draft-ietf-idr-bgp-open-policy-07.txt   draft-ietf-idr-bgp-open-policy-08.txt 
Network Working Group A. Azimov Network Working Group A. Azimov
Internet-Draft E. Bogomazov Internet-Draft E. Bogomazov
Intended status: Standards Track Qrator Labs Intended status: Standards Track Qrator Labs
Expires: July 12, 2020 R. Bush Expires: September 10, 2020 R. Bush
Internet Initiative Japan & Arrcus Internet Initiative Japan & Arrcus
K. Patel K. Patel
Arrcus, Inc. Arrcus, Inc.
K. Sriram K. Sriram
US NIST US NIST
January 9, 2020 March 9, 2020
Route Leak Prevention using Roles in Update and Open messages Route Leak Prevention using Roles in Update and Open messages
draft-ietf-idr-bgp-open-policy-07 draft-ietf-idr-bgp-open-policy-08
Abstract Abstract
Route leaks are the propagation of BGP prefixes which violate Route leaks are the propagation of BGP prefixes which violate
assumptions of BGP topology relationships; e.g. passing a route assumptions of BGP topology relationships; e.g. passing a route
learned from one peer to another peer or to a transit provider, learned from one peer to another peer or to a transit provider,
passing a route learned from one transit provider to another transit passing a route learned from one transit provider to another transit
provider or to a peer. Today, approaches to leak prevention rely on provider or to a peer. Today, approaches to leak prevention rely on
marking routes by operator configuration, with no check that the marking routes by operator configuration, with no check that the
configuration corresponds to that of the BGP neighbor, or enforcement configuration corresponds to that of the BGP neighbor, or enforcement
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Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Peering Relationships . . . . . . . . . . . . . . . . . . . . 3 2. Peering Relationships . . . . . . . . . . . . . . . . . . . . 3
3. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. BGP Role Capability . . . . . . . . . . . . . . . . . . . . . 4 4. BGP Role Capability . . . . . . . . . . . . . . . . . . . . . 4
5. Role correctness . . . . . . . . . . . . . . . . . . . . . . 5 5. Role correctness . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Strict mode . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Strict mode . . . . . . . . . . . . . . . . . . . . . . . 6
6. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 6 6. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 6
7. Enforcement . . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Enforcement . . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Additional Considerations . . . . . . . . . . . . . . . . . . 7 8. Additional Considerations . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Security Considerations . . . . . . . . . . . . . . . . . . . 8 10. Security Considerations . . . . . . . . . . . . . . . . . . . 8
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
12.1. Normative References . . . . . . . . . . . . . . . . . . 8 12.1. Normative References . . . . . . . . . . . . . . . . . . 8
12.2. Informative References . . . . . . . . . . . . . . . . . 9 12.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
BGP route leak occurs when a route is learned from a transit provider A BGP route leak occurs when a route is learned from a transit
or peer and then announced to another provider or peer. See provider or peer and then announced to another provider or peer. See
[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 two BGP speakers. BGP route filtering or lack of coordination between two BGP speakers.
The mechanism proposed in The mechanism proposed in
[I-D.ietf-grow-route-leak-detection-mitigation] uses large- [I-D.ietf-grow-route-leak-detection-mitigation] uses large-
communities to perform detection and mitigation of route leaks. communities to perform detection and mitigation of route leaks.
While signaling using communities is easy to implement and deploy While signaling using communities is easy to implement and deploy
quickly, it normally relies on operator-maintained policy quickly, it normally relies on operator-maintained policy
configuration, which is often vulnerable to misconfiguration. There configuration, which is often vulnerable to misconfiguration and even
is also the vulnerability that the community signal may be stripped, attack [Streibelt]. There is also the vulnerability that the
accidentally or maliciously. community signal may be stripped, accidentally or maliciously.
This document provides configuration automation using 'BGP roles', This document provides configuration automation using 'BGP roles',
which are negotiated using a new BGP Capability Code in OPEN message which are negotiated using a new BGP Capability Code in OPEN message
(see Section 4 in [RFC5492]). Either or both BGP speakers MAY be (see Section 4 in [RFC5492]). Either or both BGP speakers MAY be
configured to require that this capability be agreed for the BGP OPEN configured to require that this capability be agreed for the BGP OPEN
to succeed. to succeed.
A new BGP Path Attribute is specified that SHOULD be automatically A new BGP Path Attribute is specified that SHOULD be automatically
configured using BGP roles. This attribute prevents networks from configured using BGP roles. This attribute prevents networks from
creating leaks, and detects leaks created by third parties. creating leaks, and detects leaks created by third parties.
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its customers. A peer MUST NOT send to a peer prefixes learned its customers. A peer MUST NOT send to a peer prefixes learned
from other peers, from its providers, or from RS(s). from other peers, from its providers, or from RS(s).
Of course, any BGP speaker may apply policy to reduce what is Of course, any BGP speaker may apply policy to reduce what is
announced, and a recipient may apply policy to reduce the set of announced, and a recipient may apply policy to reduce the set of
routes they accept. Violation of the above rules may result in route routes they accept. Violation of the above rules may result in route
leaks and MUST not be allowed. Automatic enforcement of these rules leaks and MUST not be allowed. Automatic enforcement of these rules
should significantly reduce route leaks that may otherwise occur due should significantly reduce route leaks that may otherwise occur due
to manual configuration mistakes. While enforcing the above rules to manual configuration mistakes. While enforcing the above rules
will address most BGP peering scenarios, their configuration is not will address most BGP peering scenarios, their configuration is not
part of BGP itself; therefore, additionally requiring configuration part of BGP itself; therefore,configuration of ingress and egress
of ingress and egress prefix filters is still strongly advised. prefix filters is still strongly advised.
3. BGP Role 3. BGP Role
BGP Role is new configuration option that SHOULD be configured on BGP Role is new configuration option that SHOULD be configured on
each BGP session. It reflects the real-world agreement between two each BGP session. It reflects the real-world agreement between two
BGP speakers about their relationship. BGP speakers about their relationship.
Allowed Role values for eBGP sessions are: Allowed Role values for eBGP sessions are:
o Provider - sender is a transit provider to neighbor; o Provider - sender is a transit provider to neighbor;
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| Customer | Provider | | Customer | Provider |
| RS | RS-Client | | RS | RS-Client |
| RS-Client | RS | | RS-Client | RS |
| Peer | Peer | | Peer | Peer |
+-------------+---------------+ +-------------+---------------+
Table 2: Allowed Role Capabilities Table 2: Allowed Role Capabilities
If the observed Role pair is not in the above table, then the If the observed Role pair is not in the above table, then the
receiving speaker MUST send a Role Mismatch Notification (code 2, receiving speaker MUST send a Role Mismatch Notification (code 2,
subcode <TBD2>). subcode <TBD2>) and reset the BGP session.
5.1. Strict mode 5.1. Strict mode
A new BGP configuration option "strict mode" is defined with values 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 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 establish a BGP session with a neighbor which does not announce the
BGP Role capability in the OPEN message. If a speaker rejects a BGP Role capability in the OPEN message. If a speaker rejects a
connection, it MUST send a Connection Rejected Notification [RFC4486] connection, it MUST send a Connection Rejected Notification [RFC4486]
(Notification with error code 6, subcode 5). By default, strict mode (Notification with error code 6, subcode 5). By default, strict mode
SHOULD be set to false for backward compatibility with BGP speakers SHOULD be set to false for backward compatibility with BGP speakers
that do not yet support this mechanism. that do not yet support this mechanism.
6. BGP Only to Customer (OTC) Attribute 6. BGP Only to Customer (OTC) Attribute
Newly defined here, the Only to Customer (OTC) is an optional, Newly defined here, the Only to Customer (OTC) is an optional, 4 byte
transitive BGP Path attribute with the Type Code <TBD3>. The OTC long, transitive BGP Path attribute with the Type Code <TBD3>. The
attribute is four bytes long and its value equals an AS number. The purpose of this attribute is to guarantee that once route is sent to
customer, peer or RS-client it will go only to customers. The
semantics and usage of the OTC attribute are made clear by the semantics and usage of the OTC attribute are made clear by the
ingress and egress policies described below. ingress and egress policies described below.
The following ingress policy applies to the OTC attribute: The following ingress policy applies to the OTC attribute:
1. If a route with OTC attribute is received from a Customer or RS- 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. client, then it is a route leak and MUST be rejected.
2. If a route with OTC attribute is received from a Peer and its 2. If a route with OTC attribute is received from a Peer and its
value is not equal to the neighbor's ASN, then it is a route leak value is not equal to the neighbor's ASN, then it is a route leak
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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 value equal attribute is not present, then it MUST be added with value equal
to the neighbor's AS number. to the neighbor's AS number.
The egress policy MUST be: The egress policy MUST be:
1. A route with the OTC attribute set MUST NOT be sent to providers, 1. A route with the OTC attribute set MUST NOT be sent to providers,
peers, or RS(s). peers, or RS(s).
2. If route is sent to a customer or peer, or an RS clien and the 2. If route is sent to a customer or peer, or an RS-Client and the
OTC attribute is not present, then it MUST be added with value OTC attribute is not present, then it MUST be added with value
equal to AS number of the sender. equal to AS number of the sender.
Once the OTC attribute has been set, it MUST be preserved unchanged. Once the OTC attribute has been set, it MUST be preserved unchanged.
7. Enforcement 7. Enforcement
Having the relationship unequivocally agreed between the two peers in Having the relationship unequivocally agreed between the two peers in
BGP OPEN is critical; BGP implementations MUST enforce the BGP OPEN is critical; BGP implementations MUST enforce the
relationship/role establishment rules (see Section 5) in order to relationship/role establishment rules (see Section 5) in order to
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There are peering relationships that are 'complex', i.e., both There are peering relationships that are 'complex', i.e., both
parties are intentionally sending prefixes received from each other parties are intentionally sending prefixes received from each other
to their non-transit peers and/or transit providers. If multiple BGP to their non-transit peers and/or transit providers. If multiple BGP
peerings can segregate the 'complex' parts of the relationship, the peerings can segregate the 'complex' parts of the relationship, the
complex peering roles can be segregated into different normal BGP complex peering roles can be segregated into different normal BGP
sessions, and BGP Roles MUST be used on each of the resulting normal sessions, and BGP Roles MUST be used on each of the resulting normal
(non-complex) BGP sessions. (non-complex) BGP sessions.
No Roles SHOULD be configured on a 'complex' BGP session (assuming it 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 is not segregated) and in that case, OTC MUST be set by configuration
on a per-prefix basis. However, there can be no measures to check on a per-prefix basis. However, there are no built-in measures to
correctness of OTC use if BGP Role is not configured. check correctness of OTC use if BGP Role is not configured.
As the BGP Role reflects the peering relationship between neighbors, As the BGP Role reflects the peering relationship between neighbors,
it might have other uses beyond the route leaks solution discussed so it might have other uses beyond the route leaks solution discussed so
far. For example, BGP Role might affect route priority, or be used far. For example, BGP Role might affect route priority, or be used
to distinguish borders of a network if a network consists of multiple 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 ASs. Though such uses may be worthwhile, they are not the goal of
this document. Note that such uses would require local policy this document. Note that such uses would require local policy
control. control.
As BGP role configuration results in automatic creation of inbound/ As BGP role configuration results in automatic creation of inbound/
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option, named "Only to Customer (OTC)" with an assigned value <TBD3> option, named "Only to Customer (OTC)" with an assigned value <TBD3>
[To be removed upon publication: http://www.iana.org/assignments/bgp- [To be removed upon publication: http://www.iana.org/assignments/bgp-
parameters/bgp-parameters.xhtml#bgp-parameters-2] [RFC4271]. The parameters/bgp-parameters.xhtml#bgp-parameters-2] [RFC4271]. The
length of this attribute is four bytes. length of this attribute is four bytes.
10. Security Considerations 10. Security Considerations
This document proposes a mechanism for prevention of route leaks that This document proposes a mechanism for prevention of route leaks that
are the result of BGP policy mis-configuration. are the result of BGP policy mis-configuration.
Deliberate sending of a known conflicting BGP Role could be used to
sabotage a BGP connection. This is easily detectable.
A misconfiguration in OTC setup may affect prefix propagation. But A misconfiguration in OTC setup may affect prefix propagation. But
the automation that is provided by BGP roles should make such the automation that is provided by BGP roles should make such
misconfiguration unlikely. misconfiguration unlikely.
11. Acknowledgments 11. Acknowledgments
The authors wish to thank Douglas Montgomery, Brian Dickson, Andrei The authors wish to thank Douglas Montgomery, Brian Dickson, Andrei
Robachevsky, and Daniel Ginsburg for their contributions to a variant Robachevsky, and Daniel Ginsburg for their contributions to a variant
of this work. of this work.
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[RFC7908] Sriram, K., Montgomery, D., McPherson, D., Osterweil, E., [RFC7908] Sriram, K., Montgomery, D., McPherson, D., Osterweil, E.,
and B. Dickson, "Problem Definition and Classification of and B. Dickson, "Problem Definition and Classification of
BGP Route Leaks", RFC 7908, DOI 10.17487/RFC7908, June BGP Route Leaks", RFC 7908, DOI 10.17487/RFC7908, June
2016, <https://www.rfc-editor.org/info/rfc7908>. 2016, <https://www.rfc-editor.org/info/rfc7908>.
[RFC8212] Mauch, J., Snijders, J., and G. Hankins, "Default External [RFC8212] Mauch, J., Snijders, J., and G. Hankins, "Default External
BGP (EBGP) Route Propagation Behavior without Policies", BGP (EBGP) Route Propagation Behavior without Policies",
RFC 8212, DOI 10.17487/RFC8212, July 2017, RFC 8212, DOI 10.17487/RFC8212, July 2017,
<https://www.rfc-editor.org/info/rfc8212>. <https://www.rfc-editor.org/info/rfc8212>.
[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",
<https://people.mpi-inf.mpg.de/~fstreibelt/preprint/
communities-imc2018.pdf>.
Authors' Addresses Authors' Addresses
Alexander Azimov Alexander Azimov
Qrator Labs Qrator Labs
Email: a.e.azimov@gmail.com Email: a.e.azimov@gmail.com
Eugene Bogomazov Eugene Bogomazov
Qrator Labs Qrator Labs
Email: eb@qrator.net Email: eb@qrator.net
Randy Bush Randy Bush
Internet Initiative Japan & Arrcus Internet Initiative Japan & Arrcus
Email: randy@psg.com Email: randy@psg.com
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