Network Working Group R. Bush
Internet-Draft Internet Initiative Japan
Intended status: Best Current Practice June 16, 2016
Expires: December 18, 2016
BGPsec Operational Considerations
draft-ietf-sidr-bgpsec-ops-09
Abstract
Deployment of the BGPsec architecture and protocols has many
operational considerations. This document attempts to collect and
present the most critical and universal. It is expected to evolve as
BGPsec is formalized and initially deployed.
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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This Internet-Draft will expire on December 18, 2016.
Copyright Notice
Copyright (c) 2016 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
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 3
3. RPKI Distribution and Maintenance . . . . . . . . . . . . . . 3
4. AS/Router Certificates . . . . . . . . . . . . . . . . . . . 3
5. Within a Network . . . . . . . . . . . . . . . . . . . . . . 3
6. Considerations for Edge Sites . . . . . . . . . . . . . . . . 4
7. Routing Policy . . . . . . . . . . . . . . . . . . . . . . . 5
8. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
12.1. Normative References . . . . . . . . . . . . . . . . . . 7
12.2. Informative References . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
BGPsec, [I-D.ietf-sidr-bgpsec-overview], is a new protocol with many
operational considerations. It is expected to be deployed
incrementally over a number of years. As core BGPsec-capable routers
may require large memory and/or modern CPUs, it is thought that
origin validation based on the RPKI, [RFC6811], will occur over the
next two to three years and that BGPsec will start to deploy well
after that.
BGPsec relies on widespread propagation of the Resource Public Key
Infrastructure (RPKI) [RFC6480]. How the RPKI is distributed and
maintained globally and within an operator's infrastructure may be
different for BGPsec than for origin validation.
BGPsec need be spoken only by an AS's eBGP speaking, AKA border,
routers, and is designed so that it can be used to protect
announcements which are originated by small edge routers. This has
special operational considerations.
Different prefixes may have different timing and replay protection
considerations.
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2. Suggested Reading
It is assumed that the reader understands BGP, [RFC4271], BGPsec,
[I-D.ietf-sidr-bgpsec-overview], the RPKI, see [RFC6480], the RPKI
Repository Structure, see [RFC6481], and ROAs, see [RFC6482].
3. RPKI Distribution and Maintenance
All non-ROA considerations in the section on RPKI Distribution and
Maintenance of [RFC7115] apply.
4. AS/Router Certificates
As described in [I-D.ietf-sidr-rtr-keying] BGPsec-speaking routers
are either capable of generating their own public/private key-pairs
and having their certificates signed and published in the RPKI by the
RPKI CA system, and/or are given public/private key-pairs by the
operator.
A site/operator MAY use a single certificate/key in all their
routers, one certificate/key per router, or any granularity in
between.
A large operator, concerned that a compromise of one router's key
would make other routers vulnerable, may accept a more complex
certificate/key distribution burden to reduce this exposure.
On the other extreme, an edge site with one or two routers may choose
to use a single certificate/key.
In anticipation of possible key compromise, a prudent operator will
pre-provision each router's 'next' key in the RPKI so there is no
propagation delay for provisioning the new key.
5. Within a Network
BGPsec is spoken by edge routers in a network, those which border
other networks/ASs.
In a fully BGPsec enabled AS, Route Reflectors MUST have BGPsec
enabled if and only if there are eBGP speakers in their client cone,
i.e. an RR client or the transitive closure of their customers'
customers' customers' ....
A BGPsec capable router MAY use the data it receives to influence
local policy within its network, see Section 7. In deployment this
policy should fit into the AS's existing policy, preferences, etc.
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This allows a network to incrementally deploy BGPsec enabled border
routers.
eBGP speakers which face more critical peers or up/downstreams would
be candidates for early deployment. Both securing one's own
announcements and validating received announcements should be
considered in partial deployment.
The operator should be aware that BGPsec, as any other policy change,
can cause traffic shifts in their network. And, as with normal
policy shift practice, a prudent operator has tools and methods to
predict, measure, modify, etc.
On the other hand, an operator wanting to monitor router loading,
shifts in traffic, etc. might deploy incrementally while watching
those and similar effects.
As they are not formally verifiable, an eBGP listener SHOULD NOT
strongly trust unsigned security markings such as communities
received across a trust boundary.
6. Considerations for Edge Sites
An edge site which does not provide transit and trusts its
upstream(s) SHOULD only originate a signed prefix announcement and
need not validate received announcements.
BGPsec protocol capability negotiation provides for a speaker signing
the data it sends without being able to accept signed data. Thus a
smallish edge router may hold only its own signing key(s), sign its
announcements, but not receive signed announcements and therefore not
need to deal with the majority of the RPKI. Thus such routers CPU,
RAM, and crypto needs are trivial and additional hardware should not
be needed.
Operators might need to use hardware with limited resources. In such
cases, BGPsec protocol capability negotiation allows for a resource
constrained edge router to hold only its own signing key(s) and sign
its announcements, but not receive signed announcements. Therefore,
the router would not have to deal with the majority of the RPKI,
potentially saving the need for additional hardware.
As the vast majority (84%) of ASs are stubs, and they announce the
majority of prefixes, this allows for simpler and less expensive
incremental deployment. It may also mean that edge sites concerned
with routing security will be attracted to upstreams which support
BGPsec.
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7. Routing Policy
Unlike origin validation based on the RPKI, BGPsec marks a received
announcement as Valid or Invalid, there is no explicit NotFound
state. In some sense, an unsigned BGP4 path is the equivalent of
NotFound. How this is used in routing is up to the operator's local
policy. See [RFC6811].
As BGPsec will be rolled out over years and does not allow for
intermediate non-signing edge routers, coverage will be spotty for a
long time. Hence a normal operator's policy SHOULD NOT be overly
strict, perhaps preferring Valid paths and giving very low
preference, but still using, Invalid paths.
Operators should be aware that accepting Invalid announcements, no
matter how de-preffed, will often be the equivalent of treating them
as fully Valid. Consider having a Valid announcement from neighbor V
for prefix 10.0.0.0/16 and an Invalid announcement for 10.0.666.0/24
from neighbor I. If local policy on the router is not configured to
discard the Invalid announcement from I, then longest match
forwarding will send packets to neighbor I no matter the value of
local preference.
A BGPsec speaker validates signed paths at the eBGP edge.
Local policy on the eBGP edge MAY convey the validation state of a
BGP signed path through normal local policy mechanisms, e.g. setting
a BGP community for internal use, or modifying a metric value such as
local-preference or MED. Some may choose to use the large Local-Pref
hammer. Others may choose to let AS-Path rule and set their internal
metric, which comes after AS-Path in the BGP decision process.
Because of possible RPKI version skew, an AS Path which does not
validate at router R0 might validate at R1. Therefore, signed paths
that are Invalid and yet propagated (because they are chosen as best
path) SHOULD have their signatures kept intact and MUST be signed if
sent to external BGPsec speakers.
This implies that updates which a speaker judges to be Invalid MAY be
propagated to iBGP peers. Therefore, unless local policy ensures
otherwise, a signed path learned via iBGP MAY be Invalid. If needed,
the validation state should be signaled by normal local policy
mechanisms such as communities or metrics.
On the other hand, local policy on the eBGP edge might preclude iBGP
or eBGP announcement of signed AS Paths which are Invalid.
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A BGPsec speaker receiving a path SHOULD perform origin validation
per [RFC6811] and [RFC7115].
A route server is usually 'transparent', most importantly not
inserting its own AS into the AS_Path, to not lengthen the AS hop
count and thereby reduce the likelihood of best path selection. See
2.2.2 of [I-D.ietf-idr-ix-bgp-route-server]. A BGPsec-aware route
server needs to validate the incoming BGPSEC_Path, and to forward
updates which can be validated by clients which know the route
server's AS. The route server uses pCount of zero to not increase
the effective AS hop count.
If it is known that a BGPsec neighbor is not a transparent route
server, and the router provides a knob to disallow a received pCount
(prepend count, zero for transparent route servers) of zero, that
knob SHOULD be applied. Routers should default to this knob
disallowing pCount 0.
To prevent exposure of the internals of BGP Confederations [RFC5065],
a BGPsec speaker which is a Member-AS of a Confederation MUST NOT
sign updates sent to another Member-AS of the same Confederation.
8. Notes
For protection from attacks replaying BGP data on the order of a day
or longer old, re-keying routers with new keys (previously)
provisioned in the RPKI is sufficient. For one approach, see
[I-D.ietf-sidr-bgpsec-rollover]
Like the DNS, the global RPKI presents only a loosely consistent
view, depending on timing, updating, fetching, etc. Thus, one cache
or router may have different data about a particular prefix or router
than another cache or router. There is no 'fix' for this, it is the
nature of distributed data with distributed caches.
Operators who manage certificates SHOULD have RPKI GhostBuster
Records (see [RFC6493]), signed indirectly by End Entity
certificates, for those certificates on which others' routing depends
for certificate and/or ROA validation.
Operators should be aware of impending algorithm transitions, which
will be rare and slow-paced, see [RFC6916]. They should work with
their vendors to ensure support for new algorithms.
As a router must evaluate certificates and ROAs which are time
dependent, routers' clocks MUST be correct to a tolerance of
approximately an hour.
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If a router has reason to believe its clock is seriously incorrect,
e.g. it has a time earlier than 2011, it SHOULD NOT attempt to
validate incoming updates. It SHOULD defer validation until it
believes it is within reasonable time tolerance.
Servers should provide time service, such as [RFC5905], to client
routers.
9. Security Considerations
The major security considerations for the BGPsec protocol are
described in [I-D.ietf-sidr-bgpsec-protocol].
10. IANA Considerations
This document has no IANA Considerations.
11. Acknowledgments
The author wishes to thank the BGPsec design group, Thomas King, and
Arnold Nipper.
12. References
12.1. Normative References
[I-D.ietf-sidr-bgpsec-overview]
Lepinski, M. and S. Turner, "An Overview of BGPSEC",
draft-ietf-sidr-bgpsec-overview-02 (work in progress), May
2012.
[I-D.ietf-sidr-bgpsec-protocol]
Lepinski, M., "BGPSEC Protocol Specification", draft-ietf-
sidr-bgpsec-protocol-07 (work in progress), February 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, February 2012.
[RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for
Resource Certificate Repository Structure", RFC 6481,
February 2012.
[RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)", RFC 6482, February 2012.
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[RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI)
Ghostbusters Record", RFC 6493, February 2012.
[RFC7115] Bush, R., "Origin Validation Operation Based on the
Resource Public Key Infrastructure (RPKI)", BCP 185,
RFC 7115, DOI 10.17487/RFC7115, January 2014,
<http://www.rfc-editor.org/info/rfc7115>.
12.2. Informative References
[I-D.ietf-idr-ix-bgp-route-server]
Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
"Internet Exchange Route Server", draft-ietf-idr-ix-bgp-
route-server-02 (work in progress), February 2013.
[I-D.ietf-sidr-bgpsec-rollover]
Gagliano, R., Patel, K., and B. Weis, "BGPSEC router key
rollover as an alternative to beaconing", draft-ietf-sidr-
bgpsec-rollover-01 (work in progress), October 2012.
[I-D.ietf-sidr-rtr-keying]
Turner, S., Patel, K., and R. Bush, "Router Keying for
BGPsec", draft-ietf-sidr-rtr-keying-01 (work in progress),
February 2013.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065, August 2007.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
Austein, "BGP Prefix Origin Validation", RFC 6811, January
2013.
[RFC6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility
Procedure for the Resource Public Key Infrastructure
(RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC6916, April
2013, <http://www.rfc-editor.org/info/rfc6916>.
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Author's Address
Randy Bush
Internet Initiative Japan
5147 Crystal Springs
Bainbridge Island, Washington 98110
US
Email: randy@psg.com
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