BGPsec Operational Considerations
draft-ietf-sidr-bgpsec-ops-06

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Author Randy Bush 
Last updated 2015-07-02
Replaces draft-ymbk-bgpsec-ops
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Network Working Group                                            R. Bush
Internet-Draft                                 Internet Initiative Japan
Intended status: Best Current Practice                      July 3, 2015
Expires: January 4, 2016

                   BGPsec Operational Considerations
                     draft-ietf-sidr-bgpsec-ops-06

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 January 4, 2016.

Copyright Notice

   Copyright (c) 2015 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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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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  . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

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 twp 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 it's
   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.

   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.

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].

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   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.

   A BGPsec speaker receiving a path SHOULD perform origin validation
   per [RFC6811] and [RFC7115].

   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.

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   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 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.

   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.

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11.  References

11.1.  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.

   [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, January 2014.

11.2.  Informative References

   [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.

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   [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, April 2013.

Author's Address

   Randy Bush
   Internet Initiative Japan
   5147 Crystal Springs
   Bainbridge Island, Washington  98110
   US

   Email: randy@psg.com

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