Internet DRAFT - draft-ymbk-idr-bgp-eotr-policy
draft-ymbk-idr-bgp-eotr-policy
Network Working Group A. Azimov
Internet-Draft E. Bogomazov
Intended status: Standards Track Qrator Labs
Expires: September 18, 2018 R. Bush
Internet Initiative Japan
K. Patel
Arrcus, Inc.
March 17, 2018
Route Leak Detection and Filtering using Roles in Update and Open
messages
draft-ymbk-idr-bgp-eotr-policy-02
Abstract
[draft-ietf-idr-bgp-open-policy] defines a BGP OPEN capability and
consequent route marking which enforces a valley-free peering
relationship. This document defines an eOTC (external Only To
Customer) transitive BGP attribute which propagates the specific
marking to automatically detect route leaks. The goal is to allow a
distant AS to determine a violation of valley-free peering.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
be interpreted as described in RFC 2119 [RFC2119] only when they
appear in all upper case. They may also appear in lower or mixed
case as English words, without normative meaning.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 18, 2018.
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Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BGP External Only To Customer attribute . . . . . . . . . . . 3
3. Compatibility with BGPsec . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
For the purpose of this document, BGP route leaks are when a BGP
route was learned from transit provider or peer is announced to
another provider or peer. See [RFC7908]. These are usually the
result of misconfigured or absent BGP route filtering or lack of
coordination between two BGP speakers.
[I-D.ietf-idr-route-leak-detection-mitigation] describes a method of
marking and detecting leaks which relies on operator maintained
markings. Unfortunately, in most cases, a leaking router will likely
also be misconfigured to mark incorrectly.
It has been suggested to use white list filtering, relying on knowing
the prefixes in the peer's customer cone as import filtering, in
order to detect route leaks. Unfortunately, a large number of medium
transit operators use a single prefix list as only the ACL for export
filtering, without community tagging and without paying attention to
the source of a learned route. So, if they learn a customer's route
from their provider or peer - they will announce it in all
directions, including other providers or peers. This
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misconfiguration affects a limited number of prefixes; but such route
leaks will obviously bypass customer cone import filtering made by
upper level upstream providers.
This document specifies a way to to create automatic filters for
detection of route leaks via new BGP Path Attribute which is set
according to BGP Roles ([I-D.ietf-idr-bgp-open-policy]) . While iOTC
provides strong vendor-code-based enforcement of route leak
prevention, route leaks could still exist as result of misconfigured
old BGP implementations. Route leaks could also be result of
malicious activity such as MITM attacks or DoS. The goal of this
proposal is to allow a distant AS to determine a violation of valley-
free peering that is made by mistake or by purpose.
2. BGP External Only To Customer attribute
The External Only To Customer (eOTC) attribute is a new optional,
transitive BGP Path attribute with the Type Code <TBD1>. This
attribute is four bytes and contains an AS number of the AS that
added the attribute to the route.
There are two rules for setting the eOTC attribute:
1. If eOTC is not set and the sender's Role is Provider or Peer, the
eOTC attribute MUST be added with value equal to the sender's AS
number.
2. If eOTC is set, the receiver's Role is Provider or Peer, and its
value is not the neighbor's AS number then the incoming route is
route leak and MUST be given a lower local preference, or MAY be
dropped.
These two rules provide mechanism for route leak detection that is
created by a distant party in the AS_Path.
3. Compatibility with BGPsec
For BGPsec [I-D.ietf-sidr-bgpsec-protocol] enabled routers, the Flags
field will have a bit added to indicate that an eOTC attribute
exists. The eOTC value will be automatically carried in AS field of
the added Secure_Path Segment.
When a route is translated from a BGPsec enabled router to a non-
BGPsec router, in addition to AS_PATH reconstruction, reconstruction
MUST be performed for the eOTC attribute. If Flag bit was set in one
of Secure_Path Segments, the eOTC attribute SHOULD be added with the
AS number of the segment in which it appears for the first time.
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4. IANA Considerations
This document defines a new optional, transitive BGP Path Attributes
option, named "External Only To Customer", assigned value <TBD1> [To
be removed upon publication: http://www.iana.org/assignments/bgp-
parameters/bgp-parameters.xhtml#bgp-parameters-2] [RFC4271]. The
length of this attribute is 4.
5. Security Considerations
This document proposes a mechanism for detection of route leaks that
are the result of BGP policy misconfiguration. If BGPSec is enabled
it will also provide mechanism to detect leaks that are result of
malicious activity.
Deliberate mis-marking of the eOTC flag could be used to affect the
BGP decision process, but could not sabotage a route's propagation.
eOTC is a transitive BGP AS_PATH attribute which reveals a
information about a BGP speaker's peering relationship. It will give
a strong hint that some link isn't customer to provider, but will not
help to distinguish if it is provider to customer or peer to peer.
In addition it could reveal sequence of p2c to downstream ISPs. If
eOTC is BGPsec signed, it can not be removed for peering
confidentiality.
Still, any Tier-1 number in AS_PATH could be used in the same way to
reveal possible p2c sequence.
6. References
6.1. Normative References
[I-D.ietf-idr-bgp-open-policy]
Azimov, A., Bogomazov, E., Bush, R., Patel, K., and K.
Sriram, "Route Leak Prevention using Roles in Update and
Open messages", draft-ietf-idr-bgp-open-policy-02 (work in
progress), January 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, <https://www.rfc-
editor.org/info/rfc4271>.
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[RFC7908] Sriram, K., Montgomery, D., McPherson, D., Osterweil, E.,
and B. Dickson, "Problem Definition and Classification of
BGP Route Leaks", RFC 7908, DOI 10.17487/RFC7908, June
2016, <https://www.rfc-editor.org/info/rfc7908>.
6.2. Informative References
[I-D.ietf-idr-route-leak-detection-mitigation]
Sriram, K., Montgomery, D., Dickson, B., Patel, K., and A.
Robachevsky, "Methods for Detection and Mitigation of BGP
Route Leaks", draft-ietf-idr-route-leak-detection-
mitigation-03 (work in progress), May 2016.
[I-D.ietf-sidr-bgpsec-protocol]
Lepinski, M. and K. Sriram, "BGPsec Protocol
Specification", draft-ietf-sidr-bgpsec-protocol-15 (work
in progress), March 2016.
Authors' Addresses
Alexander Azimov
Qrator Labs
Email: aa@qrator.net
Eugene Bogomazov
Qrator Labs
Email: eb@qrator.net
Randy Bush
Internet Initiative Japan
Email: randy@psg.com
Keyur Patel
Arrcus, Inc.
Email: keyur@arrcus.com
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