Network Working Group                                            R. Bush
Internet-Draft                           Internet Initiative Japan, Inc.
Intended status: BCP                                       March 8, 2011
Expires: September 9, 2011


                   BGPsec Operational Considerations
                        draft-ymbk-bgpsec-ops-00

Abstract

   Deployment of the BGPsec architecture and protocols has many
   operational considerations.  This document attempts to collect and
   present them.  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" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may not be modified,
   and derivative works of it may not be created, and it may not be
   published except as an Internet-Draft.

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   This Internet-Draft will expire on September 9, 2011.

Copyright Notice

   Copyright (c) 2011 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
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Suggested Reading . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  RPKI Distribution and Maintenance . . . . . . . . . . . . . . . 3
   4.  AS/Router Certificates  . . . . . . . . . . . . . . . . . . . . 4
   5.  Within a Network  . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Considerations for Edge Sites . . . . . . . . . . . . . . . . . 5
   7.  Beaconing Considerations  . . . . . . . . . . . . . . . . . . . 5
   8.  Routing Policy  . . . . . . . . . . . . . . . . . . . . . . . . 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  . . . . . . . . . . . . . . . . . . . . . . . . . 8

























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1.  Introduction

   BGPsec 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 crypto
   assist, it is thought that origin validation based on the RPKI will
   occur over the next two to five years and that BGPsec will start to
   deploy late in that window.

   BGPsec relies on widespread propagation of the Resource Public Key
   Infrastructure (RPKI) [I-D.ietf-sidr-arch].  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 a 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, and this
   has special operational considerations.

   Different prefixes have different timing and replay protection
   considerations.


2.  Suggested Reading

   It is assumed that the reader understands BGP, [RFC4271], BGPsec,
   [bgpsec docs], the RPKI, see [I-D.ietf-sidr-arch], the RPKI
   Repository Structure, see [I-D.ietf-sidr-repos-struct], and ROAs, see
   [I-D.ietf-sidr-roa-format].


3.  RPKI Distribution and Maintenance

   The RPKI is a distributed database containing certificates, CRLs,
   manifests, ROAs, and Ghostbuster Records as described in
   [I-D.ietf-sidr-repos-struct].  Policies and considerations for RPKI
   object generation and maintenance are discussed elsewhere.

   A local valid cache containing all RPKI data MAY be gathered from the
   global distributed database using the rcync protocol, see
   [I-D.weiler-rsync-uri] and a validation tool such as rcynic.

   Validated caches MAY also be created and maintained from other
   validated caches.  An operator SHOULD take maximum advantage of this
   feature to minimize load on the global distributed RPKI database.

   Like the DNS, the global RPKI presents only a loosely consistent



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   view, depending on timing, updating, fetching, etc.  Thus, one cache
   or router MAY have different data than another cache or router.
   There is no 'fix' for this, it is the nature of distributed data with
   distributed caches.

   As secured routing depends on availability of RPKI data, operators
   will likely want border routers to have one or more nearby caches.

   If an operator or site trusts upstreams to carry their traffic, they
   might as well trust the RPKI data those upstreams cache and therefore
   SHOULD feed off of those caches.  Note that this places an obligation
   on those upstreams to maintain fresh and reliable caches.

   A transit provider or a network with peers MUST validate
   announcements made by downstreams and peers.  They still MAY choose
   to trust the caches provided by their upstreams.

   To deal with private address space or other resources outside the
   'normal' RPKI, operators will use the features of
   [I-D.ietf-sidr-ltamgmt] with great caution.


4.  AS/Router Certificates

   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 many routers vulnerable, would likely accept a more
   complex certificate/key distribution burden to reduce this exposure.

   On the other extreme, an edge site with one or two routers might use
   a single certificate/key.

   Routers MAY be capable of generating their own keys and having their
   certificates signed and published in the RPKI by their NOC.  This
   would mean that a router's private key need never leave the router.


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.




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   A BGPsec capable router MAY use the data it receives to influence
   local policy within its network, see Section 8.  In deployment this
   policy should fit into the AS's existing policy, preferences, etc.
   This allows a network to incrementally deploy BGPsec capable border
   routers.

   eBGP speakers which face more critical peers or up/downstreams would
   be candidates for the earliest deployment.  Both securing one's own
   announcements and validating received announcements should be
   considered in partial deployment.

   An eBGP listener MUST NOT trust non-BGPsec 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) need only originate a signed prefix announcement and need
   not validate received announcements.

   The BGPsec protocol capability negotiation provides for a speaker
   signing the data it sends but being unable to accept signed data.
   Thus a smallish edge router may hold only its own signing key(s) and
   sign it's announcement but not receive signed announcements and
   therefore not need to deal with the majority of the RPKI.

   As the vast majority (84%) of ASs are stubs, and they announce the
   majority of prefixes, this allows for simpler and cheaper early
   incremental deployment.  It may also mean that edge sites concerned
   with routing security will be attracted to upstreams which support
   BGPsec.


7.  Beaconing Considerations

   The BGPsec protocol attempts to reduce exposure to replay attacks by
   allowing the route originator to sign an announcement with a validity
   period and re-announce well within that period.

   This re-announcement is termed 'beaconing'.  All timing values are,
   of course, jittered.

   It is only the originator of an NLRI which signs the announcement
   with a validity period.

   To reduce vulnerability to a lost beacon announcement, a router
   SHOULD beacon at a rate somewhat greater than half the signature



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   validity period it uses.

   As beaconing places a load on the entire global routing system,
   careful thought MUST be given to any need to beacon frequently.  This
   would be based on a conservative estimation of the vulnerability to a
   replay attack.

   Beacon timing and signature validity periods SHOULD be as follows:

   The Exemplary Citizen:  Prefix originators who are not overly
      concerned about replay attacks might announce with a signature
      validity of multiple weeks and beacon one third of the validity
      period.

   Normal Prefix:  Most prefixes SHOULD announce with a signature
      validity of a week and beacon every three days.

   Critical Prefix:  Of course, we all think what we do is critical.
      But prefixes of top level DNS servers, and RPKI publication points
      are actually critical to large swaths of the Internet and are
      therefore tempting targets for replay attacks.  It is suggested
      that the beaconing of these prefixes SHOULD be two to four hours,
      with a signature validity of six to twelve hours.

      Note that this may incur route flap damping (RFD) with current
      default but deprecated RFD parameters, see [I-D.ymbk-rfd-usable].


8.  Routing Policy

   Unlike origin validation based on the RPKI, BGPsec marks a received
   announcement as Valid or Invalid, there is no NotFound state.  How
   this is used in routing is up to the operator's local policy.  See
   [I-D.pmohapat-sidr-pfx-validate].

   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 announcements and giving very low
   preference, but still using, invalid announcements.

   Local policy on the eBGP edge MAY convey the validation status of a
   BGP signed path through various pre-existing mechanisms, e.g. setting
   a BGP community, 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.




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   A BGPsec speaker validates signed paths at the eBGP edge.

   Because of possible RPKI version skew, an AS Path which does not
   validate at router R0 might validate at R1.  Therefore, signed paths
   that can not be validated SHOULD have their signatures kept intact
   and should be signed when sent to external BGPsec speakers.

   This implies that AS Paths with non-validated signatures MAY be
   propagated to iBGP peers.  Therefore, unless local policy ensures
   otherwise, a signed path learned via iBGP MAY NOT have been
   validated.  If needed, the validation state SHOULD be signaled by
   normal 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 not validated.

   If a BGPsec speaker receives an unsigned path, it SHOULD perform
   origin validation per [I-D.pmohapat-sidr-pfx-validate].


9.  Security Considerations

   BGPsec is all about security, routing security.  The major security
   considerations for the protocol are described in [BGPsec].


10.  IANA Considerations

   This document has no IANA Considerations.


11.  Acknowledgments

   The author wishes to thank the entire BGPsec foundation team.


12.  References

12.1.  Normative References

   [I-D.ietf-sidr-roa-format]
              Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
              Origin Authorizations (ROAs)",
              draft-ietf-sidr-roa-format-10 (work in progress),
              February 2011.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.



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12.2.  Informative References

   [I-D.ietf-sidr-arch]
              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch-12 (work in
              progress), February 2011.

   [I-D.ietf-sidr-ltamgmt]
              Kent, S. and M. Reynolds, "Local Trust Anchor Management
              for the Resource Public Key Infrastructure",
              draft-ietf-sidr-ltamgmt-00 (work in progress),
              November 2010.

   [I-D.ietf-sidr-repos-struct]
              Huston, G., Loomans, R., and G. Michaelson, "A Profile for
              Resource Certificate Repository Structure",
              draft-ietf-sidr-repos-struct-07 (work in progress),
              February 2011.

   [I-D.pmohapat-sidr-pfx-validate]
              Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation",
              draft-pmohapat-sidr-pfx-validate-07 (work in progress),
              April 2010.

   [I-D.weiler-rsync-uri]
              Weiler, S., Ward, D., and R. Housley, "The rsync URI
              Scheme", draft-weiler-rsync-uri-01 (work in progress),
              July 2009.

   [I-D.ymbk-rfd-usable]
              Pelsser, C., Bush, R., Patel, K., Mohapatra, P., and O.
              Maennel, "Making Route Flap Damping Usable",
              draft-ymbk-rfd-usable-00 (work in progress), March 2011.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.














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Author's Address

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

   Phone: +1 206 780 0431 x1
   Email: randy@psg.com









































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