===============================+===============+
| 0 | Provider | This document | | 0 | Provider | This document |
+-------+-------------------------------+---------------+ +-------+-------------------------------+---------------+
| 1 | RS | This document | | 1 | RS | This document |
+-------+-------------------------------+---------------+ +-------+-------------------------------+---------------+
| 2 | RS-Client | This document | | 2 | RS-Client | This document |
+-------+-------------------------------+---------------+ +-------+-------------------------------+---------------+
| 3 | Customer | This document | | 3 | Customer | This document |
+-------+-------------------------------+---------------+ +-------+-------------------------------+---------------+
| 4 | Peer (i.e., Lateral Peer) | This document | | 4 | Peer (i.e., Lateral Peer) | This document |
+-------+-------------------------------+---------------+ +-------+-------------------------------+---------------+
| 5-255 | To be assigned by IETF Review | | | 5-255 | To be assigned by IETF Review | |
+-------+-------------------------------+---------------+ +-------+-------------------------------+---------------+
Table 3: IANA Registry for BGP Role Table 3: IANA Registry for BGP Role
IANA has registered a new OPEN Message Error subcode named the "Role IANA has registered a new OPEN Message Error subcode named "Role
Mismatch" (see Section 3.2) in the OPEN Message Error subcodes Mismatch" (see Section 4.2) in the "OPEN Message Error subcodes"
registry. IANA has assigned the value 11 [to be removed upon registry. IANA has assigned the value 11. This document is the
publication: https://www.iana.org/assignments/bgp-parameters/bgp- reference for the new subcode.
parameters.xhtml#bgp-parameters-6]. This document is the reference
for the new subcode.
Due to improper use of the values 8, 9, and 10 in the OPEN Message Due to improper use of the values 8, 9, and 10, IANA has marked
Error subcodes registry, this document requested IANA to mark these values 8-10 as "Deprecated" in the "OPEN Message Error subcodes"
values as "Deprecated". IANA has marked values 8-10 as "Deprecated" registry. This document is listed as the reference.
in the OPEN Message Error subcodes registry. This document is listed
as the reference.
IANA has also registered a new path attribute named "Only to Customer IANA has also registered a new Path Attribute named "Only to Customer
(OTC)" (see Section 4) in the "BGP Path Attributes" registry. IANA (OTC)" (see Section 5) in the "BGP Path Attributes" registry. IANA
has assigned code value 35 [To be removed upon publication: has assigned code value 35. This document is the reference for the
http://www.iana.org/assignments/bgp-parameters/bgp- new attribute.
parameters.xhtml#bgp-parameters-2]. This document is the reference
for the new attribute.
7. Security Considerations 8. Security Considerations
The security considerations of BGP (as specified in [RFC4271] and The security considerations of BGP (as specified in [RFC4271] and
[RFC4272]) apply. [RFC4272]) apply.
This document proposes a mechanism using BGP Role for the prevention This document proposes a mechanism that uses the BGP Role for the
and detection of route leaks that are the result of BGP policy prevention and detection of route leaks that are the result of BGP
misconfiguration. A misconfiguration of the BGP Role may affect policy misconfiguration. A misconfiguration of the BGP Role may
prefix propagation. For example, if a downstream (i.e., towards a affect prefix propagation. For example, if a downstream (i.e.,
Customer) peering link were misconfigured with a Provider or Peer towards a Customer) peering link were misconfigured with a Provider
Role, this will limit the number of prefixes that can be advertised or Peer Role, it would limit the number of prefixes that can be
in this direction. On the other hand, if an upstream provider were advertised in this direction. On the other hand, if an upstream
misconfigured (by a local AS) with the Customer Role, this may result provider were misconfigured (by a local AS) with the Customer Role,
in propagating routes that are received from other Providers or it may result in propagating routes that are received from other
Peers. But the BGP Role negotiation and the resulting confirmation Providers or Peers. But the BGP Role negotiation and the resulting
of Roles make such misconfigurations unlikely. confirmation of Roles make such misconfigurations unlikely.
Setting the strict mode of operation for BGP Role negotiation as the Setting the strict mode of operation for BGP Role negotiation as the
default may result in a situation where the eBGP session will not default may result in a situation where the eBGP session will not
come up after a software update. Implementations with such default come up after a software update. Implementations with such default
behavior are strongly discouraged. behavior are strongly discouraged.
Removing the OTC Attribute or changing its value can limit the Removing the OTC Attribute or changing its value can limit the
opportunity for route leak detection. Such activity can be done on opportunity for route leak detection. Such activity can be done on
purpose as part of an on-path attack. For example, an AS can remove purpose as part of an on-path attack. For example, an AS can remove
the OTC Attribute on a received route and then leak the route to its the OTC Attribute on a received route and then leak the route to its
transit provider. This kind of threat is not new in BGP and it may transit provider. This kind of threat is not new in BGP, and it may
affect any Attribute (Note: BGPsec [RFC8205] offers protection only affect any Attribute (note that BGPsec [RFC8205] offers protection
for the AS_PATH Attribute). only for the AS_PATH Attribute).
Adding an OTC Attribute when the route is advertised from Customer to Adding an OTC Attribute when the route is advertised from Customer to
Provider will limit the propagation of the route. Such a route may Provider will limit the propagation of the route. Such a route may
be considered as ineligible by the immediate Provider or its Peers or be considered as ineligible by the immediate Provider or its Peers or
upper layer Providers. This kind of OTC Attribute addition is upper-layer Providers. This kind of OTC Attribute addition is
unlikely to happen on the Provider side because it will limit the unlikely to happen on the Provider side because it will limit the
traffic volume towards its Customer. On the Customer side, adding an traffic volume towards its Customer. On the Customer side, adding an
OTC Attribute for traffic engineering purposes is also discouraged OTC Attribute for traffic-engineering purposes is also discouraged
because it will limit route propagation in an unpredictable way. because it will limit route propagation in an unpredictable way.
8. References 9. References
8.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>. <https://www.rfc-editor.org/info/rfc4271>.
skipping to change at page 13, line 28 skipping to change at line 553
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References 9.2. Informative References
[Gao] Gao, L. and J. Rexford, "Stable Internet routing without [GAO-REXFORD]
global coordination", IEEE/ACM Transactions on Gao, L. and J. Rexford, "Stable Internet routing without
Networking, Volume 9, Issue 6, pp 689-692, DOI global coordination", IEEE/ACM Transactions on Networking,
10.1109/90.974523, December 2001, Volume 9, Issue 6, pp. 689-692, DOI 10.1109/90.974523,
December 2001,
<https://ieeexplore.ieee.org/document/974523>. <https://ieeexplore.ieee.org/document/974523>.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006, RFC 4272, DOI 10.17487/RFC4272, January 2006,
<https://www.rfc-editor.org/info/rfc4272>. <https://www.rfc-editor.org/info/rfc4272>.
[RFC7705] George, W. and S. Amante, "Autonomous System Migration [RFC7705] George, W. and S. Amante, "Autonomous System Migration
Mechanisms and Their Effects on the BGP AS_PATH Mechanisms and Their Effects on the BGP AS_PATH
Attribute", RFC 7705, DOI 10.17487/RFC7705, November 2015, Attribute", RFC 7705, DOI 10.17487/RFC7705, November 2015,
<https://www.rfc-editor.org/info/rfc7705>. <https://www.rfc-editor.org/info/rfc7705>.
skipping to change at page 14, line 10 skipping to change at line 585
[RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol [RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
Specification", RFC 8205, DOI 10.17487/RFC8205, September Specification", RFC 8205, DOI 10.17487/RFC8205, September
2017, <https://www.rfc-editor.org/info/rfc8205>. 2017, <https://www.rfc-editor.org/info/rfc8205>.
Acknowledgments Acknowledgments
The authors wish to thank Alvaro Retana, Bruno Decraene, Jeff Haas, The authors wish to thank Alvaro Retana, Bruno Decraene, Jeff Haas,
John Scudder, Sue Hares, Ben Maddison, Andrei Robachevsky, Daniel John Scudder, Sue Hares, Ben Maddison, Andrei Robachevsky, Daniel
Ginsburg, Ruediger Volk, Pavel Lunin, Gyan Mishra, and Ignas Bagdonas Ginsburg, Ruediger Volk, Pavel Lunin, Gyan Mishra, and Ignas Bagdonas
for review, comments, and suggestions during the course of this work. for their reviews, comments, and suggestions during the course of
Thanks are also due to many IESG reviewers whose comments greatly this work. Thanks are also due to many IESG reviewers whose comments
helped improve the clarity, accuracy, and presentation in the greatly helped improve the clarity, accuracy, and presentation in the
document. document.
Contributors Contributors
Brian Dickson Brian Dickson
Independent Independent
Email: brian.peter.dickson@gmail.com Email: brian.peter.dickson@gmail.com
Doug Montgomery Doug Montgomery
USA National Institute of Standards and Technology USA National Institute of Standards and Technology
skipping to change at page 15, line 4 skipping to change at line 624
123290 123290
Russian Federation Russian Federation
Email: eb@qrator.net Email: eb@qrator.net
Randy Bush Randy Bush
Internet Initiative Japan & Arrcus, Inc. Internet Initiative Japan & Arrcus, Inc.
5147 Crystal Springs 5147 Crystal Springs
Bainbridge Island, Washington 98110 Bainbridge Island, Washington 98110
United States of America United States of America
Email: randy@psg.com Email: randy@psg.com
Keyur Patel Keyur Patel
Arrcus Arrcus
2077 Gateway Place, Suite #400 2077 Gateway Place
Suite #400
San Jose, CA 95119 San Jose, CA 95119
United States of America United States of America
Email: keyur@arrcus.com Email: keyur@arrcus.com
Kotikalapudi Sriram Kotikalapudi Sriram
USA National Institute of Standards and Technology USA National Institute of Standards and Technology
100 Bureau Drive 100 Bureau Drive
Gaithersburg, MD 20899 Gaithersburg, MD 20899
United States of America United States of America
Email: ksriram@nist.gov Email: ksriram@nist.gov
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