draft-ietf-idr-bgp-open-policy-18.txt   draft-ietf-idr-bgp-open-policy-19.txt 
Network Working Group A. Azimov Network Working Group A. Azimov
Internet-Draft Qrator Labs & Yandex Internet-Draft Qrator Labs & Yandex
Intended status: Standards Track E. Bogomazov Intended status: Standards Track E. Bogomazov
Expires: June 7, 2022 Qrator Labs Expires: July 11, 2022 Qrator Labs
R. Bush R. Bush
Internet Initiative Japan & Arrcus, Inc. Internet Initiative Japan & Arrcus, Inc.
K. Patel K. Patel
Arrcus Arrcus
K. Sriram K. Sriram
USA NIST USA NIST
December 4, 2021 January 7, 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-18 draft-ietf-idr-bgp-open-policy-19
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).
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Peering Relationships . . . . . . . . . . . . . . . . . . . . 4 2. Peering Relationships . . . . . . . . . . . . . . . . . . . . 4
3. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. BGP Role Capability . . . . . . . . . . . . . . . . . . . 5 3.1. BGP Role Capability . . . . . . . . . . . . . . . . . . . 5
3.2. Role Correctness . . . . . . . . . . . . . . . . . . . . 6 3.2. Role Correctness . . . . . . . . . . . . . . . . . . . . 6
4. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 7 4. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 7
5. Additional Considerations . . . . . . . . . . . . . . . . . . 8 5. Additional Considerations . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . 12
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
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
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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).
RS-Client: MAY propagate any route learned from a Customer, or RS-Client: MAY propagate any route learned from a Customer, or
locally originated, to an RS. All other routes MUST NOT be locally originated, to an RS. All other routes MUST NOT be
propagated. propagated.
Peer: MAY propagate any route learned from a Customer, or locally Peer: MAY propagate any route learned from a Customer, or locally
originated, to a Peer. All other routes MUST NOT be propagated. 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
the corresponding peering relationship with the remote AS is
Provider-to-Customer, Customer-to-Provider, RS-to-RS-Client, RS-
Client-to-RS, or Peer-to-Peer (i.e., lateral peers), respectively.
These are called normal peering relationships.
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
peering relationship is Provider-to-Customer for some prefixes while
it is Peer-to-Peer for other prefixes [Gao].
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 above rules may result in route leaks. Automatic Violation of the above rules may result in route leaks. Automatic
enforcement of these rules should significantly reduce route leaks enforcement of these rules should significantly reduce route leaks
that may otherwise occur due to manual configuration mistakes. that may otherwise occur due to manual configuration mistakes.
As specified in Section 4, the Only to Customer (OTC) Attribute is As specified in Section 4, the Only to Customer (OTC) Attribute is
used to identify all the routes in the AS that have been received used to identify all the routes in the AS that have been received
from a Peer, Provider, or RS. from a Peer, Provider, or RS.
3. BGP Role 3. 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 1.1) based on the local AS's knowledge of its Role. The only Section 1.1) 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 5).
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 3.1) on each eBGP session.
Allowed Roles for eBGP sessions are: Allowed Roles for eBGP sessions are:
o Provider - the local AS is a transit Provider of the remote AS; 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 Customer - the local AS is a transit Customer of the remote AS;
o RS - the local AS is a Route Server (usually at an Internet o RS - the local AS is a Route Server (usually at an Internet
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3.2. Role Correctness 3.2. Role Correctness
Section 3.1 described how BGP Role encodes the relationship on each Section 3.1 described how BGP Role encodes the relationship on each
eBGP session between autonomous systems (ASes). eBGP session between autonomous systems (ASes).
The mere receipt of BGP Role Capability does not automatically The mere receipt of 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 8). connection using the Role Mismatch Notification (code 2, subcode
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 |
| RS-Client | RS | | RS-Client | RS |
| Peer | Peer | | Peer | Peer |
+---------------+----------------+ +---------------+----------------+
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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 4.
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, then the connection is rejected using the
Role Mismatch Notification (code 2, subcode 8). See comments in Role Mismatch Notification (code 2, subcode TBD). See comments in
Section 7. Section 7.
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 must Capabilities with the same value in each, then the speaker must
consider it to be a single BGP Role Capability and proceed [RFC5492]. consider it to be a single BGP Role Capability and proceed [RFC5492].
If multiple BGP Role Capabilities are received and not all of them If multiple BGP Role Capabilities are received and not all of them
have the same value, then the BGP speaker MUST reject the connection have the same value, then the BGP speaker MUST reject the connection
using the Role Mismatch Notification (code 2, subcode 8). using the Role Mismatch Notification (code 2, subcode TBD).
The BGP Role value for the local AS is used in the route leak 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
prevention and detection procedures described in Section 4. prevention and detection procedures described in Section 4.
4. BGP Only to Customer (OTC) Attribute 4. BGP Only to Customer (OTC) Attribute
The Only to Customer (OTC) Attribute is an optional transitive path The Only to Customer (OTC) Attribute is an optional transitive path
attribute with Attribute Type Code 35 and a length of 4 octets. The attribute of the UPDATE message with Attribute Type Code 35 and a
purpose of this attribute is to guarantee that once a route is sent length of 4 octets. The purpose of this attribute is to guarantee
to a Customer, Peer, or RS-Client, it will subsequently go only to that once a route is sent to a Customer, Peer, or RS-Client, it will
Customers. The attribute value is an AS number (ASN) determined by subsequently go only to Customers. The attribute value is an AS
the policy described below. number (ASN) determined by the policy described below.
The following ingress policy applies to the processing of the OTC The following ingress policy applies to the processing of the OTC
Attribute: Attribute:
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 RS-Client, then it is a route leak and MUST be considered
ineligible (see Section 1.1). ineligible (see Section 1.1).
2. If a route with the OTC Attribute is received from a Peer and at 2. If a route with the OTC Attribute is received from a Peer and the
least one of the OTC Attributes has a value that is not equal to Attribute has a value that is not equal to the remote (i.e.,
the remote (i.e., Peer's) AS number, then it is a route leak and Peer's) AS number, then it is a route leak and MUST be considered
MUST be considered ineligible. 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, Peer, or RS, and the OTC
Attribute is not present, then it MUST be added with a value 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 policy applies to the processing of the OTC The following egress policy applies to the processing of the OTC
Attribute: Attribute:
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, Peer, or RS-Client
(when the sender is an RS), and the OTC Attribute is not present, (when the sender is an RS), and the OTC Attribute is not present,
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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).
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.
The described ingress and egress policies are applicable only for The described ingress and egress policies are applicable only for
unicast IPv4 and IPv6 address families and MUST NOT be applied to unicast IPv4 and IPv6 address families and MUST NOT be applied to
other address families by default. The operator MUST NOT have the other address families by default. The operator MUST NOT have the
ability to modify the policies defined in this section. ability to modify the policies defined in this section.
5. Additional Considerations 5. Additional Considerations
There are peering relationships that are 'complex', i.e., both Roles MUST NOT be configured on an eBGP session with a Complex
parties intentionally advertise prefixes received from each other to peering relationship. If multiple eBGP sessions can segregate the
their Peers and/or transit Providers. If multiple eBGP sessions can Complex peering relationship into eBGP sessions with normal peering
segregate the 'complex' parts of the relationship, then the complex relationships, BGP Roles SHOULD be used on each of the resulting eBGP
peering roles can be segregated into different normal eBGP sessions, 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' eBGP session (assuming An operator may want to achieve an equivalent outcome by configuring
it is not segregated). An operator may want to achieve an equivalent policies on a per-prefix basis to follow the definitions of peering
outcome by configuring policies on a per-prefix basis to follow the relations as described in Section 2. However, in this case, there
definitions of peering relations as described in Section 2. However, are no built-in measures to check the correctness of the per-prefix
in this case, there are no built-in measures to check the correctness peering configuration.
of the per-prefix 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 incorrect AS numbers in the OTC Attribute. special handling of incorrect AS numbers in the OTC Attribute.
6. IANA Considerations 6. IANA Considerations
IANA has registered a new BGP Capability (Section 3.1) in the IANA has registered a new BGP Capability (Section 3.1) in the
"Capability Codes" registry's "IETF Review" range [RFC5492]. The "Capability Codes" registry's "IETF Review" range [RFC5492]. The
description for the new capability is "BGP Role". IANA has assigned description for the new capability is "BGP Role". IANA has assigned
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| 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 the "Role
Mismatch" (see Section 3.2) in the OPEN Message Error subcodes Mismatch" (see Section 3.2) in the OPEN Message Error subcodes
registry. IANA has assigned the value 8 [to be removed upon registry. IANA has assigned the value TBD [to be removed upon
publication: https://www.iana.org/assignments/bgp-parameters/bgp- publication: https://www.iana.org/assignments/bgp-parameters/bgp-
parameters.xhtml#bgp-parameters-6]. This document is the reference parameters.xhtml#bgp-parameters-6]. This document is the reference
for the new subcode. for the new subcode.
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 4) in the "BGP Path Attributes" registry. IANA
has assigned code value 35 [To be removed upon publication: has assigned code value 35 [To be removed upon publication:
http://www.iana.org/assignments/bgp-parameters/bgp- http://www.iana.org/assignments/bgp-parameters/bgp-
parameters.xhtml#bgp-parameters-2]. This document is the reference parameters.xhtml#bgp-parameters-2]. This document is the reference
for the new attribute. for the new attribute.
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