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Global Routing Operations                                      K. Sriram
Internet-Draft                                             D. Montgomery
Intended status: Informational                                   US NIST
Expires: August 14, 2016                                    D. McPherson
                                                            E. Osterweil
                                                          Verisign, Inc.
                                                              B. Dickson
                                                       February 11, 2016


        Problem Definition and Classification of BGP Route Leaks
            draft-ietf-grow-route-leak-problem-definition-04

Abstract

   A systemic vulnerability of the Border Gateway Protocol routing
   system, known as 'route leaks', has received significant attention in
   recent years.  Frequent incidents that result in significant
   disruptions to Internet routing are labeled "route leaks", but to
   date we have lacked a common definition of the term.  In this
   document, we provide a working definition of route leaks, keeping in
   mind the real occurrences that have received significant attention.
   Further, we attempt to enumerate (though not exhaustively) different
   types of route leaks based on observed events on the Internet.  We
   aim to provide a taxonomy that covers several forms of route leaks
   that have been observed and are of concern to Internet user community
   as well as the network operator community.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on August 14, 2016.







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Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Working Definition of Route Leaks . . . . . . . . . . . . . .   3
   3.  Classification of Route Leaks Based on Documented Events  . .   3
     3.1.  Type 1: Hairpin Turn with Full Prefix . . . . . . . . . .   4
     3.2.  Type 2: Lateral ISP-ISP-ISP Leak  . . . . . . . . . . . .   5
     3.3.  Type 3: Leak of Transit-Provider Prefixes to Peer . . . .   5
     3.4.  Type 4: Leak of Peer Prefixes to Transit Provider . . . .   5
     3.5.  Type 5: Prefix Re-Origination with Data Path to
           Legitimate Origin . . . . . . . . . . . . . . . . . . . .   6
     3.6.  Type 6: Accidental Leak of Internal Prefixes and More
           Specifics . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Additional Comments about the Classification  . . . . . . . .   7
   5.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Frequent incidents [Huston2012][Cowie2013][Toonk2015-A][Toonk2015-B][
   Cowie2010][Madory][Zmijewski][Paseka][LRL][Khare] that result in
   significant disruptions to Internet routing are commonly called
   "route leaks".  Examination of the details of some of these incidents
   reveals that they vary in their form and technical details.  Before
   we can discuss solutions to "the route leak problem" we need a clear,
   technical definition of the problem and its most common forms.  In
   Section 2, we provide a working definition of route leaks, keeping in
   view many recent incidents that have received significant attention.
   Further, in Section 3, we attempt to enumerate (though not



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   exhaustively) different types of route leaks based on observed events
   on the Internet.  We aim to provide a taxonomy that covers several
   forms of route leaks that have been observed and are of concern to
   Internet user community as well as the network operator community.
   This document builds on and extends earlier work in the IETF by
   Dickson [draft-dickson-sidr-route-leak-def][draft-dickson-sidr-route-
   leak-reqts].

2.  Working Definition of Route Leaks

   A proposed working definition of route leak is as follows:

   A "route leak" is the propagation of routing announcement(s) beyond
   their intended scope.  That is, an AS's announcement of a learned BGP
   route to another AS is in violation of the intended policies of the
   receiver, the sender and/or one of the ASes along the preceding AS
   path.  The intended scope is usually defined by a set of local
   redistribution/filtering policies distributed among the ASes
   involved.  Often, these intended policies are defined in terms of the
   pair-wise peering business relationship between ASes (e.g., customer,
   transit provider, peer).  (For literature related to AS relationships
   and routing policies, see [Gao] [Luckie] [Gill].  For measurements of
   valley-free violations in Internet routing, see [Anwar] [Giotsas]
   [Wijchers].)

   The result of a route leak can be redirection of traffic through an
   unintended path which may enable eavesdropping or traffic analysis,
   and may or may not result in an overload or black-hole.  Route leaks
   can be accidental or malicious, but most often arise from accidental
   misconfigurations.

   The above definition is not intended to be all encompassing.
   Perceptions vary widely about what constitutes a route leak.  Our aim
   here is to have a working definition that fits enough observed
   incidents so that the IETF community has a basis for developing
   solutions for route leak detection and mitigation.

3.  Classification of Route Leaks Based on Documented Events

   As illustrated in Figure 1, a common form of route leak occurs when a
   multi-homed customer AS (such as AS3 in Figure 1) learns a prefix
   update from one transit provider (ISP1) and leaks the update to
   another transit provider (ISP2) in violation of intended routing
   policies, and further the second transit provider does not detect the
   leak and propagates the leaked update to its customers, peers, and
   transit ISPs.





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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.

   We propose the following taxonomy for classification of route leaks
   aiming to cover several types of recently observed route leaks, while
   acknowledging that the list is not meant to be exhaustive.  In what
   follows, we refer to the AS that announces a route that is in
   violation of the intended policies as the "offending AS".

3.1.  Type 1: Hairpin Turn with Full Prefix

   Description: A multi-homed AS learns a route from one upstream ISP
   and simply propagates it to another upstream ISP (the turn
   essentially resembling a hairpin).  Neither the prefix nor the AS
   path in the update is altered.  This is similar to a straight forward
   path-poisoning attack [Kapela-Pilosov], but with full prefix.  It
   should be noted that leaks of this type are often accidental (i.e.
   not malicious).  The update basically makes a hairpin turn at the
   offending AS's multi-homed AS.  The leak often succeeds because the
   second ISP prefers customer announcement over peer announcement of
   the same prefix.  Data packets would reach the legitimate destination
   albeit via the offending AS, unless they are dropped at the offending
   AS due to its inability to handle resulting large volumes of traffic.

   o  Example incidents: Examples of Type 1 route-leak incidents are (1)
      the Dodo-Telstra incident in March 2012 [Huston2012], (2) the
      VolumeDrive-Atrato incident in September 2014 [Madory], and (3)
      the massive Telekom Malaysia route leak of about 179,000 prefixes,
      which in turn Level3 accepted and propagated [Toonk2015-B].





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3.2.  Type 2: Lateral ISP-ISP-ISP Leak

   Description: The term "lateral" here is synonymous with "non-transit"
   or "peer-to-peer".  This type of route leak typically occurs when,
   for example, three sequential ISP peers (e.g.  ISP-A, ISP-B, and ISP-
   C) are involved, and ISP-B receives a route from ISP-A and in turn
   leaks it to ISP-C.  The typical routing policy between laterally
   (i.e. non-transit) peering ISPs is that they should only propagate to
   each other their respective customer prefixes.

   o  Example incidents: In [Mauch-nanog][Mauch], route leaks of this
      type are reported by monitoring updates in the global BGP system
      and finding three or more very large ISP ASNs in a sequence in a
      BGP update's AS path.  Mauch [Mauch] observes that these are
      anomalies and potentially route leaks because very large ISPs such
      as ATT, Sprint, Verizon, and Globalcrossing do not in general buy
      transit services from each other.  However, he also notes that
      there are exceptions when one very large ISP does indeed buy
      transit from another very large ISP, and accordingly exceptions
      are made in his detection algorithm for known cases.

3.3.  Type 3: Leak of Transit-Provider Prefixes to Peer

   Description: This type of route leak occurs when an offending AS
   leaks routes learned from its transit provider to a lateral (i.e.
   non-transit) peer.

   o  Example incidents: The incidents reported in [Mauch] include the
      Type 3 leaks.

3.4.  Type 4: Leak of Peer Prefixes to Transit Provider

   Description: This type of route leak occurs when an offending AS
   leaks routes learned from a lateral (i.e. non-transit) peer to its
   (the AS's) own transit provider.  These leaked routes typically
   originate from the customer cone of the lateral peer.

   o  Example incidents: Examples of Type 4 route-leak incidents are (1)
      the Axcelx-Hibernia route leak of Amazon Web Services (AWS)
      prefixes causing disruption of AWS and a variety of services that
      run on AWS [Kephart],(2) the Hathway-Airtel route leak of 336
      Google prefixes causing widespread interruption of Google services
      in Europe and Asia [Toonk2015-A], (3) the Moratel-PCCW route leak
      of Google prefixes causing Google's services to go offline
      [Paseka], and (4) Some of the example incidents cited for Type 1
      route leaks above are also inclusive of Type 4 route leaks.  For
      instance, in the Dodo-Telstra incident [Huston2012], the leaked




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      routes from Dodo to Telstra included routes that Dodo learned from
      its transit providers as well as lateral peers.

3.5.  Type 5: Prefix Re-Origination with Data Path to Legitimate Origin

   Description: A multi-homed AS learns a route from one upstream ISP
   and announces the prefix to another upstream ISP as if it is being
   originated by it (i.e. strips the received AS path, and re-originates
   the prefix).  This can be called re-origination or mis-origination.
   However, somehow (not attributable to the use of path poisoning trick
   by the offending AS) a reverse path is present, and data packets
   reach the legitimate destination albeit via the offending AS.  But
   sometimes the reverse path may not be there, and data packets get
   dropped following receipt by the offending AS.

   o  Example incidents: Examples of Type 5 route leak include (1) the
      China Telecom incident in April 2010 [Hiran][Cowie2010][Labovitz],
      (2) the Belarusian GlobalOneBel route leak incidents in February-
      March 2013 and May 2013 [Cowie2013], (3) the Icelandic Opin Kerfi-
      Simmin route leak incidents in July-August 2013 [Cowie2013], and
      (4) the Indosat route leak incident in April 2014 [Zmijewski].
      The reverse paths (i.e. data paths from the offending AS to the
      legitimate destinations) were present in incidents #1, #2 and #3
      cited above, but not in incident #4.  In incident #4, the
      misrouted data packets were dropped at Indosat's AS.

3.6.  Type 6: Accidental Leak of Internal Prefixes and More Specifics

   Description: An offending AS simply leaks its internal prefixes to
   one or more of its transit-provider ASes and/or ISP peers.  The
   leaked internal prefixes are often more specifics subsumed by an
   already announced less specific prefix.  The more specifics were not
   intended to be routed in eBGP.  Further, the AS receiving those leaks
   fails to filter them.  Typically these leaked announcements are due
   to some transient failures within the AS; they are short-lived, and
   typically withdrawn quickly following the announcements.  However,
   these more specifics may momentarily cause the routes to be preferred
   over other aggregate route announcements, thus redirecting traffic
   from its normal best path.

   o  Example incidents: Leaks of internal routes occur frequently (e.g.
      multiple times in a week), and the number of prefixes leaked range
      from hundreds to thousands per incident.  One highly conspicuous
      and widely disruptive leak of internal routes happened recently in
      August 2014 when AS701 and AS705 leaked about 22,000 more
      specifics of already announced aggregates [Huston2014][Toonk2014].





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4.  Additional Comments about the Classification

   It is worth noting that Types 1 through 4 are similar in that a route
   is leaked in violation of policy in each case, but what varies is the
   context of the leaked-route source AS and destination AS roles.

   Type 5 route leak (i.e. prefix mis-origination with data path to
   legitimate origin) can also happen in conjunction with the AS
   relationship contexts in Types 2, 3, and 4.  While these
   possibilities are acknowledged, simply enumerating more types to
   consider all such special cases does not add value as far as solution
   development for route leaks is concerned.  Hence, the special cases
   mentioned here are not included in enumerating route leak types.

5.  Summary

   We attempted to provide a working definition of route leak.  We also
   presented a taxonomy for categorizing route leaks.  It covers not all
   but at least several forms of route leaks that have been observed and
   are of concern to Internet user and network operator communities.  We
   hope that this work provides the IETF community a basis for pursuing
   possible BGP enhancements for route leak detection and mitigation.

6.  Security Considerations

   No security considerations apply since this is a problem definition
   document.

7.  IANA Considerations

   No updates to the registries are suggested by this document.

8.  Acknowledgements

   The authors wish to thank Jared Mauch, Jeff Haas, Warren Kumari,
   Amogh Dhamdhere, Jakob Heitz, Geoff Huston, Randy Bush, Job Snijders,
   Ruediger Volk, Andrei Robachevsky, Charles van Niman, 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.

9.  Informative References

   [Anwar]    Anwar, R., Niaz, H., Choffnes, D., Cunha, I., Gill, P.,
              and N. Katz-Bassett, "Investigating Interdomain Routing
              Policies in the Wild",  ACM Internet Measurement
              Conference (IMC), October 2015,
              <http://www.cs.usc.edu/assets/007/94928.pdf>.



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   [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/>.

   [draft-dickson-sidr-route-leak-def]
              Dickson, B., "Route Leaks -- Definitions",  IETF Internet
              Draft (expired), October 2012,
              <https://tools.ietf.org/html/draft-dickson-sidr-route-
              leak-def-03>.

   [draft-dickson-sidr-route-leak-reqts]
              Dickson, B., "Route Leaks -- Requirements for Detection
              and Prevention thereof",  IETF Internet Draft (expired),
              March 2012, <http://tools.ietf.org/html/
              draft-dickson-sidr-route-leak-reqts-02>.

   [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,
              <http://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.

   [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/>.



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

   [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>.

   [Kephart]  Kephart, N., "Route Leak Causes Amazon and AWS Outage",
               ThousandEyes Blog, June 2015,
              <https://blog.thousandeyes.com/route-leak-causes-amazon-
              and-aws-outage>.

   [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>.

   [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/>.

   [Toonk2014]
              Toonk, A., "What caused today's Internet hiccup", August
              2014, <http://www.bgpmon.net/
              what-caused-todays-internet-hiccup/>.

   [Toonk2015-A]
              Toonk, A., "What caused the Google service interruption",
              March 2015, <http://www.bgpmon.net/
              what-caused-the-google-service-interruption/>.

   [Toonk2015-B]
              Toonk, A., "Massive route leak causes Internet slowdown",
              June 2015, <http://www.bgpmon.net/
              massive-route-leak-cause-internet-slowdown/>.

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

   [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







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   Doug Montgomery
   US NIST

   Email: dougm@nist.gov


   Danny McPherson
   Verisign, Inc.

   Email: dmcpherson@verisign.com


   Eric Osterweil
   Verisign, Inc.

   Email: eosterweil@verisign.com


   Brian Dickson

   Email: brian.peter.dickson@gmail.com






























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