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Versions: (draft-jdurand-bgp-security) 00 01 02 03 04 05 06 07 RFC 7454

Internet Engineering Task Force                                J. Durand
Internet-Draft                                       CISCO Systems, Inc.
Intended status: Best Current Practice                      I. Pepelnjak
Expires: June 2, 2015                                                NIL
                                                              G. Doering
                                                                SpaceNet
                                                        December 2, 2014


                      BGP operations and security
                  draft-ietf-opsec-bgp-security-07.txt

Abstract

   BGP (Border Gateway Protocol) is the protocol almost exclusively used
   in the Internet to exchange routing information between network
   domains.  Due to this central nature, it is important to understand
   the security measures that can and should be deployed to prevent
   accidental or intentional routing disturbances.

   This document describes measures to protect the BGP sessions itself
   (like TTL, TCP-AO, control plane filtering) and to better control the
   flow of routing information, using prefix filtering and
   automatization of prefix filters, max-prefix filtering, AS path
   filtering, route flap dampening and BGP community scrubbing.

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 [1].

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
   working documents as Internet-Drafts.  The list of current Internet-
   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 May 29, 2015.



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Copyright Notice

   Copyright (c) 2014 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
   (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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Scope of the document . . . . . . . . . . . . . . . . . . . .   3
   3.  Definitions and Accronyms . . . . . . . . . . . . . . . . . .   4
   4.  Protection of the BGP speaker . . . . . . . . . . . . . . . .   4
   5.  Protection of BGP sessions  . . . . . . . . . . . . . . . . .   5
     5.1.  Protection of TCP sessions used by BGP  . . . . . . . . .   5
     5.2.  BGP TTL security (GTSM) . . . . . . . . . . . . . . . . .   6
   6.  Prefix filtering  . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Definition of prefix filters  . . . . . . . . . . . . . .   6
       6.1.1.  Special purpose prefixes  . . . . . . . . . . . . . .   6
       6.1.2.  Prefixes not allocated  . . . . . . . . . . . . . . .   7
       6.1.3.  Prefixes too specific . . . . . . . . . . . . . . . .  11
       6.1.4.  Filtering prefixes belonging to the local AS and
               downstreams . . . . . . . . . . . . . . . . . . . . .  11
       6.1.5.  IXP LAN prefixes  . . . . . . . . . . . . . . . . . .  11
       6.1.6.  The default route . . . . . . . . . . . . . . . . . .  12
     6.2.  Prefix filtering recommendations in full routing networks  13
       6.2.1.  Filters with Internet peers . . . . . . . . . . . . .  13
       6.2.2.  Filters with customers  . . . . . . . . . . . . . . .  15
       6.2.3.  Filters with upstream providers . . . . . . . . . . .  15
     6.3.  Prefix filtering recommendations for leaf networks  . . .  16
       6.3.1.  Inbound filtering . . . . . . . . . . . . . . . . . .  16
       6.3.2.  Outbound filtering  . . . . . . . . . . . . . . . . .  16
   7.  BGP route flap dampening  . . . . . . . . . . . . . . . . . .  17
   8.  Maximum prefixes on a peering . . . . . . . . . . . . . . . .  17
   9.  AS-path filtering . . . . . . . . . . . . . . . . . . . . . .  17
   10. Next-Hop Filtering  . . . . . . . . . . . . . . . . . . . . .  19
   11. BGP community scrubbing . . . . . . . . . . . . . . . . . . .  20
   12. Change logs . . . . . . . . . . . . . . . . . . . . . . . . .  20
     12.1.  Diffs between draft-jdurand-bgp-security-01 and draft-
            jdurand-bgp-security-00  . . . . . . . . . . . . . . . .  20



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     12.2.  Diffs between draft-jdurand-bgp-security-02 and draft-
            jdurand-bgp-security-01  . . . . . . . . . . . . . . . .  21
     12.3.  Diffs between draft-ietf-opsec-bgp-security-00 and
            draft-jdurand-bgp-security-02  . . . . . . . . . . . . .  22
     12.4.  Diffs between draft-ietf-opsec-bgp-security-01 and
            draft-ietf-opsec-bgp-security-00 . . . . . . . . . . . .  22
     12.5.  Diffs between draft-ietf-opsec-bgp-security-02 and
            draft-ietf-opsec-bgp-security-01 . . . . . . . . . . . .  23
     12.6.  Diffs between draft-ietf-opsec-bgp-security-03 and
            draft-ietf-opsec-bgp-security-02 . . . . . . . . . . . .  24
     12.7.  Diffs between draft-ietf-opsec-bgp-security-04 and
            draft-ietf-opsec-bgp-security-03 . . . . . . . . . . . .  25
     12.8.  Diffs between draft-ietf-opsec-bgp-security-05 and
            draft-ietf-opsec-bgp-security-04 . . . . . . . . . . . .  25
     12.9.  Diffs between draft-ietf-opsec-bgp-security-06 and
            draft-ietf-opsec-bgp-security-05 . . . . . . . . . . . .  25
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  26
   14. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  26
   16. References  . . . . . . . . . . . . . . . . . . . . . . . . .  27
     16.1.  Normative References . . . . . . . . . . . . . . . . . .  27
     16.2.  Informative References . . . . . . . . . . . . . . . . .  27
   Appendix A.  IXP LAN prefix filtering - example . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   BGP (Border Gateway Protocol - RFC 4271 [2]) is the protocol used in
   the Internet to exchange routing information between network domains.
   BGP does not directly include mechanisms that control that routes
   exchanged conform to the various guidelines defined by the Internet
   community.  This document intends to both summarize common existing
   guidelines and help network administrators apply coherent BGP
   policies.

2.  Scope of the document

   The guidelines defined in this document are intended for generic
   Internet BGP peerings.  The nature of the Internet is such that
   Autonomous Systems can always agree on exceptions to a common
   framework for relevant local needs, and therefore configure a BGP
   session in a manner that may differ from the recommendations provided
   in this document.  While this is perfectly acceptable, every
   configured exception might have an impact on the entire inter-domain
   routing environment and network administrators SHOULD carefully
   appraise this impact before implementation.





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3.  Definitions and Accronyms

   o  ACL: Access Control List

   o  ASN: Autonomous System Number

   o  IRR: Internet Routing Registry

   o  IXP: Internet eXchange Point

   o  LIR: Local Internet Registry

   o  pMTUd: Path MTU Discovery

   o  RIR: Regional Internet Registry

   o  Tier 1 transit provider: an IP transit provider which can reach
      any network on the Internet without purchasing transit services

   o  uRPF: Unicast Reverse Path Forwarding

4.  Protection of the BGP speaker

   The BGP speaker needs to be protected from attempts to subvert the
   BGP session.  This protection SHOULD be achieved by an Access Control
   List (ACL) which would discard all packets directed to TCP port 179
   on the local device and sourced from an address not known or
   permitted to become a BGP neighbor.  Experience has shown that
   natural protection TCP should offer is not always sufficient as it is
   sometimes run in control-plane software: in the absence of ACLs it is
   possible to attack a BGP speaker by simply sending a high volume of
   connection requests to it.

   If supported, an ACL specific to the control-plane of the router
   SHOULD be used (receive-ACL, control-plane policing, etc.), to avoid
   configuration of data-plane filters for packets transiting through
   the router (and therefore not reaching the control plane).  If the
   hardware can not do that, interface ACLs can be used to block packets
   addressed to the local router.

   Some routers automatically program such an ACL upon BGP
   configuration.  On other devices this ACL should be configured and
   maintained manually or using scripts.

   In addition to strict filtering, rate-limiting MAY be configured for
   accepted BGP traffic.  Rate-limiting BGP traffic consists in
   permitting only a certain quantity of bits per second (or packets per
   second) of BGP traffic to the control plane.  This protects the BGP



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   router control plane in case the amount of BGP traffic overcomes
   platform capabilities.

   Filtering and rate-limiting of control-plane traffic is a wider topic
   than "just for BGP" (if network administrator brings down a router by
   overloading one of the other protocols from remote, BGP is harmed as
   well).  For a more detailed recommendation on how to protect the
   router's control plane, see RFC 6192 [11].

5.  Protection of BGP sessions

   Current security issues of TCP-based protocols (therefore including
   BGP) have been documented in RFC 6952 [14].  The following sub-
   sections list the major points raised in this RFC and give best
   practices related to TCP session protection for BGP operation.

5.1.  Protection of TCP sessions used by BGP

   Attacks on TCP sessions used by BGP (aka BGP sessions), for example
   sending spoofed TCP RST packets, could bring down a BGP peering.
   Following a successful ARP spoofing attack (or other similar Man-in-
   the-Middle attack), the attacker might even be able to inject packets
   into the TCP stream (routing attacks).

   BGP sessions can be secured with a variety of mechanisms.  MD5
   protection of TCP session header, described in RFC 2385 [7], was the
   first such mechanism.  It is now deprecated by TCP Authentication
   Option (TCP-AO, RFC 5925 [4]) which offers stronger protection.
   While MD5 is still the most used mechanism due to its availability in
   vendor's equipment, TCP-AO SHOULD be preferred when implemented.

   IPsec could also be used for session protection.  At the time this
   document is published, there is not enough experience on impacts of
   the use of IPsec for BGP peerings and further analysis is required to
   define guidelines.

   The drawback of TCP session protection is additional configuration
   and management overhead for authentication information (ex: MD5
   password) maintenance.  Protection of TCP sessions used by BGP is
   thus NOT REQUIRED even when peerings are established over shared
   networks where spoofing can be done (like IXPs), but operators are
   RECOMMENDED to consider the trade-offs and to apply TCP session
   protection where appropriate.

   Network administrators SHOULD block spoofed packets (packets with a
   source IP address belonging to their IP address space) at all edges
   of their network (see RFC 2827 [8] and RFC 3704 [9]).  This protects




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   the TCP session used by iBGP from attackers outside the Autonomous
   System.

5.2.  BGP TTL security (GTSM)

   BGP sessions can be made harder to spoof with the Generalized TTL
   Security Mechanisms (GTSM, aka TTL security), defined in RFC 5082
   [3].  Instead of sending TCP packets with TTL value of 1, the BGP
   speakers send the TCP packets with TTL value of 255 and the receiver
   checks that the TTL value equals 255.  Since it's impossible to send
   an IP packet with TTL of 255 to a non-directly-connected IP host, BGP
   TTL security effectively prevents all spoofing attacks coming from
   third parties not directly connected to the same subnet as the BGP-
   speaking routers.  Network administrators SHOULD implement TTL
   security on directly connected BGP peerings.

   GTSM could also be applied to multi-hop BGP peering as well.  To
   achieve this TTL needs to be configured with proper value depending
   on the distance between BGP speakers (using principle described
   above).  Nevertheless it is not as effective as anyone inside the TTL
   diameter could spoof the TTL.

   Like MD5 protection, TTL security has to be configured on both ends
   of a BGP session.

6.  Prefix filtering

   The main aspect of securing BGP resides in controlling the prefixes
   that are received/advertised on the BGP peerings.  Prefixes exchanged
   between BGP peers are controlled with inbound and outbound filters
   that can match on IP prefixes (prefix filters, Section 6), AS paths
   (as-path filters, Section 9) or any other attributes of a BGP prefix
   (for example, BGP communities, Section 11).

6.1.  Definition of prefix filters

   This section list the most commonly used prefix filters.  Following
   sections will clarify where these filters should be applied.

6.1.1.  Special purpose prefixes

6.1.1.1.  IPv4 special purpose prefixes

   IANA IPv4 Special-Purpose Address Registry [22] maintains the list of
   IPv4 special purpose prefixes and their routing scope, and SHOULD be
   used for prefix filters configuration.  Prefixes with value "False"
   in column "Global" SHOULD be discarded on Internet BGP peerings.




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6.1.1.2.  IPv6 special purpose prefixes

   IANA IPv6 Special-Purpose Address Registry [23] maintains the list of
   IPv6 special purpose prefixes and their routing scope, and SHOULD be
   used for prefix filters configuration.  Only prefixes with value
   "False" in column "Global" SHOULD be discarded on Internet BGP
   peerings.

6.1.2.  Prefixes not allocated

   IANA allocates prefixes to RIRs which in turn allocate prefixes to
   LIRs (Local Internet Registries).  It is wise not to accept routing
   table prefixes that are not allocated by IANA and/or RIRs.  This
   section details the options for building a list of allocated prefixes
   at every level.  It is important to understand that filtering
   prefixes not allocated requires constant updates as prefixes are
   continually allocated.  Therefore automation of such prefix filters
   is key for the success of this approach.  Network administrators
   SHOULD NOT consider solutions described in this section if they are
   not capable of maintaining updated prefix filters: the damage would
   probably be worse than the intended security policy.

6.1.2.1.  IANA allocated prefix filters

   IANA has allocated all the IPv4 available space.  Therefore there is
   no reason why network administrators would keep checking that
   prefixes they receive from BGP peers are in the IANA allocated IPv4
   address space [24].  No specific filters need to be put in place by
   administrators who want to make sure that IPv4 prefixes they receive
   in BGP updates have been allocated by IANA.

   For IPv6, given the size of the address space, it can be seen as wise
   accepting only prefixes derived from those allocated by IANA.
   Administrators can dynamically build this list from the IANA
   allocated IPv6 space [25].  As IANA keeps allocating prefixes to
   RIRs, the aforementioned list should be checked regularly against
   changes and if they occur, prefix filters should be computed and
   pushed on network devices.  The list could also be pulled directly by
   routers when they implement such mechanisms.  As there is delay
   between the time a RIR receives a new prefix and the moment it starts
   allocating portions of it to its LIRs, there is no need for doing
   this step quickly and frequently.  However, network administrators
   SHOULD ensure that all IPv6 prefix filters are updated within maximum
   one month after any change in the list of IPv6 prefix allocated by
   IANA.

   If process in place (manual or automatic) cannot guarantee that the
   list is updated regularly then it's better not to configure any



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   filters based on allocated networks.  The IPv4 experience has shown
   that many network operators implemented filters for prefixes not
   allocated by IANA but did not update them on a regular basis.  This
   created problems for latest allocations and required a extra work for
   RIRs that had to "de-bogonize" the newly allocated prefixes.

6.1.2.2.  RIR allocated prefix filters

   A more precise check can be performed when one would like to make
   sure that prefixes they receive are being originated or transited by
   autonomous systems entitled to do so.  It has been observed in the
   past that an AS (Autonomous System) could easily advertise someone
   else's prefix (or more specific prefixes) and create black holes or
   security threats.  To partially mitigate this risk, administrators
   would need to make sure BGP advertisements correspond to information
   located in the existing registries.  At this stage 2 options can be
   considered (short and long term options).  They are described in the
   following subsections.

6.1.2.2.1.  Prefix filters creation from Internet Routing Registries
            (IRR)

   An Internet Routing Registry (IRR) is a database containing Internet
   routing information, described using Routing Policy Specification
   Language objects - RFC 4012 [10].  Network administrators are given
   privileges to describe routing policies of their own networks in the
   IRR and information is published, usually publicly.  A majority of
   Regional Internet Registries do also operate an IRR and can control
   that registered routes conform to prefixes allocated or directly
   assigned.However, it should be noted that the list of such prefixes
   is not necessarily a complete list, and as such the list of routes in
   an IRR is not the same as the set of RIR allocated prefixes.

   It is possible to use the IRR information to build, for a given
   neighbor autonomous system, a list of prefixes originated or
   transited which one may accept.  This can be done relatively easily
   using scripts and existing tools capable of retrieving this
   information in the registries.  This approach is exactly the same for
   both IPv4 and IPv6.

   The macro-algorithm for the script is described as follows.  For the
   peer that is considered, the distant network administrator has
   provided the autonomous system and may be able to provide an AS-SET
   object (aka AS-MACRO).  An AS-SET is an object which contains AS
   numbers or other AS-SETs.  An operator may create an AS-SET defining
   all the AS numbers of its customers.  A tier 1 transit provider might
   create an AS-SET describing the AS-SET of connected operators, which
   in turn describe the AS numbers of their customers.  Using recursion,



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   it is possible to retrieve from an AS-SET the complete list of AS
   numbers that the peer is likely to announce.  For each of these AS
   numbers, it is also easy to check in the corresponding IRR for all
   associated prefixes.  With these two mechanisms a script can build
   for a given peer the list of allowed prefixes and the AS number from
   which they should be originated.  One could decide not use the origin
   information and only build monolithic prefix filters from fetched
   data.

   As prefixes, AS numbers and AS-SETs may not all be under the same RIR
   authority, a difficulty resides choosing for each object the
   appropriate IRR to poll.  Some IRRs have been created and are not
   restricted to a given region or authoritative RIR.  They allow RIRs
   to publish information contained in their IRR in a common place.
   They also make it possible for any subscriber (probably under
   contract) to publish information too.  When doing requests inside
   such an IRR, it is possible to specify the source of information in
   order to have the most reliable data.  One could check a popular IRR
   containing many sources (such as RADB [26], the Routing Assets
   Database) and only select as sources some desired RIRs and trusted
   major ISPs (Internet Service Providers).

   As objects in IRRs may frequently vary over time, it is important
   that prefix filters computed using this mechanism are refreshed
   regularly.  A daily basis could even be considered as some routing
   changes must be done sometimes in a certain emergency and registries
   may be updated at the very last moment.  It has to be noted that this
   approach significantly increases the complexity of the router
   configurations as it can quickly add tens of thousands configuration
   lines for some important peers.  To manage this complexity, network
   adminstrators could for example use IRRToolSet [29], a set of tools
   making it possible to simplify the creation of automated filters
   configuration from policies stored in IRR.

   Last but not least, network administrators SHOULD publish and
   maintain their resources properly in IRR database maintained by their
   RIR, when available.

6.1.2.2.2.  SIDR - Secure Inter Domain Routing

   An infrastructure called SIDR (Secure Inter-Domain Routing),
   described in RFC 6480 [12] has been designed to secure Internet
   advertisements.  At the time this document is written, many documents
   have been published and a framework with a complete set of protocols
   is proposed so that advertisements can be checked against signed
   routing objects in RIR routing registries.  There are basically two
   services that SIDR offers:




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   o  Origin validation, described in RFC 6811 [5], seeks at making sure
      that attributes associated with a routes are correct (the major
      point being the validation of the AS number originating this
      route).  Origin validation is now operational (Internet
      registries, protocols, implementations on some routers...) and in
      theory it can be implemented knowing that the proportion of signed
      resources is still low at the time this document is written.

   o  Path validation provided by BGPsec [27] seeks at making sure that
      no ones announce fake/wrong BGP paths that would attract trafic
      for a given destination, see RFC 7132 [16].  BGPsec is still an
      on-going work item at the time this document is written and
      therefore cannot be implemented.

   Implementing SIDR mechanisms is expected to solve many of BGP routing
   security problems in the long term but it may take time for
   deployments to be made and objects to become signed.  It also has to
   be pointed that SIDR infrastructure is complementing (not replacing)
   the security best practices listed in this document.  Network
   administrators SHOULD therefore implement any SIDR proposed mechanism
   (example: route origin validation) on top of the other existing
   mechanisms even if they could sometimes appear targeting the same
   goal.

   If route origin validation is implemented, reader SHOULD refer to
   rules described in RFC 7115 [15].  In short, each external route
   received on a router SHOULD be checked against the RPKI data set:

   o  If a corresponding ROA (Route Origin Authorization) is found and
      is valid then the prefix SHOULD be accepted.

   o  It the ROA is found and is INVALID then the prefix SHOULD be
      discarded.

   o  If an ROA is not found then the prefix SHOULD be accepted but
      corresponding route SHOULD be given a low preference.

   In addition to this, network administrators SHOULD sign their routing
   objects so their routes can be validated by other networks running
   origin validation.

   One should understand that the RPKI model brings new interesting
   challenges.  The paper On the Risk of Misbehaving RPKI Authorities
   [30] explains how RPKI model can impact the Internet if authorities
   don't behave as they are supposed to do.  Further analysis is
   certainly required on RPKI, which carries part of BGP security.





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6.1.3.  Prefixes too specific

   Most ISPs will not accept advertisements beyond a certain level of
   specificity (and in return do not announce prefixes they consider as
   too specific).  That acceptable specificity is decided for each
   peering between the 2 BGP peers.  Some ISP communities have tried to
   document acceptable specificity.  This document does not make any
   judgement on what the best approach is, it just recalls that there
   are existing practices on the Internet and recommends the reader to
   refer to what those are.  As an example the RIPE community has
   documented that as of the time of writing of this document, IPv4
   prefixes longer than /24 and IPv6 prefixes longer than /48 are
   generally not announced/accepted in the Internet [19] [20].  These
   values may change in the future.

6.1.4.  Filtering prefixes belonging to the local AS and downstreams

   A network SHOULD filter its own prefixes on peerings with all its
   peers (inbound direction).  This prevents local traffic (from a local
   source to a local destination) from leaking over an external peering
   in case someone else is announcing the prefix over the Internet.
   This also protects the infrastructure which may directly suffer in
   case backbone's prefix is suddenly preferred over the Internet.

   In some cases, for example in multi-homing scenarios, such filters
   SHOULD NOT be applied as this would break the desired redundancy.

   To an extent, such filters can also be configured on a network for
   the prefixes of its downstreams in order to protect them too.  Such
   filters must be defined with caution as they can break existing
   redundancy mechanisms.  For example in case an operator has a
   multihomed customer, it should keep accepting the customer prefix
   from its peers and upstreams.  This will make it possible for the
   customer to keep accessing its operator network (and other customers)
   via the Internet in case the BGP peering between the customer and the
   operator is down.

6.1.5.  IXP LAN prefixes

6.1.5.1.  Network security

   When a network is present on an IXP and peers with other IXP members
   over a common subnet (IXP LAN prefix), it SHOULD NOT accept more
   specific prefixes for the IXP LAN prefix from any of its external BGP
   peers.  Accepting these routes may create a black hole for
   connectivity to the IXP LAN.





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   If the IXP LAN prefix is accepted as an "exact match", care needs to
   be taken to avoid other routers in the network sending IXP traffic
   towards the externally-learned IXP LAN prefix (recursive route lookup
   pointing into the wrong direction).  This can be achieved by
   preferring IGP routes before eBGP, or by using "BGP next-hop-self" on
   all routes learned on that IXP.

   If the IXP LAN prefix is accepted at all, it SHOULD only be accepted
   from the ASes that the IXP authorizes to announce it - which will
   usually be automatically achieved by filtering announcements by IRR
   DB.

6.1.5.2.  pMTUd and the loose uRPF problem

   In order to have pMTUd working in the presence of loose uRPF, it is
   necessary that all the networks that may source traffic that could
   flow through the IXP (ie.  IXP members and their downstreams) have a
   route for the IXP LAN prefix.  This is necessary as "packet too big"
   ICMP messages sent by IXP members' routers may be sourced using an
   address of the IXP LAN prefix.  In the presence of loose uRPF, this
   ICMP packet is dropped if there is no route for the IXP LAN prefix or
   a less specific route covering IXP LAN prefix.

   In that case, any IXP member SHOULD make sure it has a route for the
   IXP LAN prefix or a less specific prefix on all its routers and that
   it announces the IXP LAN prefix or less specific (up to a default
   route) to its downstreams.  The announcements done for this purpose
   SHOULD pass IRR-generated filters described in Section 6.1.2.2.1 as
   well as "prefixes too specific" filters described in Section 6.1.3.
   The easiest way to implement this is that the IXP itself takes care
   of the origination of its prefix and advertises it to all IXP members
   through a BGP peering.  Most likely the BGP route servers would be
   used for this.  The IXP would most likely send its entire prefix
   which would be equal or less specific than the IXP LAN prefix.

   Appendix Appendix A gives an example of guidelines regarding IXP LAN
   prefix.

6.1.6.  The default route

6.1.6.1.  IPv4

   The 0.0.0.0/0 prefix is likely not intended to be accepted nor
   advertised other than in specific customer / provider configurations,
   general filtering outside of these is RECOMMENDED.






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6.1.6.2.  IPv6

   The ::/0 prefix is likely not intended to be accepted nor advertised
   other than in specific customer / provider configurations, general
   filtering outside of these is RECOMMENDED.

6.2.  Prefix filtering recommendations in full routing networks

   For networks that have the full Internet BGP table, some policies
   should be applied on each BGP peer for received and advertised
   routes.  It is RECOMMENDED that each autonomous system configures
   rules for advertised and received routes at all its borders as this
   will protect the network and its peer even in case of
   misconfiguration.  The most commonly used filtering policy is
   proposed in this section and uses prefix filters defined in previous
   section Section 6.1.

6.2.1.  Filters with Internet peers

6.2.1.1.  Inbound filtering

   There are basically 2 options, the loose one where no check will be
   done against RIR allocations and the strict one where it will be
   verified that announcements strictly conform to what is declared in
   routing registries.

6.2.1.1.1.  Inbound filtering loose option

   In this case, the following prefixes received from a BGP peer will be
   filtered:

   o  Prefixes not globally routable (Section 6.1.1)

   o  Prefixes not allocated by IANA (IPv6 only) (Section 6.1.2.1)

   o  Routes too specific (Section 6.1.3)

   o  Prefixes belonging to the local AS (Section 6.1.4)

   o  IXP LAN prefixes (Section 6.1.5)

   o  The default route (Section 6.1.6)

6.2.1.1.2.  Inbound filtering strict option

   In this case, filters are applied to make sure advertisements
   strictly conform to what is declared in routing registries
   (Section 6.1.2.2).  Warning is given as registries are not always



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   accurate (prefixes missing, wrong information...) This varies across
   the registries and regions of the Internet.  Before applying a strict
   policy the reader SHOULD check the impact on the filter and make sure
   solution is not worse than the problem.

   Also in case of script failure each administrator may decide if all
   routes are accepted or rejected depending on routing policy.  While
   accepting the routes during that time frame could break the BGP
   routing security, rejecting them might re-route too much traffic on
   transit peers, and could cause more harm than what a loose policy
   would have done.

   In addition to this, network administrators could apply the following
   filters beforehand in case the routing registry used as source of
   information by the script is not fully trusted:

   o  Prefixes not globally routable (Section 6.1.1)

   o  Routes too specific (Section 6.1.3)

   o  Prefixes belonging to the local AS (Section 6.1.4)

   o  IXP LAN prefixes (Section 6.1.5)

   o  The default route (Section 6.1.6)

6.2.1.2.  Outbound filtering

   Configuration should be put in place to make sure that only
   appropriate prefixes are sent.  These can be, for example, prefixes
   belonging to both the network in question and its downstreams.  This
   can be achieved by using a combination of BGP communities, AS-paths
   or both.  It can also be desirable that following filters are
   positioned before to avoid unwanted route announcement due to bad
   configuration:

   o  Prefixes not globally routable (Section 6.1.1)

   o  Routes too specific (Section 6.1.3)

   o  IXP LAN prefixes (Section 6.1.5)

   o  The default route (Section 6.1.6)

   In case it is possible to list the prefixes to be advertised, then
   just configuring the list of allowed prefixes and denying the rest is
   sufficient.




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6.2.2.  Filters with customers

6.2.2.1.  Inbound filtering

   The inbound policy with end customers is pretty straightforward: only
   customers prefixes SHOULD be accepted, all others SHOULD be
   discarded.  The list of accepted prefixes can be manually specified,
   after having verified that they are valid.  This validation can be
   done with the appropriate IP address management authorities.

   The same rules apply in case the customer is also a network
   connecting other customers (for example a tier 1 transit provider
   connecting service providers).  An exception can be envisaged in case
   it is known that the customer network applies strict inbound/outbound
   prefix filtering, and the number of prefixes announced by that
   network is too large to list them in the router configuration.  In
   that case filters as in Section 6.2.1.1 can be applied.

6.2.2.2.  Outbound filtering

   The outbound policy with customers may vary according to the routes
   customer wants to receive.  In the simplest possible scenario, the
   customer may only want to receive only the default route, which can
   be done easily by applying a filter with the default route only.

   In case the customer wants to receive the full routing (in case it is
   multihomed or if wants to have a view of the Internet table), the
   following filters can be simply applied on the BGP peering:

   o  Prefixes not globally routable (Section 6.1.1)

   o  Routes too specific (Section 6.1.3)

   o  The default route (Section 6.1.6)

   There can be a difference for the default route that can be announced
   to the customer in addition to the full BGP table.  This can be done
   simply by removing the filter for the default route.  As the default
   route may not be present in the routing table, network administrators
   may decide to originate it only for peerings where it has to be
   advertised.

6.2.3.  Filters with upstream providers








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6.2.3.1.  Inbound filtering

   In case the full routing table is desired from the upstream, the
   prefix filtering to apply is the same as the one for peers
   Section 6.2.1.1 with the exception of the default route.  The default
   route can be desired from an upstream provider in addition to the
   full BGP table.  In case the upstream provider is supposed to
   announce only the default route, a simple filter will be applied to
   accept only the default prefix and nothing else.

6.2.3.2.  Outbound filtering

   The filters to be applied would most likely not differ much from the
   ones applied for Internet peers (Section 6.2.1.2).  But different
   policies could be applied in case it is desired that a particular
   upstream does not provide transit to all the prefixes.

6.3.  Prefix filtering recommendations for leaf networks

6.3.1.  Inbound filtering

   The leaf network will deploy the filters corresponding to the routes
   it is requesting from its upstream.  In case a default route is
   requested, a simple inbound filter can be applied to accept only the
   default route (Section 6.1.6).  In case the leaf network is not
   capable of listing the prefixes because the amount is too large (for
   example if it requires the full Internet routing table) then it
   should configure filters to avoid receiving bad announcements from
   its upstream:

   o  Prefixes not routable (Section 6.1.1)

   o  Routes too specific (Section 6.1.3)

   o  Prefixes belonging to local AS (Section 6.1.4)

   o  The default route (Section 6.1.6) depending if the route is
      requested or not

6.3.2.  Outbound filtering

   A leaf network will most likely have a very straightforward policy:
   it will only announce its local routes.  It can also configure the
   following prefixes filters described in Section 6.2.1.2 to avoid
   announcing invalid routes to its upstream provider.






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7.  BGP route flap dampening

   The BGP route flap dampening mechanism makes it possible to give
   penalties to routes each time they change in the BGP routing table.
   Initially this mechanism was created to protect the entire Internet
   from multiple events impacting a single network.  Studies have shown
   that implementations of BGP route flap dampening could cause more
   harm than they solve problems and therefore RIPE community has in the
   past recommended not using BGP route flap dampening [18].  Studies
   have then been conducted to propose new route flap dampening
   thresholds in order to make the solution "usable", see RFC 7196 [6]
   and RIPE has reviewed its recommendations in [21].  This document
   RECOMMENDS following IETF and RIPE recommendations and only use BGP
   route flap dampening with the adjusted configured thresholds.

8.  Maximum prefixes on a peering

   It is RECOMMENDED to configure a limit on the number of routes to be
   accepted from a peer.  Following rules are generally RECOMMENDED:

   o  From peers, it is RECOMMENDED to have a limit lower than the
      number of routes in the Internet.  This will shut down the BGP
      peering if the peer suddenly advertises the full table.  Network
      admistrators can also configure different limits for each peer,
      according to the number of routes they are supposed to advertise
      plus some headroom to permit growth.

   o  From upstreams which provide full routing, it is RECOMMENDED to
      have a limit higher than the number of routes in the Internet.  A
      limit is still useful in order to protect the network (and in
      particular the routers' memory) if too many routes are sent by the
      upstream.  The limit should be chosen according to the number of
      routes that can actually be handled by routers.

   It is important to regularly review the limits that are configured as
   the Internet can quickly change over time.  Some vendors propose
   mechanisms to have two thresholds: while the higher number specified
   will shutdown the peering, the first threshold will only trigger a
   log and can be used to passively adjust limits based on observations
   made on the network.

9.  AS-path filtering

   This section lists the RECOMMENDED practices when processing BGP AS-
   paths:

   o  Network administrators SHOULD accept from customers only AS(4)-
      Paths containing ASNs belonging to (or authorized to transit



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      through) the customer.  If network administrators can not build
      and generate filtering expressions to implement this, they SHOULD
      consider accepting only path lengths relevant to the type of
      customer they have (as in, if these customers are a leaf or have
      customers of their own), and try to discourage excessive
      prepending in such paths.  This loose policy could be combined
      with filters for specific AS(4)-Paths that must not be accepted if
      advertised by the customer, such as upstream transit provider or
      peer ASNs.

   o  Network administrators SHOULD NOT accept prefixes with private AS
      numbers in the AS-path except from customers.  Exception: an
      upstream offering some particular service like black-hole
      origination based on a private AS number.  Customers should be
      informed by their upstream in order to put in place ad-hoc policy
      to use such services.

   o  Network administrators SHOULD NOT accept prefixes when the first
      AS number in the AS-path is not the one of the peer unless the
      peering is done toward a BGP route-server [17] (for example on an
      IXP) with transparent AS path handling.  In that case this
      verification needs to be de-activated as the first AS number will
      be the one of an IXP member whereas the peer AS number will be the
      one of the BGP route-server.

   o  Network administrators SHOULD NOT advertise prefixes with non-
      empty AS-path unless they intend to be transit for these prefixes.

   o  Network administrators SHOULD NOT advertise prefixes with upstream
      AS numbers in the AS-path to their peering AS unless they intend
      to be transit for these prefixes.

   o  Private AS numbers are conventionally used in contexts that are
      "private" and SHOULD NOT be used in advertisements to BGP peers
      that are not party to such private arrangements, and should be
      stripped when received from BGP peers that are not party to such
      private arrangements.

   o  Network administrators SHOULD NOT override BGP's default behavior
      accepting their own AS number in the AS-path.  In case an
      exception to this is required, impacts should be studied carefully
      as this can create severe impact on routing.

   AS-path filtering should be further analyzed when ASN renumbering is
   done.  Such operation is common and mechanisms exist to allow smooth
   ASN migration [28].  The usual migration technique, local to a
   router, consists in modifying the AS-path so it is presented to a
   peer with the previous ASN, as if no renumbering was done.  This



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   makes it possible to change ASN of a router without reconfiguring all
   eBGP peers at the same time (as this operation would require
   synchronization with all peers attached to that router).  During this
   renumbering operation, rules described above may be adjusted.

10.  Next-Hop Filtering

   If peering on a shared network, like an IXP, BGP can advertise
   prefixes with a 3rd-party next-hop, thus directing packets not to the
   peer announcing the prefix but somewhere else.

   This is a desirable property for BGP route-server setups [17], where
   the route-server will relay routing information, but has neither
   capacity nor desire to receive the actual data packets.  So the BGP
   route-server will announce prefixes with a next-hop setting pointing
   to the router that originally announced the prefix to the route-
   server.

   In direct peerings between ISPs, this is undesirable, as one of the
   peers could trick the other one to send packets into a black hole
   (unreachable next-hop) or to an unsuspecting 3rd party who would then
   have to carry the traffic.  Especially for black-holing, the root
   cause of the problem is hard to see without inspecting BGP prefixes
   at the receiving router at the IXP.

   Therefore, an inbound route policy SHOULD be applied on IXP peerings
   in order to set the next-hop for accepted prefixes to the BGP peer IP
   address (belonging to the IXP LAN) that sent the prefix (which is
   what "next-hop-self" would enforce on the sending side).

   This policy SHOULD NOT be used on route-server peerings, or on
   peerings where network administrators intentionally permit the other
   side to send 3rd-party next-hops.

   This policy also SHOULD be adjusted if Remote Triggered Black Holing
   best practice (aka RTBH - RFC 6666 [13]) is implemented.  In that
   case network administrators would apply a well-known BGP next-hop for
   routes they want to filter (if an Internet threat is observed from/to
   this route for example).  This well known next-hop will be statically
   routed to a null interface.  In combination with unicast RPF check,
   this will discard traffic from and toward this prefix.  Peers can
   exchange information about black-holes using for example particular
   BGP communities.  Network administrators could propagate black-holes
   information to their peers using agreed BGP community: when receiving
   a route with that community a configured policy could change the
   next-hop in order to create the black hole.





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11.  BGP community scrubbing

   Optionally we can consider the following rules on BGP AS-paths:

   o  Network administrators SHOULD scrub inbound communities with their
      number in the high-order bits, and allow only those communities
      that customers/peers can use as a signaling mechanism

   o  Networks administrators SHOULD NOT remove other communities
      applied on received routes (communities not removed after
      application of previous statement).  In particular they SHOULD
      keep original communities when they apply a community.  Customers
      might need them to communicate with upstream providers.  In
      particular network administrators SHOULD NOT (generally) remove
      the no-export community as it is usually announced by their peer
      for a certain purpose.

12.  Change logs

   !!! NOTE TO THE RFC EDITOR: THIS SECTION WAS ADDED TO TRACK CHANGES
   AND FACILITATE WORKING GROUP COLLABORATION.  IT MUST BE DELETED
   BEFORE PUBLICATION !!!

12.1.  Diffs between draft-jdurand-bgp-security-01 and draft-jdurand-
       bgp-security-00

   Following changes have been made since previous document draft-
   jdurand-bgp-security-00:

   o  "This documents" typo corrected in the former abstract

   o  Add normative reference for RFC5082 in former section 3.2

   o  "Non routable" changed in title of former section 4.1.1

   o  Correction of typo for IPv4 loopback prefix in former section
      4.1.1.1

   o  Added shared transition space 100.64.0.0/10 in former section
      4.1.1.1

   o  Clarification that 2002::/16 6to4 prefix can cross network
      boundaries in former section 4.1.1.2

   o  Rationale of 2000::/3 explained in former section 4.1.1.2






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   o  Added 3FFE::/16 prefix forgotten initially in the simplified list
      of prefixes that must not be routed by definition in former
      section 4.1.1.2

   o  Warn that filters for prefixes not allocated by IANA MUST only be
      done if regular refresh is guaranteed, with some words about the
      IPv4 experience, in former section 4.1.2.1

   o  Replace RIR database with IRR.  A definition of IRR is added in
      former section 4.1.2.2

   o  Remove any reference to anti-spoofing in former section 4.1.4

   o  Clarification for IXP LAN prefix and pMTUd problem in former
      section 4.1.5

   o  "Autonomous filters" typo (instead of Autonomous systems)
      corrected in the former section 4.2

   o  Removal of an example for manual address validation in former
      section 4.2.2.1

   o  RFC5735 obsoletes RFC3300

   o  Ingress/Egress replaced by Inbound/Outbound in all the document

12.2.  Diffs between draft-jdurand-bgp-security-02 and draft-jdurand-
       bgp-security-01

   Following changes have been made since previous document draft-
   jdurand-bgp-security-01:

   o  2 documentation prefixes were forgotten due to errata in RFC5735.
      But all prefixes were removed from that document which now point
      to other references for sake of not creating a new "registry" that
      would become outdated sooner or later

   o  Change MD5 section with global TCP security session and
      introducing TCP-AO in former section 3.1.  Added reference to
      BCP38

   o  Added new section 3 about BGP router protection with forwarding
      plane ACL

   o  Change text about prefix acceptable specificity in former section
      4.1.3 to explain this doc does not try to make recommendations





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   o  Refer as much as possible to existing registries to avoid creating
      a new one in former section 4.1.1.1 and 4.1.1.2

   o  Abstract reworded

   o  6to4 exception described (only more specifics MUST be filtered)

   o  More specific -> more specifics

   o  should -> MUST for the prefixes an ISP needs to filter from its
      customers in former section 4.2.2.1

   o  Added "plus some headroom to permit growth" in former section 7

   o  Added new section on Next-Hop filtering

12.3.  Diffs between draft-ietf-opsec-bgp-security-00 and draft-jdurand-
       bgp-security-02

   Following changes have been made since previous document draft-
   jdurand-bgp-security-02:

   o  Added a subsection for RTBH in next-hop section with reference to
      RFC6666

   o  Changed last sentence of introduction

   o  Many edits throughout the document

   o  Added definition of tier 1 transit provider

   o  Removed definition of a BGP peering

   o  Removed description of routing policies for IPv6 prefixes in IANA
      special registry as this now contains a routing scope field

   o  Added reference to RFC6598 and changed the IPv4 prefixes to be
      filtered by definition section

   o  IXP added in accronym/definition section and only term used
      throughout the doc now

12.4.  Diffs between draft-ietf-opsec-bgp-security-01 and draft-ietf-
       opsec-bgp-security-00

   Following changes have been made since previous document draft-ietf-
   opsec-bgp-security-00:




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   o  Obsolete RFC2385 moved from normative to informative reference

   o  Clarification of preference of TCP-AO over MD5 in former section
      4.1

   o  Mentioning KARP efforts in TCP session protection section in
      former section 4 and adding 3 RFC as informative references: 6518,
      6862 and 6952

   o  Removing reference to SIDR working-group

   o  Better dissociating origin validation and path validation to
      clarify what's potentially available for deployment

   o  Adding that SIDR mechanisms should be implemented in addition to
      the other ones mentioned throughout this document

   o  Added a paragraph in former section 8 about ASN renumbering

   o  Change of security considerations section

   o  Added the newly created IANA IPv4 Special Purpose Address Registry
      instead of references to RFCs listing these addresses

12.5.  Diffs between draft-ietf-opsec-bgp-security-02 and draft-ietf-
       opsec-bgp-security-01

   Following changes have been made since previous document draft-ietf-
   opsec-bgp-security-01:

   o  Added a reference to draft-ietf-sidr-origin-ops

   o  Added a reference to RFC6811 and RFC6907

   o  Changes "Most of RIR's" to "A majority of RIR's" on IRR
      availability

   o  Various edits

   o  Added NIST BGP security recommendations document

   o  Added that it's possible to get info from ISPs from RADB

   o  Correction of the url for IPv4 special use prefixes repository

   o  Clarification of the fact only prefixes with Global Scope set to
      False MUST be discarded




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   o  IANA list could be pulled directly by routers (not just pushed on
      routers).

   o  Warning added when prefixes are checked against IRR

   o  Recommend network operators to sign their routing objects

   o  Recommend network operators to publish their routing objects in
      IRR of their IRR when available

   o  Dissociate rules for local AS and downstreams in former section
      5.1.4

12.6.  Diffs between draft-ietf-opsec-bgp-security-03 and draft-ietf-
       opsec-bgp-security-02

   Following changes have been made since previous document draft-ietf-
   opsec-bgp-security-02:

   o  Added a note on TCP-AO to be preferred over MD5

   o  Mention that loose AS filtering with customers can be combined
      with precise filters for important ASNs (example those of
      transits) that are must not be received on theses peers in former
      section 8.

   o  MD5 removed from abstract

   o  recommended -> RECOMMENDED where appropriate

   o  Reference to BCP38 and BCP84 in former section 4.1

   o  Added a note to RFC Editor to remove change section before
      publication

   o  Removal of "future work" section

   o  Added rate-limiting in addition to filtering in former section 3

   o  Reference to IRRToolSet in former section 5.1.2.3

   o  Removed "foreword" section









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12.7.  Diffs between draft-ietf-opsec-bgp-security-04 and draft-ietf-
       opsec-bgp-security-03

   Following changes have been made since previous document draft-ietf-
   opsec-bgp-security-03:

   o  RFC6890 updates RFC5735

   o  RFC6890 updates RFC5156

   o  Removed reference RFC2234 and RFC 4234

   o  Moved route-server draft into informative reference section

12.8.  Diffs between draft-ietf-opsec-bgp-security-05 and draft-ietf-
       opsec-bgp-security-04

   Following changes have been made since previous document draft-ietf-
   opsec-bgp-security-04:

   o  RFC7196 updates draft-ietf-idr-rfd-usable

   o  RFC7115 updates draft-ietf-sidr-origin-ops

   o  draft-ietf-idr-ix-bgp-route-server-05 updates ietf-idr-ix-bgp-
      route-server-00

12.9.  Diffs between draft-ietf-opsec-bgp-security-06 and draft-ietf-
       opsec-bgp-security-05

   Following changes have been made since previous document draft-ietf-
   opsec-bgp-security-05:

   o  Wording improvements

   o  Introduction improved

   o  References are expanded (not just reference numbers are displayed
      but also the title of the document

   o  First occurence of accronyms expanded

   o  GTSM for multi-hop peerings

   o  Remove eBGP as protected by BCP38

   o  Add a caveat for IPsec for session protection




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   o  Changed MUST for SHOULD everywhere

   o  Small changes in communities section

   o  Removed simplified IPv6 prefix list

   o  Removed note in section 9 about 32 bits ASN

   o  IXP LAN prefix example in appendix

   o  Make sure all references are in the text.  Most of them were
      removed as they were initially here for previous version when IANA
      registries with routing scopes did not exist

13.  Acknowledgements

   The authors would like to thank the following people for their
   comments and support: Marc Blanchet, Ron Bonica, Randy Bush, David
   Freedman, Wesley George, Daniel Ginsburg, David Groves, Mike Hugues,
   Joel Jaeggli, Tim Kleefass, Warren Kumari, Jacques Latour, Lionel
   Morand, Jerome Nicolle, Hagen Paul Pfeifer, Thomas Pinaud, Carlos
   Pignataro, Jean Rebiffe, Donald Smith, Kotikalapudi Sriram, Matjaz
   Straus, Tony Tauber, Gunter Van de Velde, Sebastian Wiesinger,
   Matsuzaki Yoshinobu.

   Authors would like to thank once again Gunter Van de Velde for
   presenting the draft at several IETF meetings in various working
   groups, indeed helping dissemination of this document and gathering
   of precious feedback.

14.  IANA Considerations

   This memo includes no request to IANA.

15.  Security Considerations

   This document is entirely about BGP operational security.  It depicts
   best practices that one should adopt to secure its BGP
   infrastructure: protecting BGP router and BGP sessions, adopting
   consistent BGP prefix and AS-path filters and configure other options
   to secure the BGP network.

   On the other hand this document doesn't aim at depicting existing BGP
   implementations and their potential vulnerabilities and ways they
   handle errors.  It does not detail how protection could be enforced
   against attack techniques using crafted packets.





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16.  References

16.1.  Normative References

   [1]        Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997,
              <http://xml.resource.org/public/rfc/html/rfc2119.html>.

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

   [3]        Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, October 2007.

   [4]        Touch, J., Mankin, A., and R. Bonica, "The TCP
              Authentication Option", RFC 5925, June 2010.

   [5]        Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation", RFC 6811, January
              2013.

   [6]        Pelsser, C., Bush, R., Patel, K., Mohapatra, P., and O.
              Maennel, "Making Route Flap Damping Usable", RFC 7196, May
              2014.

16.2.  Informative References

   [7]        Heffernan, A., "Protection of BGP Sessions via the TCP MD5
              Signature Option", RFC 2385, August 1998.

   [8]        Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.

   [9]        Baker, F. and P. Savola, "Ingress Filtering for Multihomed
              Networks", BCP 84, RFC 3704, March 2004.

   [10]       Blunk, L., Damas, J., Parent, F., and A. Robachevsky,
              "Routing Policy Specification Language next generation
              (RPSLng)", RFC 4012, March 2005.

   [11]       Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
              Router Control Plane", RFC 6192, March 2011.

   [12]       Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", RFC 6480, February 2012.




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   [13]       Hilliard, N. and D. Freedman, "A Discard Prefix for IPv6",
              RFC 6666, August 2012.

   [14]       Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, May 2013.

   [15]       Bush, R., "Origin Validation Operation Based on the
              Resource Public Key Infrastructure (RPKI)", BCP 185, RFC
              7115, January 2014.

   [16]       Kent, S. and A. Chi, "Threat Model for BGP Path Security",
              RFC 7132, February 2014.

   [17]       "Internet Exchange Route Server",
              <http://tools.ietf.org/id/
              draft-ietf-idr-ix-bgp-route-server-05.txt>.

   [18]       Smith, P. and C. Panigl, "RIPE-378 - RIPE Routing Working
              Group Recommendations On Route-flap Damping", May 2006.

   [19]       Smith, P., Evans, R., and M. Hughes, "RIPE-399 - RIPE
              Routing Working Group Recommendations on Route
              Aggregation", December 2006.

   [20]       Smith, P. and R. Evans, "RIPE-532 - RIPE Routing Working
              Group Recommendations on IPv6 Route Aggregation", November
              2011.

   [21]       Smith, P., Bush, R., Kuhne, M., Pelsser, C., Maennel, O.,
              Patel, K., Mohapatra, P., and R. Evans, "RIPE-580 - RIPE
              Routing Working Group Recommendations On Route-flap
              Damping", January 2013.

   [22]       "IANA IPv4 Special Purpose Address Registry",
              <http://www.iana.org/assignments/iana-ipv4-special-
              registry/iana-ipv4-special-registry.xhtml>.

   [23]       "IANA IPv6 Special Purpose Address Registry",
              <http://www.iana.org/assignments/iana-ipv6-special-
              registry/iana-ipv6-special-registry.xml>.

   [24]       "IANA IPv4 Address Space Registry",
              <http://www.iana.org/assignments/ipv4-address-space/
              ipv4-address-space.xml>.





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   [25]       "IANA IPv6 Address Space Registry",
              <http://www.iana.org/assignments/ipv6-unicast-address-
              assignments/ipv6-unicast-address-assignments.xml>.

   [26]       "Routing Assets Database", <http://www.radb.net>.

   [27]       "Security Requirements for BGP Path Validation",
              <http://datatracker.ietf.org/doc/
              draft-ietf-sidr-bgpsec-reqs/>.

   [28]       "Autonomous System (AS) Migration Features and Their
              Effects on the BGP AS_PATH Attribute",
              <http://datatracker.ietf.org/doc/
              draft-ga-idr-as-migration/>.

   [29]       "IRRToolSet project page", <http://irrtoolset.isc.org>.

   [30]       Cooper, D., Heilman, E., Brogle, K., Reyzin, L., and S.
              Goldberg, "On the Risk of Misbehaving RPKI Authorities",
              <http://www.cs.bu.edu/~goldbe/papers/hotRPKI.pdf>.

Appendix A.  IXP LAN prefix filtering - example

   An IXP in the RIPE region is allocated an IPv4 /22 prefix by RIPE NCC
   (X.Y.0.0/22 in this example) and uses a /23 of this /22 for the IXP
   LAN (let say X.Y.0.0/23).  This IXP LAN prefix is the one used by IXP
   members to configure eBGP peerings.  The IXP could also be allocated
   an AS number (AS64496 in our example).

   Any IXP member SHOULD make sure it filters prefixes more specific
   than X.Y.0.0/23 from all its eBGP peers.  If it received X.Y.0.0/24
   or X.Y.1.0/24 this could seriously impact its routing.

   The IXP SHOULD originate X.Y.0.0/22 and advertise it to its members
   through an eBGP peering (most likely from its BGP route servers,
   configured with AS64496).

   The IXP members SHOULD accept the IXP prefix only if it passes the
   IRR generated filters (see Section 6.1.2.2.1)

   IXP members SHOULD then advertise X.Y.0.0/22 prefix to their
   downstreams.  This announce would pass IRR based filters as it is
   originated by the IXP.








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Authors' Addresses

   Jerome Durand
   CISCO Systems, Inc.
   11 rue Camille Desmoulins
   Issy-les-Moulineaux  92782 CEDEX
   FR

   Email: jerduran@cisco.com


   Ivan Pepelnjak
   NIL Data Communications
   Tivolska 48
   Ljubljana  1000
   Slovenia

   Email: ip@ipspace.net


   Gert Doering
   SpaceNet AG
   Joseph-Dollinger-Bogen 14
   Muenchen  D-80807
   Germany

   Email: gert@space.net
























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