draft-ietf-idr-bgp-open-policy-10.txt   draft-ietf-idr-bgp-open-policy-11.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: November 16, 2020 R. Bush Expires: December 18, 2020 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
May 15, 2020 June 16, 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-10 draft-ietf-idr-bgp-open-policy-11
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 lateral peer to another lateral peer or a transit
passing a route learned from one transit provider to another transit provider, passing a route learned from one transit provider to
provider or to a peer. Today, approaches to leak prevention rely on another transit provider or a lateral peer. Existing approaches to
marking routes by operator configuration, with no check that the leak prevention rely on marking routes by operator configuration,
configuration corresponds to that of the BGP neighbor, or enforcement with no check that the configuration corresponds to that of the eBGP
that the two BGP speakers agree on the relationship. This document neighbor, or enforcement that the two eBGP speakers agree on the
enhances BGP OPEN to establish agreement of the (peer, customer, relationship. This document enhances BGP OPEN to establish agreement
provider, Route Server, Route Server client) relationship of two of the (peer, customer, provider, Route Server, Route Server client)
neighboring BGP speakers to enforce appropriate configuration on both relationship of two neighboring eBGP speakers to enforce appropriate
sides. Propagated routes are then marked with an OTC attribute configuration on both sides. Propagated routes are then marked with
according to the agreed relationship, allowing both prevention and an OTC attribute according to the agreed relationship, allowing both
detection of route leaks. prevention and detection of route leaks.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 16, 2020. This Internet-Draft will expire on December 18, 2020.
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
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Enforcement . . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Additional Considerations . . . . . . . . . . . . . . . . . . 7 8. Additional Considerations . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. Security Considerations . . . . . . . . . . . . . . . . . . . 8 10. Security Considerations . . . . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . 8 11.1. Normative References . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . 9 11.2. Informative References . . . . . . . . . . . . . . . . . 9
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
A BGP route leak occurs when a route is learned from a transit A BGP route leak occurs when a route is learned from a transit
provider or peer and then announced to another provider or peer. See provider or lateral peer and then announced to another provider or
[RFC7908]. These are usually the result of misconfigured or absent lateral peer. See [RFC7908]. These are usually the result of
BGP route filtering or lack of coordination between two BGP speakers. misconfigured or absent BGP route filtering or lack of coordination
between two eBGP 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 and even configuration, which is often vulnerable to misconfiguration and even
attack [Streibelt]. There is also the vulnerability that the attack [Streibelt]. There is also the vulnerability that the
community signal may be stripped, 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.
In the rest of this document, we use the term "peer" to refer to
"lateral peer" for simplicity.
2. Peering Relationships 2. Peering Relationships
Despite the use of terms such as "customer", "peer", etc. in this Despite the use of terms such as "customer", "peer", etc. in this
document, these are not necessarily business relationships based on document, these are not necessarily business relationships based on
payment agreements. These terms are used to represent restrictions payment agreements. These terms are used to represent restrictions
on BGP route propagation, sometimes known as the Gao-Rexford model on BGP route propagation, sometimes known as the Gao-Rexford model
[Gao]. The following is a list of various roles in BGP peering and [Gao]. The following is a list of various roles in eBGP peering and
the corresponding rules for route propagation: the corresponding rules for route propagation:
Provider: MAY send to a customer all available prefixes. Provider: MAY send to a customer all available prefixes.
Customer: MAY send to a provider their own prefixes and prefixes Customer: MAY send to a provider prefixes which the sender
learned from any of their customers. A customer MUST NOT send to originates and prefixes learned from any of their customers. A
a provider prefixes learned from its peers, from other providers, customer MUST NOT send to a provider prefixes learned from its
or from Route Servers. peers, from other providers, or from Route Servers.
Route Server (RS): MAY send to an Route Server client (RS-client) Route Server (RS): MAY send to an Route Server client (RS-client)
all available prefixes. all available prefixes.
RS-client: MAY send to an RS its own prefixes and prefixes learned RS-client: MAY send to an RS prefixes which the sender originates
from its customers. An RS-client MUST NOT send to an RS prefixes and prefixes learned from its customers. An RS-client MUST NOT
learned from its peers or providers, or from another RS. send to an RS prefixes learned from its peers or providers, or
from another RS.
Peer: MAY send to a peer its own prefixes and prefixes learned from Peer: MAY send to a peer prefixes which the sender originates and
its customers. A peer MUST NOT send to a peer prefixes learned prefixes learned from its customers. A peer MUST NOT send to a
from other peers, from its providers, or from RS(s). peer prefixes learned 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, configuration of ingress and egress part of BGP itself; therefore, configuration 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 a new configuration option that SHOULD be configured on
each BGP session. It reflects the real-world agreement between two each eBGP session between ISPs that carry IPv4 and(or) IPv6 unicast
BGP speakers about their relationship. prefixes. It reflects the real-world agreement between two BGP
speakers about their relationship.
Allowed Role values for eBGP sessions are: Allowed Role values for eBGP sessions between ISPs are:
o Provider - sender is a transit provider to neighbor; o Provider - sender is a transit provider to neighbor;
o Customer - sender is a transit customer of neighbor; o Customer - sender is a transit customer of neighbor;
o RS - sender is a Route Server, usually at an Internet exchange o RS - sender is a Route Server, usually at an Internet exchange
point (IX); point (IX);
o RS-client - sender is client of an RS; o RS-client - sender is client of an RS;
o Peer - sender and neighbor are peers. o Peer - sender and neighbor are peers.
Since BGP Role reflects the relationship between two BGP speakers, it Since BGP Role reflects the relationship between two BGP speakers, it
could also be used for other purposes besides route leak mitigation. could also be used for other purposes besides route leak mitigation.
4. BGP Role Capability 4. BGP Role Capability
The TLV (type, length, value) of the BGP Role capability are: The TLV (type, length, value) of the BGP Role capability are:
o Type - <TBD1>; o Type - <TBD1>;
o Length - 1 (byte);
o Length - 1 (octet); o Value - integer corresponding to speaker's BGP Role (see Table 1).
o Value - integer corresponding to speaker's BGP Role.
+-------+---------------------+ +-------+---------------------+
| Value | Role name | | Value | Role name |
+-------+---------------------+ +-------+---------------------+
| 0 | Sender is Provider | | 0 | Sender is Provider |
| 1 | Sender is RS | | 1 | Sender is RS |
| 2 | Sender is RS-client | | 2 | Sender is RS-client |
| 3 | Sender is Customer | | 3 | Sender is Customer |
| 4 | Sender is Peer | | 4 | Sender is Peer |
+-------+---------------------+ +-------+---------------------+
Table 1: Predefined BGP Role Values Table 1: Predefined BGP Role Values
5. Role correctness 5. Role correctness
Section 3 described how BGP Role encodes the relationship between two Section 3 described how BGP Role encodes the relationship between two
BGP speakers. But the mere presence of BGP Role doesn't eBGP speakers. But the mere presence of BGP Role doesn't
automatically guarantee role agreement between two BGP peers. automatically guarantee role agreement between two BGP peers.
To enforce correctness, the BGP Role check is applied with a set of To enforce correctness, the BGP Role check is applied with a set of
constraints on how speakers' BGP Roles MUST correspond. Of course, constraints on how speakers' BGP Roles MUST correspond. Of course,
each speaker MUST announce and accept the BGP Role capability in the each speaker MUST announce and accept the BGP Role capability in the
BGP OPEN message exchange. BGP OPEN message exchange.
If a speaker receives a BGP Role capability, it MUST check the value 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 of the received capability (i.e., the sender's role) with its own BGP
Role. The allowed pairings are as follow: Role. The allowed pairings are as follow:
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+---------------+-----------------+ +---------------+-----------------+
| Provider | Customer | | Provider | Customer |
| Customer | Provider | | Customer | Provider |
| RS | RS-client | | RS | RS-client |
| RS-client | RS | | RS-client | RS |
| Peer | Peer | | Peer | Peer |
+---------------+-----------------+ +---------------+-----------------+
Table 2: Allowed Pairs of Role Capabilities Table 2: Allowed Pairs of Role Capabilities
If the observed Role pair is not in the above table, then the If the role of the receiving speaker for the eBGP session in
receiving speaker MUST reject the BGP connection, send a Role consideration is included in Table 1 and the observed Role pair is
Mismatch Notification (code 2, subcode <TBD2>), and also send a not in the above table, then the receiving speaker MUST reject the
Connection Rejected Notification [RFC4486] (Notification with error eBGP connection, send a Role Mismatch Notification (code 2, subcode
code 6, subcode 5). <TBD2>), and also send a Connection Rejected Notification [RFC4486]
(Notification with error code 6, subcode 5).
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
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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 are no built-in measures to on a per-prefix basis. However, there are no built-in measures to
check correctness of OTC use if BGP Role is not configured. check correctness of OTC use if BGP Role is not configured.
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
errors should not happen with proper configuration.
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 leak solution discussed so it might have other uses beyond the route leak 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.
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.
As BGP role configuration results in automatic creation of inbound/ As BGP role configuration results in automatic creation of inbound/
outbound filters, existence of roles should be treated as existence outbound filters, existence of roles should be treated as existence
of Import and Export policy [RFC8212]. of Import and Export policy [RFC8212].
9. IANA Considerations 9. IANA Considerations
This document defines a new Capability Codes option [to be removed This document defines a new Capability Codes option [to be removed
upon publication: https://www.iana.org/assignments/capability-codes/ upon publication: https://www.iana.org/assignments/capability-codes/
capability-codes.xhtml ] [RFC5492], named "BGP Role" with an assigned capability-codes.xhtml ] [RFC5492], named "BGP Role" with an assigned
value <TBD1>. The length of this capability is 1. value <TBD1>. The length of this capability is 1.
The BGP Role capability includes a Value field, for which IANA is The BGP Role capability includes a Value field, for which IANA is
requested to create and maintain a new sub-registry called "BGP Role requested to create and maintain a new sub-registry called "BGP Role
Value". Assignments consist of Value and corresponding Role name. Value". Assignments consist of Value and corresponding Role name.
Initially this registry is to be populated with the data in Table 1. Initially this registry is to be populated with the data in Table 1.
Future assignments may be made by a standard action procedure Future assignments may be made by a standard action procedure
[RFC5226]. [RFC5226]. The allocation policy for new entries up to and including
value 127 is "Expert Review" [RFC5226]. The allocation policy for
values 128 through 251 is "First Come First Served". The values from
252 through 255 are for "Experimental Use".
This document defines a new subcode, "Role Mismatch" with an assigned This document defines a new subcode, "Role Mismatch" with an assigned
value <TBD2> in the OPEN Message Error subcodes registry [to be value <TBD2> in the OPEN Message Error subcodes registry [to be
removed upon publication: http://www.iana.org/assignments/bgp- removed upon publication: http://www.iana.org/assignments/bgp-
parameters/bgp-parameters.xhtml#bgp-parameters-6] [RFC4271]. parameters/bgp-parameters.xhtml#bgp-parameters-6] [RFC4271].
This document defines a new optional, transitive BGP Path Attributes This document defines a new optional, transitive BGP Path Attributes
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
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[Streibelt] [Streibelt]
Streibelt, F., Lichtblau, F., Beverly, R., Feldmann, A., Streibelt, F., Lichtblau, F., Beverly, R., Feldmann, A.,
Cristel, C., Smaragdakis, G., and R. Bush, "BGP Cristel, C., Smaragdakis, G., and R. Bush, "BGP
Communities: Even more Worms in the Routing Can", Communities: Even more Worms in the Routing Can",
<https://people.mpi-inf.mpg.de/~fstreibelt/preprint/ <https://people.mpi-inf.mpg.de/~fstreibelt/preprint/
communities-imc2018.pdf>. communities-imc2018.pdf>.
Acknowledgements Acknowledgements
The authors wish to thank Andrei Robachevsky, Daniel Ginsburg, Jeff The authors wish to thank Andrei Robachevsky, Daniel Ginsburg, Jeff
Haas, Ruediger Volk, Sue Hares, and John Scudder for comments, Haas, Ruediger Volk, Pavel Lunin, Gyan Mishra, Ignas Bagdonas, Sue
suggestions, and critique. Hares, and John Scudder for comments, suggestions, and critique.
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
Email: dougm@nist.gov Email: dougm@nist.gov
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