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Versions: 00 01 draft-ietf-idr-route-leak-detection-mitigation

IDR and SIDR                                                   K. Sriram
Internet-Draft                                             D. Montgomery
Intended status: Standards Track                                 US NIST
Expires: January 6, 2016                                      B. Dickson
                                                           Twitter, Inc.
                                                            July 5, 2015


        Methods for Detection and Mitigation of BGP Route Leaks
          draft-sriram-idr-route-leak-detection-mitigation-01

Abstract

   In [I-D.ietf-grow-route-leak-problem-definition], the authors have
   provided a definition of the route leak problem, and also enumerated
   several types of route leaks.  In this document, we first examine
   which of those route-leak types are detected and mitigated by the
   existing origin validation (OV) [RFC 6811] and BGPSEC path validation
   [I-D.ietf-sidr-bgpsec-protocol].  Where the current OV and BGPSEC
   protocols don't offer a solution, this document suggests an
   enhancement that would extend the route-leak detection and mitigation
   capability of BGPSEC.  The solution can be implemented in BGP without
   necessarily tying it to BGPSEC.  Incorporating the solution in BGPSEC
   is one way of implementing it in a secure way.  We do not claim to
   have provided a solution for all possible types of route leaks, but
   the solution covers several, especially considering some significant
   route-leak attacks or occurrences that have been observed in recent
   years.  The document also includes a stopgap method for detection and
   mitigation of route leaks for the phase when BGPSEC (path validation)
   is not yet deployed but only origin validation is deployed.

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 January 6, 2016.




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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Related Prior Work  . . . . . . . . . . . . . . . . . . . . .   3
   3.  Mechanisms for Detection and Mitigation of Route Leaks  . . .   4
     3.1.  Route Leak Protection (RLP) Field Encoding by Sending
           Router  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Recommended Actions at a Receiving Router for Detection
           of Route Leaks  . . . . . . . . . . . . . . . . . . . . .   8
       3.2.1.  Recommended Actions at a Receiving Router when the
               Sender is a Customer  . . . . . . . . . . . . . . . .   8
       3.2.2.  Recommended Actions at a Receiving Router when the
               Sender is a Peer  . . . . . . . . . . . . . . . . . .   9
     3.3.  Possible Actions at a Receiving Router for Mitigation . .  10
   4.  Stopgap Solution when Only Origin Validation is Deployed  . .  10
   5.  Design Rationale and Discussion . . . . . . . . . . . . . . .  11
     5.1.  Is route-leak solution without BGPSEC a serious attack
           vector? . . . . . . . . . . . . . . . . . . . . . . . . .  11
     5.2.  Comparison with other methods, routing security BCP . . .  12
   6.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   In [I-D.ietf-grow-route-leak-problem-definition], the authors have
   provided a definition of the route leak problem, and also enumerated
   several types of route leaks.  In this document, we first examine



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   which of those route-leak types are detected and mitigated by the
   existing Origin Validation (OV) [RFC6811] and BGPSEC path validation
   [I-D.ietf-sidr-bgpsec-protocol].  For the rest of this document, we
   use the term BGPSEC as synonymous with path validation.  The BGPSEC
   protocol provides cryptographic protection for some aspects of BGP
   update messages.  OV and BGPSEC together offer mechanisms to protect
   against mis-originations and hijacks of IP prefixes as well as man-
   in-the-middle (MITM) AS path modifications.  Route leaks (see
   [I-D.ietf-grow-route-leak-problem-definition] and references cited at
   the back) are another type of vulnerability in the global BGP routing
   system against which OV and BGPSEC so far offer only partial
   protection.

   For the types of route leaks enumerated in
   [I-D.ietf-grow-route-leak-problem-definition], where the current OV
   and BGPSEC protocols don't offer a solution, this document suggests
   an enhancement that would extend the detection and mitigation
   capability of BGPSEC.  The solution can be implemented in BGP without
   necessarily tying it to BGPSEC.  Incorporating the solution in BGPSEC
   is one way of implementing it in a secure way.  We do not claim to
   provide a solution for all possible types of route leaks, but the
   solution covers several relevant types, especially considering some
   significant route-leak occurrences that have been observed frequently
   in recent years.  The document also includes (in Section 4) a stopgap
   method for detection and mitigation of route leaks for the phase when
   BGPSEC (path validation) is not yet deployed but only origin
   validation is deployed.

2.  Related Prior Work

   The basic idea and mechanism embodied in the proposed solution is
   based on setting an attribute in BGP route announcement to manage the
   transmission/receipt of the announcement based on the type of
   neighbor (e.g. customer, provider, etc.).  Documented prior work
   related to said basic idea and mechanism dates back to at least the
   1980's.  Some examples of prior work are: (1) Information flow rules
   described in [proceedings-sixth-ietf] (see pp. 195-196); (2) Link
   Type described in [RFC1105-obsolete] (see pp. 4-5); (3) Hierarchical
   Recording described in [draft-kunzinger-idrp-ISO10747-01] (see
   Section 6.3.1.12).  The problem of route leaks and possible solution
   mechanisms based on encoding peering-link type information (e.g. p2c,
   c2p, p2p, etc.) in BGPSEC updates and protecting the same under
   BGPSEC path signatures have been discussed in IETF SIDR WG at least
   since 2011.  Dickson developed the initial Internet draft of these
   mechanisms in a BGPSEC context; see
   [draft-dickson-sidr-route-leak-solns].  The draft expired in 2012.
   [draft-dickson-sidr-route-leak-solns] defined neighbor relationships
   on a per link basis, but in the current draft the relationship in



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   encoded per prefix, as prefixes with different business models are
   often sent over the same link.  Also
   [draft-dickson-sidr-route-leak-solns] proposed a second signature
   block for the link type encoding, separate from the path signature
   block in BGPSEC.  By contrast, in the current draft when BGPSEC-based
   solution is considered, cryptographic protection is provided for
   Route Leak Protection (RLP) encoding using the same signature block
   as that for path signatures (see Section 3.1).

3.  Mechanisms for Detection and Mitigation of Route Leaks

   Referring to the enumeration of route leaks discussed in
   [I-D.ietf-grow-route-leak-problem-definition], Table 1 summarizes the
   route-leak detection capability offered by OV and BGPSEC for
   different types of route leaks.  (Note: Prefix filtering is not
   considered here in this table.  Please see Section 4.)

   A detailed explanation of the contents of Table 1 is as follows.  It
   is readily observed that route leaks of Types 1, 5, 6, and 7 are not
   detected by OV or even by BGPSEC.  Type 2 route leak involves
   changing a prefix to a subprefix (i.e. more specific); such a
   modified update will fail BGPSEC checks.  Clearly, Type 3 route leak
   involves mis-origination or hijacking, and hence can be detected by
   OV.  In the case of Type 3 route leak, there would be no existing
   ROAs to validate a re-originated prefix or subprefix, but instead a
   covering ROA would normally exist with the legitimate AS, and hence
   the update will be considered Invalid by OV.
























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   +---------------------------------+---------------------------------+
   | Type of Route Leak              | Detection Coverage and Comments |
   +---------------------------------+---------------------------------+
   | Type 1: U-Turn with Full Prefix | Neither OV nor BGPSEC (in its   |
   |                                 | current form) detects Type 1.   |
   | ------------------------------- | ------------------------------- |
   | Type 2: U-Turn with More        | In OV, the ROA maxLength may    |
   | Specific Prefix                 | offer detection of Type 2 in    |
   |                                 | some cases; BGPSEC (in its      |
   |                                 | current form) always detects    |
   |                                 | Type 2.                         |
   | ------------------------------- | ------------------------------- |
   | Type 3: Prefix Mis-Origination  | OV by itself detects Type 3;    |
   | with Data Path to Legitimate    | BGPSEC does not detect Type 3.  |
   | Origin                          |                                 |
   | ------------------------------- | ------------------------------- |
   | Type 4: Leak of Internal        | For internal prefixes never     |
   | Prefixes and Accidental         | meant to be seen (i.e. routed)  |
   | Deaggregation                   | on the Internet, OV helps       |
   |                                 | detect their leak; they might   |
   |                                 | either have no covering ROA or  |
   |                                 | have an AS0-ROA to always       |
   |                                 | filter them. In the case of     |
   |                                 | accidental deaggregation, OV    |
   |                                 | may offer some detection due to |
   |                                 | ROA maxLength. BGPSEC does not  |
   |                                 | catch Type 4.                   |
   | ------------------------------- | ------------------------------- |
   | Type 5: Lateral ISP-ISP-ISP     | Neither OV nor BGPSEC (in its   |
   | Leak                            | current form) detects Type 5.   |
   | ------------------------------- | ------------------------------- |
   | Type 6: Leak of Provider        | Neither OV nor BGPSEC (in its   |
   | Prefixes to Peer                | current form) detects Type 6.   |
   | ------------------------------- | ------------------------------- |
   | Type 7: Leak of Peer Prefixes   | Neither OV nor BGPSEC (in its   |
   | to Provider                     | current form) detects Type 7.   |
   +---------------------------------+---------------------------------+

     Table 1: Examination of Route-Leak Detection Capability of Origin
               Validation and Current BGPSEC Path Validation

   In the case of Type 4 leaks involving internal prefixes that are not
   meant to be routed in the Internet, they are likely to be detected by
   OV.  That is because such prefixes might either have no covering ROA
   or have an AS0-ROA to always filter them.  In the case of Type 4
   leaks that are due to accidental deaggregation, they may be detected
   due to violation of ROA maxLength.  BGPSEC does not catch Type 4.
   However, route leaks of Type 4 are least problematic due to the



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   following reasons.  In the case of accidental deaggregation, the
   offending AS is itself the legitimate destination of the leaked more-
   specific prefixes.  Hence, in most cases of this type, the data
   traffic is neither misrouted not denied service.  Also, leaked
   announcements of Type 4 are short-lived and typically withdrawn
   quickly following the announcements.  Further, the MaxPrefix limit
   may kick-in in some receiving routers and that helps limit the
   propagation of sometimes large number of leaked routes of Type 4.

   Realistically, BGPSEC may take a much longer time being deployed than
   OV.  Hence solution proposals for route leaks should consider both
   scenarios: (A) OV only (without BGPSEC) and (B) OV plus BGPSEC.
   Assuming an initial scenario A, and based on the above discussion and
   Table 1, it is evident that in our proposed solution method, we need
   to focus primarily on route leaks of Types 1, 2, 5, 6, and 7.  In
   Section 3.1 and Section 3.2, we describe a simple addition to BGP
   that facilitates detection of route leaks of Types 1, 2, 5, 6, and 7.
   The simple addition involves a Route Leak Protection (RLP) field,
   which is carried in an optional transitive path attribute in BGP.
   When BGPSEC is deployed, the RLP field will be accommodated in the
   existing Flags field (see [I-D.ietf-sidr-bgpsec-protocol]) which is
   cryptographically protected under path signatures.

3.1.  Route Leak Protection (RLP) Field Encoding by Sending Router

   The key principle is that, in the event of a route leak, a receiving
   router in a provider AS (e.g. referring to Figure 1, ISP2 (AS2)
   router) should be able to detect from the prefix-update that its
   customer AS (e.g.  AS3 in Figure 1) SHOULD NOT have forwarded the
   update (towards the provider AS).  This means that at least one of
   the ASes in the AS path of the update has indicated that it sent the
   update to its customer or peer AS, but forbade any subsequent 'Up'
   forwarding (i.e. from a customer AS to its provider AS).  For this
   purpose, a Route Leak Protection (RLP) field to be set by a sending
   router is proposed to be used for each AS hop.
















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                                      /\              /\
                                       \ route-leak(P)/
                                        \ propagated /
                                         \          /
              +------------+    peer    +------------+
        ______| ISP1 (AS1) |----------->|  ISP2 (AS2)|---------->
       /       ------------+  prefix(P) +------------+ route-leak(P)
      | prefix |          \   update      /\        \  propagated
       \  (P)  /           \              /          \
        -------   prefix(P) \            /            \
                     update  \          /              \
                              \        /route-leak(P)  \/
                              \/      /
                           +---------------+
                           | customer(AS3) |
                           +---------------+


        Figure 1: Illustration of the basic notion of a route leak.

   For the purpose of route leak detection and mitigation proposed in
   this document, the RLP field value SHOULD be set to one of two values
   as follows:

   o  00: This is the default value (i.e. "nothing specified"),

   o  01: This is the 'Do not Propagate Up' indication; sender
      indicating that the prefix-update SHOULD NOT be forwarded 'Up'
      towards a provider AS.

   There are two different scenarios when a sending AS SHOULD set the
   '01' indication in a prefix-update: (1) when sending the prefix-
   update to a customer AS, and (2) to let a peer AS know not to forward
   the prefix-update 'Up' towards a provide AS.  In essence, in both
   scenarios, the intent of '01' indication is that any receiving AS
   along the subsequent AS path SHOULD NOT forward the prefix-update
   'Up' towards its (receiving AS's) provider AS.

   One may argue for additional RLP indications: for example, '10' to
   specify 'Propagate to Customers Only', and possibly '11' to signal
   'Do Not Propagate' (i.e.  NO_EXPORT).  But in the interest of keeping
   the methodology simple, the choice of two RLP field values as defined
   above (00 - default, and 01 - 'Do not Propagate Up') is all that is
   needed.  This two-state specification in the RLP field can be shown
   to work for detection and mitigation of route leaks of Types 1, 2, 5,
   6, and 7, which are the focus here (see Section 3.2 and Section 3.3).





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   The proposed RLP encoding SHOULD be carried in BGP-4 [RFC4271]
   updates in an optional transitive path attribute.  In BGPSEC enabled
   routers, the RLP encoding SHOULD be accommodated in the existing
   Flags field in BGPSEC updates.  The Flags field is part of the
   Secure_Path Segment in BPGSEC updates
   [I-D.ietf-sidr-bgpsec-protocol].  It is one octet long, and one Flags
   field is available for each AS hop, and currently only the first bit
   is used in BGPSEC.  So there are 7 bits that are currently unused in
   the Flags field.  Two (or more if needed) of these bits can be
   designated for the RLP field.  Since the BGPSEC protocol
   specification requires a sending AS to include the Flags field in the
   data that are signed over, the RLP field for each hop (assuming it
   would be part of the Flags field) will be protected under the sending
   AS's signature.

3.2.  Recommended Actions at a Receiving Router for Detection of Route
      Leaks

   The recommended receiver actions differ slightly depending on whether
   the update is received from a customer or a peer.  When detecting
   route leaks of Type 1, 2, and 7, the receiving router is dealing with
   a customer as the sender.  When detecting route leaks of Type 5 and
   6, the receiving router is dealing with a peer as the sender.

3.2.1.  Recommended Actions at a Receiving Router when the Sender is a
        Customer

   We provide here an example set of receiver actions that work to
   detect and mitigate route leaks of Types 1, 2, and 7.  This example
   algorithm serves as a proof of concept.  However, other receiver
   algorithms or procedures can be designed (based on the same sender
   specification as in Section 3.1) and may perform with greater
   efficacy, and are by no means excluded.

   A recommended receiver algorithm for detecting a route leak is as
   follows:

   A receiving router SHOULD mark an update as a Route-Leak if ALL of
   the following conditions hold true:

   1.  The update is received from a customer AS.

   2.  It is Valid in accordance with the Origin Validation (OV) and
       BGPSEC protocols.  (Note: BGPSEC validation is not applicable if
       update is not signed).






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   3.  The update has the RLP field set to '01' (i.e.  'Do not Propagate
       Up') indication for one or more hops (excluding the most recent)
       in the AS path.

   The reason for stating "excluding the most recent" in the above
   algorithm is as follows.  The provider AS already knows that the most
   recent hop in the update is from its customer AS to itself, and it
   does not need to rely on the RLP field value set by the customer for
   detection of route leaks.

   A receiving router expects the RLP field value for any hop in the AS
   path to be either 00 or 01.  However, if a different value (say, 10
   or 11) is found in the RLP field, then an error condition will get
   flagged, and any further action is TBD.

3.2.2.  Recommended Actions at a Receiving Router when the Sender is a
        Peer

   The sender and receiver actions described in Section 3.1 and
   Section 3.2.1 clearly help detect and mitigate route leaks of Types
   1, 2, and 7.  With a slightly modified interpretation of the RLP
   encoding on the receiver side, they can be extended to detect lateral
   ISP-ISP-ISP route leaks (Type 5) as well as leaks of provider
   prefixes to peer (Type 6).  (Note: RLP encoding procedure by sending
   routers remains the same as described in Section 3.1.)

   A recommended receiver algorithm for an ISP to detect a route leak of
   either Type 5 or Type 6 is as follows:

   A receiving BGPSEC router SHOULD mark an update as a Route-Leak if
   ALL of the following conditions hold true:

   1.  The update is received from a lateral ISP peer.

   2.  It is Valid in accordance with the Origin Validation (OV) and
       BGPSEC protocols.  (Note: BGPSEC validation is not applicable if
       update is not signed).

   3.  The update has the RLP field set to '01' indication for one or
       more hops (excluding the most recent) in the AS path.

   In the above algorithm, the receiving AS interprets the '01'
   indication slightly strongly (i.e. stronger than in Section 3.2.1) to
   mean "the update SHOULD NOT have been propagated laterally to a peer
   ISP like me either".  The rationale here is based on the fact that
   settlement-free ISP peers accept only customer prefix-routes from
   each other.  The receiving AS applies the logic that if a preceding
   AS (excluding the most recent) set '01' indication, it means that the



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   update was sent to a peer or a customer by the (preceding) AS, and
   the update should not be traversing a lateral peer-to-peer link
   subsequently.

3.3.  Possible Actions at a Receiving Router for Mitigation

   After applying the above detection algorithm, a receiving router may
   use any policy-based algorithm of its own choosing to mitigate any
   detected route leaks.  An example receiver algorithm for mitigating a
   route leak is as follows:

   o  If an update from a customer AS is marked as a Route-Leak, then
      the receiving router SHOULD prefer a Valid signed update from a
      peer or an upstream provider over the customer's update.

   A basic principle here is that the presence of '01' value in the RLP
   field corresponding to one or more AS hops in the AS path of an
   update coming from a customer AS informs a receiving router in a
   provider AS that a route leak is likely occurring.  The provider AS
   then overrides the "prefer customer route" policy, and instead
   prefers a route learned from a peer or another upstream provider over
   the customer's route.

4.  Stopgap Solution when Only Origin Validation is Deployed

   During a phase when BGPSEC path validation has not yet been deployed
   but only origin validation has been deployed, it would be good have a
   stopgap solution for route leaks.  The stopgap solution can be in the
   form of construction of a prefix filter list from ROAs.  A suggested
   procedure for constructing such a list comprises of the following
   steps:

   o  ISP makes a list of all the ASes (Cust_AS_List) that are in its
      customer cone (ISP's own AS is also included in the list).  (Some
      of the ASes in Cust_AS_List may be multi-homed to another ISP and
      that is OK.)

   o  ISP downloads from the RPKI repositories a complete list
      (Cust_ROA_List) of valid ROAs that contain any of the ASes in
      Cust_AS_List.

   o  ISP creates a list of all the prefixes (Cust_Prfx_List) that are
      contained in any of the ROAs in Cust_ROA_List.

   o  Cust_Prfx_List is the allowed list of prefixes that is permitted
      by the ISP's AS, and will be forwarded by the ISP to upstream
      ISPs, customers, and peers.




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   o  Any prefix not in Cust_Prfx_List but announced by any of the ISP's
      customers is marked as a potential route leak.  Then the ISP's
      router SHOULD prefer a Valid (i.e. valid according to origin
      validation) and 'not marked' update from a peer or an upstream
      provider over the customer's marked update for that prefix.

   Special considerations with regard to the above procedure may be
   needed for DDoS mitigation service providers.  They typically
   originate or announce a DDoS victim's prefix to their own ISP on a
   short notice during a DDoS emergency.  Some provisions would need to
   be made for such cases, and they can be determined with the help of
   inputs from DDoS mitigation service providers.

   For developing a list of all the ASes (Cust_AS_List) that are in the
   customer cone of an ISP, the AS path based Outbound Route Filter
   (ORF) technique [draft-ietf-idr-aspath-orf] can be helpful (see
   discussion in Section 5.2).

5.  Design Rationale and Discussion

   In this section, we will try to provide design justifications for the
   methodology specified in Section 3, and also answer some anticipated
   questions.

5.1.  Is route-leak solution without BGPSEC a serious attack vector?

   It has been asked if a route-leak solution without BGPSEC, i.e. when
   RLP bits are not protected, can turn into a serious new attack
   vector.  That answer seems to be: not really!  Even the NLRI and
   AS_PATH in BGP updates are attack vectors, and RPKI/OV/BGPSEC seek to
   fix that.  Consider the following.  Say, if 99% of route leaks are
   accidental and 1% are malicious, and if route-leak solution without
   BGPSEC eliminates the 99%, then perhaps it is worth it (step in the
   right direction).  When BGPSEC comes into deployment, the route leak
   protection (RLP) bits can be mapped into BGPSEC (using the Flags
   field) and then necessary security will be in place as well (within
   each BGPSEC island as and when they emerge).

   Further, let us consider the worst-case damage that can be caused by
   maliciously manipulating the RLP bits in an implementation without
   BGPSEC.  An AS that wants to intentionally leak a route would alter
   the RLP encodings for the preceding hops from '01' (i.e.  'Do not
   Propagate Up') to '00' (default) wherever applicable.  It is true
   that in that case a receiving router would not be able to detect the
   leak for the specific prefix-route by the RLP mechanism described
   here.  However, the receiving router may still detect and mitigate it
   in some cases by applying other means such as prefix filters
   [RFC7454] and AS path filters [draft-ietf-idr-aspath-orf].  If some



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   malicious leaks go undetected (for RLP without BGPSEC) that is
   possibly a small price to pay for the ability to detect the bulk of
   route leaks that are accidental.

5.2.  Comparison with other methods, routing security BCP

   It is reasonable to ask if techniques considered in BCPs such
   as[RFC7454] (BGP Operations and Security) and [NIST-800-54] may be
   adequate to address route leaks.  The prefix filtering
   recommendations in the BCPs may be complementary but not adequate.
   The difficulty is in ISPs' ability to construct prefix filters that
   represent their customer cones (CC) accurately, especially when there
   are many levels in the hierarchy within the CC.  In the RLP-encoding
   based solution described here, AS operators signal for each prefix-
   route propagated, if it SHOULD NOT be subsequently propagated to a
   provider/peer.

   AS path based Outbound Route Filter (ORF) described in
   [draft-ietf-idr-aspath-orf] is also an interesting complementary
   technique.  It can be used as an automated collaborative messaging
   system (implemented in BGP) for ISPs to try to develop a complete
   view of the ASes and AS paths in their CCs.  Once an ISP has that
   view, then AS path filters can be possibly used to detect route
   leaks.  One limitation of this technique is that it cannot duly take
   into account the fact that prefixes with different business models
   are often sent over the same link between ASes.  Also, the success of
   it depends on ASes at all levels of the hierarchy in a CC participate
   and provide accurate information (in the ORF messages) about the AS
   paths they expect to have in their BGP updates to their provider
   ISP(s).

6.  Summary

   It should be emphasized once again that the proposed route-leak
   detection method using the RLP encoding is not intended to cover all
   forms of route leaks.  However, we feel that the solution covers
   several important types of route leaks, especially considering some
   significant route-leak attacks or occurrences that have been
   frequently observed in recent years.  The solution can be implemented
   in BGP without necessarily tying it to BGPSEC.  The proposed solution
   without BGPSEC can detect and mitigate accidental route leaks, and
   the same with BGPSEC can detect and mitigate malicious route leaks as
   well.  Carrying the proposed RLP encoding in an optional transitive
   path attribute in BGP is proposed, but in order to prevent abuse, the
   RLP encoding would require cryptographic protection.  Incorporating
   the RLP encoding in the BGPSEC Flags field is one way of implementing
   it securely using an already existing protection mechanism provided
   in BGPSEC path signatures.



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7.  Security Considerations

   The proposed Route Leak Protection (RLP) field requires cryptographic
   protection in order to prevent malicious route leaks.  Since it is
   proposed that the RLP field be included in the Flags field in the
   Secure_Path Segment in BPGSEC updates, the cryptographic security
   mechanisms in BGPSEC are expected to also apply to the RLP field.
   The reader is therefore directed to the security considerations
   provided in [I-D.ietf-sidr-bgpsec-protocol].

8.  IANA Considerations

   No updates to the registries are suggested by this document.

9.  Acknowledgements

   The authors wish to thank Danny McPherson and Eric Osterweil for
   discussions related to this work.  Also, thanks are due to Jared
   Mauch, Jeff Haas, Warren Kumari, Amogh Dhamdhere, Jakob Heitz, Geoff
   Huston, Randy Bush, Ruediger Volk, Andrei Robachevsky, Sue Hares,
   Keyur Patel, Wes George, Chris Morrow, and Sandy Murphy for comments,
   suggestions, and critique.  The authors are also thankful to Padma
   Krishnaswamy, Oliver Borchert, and Okhee Kim for their comments and
   review.

10.  References

10.1.  Normative References

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

10.2.  Informative References

   [Cowie2010]
              Cowie, J., "China's 18 Minute Mystery", Dyn Research/
              Renesys Blog, November 2010,
              <http://research.dyn.com/2010/11/
              chinas-18-minute-mystery/>.

   [Cowie2013]
              Cowie, J., "The New Threat: Targeted Internet Traffic
              Misdirection", Dyn Research/Renesys Blog, November 2013,
              <http://research.dyn.com/2013/11/
              mitm-internet-hijacking/>.






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   [draft-dickson-sidr-route-leak-solns]
              Dickson, B., "Route Leaks -- Proposed Solutions", IETF
              Internet Draft (expired), March 2012,
              <https://tools.ietf.org/html/draft-dickson-sidr-route-
              leak-solns-01>.

   [draft-ietf-idr-aspath-orf]
              Patel, K. and S. Hares, "AS path Based Outbound Route
              Filter for BGP-4", IETF Internet Draft (expired), August
              2007, <https://tools.ietf.org/html/draft-ietf-idr-aspath-
              orf-09>.

   [draft-kunzinger-idrp-ISO10747-01]
              Kunzinger, C., "Inter-Domain Routing Protocol (IDRP)",
              IETF Internet Draft (expired), November 1994,
              <https://tools.ietf.org/pdf/draft-kunzinger-idrp-
              ISO10747-01.pdf>.

   [Gao]      Gao, L. and J. Rexford, "Stable Internet routing without
              global coordination", IEEE/ACM Transactions on Networking,
              December 2001, <http://www.cs.princeton.edu/~jrex/papers/
              sigmetrics00.long.pdf>.

   [Gill]     Gill, P., Schapira, M., and S. Goldberg, "A Survey of
              Interdomain Routing Policies", ACM SIGCOMM Computer
              Communication Review, January 2014,
              <https://www.cs.bu.edu/~goldbe/papers/survey.pdf>.

   [Giotsas]  Giotsas, V. and S. Zhou, "Valley-free violation in
              Internet routing - Analysis based on BGP Community data",
              IEEE ICC 2012, June 2012,
              <http://www0.cs.ucl.ac.uk/staff/V.Giotsas/files/
              giotsas.icc.2012.pdf>.

   [Hiran]    Hiran, R., Carlsson, N., and P. Gill, "Characterizing
              Large-scale Routing Anomalies: A Case Study of the China
              Telecom Incident", PAM 2013, March 2013,
              <http://www3.cs.stonybrook.edu/~phillipa/papers/
              CTelecom.html>.

   [Huston2012]
              Huston, G., "Leaking Routes", March 2012,
              <http://labs.apnic.net/blabs/?p=139/>.

   [Huston2014]
              Huston, G., "What's so special about 512?", September
              2014, <http://labs.apnic.net/blabs/?p=520/>.




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   [I-D.ietf-grow-route-leak-problem-definition]
              Sriram, K., Montgomery, D., McPherson, D., E.
              Osterweil, and B. Dickson "Problem Definition and Classification of BGP
              Route Leaks", draft-ietf-grow-route-leak-problem-
              definition-02 (work in progress), July 2015.

   [I-D.ietf-sidr-bgpsec-protocol]
              Lepinski, M., "BGPsec Protocol Specification", draft-ietf-
              sidr-bgpsec-protocol-12 (work in progress), June 2015.

   [Kapela-Pilosov]
              Pilosov, A. and T. Kapela, "Stealing the Internet: An
              Internet-Scale Man in the Middle Attack", DEFCON-16 Las
              Vegas, NV, USA, August 2008,
              <https://www.defcon.org/images/defcon-16/dc16-
              presentations/defcon-16-pilosov-kapela.pdf/>.

   [Khare]    Khare, V., Ju, Q., and B. Zhang, "Concurrent Prefix
              Hijacks: Occurrence and Impacts", IMC 2012, Boston, MA,
              November 2012, <http://www.cs.arizona.edu/~bzhang/
              paper/12-imc-hijack.pdf/>.

   [Labovitz]
              Labovitz, C., "Additional Discussion of the April China
              BGP Hijack Incident", Arbor Networks IT Security Blog,
              November 2010,
              <http://www.arbornetworks.com/asert/2010/11/additional-
              discussion-of-the-april-china-bgp-hijack-incident/>.

   [LRL]      Khare, V., Ju, Q., and B. Zhang, "Large Route Leaks",
              Project web page, 2012,
              <http://nrl.cs.arizona.edu/projects/
              lsrl-events-from-2003-to-2009/>.

   [Luckie]   Luckie, M., Huffaker, B., Dhamdhere, A., Giotsas, V., and
              kc. claffy, "AS Relationships, Customer Cones, and
              Validation", IMC 2013, October 2013,
              <http://www.caida.org/~amogh/papers/asrank-IMC13.pdf>.

   [Madory]   Madory, D., "Why Far-Flung Parts of the Internet Broke
              Today", Dyn Research/Renesys Blog, September 2014,
              <http://research.dyn.com/2014/09/
              why-the-internet-broke-today/>.

   [Mauch]    Mauch, J., "BGP Routing Leak Detection System", Project
              web page, 2014,
              <http://puck.nether.net/bgp/leakinfo.cgi/>.




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   [Mauch-nanog]
              Mauch, J., "Detecting Routing Leaks by Counting", NANOG-41
              Albuquerque, NM, USA, October 2007,
              <https://www.nanog.org/meetings/nanog41/presentations/
              mauch-lightning.pdf/>.

   [NIST-800-54]
              Kuhn, D., Sriram, K., and D. Montgomery, "Border Gateway
              Protocol Security", NIST Special Publication 800-54, July
              2007, <http://csrc.nist.gov/publications/nistpubs/800-54/
              SP800-54.pdf>.

   [Paseka]   Paseka, T., "Why Google Went Offline Today and a Bit about
              How the Internet Works", CloudFare Blog, November 2012,
              <http://blog.cloudflare.com/
              why-google-went-offline-today-and-a-bit-about/>.

   [proceedings-sixth-ietf]
              Gross, P., "Proceedings of the April 22-24, 1987 Internet
              Engineering Task Force", April 1987,
              <https://www.ietf.org/proceedings/06.pdf>.

   [RFC1105-obsolete]
              Lougheed, K. and Y. Rekhter, "A Border Gateway Protocol
              (BGP)", IETF RFC (obsolete), June 1989,
              <https://tools.ietf.org/html/rfc1105>.

   [RFC6811]  Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation", RFC 6811, January
              2013.

   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
              and Security", BCP 194, RFC 7454, February 2015.

   [Toonk]    Toonk, A., "What Caused Today's Internet Hiccup", August
              2014, <http://www.bgpmon.net/
              what-caused-todays-internet-hiccup/>.

   [Wijchers]
              Wijchers, B. and B. Overeinder, "Quantitative Analysis of
              BGP Route Leaks", RIPE-69, November 2014,
              <https://ripe69.ripe.net/presentations/157-RIPE-69-
              Routing-WG.pdf>.








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   [Zmijewski]
              Zmijewski, E., "Indonesia Hijacks the World", Dyn
              Research/Renesys Blog, April 2014,
              <http://research.dyn.com/2014/04/
              indonesia-hijacks-world/>.

Authors' Addresses

   Kotikalapudi Sriram
   US NIST

   Email: ksriram@nist.gov


   Doug Montgomery
   US NIST

   Email: dougm@nist.gov


   Brian Dickson
   Twitter, Inc.

   Email: bdickson@twitter.com



























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