draft-ietf-idr-bgp-open-policy-16.txt   draft-ietf-idr-bgp-open-policy-17.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: February 11, 2022 Qrator Labs Expires: April 16, 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
August 10, 2021 October 13, 2021
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-16 draft-ietf-idr-bgp-open-policy-17
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., passing a route assumptions of BGP topology relationships, e.g., announcing a route
learned from one lateral peer to another lateral peer or a transit learned from one transit provider to another transit provider or a
provider and passing a route learned from one transit provider to lateral (i.e., non-transit) peer or announcing a route learned from
another transit provider or a lateral peer. Existing approaches to one lateral peer to another lateral peer or a transit provider.
leak prevention rely on marking routes by operator configuration, These are usually the result of misconfigured or absent BGP route
with no check that the configuration corresponds to that of the eBGP filtering or lack of coordination between autonomous systems (ASes).
neighbor, or enforcement that the two eBGP speakers agree on the Existing approaches to leak prevention rely on marking routes by
relationship. This document enhances the BGP OPEN message to operator configuration, with no check that the configuration
establish an agreement of the relationship on each eBGP session corresponds to that of the eBGP neighbor, or enforcement that the two
between autonomous systems in order to enforce appropriate eBGP speakers agree on the relationship. This document enhances the
configuration on both sides. Propagated routes are then marked BGP OPEN message to establish an agreement of the relationship on
according to the agreed relationship, allowing both prevention and each eBGP session between autonomous systems in order to enforce
detection of route leaks. appropriate configuration on both sides. Propagated routes are then
marked according to the agreed relationship, allowing both prevention
and detection of route leaks.
Requirements Language 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-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
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 February 11, 2022. This Internet-Draft will expire on April 16, 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 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
skipping to change at page 2, line 39 skipping to change at page 2, line 44
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
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 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. BGP Role Capability . . . . . . . . . . . . . . . . . . . 5 3.1. BGP Role Capability . . . . . . . . . . . . . . . . . . . 5
3.2. Role Correctness . . . . . . . . . . . . . . . . . . . . 5 3.2. Role Correctness . . . . . . . . . . . . . . . . . . . . 6
4. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 6 4. BGP Only to Customer (OTC) Attribute . . . . . . . . . . . . 7
5. Additional Considerations . . . . . . . . . . . . . . . . . . 8 5. Additional Considerations . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 10 8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . 12
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
A BGP route leak occurs when a route is learned from a transit Route leaks are the propagation of BGP prefixes that violate
provider or lateral peer and then announced to another provider or assumptions of BGP topology relationships, e.g., announcing a route
lateral peer [RFC7908]. These are usually the result of learned from one transit provider to another transit provider or a
misconfigured or absent BGP route filtering or lack of coordination lateral (i.e., non-transit) peer or announcing a route learned from
between autonomous systems (ASes). one lateral peer to another lateral peer or a transit provider
[RFC7908]. These are usually the result of misconfigured or absent
BGP route 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 eBGP neighbor, or enforcement that the two
eBGP speakers agree on the relationship. This document enhances the eBGP speakers agree on the relationship. This document enhances the
BGP OPEN message to establish an agreement of the relationship on 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 provides configuration automation using BGP Roles, This document provides configuration automation using BGP Roles,
which are negotiated using a BGP Role Capability in the OPEN message which are negotiated using a BGP Role Capability in the OPEN message
[RFC5492]. An eBGP speaker may require the use of this capability [RFC5492]. An eBGP speaker may require the use of this capability
and confirmation of BGP Role with a neighbor for the BGP OPEN to and confirmation of BGP Role with a neighbor for the BGP OPEN to
succeed. 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 4. 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).
1.1. Terminology 1.1. Terminology
In the rest of this document, the term "Peer" is used to refer to a In the rest of this document, the term "Peer" is used to refer to a
"lateral peer" for simplicity. Also, the terms Provider and Customer "lateral (i.e., non-transit) peer" for simplicity. Also, the terms
are used to refer to a transit provider and a transit customer, Provider and Customer are used to refer to a transit provider and a
respectively. Further, the terms RS and RS-Client are used to refer transit customer, respectively. Further, the terms RS and RS-Client
to a Route Server and its client, respectively. are used to refer to a Route Server and its client, respectively.
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."
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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.
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
used to identify all the routes in the AS that have been received
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. BGP Role is configured on a per-session basis. forming a session. One of the Roles described below SHOULD be
An eBGP speaker SHOULD configure the BGP Role locally based on the configured at the local AS for each eBGP session (see definitions in
local AS's knowledge of its Role. The only exception is when the Section 1.1) based on the local AS's knowledge of its Role. The only
eBGP connection is complex (see Section 5). BGP Roles are mutually exception is when the eBGP connection is 'complex' (see Section 5).
confirmed using the BGP Role Capability (described in Section 3.1) on
each eBGP session between autonomous systems (ASes). One of the BGP Roles are mutually confirmed using the BGP Role Capability
Roles described below SHOULD be configured at the local AS for each (described in Section 3.1) on each eBGP session.
eBGP session with a neighbor (remote AS) (see definitions in
Section 1.1).
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
exchange point) and the remote AS is its RS-Client; exchange point) and the remote AS is its RS-Client;
o RS-Client - the local AS is a client of an RS and the RS is the o RS-Client - the local AS is a client of an RS and the RS is the
remote AS; remote AS;
o Peer - the local and remote ASes are Peers (i.e., have a lateral o Peer - the local and remote ASes are Peers (i.e., have a lateral
peering relationship). peering relationship).
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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 BGP Role Capability is sent, but one is not received, then the For backward compatibility, if the BGP Role Capability is sent but
connection MAY be rejected using the Role Mismatch Notification (code one is not received, the BGP Speaker SHOULD ignore the absence of the
2, subcode 8); this mode of operation is called the "strict mode". BGP Role Capability and proceed with session establishment. The
For backward compatibility, if the BGP speaker does not receive the locally configured BGP Role is used for the procedures described in
capability from its peer, it SHOULD ignore the absence of BGP Role
Capability and proceed with session establishment; this SHOULD be the
default non-strict mode of operation. In this case, the locally
configured BGP Role is used for the procedures described in
Section 4. Section 4.
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
operating in the "strict mode", if the BGP Role Capability is sent,
but one is not received, then the connection is rejected using the
Role Mismatch Notification (code 2, subcode 8). See comments in
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 8).
The BGP Role value for the local AS is used in the route leak The BGP Role value for the local AS 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 with Attribute Type Code 35 and a length of 4 octets. The
purpose of this attribute is to guarantee that once a route is sent purpose of this attribute is to guarantee that once a route is sent
to a Customer, Peer, or RS-Client, it will subsequently go only to to a Customer, Peer, or RS-Client, it will subsequently go only to
Customers. The attribute value is an AS number determined by the Customers. The attribute value is an AS number (ASN) determined by
policy described below. 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 at
least one of the OTC Attributes has a value that is not equal to least one of the OTC Attributes has a value that is not equal to
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The described policies provide both leak prevention for the local AS The described policies provide both leak prevention for the local AS
and leak detection and mitigation multiple hops away. In the case of and leak detection and mitigation multiple hops away. In the case of
prevention at the local AS, the presence of an OTC Attribute prevention at the local AS, the presence of an OTC Attribute
indicates to the egress router that the route was learned from a indicates to the egress router that the route was learned from a
Peer, Provider, or RS, and it can be advertised only to the Peer, Provider, or RS, and it can be advertised only to the
customers. The same OTC Attribute which is set locally also provides customers. The same OTC Attribute which is set locally also provides
a way to detect route leaks by an AS multiple hops away if a route is a way to detect route leaks by an AS multiple hops away if a route is
received from a Customer, Peer, or RS-Client. received from a Customer, Peer, or RS-Client.
The OTC Attribute may be set by the egress policy of remote AS or by The OTC Attribute may be set by the egress policy of the remote AS or
the ingress policy of local AS. In both scenarios, the OTC value by the ingress policy of the local AS. In both scenarios, the OTC
will be the same. This makes the scheme more robust and benefits value will be the same. This makes the scheme more robust and
early adopters. benefits early adopters.
If an eBGP speaker receives an UPDATE with an OTC Attribute with a If an eBGP speaker receives an UPDATE with an OTC Attribute with a
length different from 4 octets, then the UPDATE SHALL be considered length different from 4 octets, then the UPDATE SHALL be considered
malformed. If malformed, the UPDATE message SHALL be handled using malformed. If malformed, the UPDATE message SHALL be handled using
the approach of "treat-as-withdraw" [RFC7606]. the approach of "treat-as-withdraw" [RFC7606].
Once the OTC Attribute has been set, it MUST be preserved unchanged. The procedures specified in this document are NOT RECOMMENDED to be
used between autonomous systems in an AS Confederation [RFC5065]. If
an OTC Attribute is added on egress from the AS Confederation, its
value MUST equal the AS Confederation Identifier. Also, on egress
from the AS Confederation, an UPDATE MUST NOT contain an OTC
Attribute with a value corresponding to any Member-AS Number other
than the AS Confederation Identifier.
The procedures specified in this document in scenarios that use
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
outside the scope of this document. On egress from the Internet-
facing AS, the OTC Attribute MUST NOT contain a value other than the
Internet-facing ASN.
Once the OTC Attribute has been set, it MUST be preserved unchanged
(this also applies to an AS Confederation).
Correct implementation of the procedures specified in this document Correct implementation of the procedures specified in this document
is not expected to result in the presence of multiple OTC Attributes is not expected to result in the presence of multiple OTC Attributes
in an UPDATE. However, if an eBGP speaker receives multiple OTC in an UPDATE. However, if an eBGP speaker receives multiple OTC
Attributes with a route, then the only difference in the processing Attributes with a route, then the only difference in the processing
is in Step 2 of the ingress policy. 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 affect other unicast IPv4 and IPv6 address families and MUST NOT be applied to
address families by default. The operator MUST NOT have the ability other address families by default. The operator MUST NOT have the
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 There are peering relationships that are 'complex', i.e., both
parties intentionally advertise prefixes received from each other to parties intentionally advertise prefixes received from each other to
their Peers and/or transit Providers. If multiple eBGP sessions can their Peers and/or transit Providers. If multiple eBGP sessions can
segregate the 'complex' parts of the relationship, then the complex segregate the 'complex' parts of the relationship, then the complex
peering roles can be segregated into different normal eBGP sessions, peering roles can be segregated into different normal eBGP sessions,
and BGP Roles MUST be used on each of the resulting normal (non- and BGP Roles MUST be used on each of the resulting normal (non-
complex) eBGP sessions. complex) eBGP sessions.
No Roles SHOULD be configured on a 'complex' eBGP session (assuming No Roles SHOULD be configured on a 'complex' eBGP session (assuming
it is not segregated) and in that case, the OTC Attribute processing it is not segregated). An operator may want to achieve an equivalent
MUST be done relying on configuration on a per-prefix basis. Also, outcome by configuring policies on a per-prefix basis to follow the
in this case, the per-prefix peering configuration MUST follow the definitions of peering relations as described in Section 2. However,
same definitions of peering relations as described in Section 2. in this case, there are no built-in measures to check the correctness
However, in this case, there are no built-in measures to check of the per-prefix peering configuration.
correctness 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. Such special handling of incorrect AS numbers in the OTC Attribute.
errors should not happen with proper configuration.
6. IANA Considerations 6. IANA Considerations
IANA has registered a new BGP Capability described in Section 3.1 in IANA has registered a new BGP Capability (Section 3.1) in the
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
the value 9 [to be removed upon publication: the value 9 [to be removed upon publication:
https://www.iana.org/assignments/capability-codes/capability- https://www.iana.org/assignments/capability-codes/capability-
codes.xhtml]. This document is the reference for the new capability. codes.xhtml]. This document is the reference for the new capability.
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" in the Capability Codes registry. Assignments consist of a Value" in the Capability Codes registry. Assignments consist of a
Value and a corresponding Role name. Initially, this registry is to Value and a corresponding Role name. Initially, this registry is to
be populated with the data contained in Table 1 found in Section 3.1. be populated with the data contained in Table 1 found in Section 3.1.
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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 using BGP Role for the prevention
and detection of route leaks that are the result of BGP policy and detection of route leaks that are the result of BGP policy
misconfiguration. A misconfiguration of the BGP Role may affect misconfiguration. A misconfiguration of the BGP Role may affect
prefix propagation. For example, if a downstream (i.e., towards a prefix propagation. For example, if a downstream (i.e., towards a
Customer) peering link were misconfigured with a Provider or Peer Customer) peering link were misconfigured with a Provider or Peer
role, this will limit the number of prefixes that can be advertised role, this will limit the number of prefixes that can be advertised
in this direction. On the other hand if an upstream provider were in this direction. On the other hand, if an upstream provider were
misconfigured (by a local AS) with the Customer role, this may result misconfigured (by a local AS) with the Customer role, this may result
in propagating routes that are received from other Providers or in propagating routes that are received from other Providers or
Peers. But the BGP Role negotiation and the resulting confirmation Peers. But the BGP Role negotiation and the resulting confirmation
of Roles make such misconfigurations unlikely. 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. Such an implementation of this come up after a software update. Implementations with such default
document is 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 of route leak detection. Such activity can be done on opportunity of route leak detection. Such activity can be done on
purpose as part of a Man in the Middle (MITM) attack. For example, purpose as part of an on-path attack. For example, an AS can remove
an AS can remove the OTC Attribute on a received route and then leak the OTC Attribute on a received route and then leak the route to its
the route to its transit provider. Such malicious activity cannot be transit provider. This kind of threat is not new in BGP and it may
prevented without cryptographically signing the BGP UPDATE [RFC8205] affect any Attribute (Note: BGPsec [RFC8205] offers protection only
or out of band detection [I-D.ietf-sidrops-aspa-verification], but for the AS_PATH Attribute).
such schemes are beyond the scope of this document.
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.
skipping to change at page 10, line 37 skipping to change at page 11, line 19
[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>.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", [RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
RFC 4272, DOI 10.17487/RFC4272, January 2006, System Confederations for BGP", RFC 5065,
<https://www.rfc-editor.org/info/rfc4272>. DOI 10.17487/RFC5065, August 2007,
<https://www.rfc-editor.org/info/rfc5065>.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
2009, <https://www.rfc-editor.org/info/rfc5492>. 2009, <https://www.rfc-editor.org/info/rfc5492>.
[RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
Patel, "Revised Error Handling for BGP UPDATE Messages", Patel, "Revised Error Handling for BGP UPDATE Messages",
RFC 7606, DOI 10.17487/RFC7606, August 2015, RFC 7606, DOI 10.17487/RFC7606, August 2015,
<https://www.rfc-editor.org/info/rfc7606>. <https://www.rfc-editor.org/info/rfc7606>.
[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>.
[RFC7938] Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of
BGP for Routing in Large-Scale Data Centers", RFC 7938,
DOI 10.17487/RFC7938, August 2016,
<https://www.rfc-editor.org/info/rfc7938>.
[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 8.2. Informative References
[Gao] Gao, L. and J. Rexford, "Stable Internet routing without [Gao] Gao, L. and J. Rexford, "Stable Internet routing without
global coordination", IEEE/ACM Transactions on global coordination", IEEE/ACM Transactions on
Networking, Volume 9, Issue 6, pp 689-692, DOI Networking, Volume 9, Issue 6, pp 689-692, DOI
10.1109/90.974523, December 2001, 10.1109/90.974523, December 2001,
<https://ieeexplore.ieee.org/document/974523>. <https://ieeexplore.ieee.org/document/974523>.
[I-D.ietf-sidrops-aspa-verification] [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
Azimov, A., Bogomazov, E., Bush, R., Patel, K., and J. RFC 4272, DOI 10.17487/RFC4272, January 2006,
Snijders, "Verification of AS_PATH Using the Resource <https://www.rfc-editor.org/info/rfc4272>.
Certificate Public Key Infrastructure and Autonomous
System Provider Authorization", draft-ietf-sidrops-aspa-
verification-07 (work in progress), February 2021.
[RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol [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>.
Acknowledgements Acknowledgments
The authors wish to thank Alvaro Retana, Andrei Robachevsky, Daniel The authors wish to thank Alvaro Retana, Andrei Robachevsky, Daniel
Ginsburg, Jeff Haas, Ruediger Volk, Pavel Lunin, Gyan Mishra, Ignas Ginsburg, Jeff Haas, Ruediger Volk, Pavel Lunin, Gyan Mishra, Ignas
Bagdonas, Sue Hares, and John Scudder for comments, suggestions, and Bagdonas, Sue Hares, and John Scudder for comments, suggestions, and
critique. 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
Authors' Addresses Authors' Addresses
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