Network Working Group                                            R. Bush
Internet-Draft                                 Internet Initiative Japan
Intended status: BCP                                    October 19, 2011
Expires: April 21, 2012

                   BGPsec Operational Considerations


   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",
   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.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 21, 2012.

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   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
   ( in effect on the date of
   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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   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  . . . . . . . . . . . . . . . . . . . . . . . . . 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.  Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
   10. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     13.1.  Normative References . . . . . . . . . . . . . . . . . . . 8
     13.2.  Informative References . . . . . . . . . . . . . . . . . . 8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9

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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

   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

2.  Suggested Reading

   It is assumed that the reader understands BGP, [RFC4271], BGPsec,
   [I-D.lepinski-bgpsec-overview], 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 rsync protocol and a validation
   tool such as rcynic.

   Validated caches may also be created and maintained from other
   validated caches.  Network operators SHOULD take maximum advantage of
   this feature to minimize load on the global distributed RPKI

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   As RPKI-based origin validation relies on the availability of RPKI
   data, operators SHOULD locate caches close to routers that require
   these data and services.  A router can peer with one or more nearby

   For redundancy, a router SHOULD peer with more than one cache at the
   same time.  Peering with two or more, at least one local and others
   remote, is recommended.

   If an operator trusts upstreams to carry their traffic, they SHOULD
   also trust the RPKI data those upstreams cache, and SHOULD peer with
   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 SHOULD validate NLRI in
   announcements made by upstreams, downstreams, and peers.  To minimize
   impact on the global RPKI, they SHOULD fetch from and then revalidate
   data from caches provided by their upstreams.

   An environment where private address space is announced in eBGP the
   operator MAY have private RPKI objects which cover these private
   spaces.  This will require a trust anchor created and owned by that
   environment, see [I-D.ietf-sidr-ltamgmt].

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

   A large operator, concerned that a compromise of one router's key
   would make many 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 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.

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   In a fully BGPsec enabled AS, Route Reflectors MUST have BGPsec
   enabled if and only if there are eBGP speakers in their client cone.

   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

   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) 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 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

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.

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

   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

   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.

   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, or modifying a metric value such as local-preference

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   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 SHOULD have their signatures kept
   intact and should 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.

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

   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.

9.  Notes

   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 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 [I-D.ietf-sidr-ghostbusters]), signed indirectly by End
   Entity certificates, for those certificates on which others' routing
   depends for certificate and/or ROA validation.

   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 seriouly 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.

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   Servers should provide time service, such as NTP [RFC5905], to client

10.  Security Considerations

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

11.  IANA Considerations

   This document has no IANA Considerations.

12.  Acknowledgments

   The author wishes to thank the BGPsec design team.

13.  References

13.1.  Normative References

              Lepinski, M., "BGPSEC Protocol Specification",
              draft-ietf-sidr-bgpsec-protocol-00 (work in progress),
              June 2011.

              Bush, R., "The RPKI Ghostbusters Record",
              draft-ietf-sidr-ghostbusters-15 (work in progress),
              October 2011.

              Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
              Origin Authorizations (ROAs)",
              draft-ietf-sidr-roa-format-12 (work in progress),
              May 2011.

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

13.2.  Informative References

              Lepinski, M. and S. Kent, "An Infrastructure to Support

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              Secure Internet Routing", draft-ietf-sidr-arch-13 (work in
              progress), May 2011.

              Reynolds, M. and S. Kent, "Local Trust Anchor Management
              for the Resource Public Key Infrastructure",
              draft-ietf-sidr-ltamgmt-02 (work in progress), June 2011.

              Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation",
              draft-ietf-sidr-pfx-validate-02 (work in progress),
              July 2011.

              Huston, G., Loomans, R., and G. Michaelson, "A Profile for
              Resource Certificate Repository Structure",
              draft-ietf-sidr-repos-struct-09 (work in progress),
              July 2011.

              Lepinski, M. and S. Turner, "An Overview of BGPSEC",
              draft-lepinski-bgpsec-overview-00 (work in progress),
              March 2011.

              Pelsser, C., Bush, R., Patel, K., Mohapatra, P., and O.
              Maennel, "Making Route Flap Damping Usable",
              draft-ymbk-rfd-usable-01 (work in progress), June 2011.

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

   [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
              Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, June 2010.

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Author's Address

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

   Phone: +1 206 780 0431 x1

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