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Versions: (draft-george-sidr-as-migration) 00 01 02 03 04 05 06 RFC 8206

Internet Engineering Task Force                                W. George
Internet-Draft                                         Time Warner Cable
Intended status: Informational                                 S. Murphy
Expires: January 11, 2014                SPARTA, Inc., a Parsons Company
                                                           July 10, 2013


                 BGPSec Considerations for AS Migration
                    draft-ietf-sidr-as-migration-00

Abstract

   This draft discusses considerations and methods for supporting and
   securing a common method for AS-Migration within the BGPSec protocol.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on January 11, 2014.

Copyright Notice

   Copyright (c) 2013 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
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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.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
     1.2.  Documentation note  . . . . . . . . . . . . . . . . . . .   3
   2.  General Scenario  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  RPKI Considerations . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Origin Validation . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Path Validation . . . . . . . . . . . . . . . . . . . . .   5
       3.2.1.  Outbound announcements (PE-->CE)  . . . . . . . . . .   5
       3.2.2.  Inbound announcements (CE-->PE) . . . . . . . . . . .   5
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Outbound (PE->CE) . . . . . . . . . . . . . . . . . . . .   8
     5.2.  Inbound (CE->PE)  . . . . . . . . . . . . . . . . . . . .   8
     5.3.  Other considerations  . . . . . . . . . . . . . . . . . .   8
     5.4.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   There is a method of managing an ASN migration using some BGP knobs
   that, while commonly-used, are not formally part of the BGP4
   [RFC4271] protocol specification and may be vendor-specific in exact
   implementation.  In order to ensure that this behavior is understood
   and considered for future modifications to the BGP4 protocol
   specification, especially as it concerns the handling of AS_PATH
   attributes, the behavior and process has been described in draft-ga-
   idr-as-migration [I-D.ga-idr-as-migration].  Accordingly, it is
   necessary to discuss this de facto standard to ensure that the
   process and features are properly supported in BGPSec
   [I-D.ietf-sidr-bgpsec-protocol], because BGPSec is explicitly
   designed to protect against changes in the BGP AS_PATH, whether by
   choice, by misconfiguration, or by malicious intent.  It is critical
   that the BGPSec protocol framework is able to support this
   operationally necessary tool without creating an unacceptable
   security risk or exploit in the process.

1.1.  Requirements Language






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   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].

1.2.  Documentation note

   This draft uses Autonomous System Numbers (ASNs) from the range
   reserved for documentation as described in RFC 5398 [RFC5398].  In
   the examples used here, they are intended to represent Globally
   Unique ASNs, not private ASNs as documented in RFC 1930 [RFC1930]
   section 10.

2.  General Scenario

   This draft assumes that the reader has read and understood the ASN
   migration method discussed in draft-ga-idr-as-migration
   [I-D.ga-idr-as-migration] including its examples, as they will be
   heavily referenced here.  The use case being discussed in the
   referenced draft is as follows: For whatever the reason, a provider
   is in the process of merging two or more ASNs, where eventually one
   subsumes the other(s).  Confederations RFC 5065 [RFC5065] are *not*
   being implemented between the ASNs, but vendor-specific configuration
   knobs are being used to allow the migrating PE to masquerade as the
   old ASN for the PE-CE eBGP session, or to manipulate the AS_PATH, or
   both.  While BGPSec [I-D.ietf-sidr-bgpsec-protocol] does have a case
   to handle standard confederation implementations, it is not
   applicable in this exact case.  The reason that this migration drives
   a slightly different solution in BGPSec than a standard confederation
   is that unlike in a confederation, eBGP peers may not be peering with
   the "correct" external ASN, and the forward-signed updates are for a
   public ASN, rather than a private one, so there is no expectation
   that the BGP speaker should strip the affected signatures before
   propagating the route to its eBGP neighbors.

   In the following examples, AS64510 is being subsumed by AS64500, and
   both ASNs represent a Service Provider (SP) network (see Figure 1 in
   draft-ga-idr-as-migration [I-D.ga-idr-as-migration]).  AS64496 and
   64499 represent end customer networks.  References to PE, CE, and P
   routers mirror the diagrams and references in the above cited draft.

3.  RPKI Considerations

   Since the methods and implementation discussed in draft-ga-idr-as-
   migration [I-D.ga-idr-as-migration] are not technically a part of the
   BGP4 protocol implementation, but rather a vendor-specific feature,
   BGPSec is not technically required to ensure that it continues
   functioning as it does today.  However, this is widely used during
   network integrations resulting from mergers and acquisitions, as well



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   as network redesigns, and therefore it is not feasible to simply
   eliminate this capability on any BGPSec-enabled routers/ASNs.  What
   follows is a discussion of the potential issues to be considered
   regarding how ASN-migration and BGPSec
   [I-D.ietf-sidr-bgpsec-protocol] validation might interact.

   One of the primary considerations for this draft and migration is
   that companies rarely stop after one merger/acquisition/divestiture,
   and end up accumulating several legacy ASNs over time.  Since they
   are using methods to migrate that do not require coordination with
   customers, they do not have a great deal of control over the length
   of the transition period as they might with something completely
   under their administrative control (e.g. a key roll).  This leaves
   many SPs with multiple legacy ASNs which don't go away very quickly,
   if at all.  As solutions were being proposed for RPKI implementations
   to solve this transition case, operational complexity and hardware
   scaling considerations associated with maintaining multiple legacy
   ASN keys on routers throughout the combined network have been
   carefully considered.  While SPs SHOULD NOT remain in this transition
   phase indefinitely because of the operational complexity and scaling
   considerations associated with maintaining multiple legacy ASN keys
   on routers throughout the combined network, this is of limited
   utility as a solution, and so every effort has been made to keep the
   additional complexity during the transition period to a minimum, on
   the assumption that it will likely be protracted.

3.1.  Origin Validation

   Origin Validation does not need a unique solution to enable
   migration, as the existing protocol and procedure allows for a
   solution.  In the scenario discussed, AS64510 is being replaced by
   AS64500.  If there are any existing routes originated by AS64510 on
   the router being moved into the new ASN, this simply requires
   generating new ROAs for the routes with the new ASN and treating them
   as new routes to be added to AS64500.  However, we also need to
   consider the situation where one or more other PEs are still in
   AS64510, and are originating one or more routes that may be distinct
   from any that the router under migration is originating.  PE1 (which
   is now a part of AS64500 and instructed to use replace-as to remove
   AS64510 from the path) needs to be able to properly handle routes
   originated from AS64510.  If the route now shows up as originating
   from AS64500, any downstream peers' validation check will fail unless
   a ROA is *also* available for AS64500 as the origin ASN, meaning that
   there will be overlapping ROAs until all routers originating prefixes
   from AS64510 are migrated to AS64500.  Overlapping ROAs are
   permissible perRFC 6480 [RFC6480] section 3.2, and so managing origin
   validation during a migration like this is merely applying the
   defined case where a set of prefixes are originated from more than



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   one ASN.  Therefore, for each ROA that authorizes AS64510 to
   originate a prefix, a new ROA SHOULD also be created that authorizes
   AS64500 to originate the same prefix.

3.2.  Path Validation

   BGPSec Path Validation requires that each router in the AS Path
   cryptographically sign its update to assert that "Every AS on the
   path of ASes through which the update message passes has explicitly
   authorized the advertisement of the route to the subsequent AS in the
   path." (see point #2 in intro of [I-D.ietf-sidr-bgpsec-protocol])
   Since the referenced AS migration technique is explicitly modifying
   the AS_PATH between two eBGP peers who are not coordinating with one
   another (are not in the same administrative domain), no level of
   trust can be assumed, and therefore it may be difficult to identify
   legitimate manipulation of the AS_PATH for migration activities when
   compared to manipulation due to misconfiguration or malicious intent.

3.2.1.  Outbound announcements (PE-->CE)

   When PE1 is moved from AS64510 to AS64500, it will be provisioned
   with the appropriate keys for AS64500 to allow it to forward-sign
   routes using AS64500.  However, there is currently no guidance in the
   BGPSec protocol specification on whether or not the forward-signed
   ASN value MUST match the configured "remote-as" to validate properly.
   That is, if CE1's BGP session is configured as "remote-as 64510", the
   presence of "local-as 64510" on PE1 will ensure that there is no ASN
   mismatch on the BGP session itself, but if CE1 receives updates from
   its remote neighbor (PE1) forward-signed from AS64500, there is no
   guidance as to whether the BGPSec validator on CE1 still consider
   those valid by default.  RFC4271 [RFC4271] section 6.3 mentions this
   match between the ASN of the peer and the AS_PATH data, but it is
   listed as an optional validation, rather than a requirement.
   Assuming that this mismatch will be allowed by vendor implementations
   and using it as a means to solve this migration case is likely to be
   problematic.

3.2.2.  Inbound announcements (CE-->PE)

   Inbound is more complicated, because the CE doesn't know that PE1 has
   changed ASNs, so it is forward-signing all of its routes with
   AS64510, not AS64500.  The BGPSec speaker cannot manipulate previous
   signatures, and therefore cannot manipulate the previous AS Path
   without causing a mismatch that will invalidate the route.  If the
   updates are simply left intact, the ISP would still need to publish
   and maintain valid and active public-keys for AS 64510 if it is to
   appear in the BGPSec_Path_Signature in order that receivers can
   validate the BGPSEC_Path_Signature arrived intact/whole.  However, if



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   the updates are left intact, this will cause the AS Path length to be
   increased, which is undesirable as discussed in draft-ga-idr-as-
   migration [I-D.ga-idr-as-migration].

4.  Requirements

   These requirements are written under the assumption that the
   currently vendor-specific implementations will be standardized via
   draft-ga-idr-as-migration [I-D.ga-idr-as-migration], as it makes
   little sense to build support into a standard for something that is
   not actually a standard itself.  However, should IETF choose not to
   standardize the discussed method of AS migration, it is possible that
   this draft could be considered implementation guidance for those
   vendors that have support for this method of AS migration and wish to
   support it in their BGPSec implementation.  In order to be
   deployable, any solution to the described problem needs to consider
   the following requirements, listed in no particular order:

   o  BGPSec MUST support AS Migration for both inbound and outbound
      route announcements (see Section 3.2.1 and 3.2.2).  It SHOULD do
      this without reducing BGPSec's protections for route path

   o  MUST NOT require any reconfiguration on the remote eBGP neighbor
      (CE)

   o  SHOULD confine configuration changes to the migrating PEs e.g.
      can't require global configuration changes to support migration

   o  MUST NOT lengthen AS Path during migration

   o  MUST operate within existing trust boundaries e.g. can't expect
      remote side to accept pCount=0 (see Section 3 of
      [I-D.ietf-sidr-bgpsec-protocol]) from untrusted/non-confed
      neighbor

5.  Solution

   As noted in [I-D.ietf-sidr-bgpsec-protocol], section 4.2, BGPSec
   already has a solution for hiding ASNs where increasing the AS Path
   length is undesirable.  So one might think that a simple solution
   would be to retain the keys for AS64510 on PE1, and forward-sign
   towards CE1 with AS64510 and pCount=0.  However, this would mean
   passing a pCount=0 between two ASNs that are in different
   administrative and trust domains such that it could represent a
   significant attack vector to manipulate BGPSec-signed paths.  The
   expectation for legitimate instances of pCount=0 (to make a route-
   server that is not part of the transit path invisible) is that there
   is some sort of existing trust relationship between the operators of



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   the route-server and the downstream peers such that the peers could
   be explicitly configured by policy to accept pCount=0 announcements
   only on the sessions where they are expected.  For the same reason
   that things like local-as are used for ASN migration without end
   customer coordination, it is unrealistic to assume any sort of
   coordination between the SP and the administrators of CE1 to ensure
   that they will by policy accept pCount=0 signatures during the
   transition period, and therefore this is not a workable solution.

   A better solution presents itself when considering how to handle
   routes coming from the CE toward the PE, where the routes are
   forward-signed to AS64510, but will eventually need to show AS64500
   in the outbound route announcement.  Because both AS64500 and AS64510
   are in the same administrative domain, a signature from AS64510
   forward-signed to AS64500 with pCount=0 would be acceptable as it
   would be within the appropriate trust boundary so that each BGP
   speaker could be explicitly configured to accept pCount=0 where
   appropriate between the two ASNs.  At the very simplest, this could
   potentially be used at the eBGP boundary between the two ASNs during
   migration.  Since the AS_PATH manipulation described above usually
   happens at the PE router on a per-session basis, and does not happen
   network-wide simultaneously, it is not generally appropriate to apply
   this AS hiding technique across all routes exchanged between the two
   ASNs, as it may result in routing loops and other undesirable
   behavior.  Therefore the most appropriate place to implement this is
   on the local PE that still has eBGP sessions associated with AS64510
   (using the transition knobs detailed in the companion draft).  Since
   that PE has been moved to AS64500, it is not possible for it to
   forward-sign AS64510 with pCount=0 without some minor changes to the
   BGPSec implementation to address this use case.

   AS migration is using AS_PATH and remote-AS manipulation to act as if
   a PE under migration exists simultaneously in both ASNs even though
   it is only configured with one global ASN.  This draft proposes
   applying a similar technique to the BGPSec signatures generated for
   routing updates processed through this migration machinery.  Each
   routing update that is received from or destined to an eBGP neighbor
   that is still using the old ASN (64510) will be signed twice, once
   with the ASN to be hidden and once with the ASN that will remain
   visible.  In essence, we are treating the update as if the PE had an
   internal BGP hop and the update was passed across an eBGP session
   between AS64500 and AS64510, configured to use and accept pCount=0,
   while eliminating the processing and storage overhead of creating an
   actual eBGP session between the two ASNs within the PE router.  This
   will result in a properly secured AS Path in the affected route
   updates, because the PE router will be provisioned with valid keys
   for both AS64500 and AS64510.  An important distinction here is that
   while AS migration under standard BGP4 is manipulating the AS_PATH



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   attribute, BGPSec uses an attribute called the Secure_Path (see
   Section 3 of [I-D.ietf-sidr-bgpsec-protocol]), and BGPSec capable
   neighbors do not exchange AS_PATH information in their route
   announcements.  However, a BGPSec neighbor peering with a non-BGPSec-
   capable neighbor will use the information found in Secure_Path to
   reconstruct a standard AS_PATH for updates sent to that neighbor.
   Unlike in Secure_Path where the ASN to be hidden is still present,
   but ignored when considering AS Path (due to pCount=0), when
   reconstructing an AS_PATH for a non-BGPSec neighbor, the pCount=0
   ASNs will not appear in the AS_PATH at all (see section 4.4 of the
   above-referenced draft).  This draft is not changing existing AS_PATH
   reconstruction behavior, merely highlighting it for clarity.

   The procedure to support AS Migration in BGPSec is slightly different
   depending on whether the PE under migration is receiving the routes
   from one of its eBGP peers ("inbound" as in section 3.2.2) or
   destined toward the eBGP peers ("outbound" as in section 3.2.1).

5.1.  Outbound (PE->CE)

   When a PE router receives an update destined for an eBGP neighbor
   that is locally configured with AS-migration knobs as discussed in
   draft-ga-idr-as-migration [I-D.ga-idr-as-migration], it MUST generate
   a valid BGPSec signature as defined in
   [I-D.ietf-sidr-bgpsec-protocol] for _both_ configured ASNs.  It MUST
   generate a signature from the new (global) ASN forward signing to the
   old (local) ASN with pCount=0, and then it MUST generate a forward
   signature from the old (local) ASN to the target eBGP ASN with
   pCount=1 as normal.

5.2.  Inbound (CE->PE)

   When a PE router receives an update from an eBGP neighbor that is
   locally configured with AS-migration knobs (i.e. the opposite
   direction of the previous route flow), it MUST generate a signature
   from the old (local) ASN forward signing to the new (global) ASN with
   pCount=0.  It is not necessary to generate the second signature from
   the new (global) ASN because the ASBR will generate that when it
   forward signs towards its eBGP peers as defined in normal BGPSec
   operation.  This is a deviation from standard BGPSec behavior in that
   typically a signature is not added when a routing update is sent
   across an iBGP session, and the next signature is added by the ASBR
   when it forward-signs toward its eBGP peer as the routing update
   exits the ASN.

5.3.  Other considerations





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   In this case, the PE is adding BGPSec attributes to routes received
   from or destined to an iBGP neighbor, and using pCount=0 to mask
   them.  While this is not prohibited by the current BGPSec
   specification, routers that receive updates from iBGP neighbors MUST
   NOT reject updates with new (valid) BGPSec attributes, including the
   presence of pCount=0 on a previous signature, or they will interfere
   with this implementation.  In similar fashion, any route-reflectors
   in the path of these updates MUST reflect them transparently to their
   clients.

   In order to secure this set of signatures, the PE router MUST be
   provisioned with valid keys for _both_ configured ASNs (old and new),
   and the key for the old ASN MUST be kept valid until all eBGP
   sessions are migrated to the new ASN.  Downstream neighbors will see
   this as a valid BGPSec path, as they will simply trust that their
   upstream neighbor accepted pCount=0 because it was explicitly
   configured to do so based on a trust relationship and business
   relationship between the upstream and its neighbor (the old and new
   ASNs).

5.4.  Example

   The following example will illustrate the method being used above.
   As with previous examples, PE1 is the router being migrated, AS64510
   is the old AS, which is being subsumed by AS64500, the "keep" AS.
   64505 is another external peer, used to demonstrate what the
   announcements will look like to a third party peer that is not part
   of the migration.  Some additional notation is used to delineate the
   details of each signature as follows:

   The origin BGPSEC signature attribute takes the form: sig(<Target
   ASN>, Origin ASN, pCount, NLRI Prefix) key

   Intermediate BGPSEC signature attributes take the form: sig(<Target
   ASN>, Signer ASN, pCount, <most recent sig field>) key

   Equivalent AS_PATH refers to what the AS_PATH would look like if it
   was reconstructed to be sent to a non-BGPSec peer, while Secure_Path
   shows the AS Path as represented between BGPSec peers.

   Note: The representation of signature attribute generation is being
   simplified here somewhat for the sake of brevity; the actual details
   of the signing process are as described Sections 4.1 and 4.2 in
   [I-D.ietf-sidr-bgpsec-protocol].  For example, what is covered by the
   signature also includes Flags, Algorithm Suite ID, NLRI length, etc.
   Also, the key is not carried in the update, instead the SKI is
   carried.




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   Before Merger

                                       64505
                                       |
             ISP B                     ISP A
   CE-1 <--- PE-1 <------------------- PE-2 <--- CE-2
   64496     Old_ASN: 64510   Old_ASN: 64500     64499

   CE-2 to PE-2:  sig(<64500>, O=64499, pCount=1, N)K_64499-CE2  [sig1]
                  Equivalent AS_PATH=(64499)
                  Secure_Path=(64499)
                  length=sum(pCount)=1

   PE-2 to 64505: sig(<64505>, 64500, pCount=1, <sig1>)K_64500-PE2  [sig2]
                  sig(<64500>, 64499, pCount=1, N)K_64499-CE2  [sig1]
                  Equivalent AS_PATH=(64500,64499)
                  Secure_Path=(64500,64499)
                  length=sum(pCount)=2

   PE-2 to PE-1:  sig(<64510>, 64500, pCount=1, <sig1>)K_64500-PE2  [sig3]
                  sig(<64500>, 64499, pCount=1, N)K_64499-CE2  [sig1]
                  Equivalent AS_PATH=(64500,64499)
                  Secure_Path=(64500,64499)
                  length=sum(pCount)=2

   PE-1 to CE-1:  sig(<64496>, 64510, pCount=1, <sig3>)K_64510-PE1  [sig4]
                  sig(<64510>, 64500, pCount=1, <sig1>)K_64500-PE2  [sig3]
                  sig(<64500>, 64499, pCount=1, N)K_64499-CE2  [sig1]
                  Equivalent AS_PATH= (64510,64500,64499)
                  Secure_Path=(64510,64500,64499)
                  length=sum(pCount)=3


   Migrating, route flow outbound PE-1 to CE-1

















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                                       64505
                                       |
             ISP A'                    ISP A'
   CE-1 <--- PE-1 <------------------- PE-2 <--- CE-2
   64496     Old_ASN: 64510   Old_ASN: 64500     64499
             New_ASN: 64500   New_ASN: 64500


   CE-2 to PE-2:  sig(<64500>, 64499, pCount=1, N)K_64499-CE2  [sig11]
                  Equivalent AS_PATH=(64499)
                  Secure_Path=(64499)
                  length=sum(pCount)=1

   PE-2 to 64505: sig(<64505>, 64500, pCount=1, <sig11>)K_64500-PE2  [sig12]
                  sig(<64500>, 64499, pCount=1, N)K_64499-CE2  [sig11]
                  Equivalent AS_PATH=(64500,64499)
                  Secure_Path=(64500,64499)
                  length=sum(pCount)=2

   PE-2 to PE-1:  sig(<64500>, 64499, pCount=1, N)K_64499-CE2  [sig11]
                  Equivalent AS_PATH=(64499)
                  Secure_Path=(64499)
                  length=sum(pCount)=1
   #PE-2 sends to PE-1 (in iBGP) the exact same update as received from AS64499.


   PE-1 to CE-1:  sig(<64496>, 64510, pCount=1, <sig13>)K_64510-PE1  [sig14]
                  sig(<64510>, 64500, pCount=0, <sig11>)K_64500-PE2  [sig13]
                  sig(<64500>, 64499, pCount=1, N)K_64499-CE2  [sig11]
                  Equivalent AS_PATH=(64510,64499)
                  Secure_Path=(64510, 64500(pCount=0),64499)
                  length=sum(pCount)=2 (length is NOT 3)
   #PE1 adds [sig13] acting as AS64500
   #PE1 accepts [sig13] with pCount=0 acting as AS64510,
   #as it would if it received sig13 from an eBGP peer


   Migrating, route flow inbound CE-1 to PE-1













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                                       64505
                                       |
             ISP A'                    ISP A'
   CE-1 ---> PE-1 -------------------> PE-2 ---> CE-2
   64496     Old_ASN: 64510   Old_ASN: 64500     64499
             New_ASN: 64500   New_ASN: 64500


   CE-1 to PE-1:  sig(<64510>, 64496, pCount=1, N)K_64496-CE1   [sig21]
                  Equivalent AS_PATH=(64496)
                  Secure_Path=(64496)
                  length=sum(pCount)=1

   PE-1 to PE-2:  sig(<64500>, 64510, pCount=0, <sig21>)K_64510-PE1  [sig22]
                  sig(<64510>, 64496, pCount=1, N)K_64496-CE1   [sig21]
                  Equivalent AS_PATH=(64496)
                  Secure_Path=(64510 (pCount=0),64496)
                  length=sum(pCount)=1 (length is NOT 2)
   #PE1 adds [sig22] acting as AS64510
   #PE1 accepts [sig22] with pCount=0 acting as AS64500,
   #as it would if it received sig22 from an eBGP peer

   PE-2 to 64505: sig(<64505>, 64500, pCount=1, <sig22>)K_64500-PE2  [sig23]
                  sig(<64500>, 64510, pCount=0, <sig21>)K_64510-PE1  [sig22]
                  sig(<64510>, 64496, pCount=1, N)K_64496-CE1   [sig21]
                  Equivalent AS_PATH=(64500,64496)
                  Secure_Path=(64500,64510 (pCount=0), 64496)
                  length=sum(pCount)=2 (length is NOT 3)

   PE-2 to CE-2:  sig(<64499>, 64500, pCount=1, <sig22>)K_64500-PE2  [sig24]
                  sig(<64500>, 64510, pCount=0, <sig21>)K_64510-PE1  [sig22]
                  sig(<64510>, 64496, pCount=1, N)K_64496-CE1   [sig21]
                  Equivalent AS_PATH=(64500,64496)
                  Secure_Path=(64500, 64510 (pCount=0), 64496)
                  length=sum(pCount)=2 (length is NOT 3)


6.  Acknowledgements

   Thanks to Kotikalapudi Sriram, Shane Amante, Warren Kumari, and Terry
   Manderson for their review comments.

   Additionally, the solution presented in this draft is an amalgam of
   several SIDR interim meeting discussions plus a discussion at IETF85,
   collected and articulated thanks to Sandy Murphy.

7.  IANA Considerations




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   This memo includes no request to IANA.

8.  Security Considerations

   This draft discusses a process by which one ASN is migrated into and
   subsumed by another.  Because this process involves manipulating the
   AS_Path in a BGP route to make it deviate from the actual path that
   it took through the network, this migration process is attempting to
   do exactly what BGPSec is working to prevent.  BGPSec MUST be able to
   manage this legitimate use of AS_Path manipulation without generating
   a vulnerability in the RPKI route security infrastructure.

   The solution discussed above is considered to be reasonably secure
   from exploitation by a malicious actor because it requires both
   signatures to be secured as if they were forward-signed between two
   eBGP neighbors.  This requires any router using this solution to be
   provisioned with valid keys for both the migrated and subsumed ASN so
   that it can generate valid signatures for each of the two ASNs it is
   adding to the path.  If the AS's keys are compromised, or zero-length
   keys are permitted, this does potentially enable an AS_PATH
   shortening attack, but this is not fundamentally altering the
   existing security risks for BGPSec.

9.  References

9.1.  Normative References

   [I-D.ga-idr-as-migration]
              George, W. and S. Amante, "Autonomous System (AS)
              Migration Features and Their Effects on the BGP AS_PATH
              Attribute", draft-ga-idr-as-migration-01 (work in
              progress), February 2013.

   [I-D.ietf-sidr-bgpsec-protocol]
              Lepinski, M., "BGPSEC Protocol Specification", draft-ietf-
              sidr-bgpsec-protocol-07 (work in progress), February 2013.

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

   [RFC5398]  Huston, G., "Autonomous System (AS) Number Reservation for
              Documentation Use", RFC 5398, December 2008.









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9.2.  Informative References

   [RFC1930]  Hawkinson, J. and T. Bates, "Guidelines for creation,
              selection, and registration of an Autonomous System (AS)",
              BCP 6, RFC 1930, March 1996.

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

   [RFC5065]  Traina, P., McPherson, D., and J. Scudder, "Autonomous
              System Confederations for BGP", RFC 5065, August 2007.

   [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", RFC 6480, February 2012.

Authors' Addresses

   Wesley George
   Time Warner Cable
   13820 Sunrise Valley Drive
   Herndon, VA  20171
   US

   Phone: +1 703-561-2540
   Email: wesley.george@twcable.com


   Sandy Murphy
   SPARTA, Inc., a Parsons Company
   7110 Samuel Morse Drive
   Columbia, MD  21046
   US

   Phone: +1 443-430-8000
   Email: sandy@tislabs.com
















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