Routing Area Working Group                                  S. Litkowski
Internet-Draft                                                    Orange
Intended status: Standards Track                              A. Simpson
Expires: January 1, 2015                                  Alcatel Lucent
                                                                K. Patel
                                                                 J. Haas
                                                        Juniper Networks
                                                           June 30, 2014

        Applying BGP flowspec rules on a specific interface set


   BGP Flow-spec is an extension to BGP that allows for the
   dissemination of traffic flow specification rules.  The primary
   application of this extension is DDoS mitigation where the flowspec
   rules are applied in most cases to all peering routers of the

   This document will present another use case of BGP Flow-spec where
   flow specifications are used to maintain some access control lists at
   network boundary.  BGP Flowspec is a very efficient distributing
   machinery that can help in saving OPEX while deploying/updating ACLs.
   This new application requires flow specification rules to be applied
   only on a specific subset of interfaces and in a specific direction.

   The current specification of BGP Flow-spec does not detail where the
   flow specification rules need to be applied.

   This document presents a new interface-set flowspec action that will
   be used in complement of other actions (marking, rate-limiting ...).
   The purpose of this extension is to inform remote routers on where to
   apply the flow specification.

   This extension can also be used in a DDoS mitigation context where a
   provider wants to apply the filtering only on specific peers.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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Status of This Memo

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   described in the Simplified BSD License.

Table of Contents

   1.  Use case  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Specific filtering for DDoS . . . . . . . . . . . . . . .   3
     1.2.  ACL maintenance . . . . . . . . . . . . . . . . . . . . .   4
   2.  Interface specific filtering using BGP flowspec . . . . . . .   5
   3.  Interface-set extended community  . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

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1.  Use case

1.1.  Specific filtering for DDoS

                       -----------------    --- (ebgp) - Peer3 (BW 10G)
                      /                  \/
                     |                   /|
                     |                PE --- (ebgp) - Transit1(BW 4x10G)
 Cust1 --- (ebgp) --- PE                  |
                     |                PE ---- (ebgp) - Peer2 (BW 4*10G)
                     |                   \|
 Cust2 --- (ebgp) --- PE                  |----- (ebgp) - Customer3
                    /|                    |
 Peer1(BW10G)-(ebgp) |                PE --- (ebgp) - Transit2(BW 4x10G)
                     |                    |
                      \                  /

                                    Figure 1

   The figure 1 above displays a typical service provider Internet
   network owing Customers, Peers and Transit.  To protect proactively
   against some attacks (e.g.  DNS, NTP ...), the service provider may
   want to deploy some rate-limiting of some flows on peers and transit
   links.  But depending on link bandwidth, the provider may want to
   apply different rate-limiting values.

   For 4*10G links peer/transit, it may want to apply a rate-limiting of
   DNS flows of 1G, while on 10G links, the rate-limiting would be set
   to 250Mbps.  Customer interfaces must not be rate-limited.

   BGP Flow-spec infrastructure may already be present on the network,
   and all PEs may have a BGP session running flowspec address family.
   The Flowspec infrastructure may be reused by the service provider to
   implement such rate-limiting in a very quick manner and being able to
   adjust values in future quickly without having to configure each node
   one by one.  Using the current BGP flowspec specification, it would
   not be possible to implement different rate limiter on different
   interfaces of a same router.  The flowspec rule is applied to all
   interfaces in all directions or on some interfaces where flowspec is
   activated but flowspec rule set would be the same among all

   Section Section 2 will detail a solution to address this use case
   using BGP Flowspec.

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1.2.  ACL maintenance

                              ---------------    --- (ebgp) - Cust4_VPN
                             /                \/
    Cust1_INT -- (ebgp) --- PE                /|
                            |              PE ------ (ebgp) - Transit1
    Cust3_VPN -- (ebgp) --- PE                 |
                            |              PE ------ (ebgp) - Peer2
                            |                 \|
    Cust2_INT -- (ebgp) --- PE                 |----- (ebgp) - Cust4_INT
                           /|                  |
    Peer1 ------ (ebgp) --  |              PE ------ (ebgp) - Transit2
                            |                  |
                             \                /

                                       Figure 2

   The figure 1 above displays a typical service provider multiservice
   network owing Customers, Peers and Transit for Internet, as well as
   VPN services.  The service provider requires to ensure security of
   its infrastructure by applying ACLs at network boundary.  Maintaing
   and deploying ACLs on hundreds/thousands of routers is really painful
   and time consuming and a service provider would be interrested to
   deploy/updates ACLs using BGP Flowspec.  In this scenario, depending
   on the interface type (Internet customer, VPN customer, Peer, Transit
   ...) the content of the ACL may be different.

   We can imagine two cases :

   o  Maintaining complete ACLs using flowspec : in this case all the
      ingress ACL are maintained and deployed using BGPFlowspec.  See
      section Section 4 for more details on security aspects.

   o  Requirement of a quick deployment of a new filtering term due to a
      security alert : new security alerts often requires a fast
      deployment of new ACL terms.  Using traditional CLI and hop by hop
      provisionning, such deployment takes time and network is
      unprotected during this time window.  Using BGP flowspec to deploy
      such rule, a service provider can protect its network in few
      seconds.  Then the SP can decide to keep the rule permanentely in
      BGP Flowspec or update its ACL or remove the entry (in case
      equipments are not vulnerable anymore).

   Section Section 2 will detail a solution to address this use case
   using BGP Flowspec.

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2.  Interface specific filtering using BGP flowspec

   The use case detailled above requires application of different BGP
   Flowspec rules on different set of interfaces.  The basic
   specification detailled in [RFC5575] does not address this and does
   not give any detail on where the FlowSpec filter need to be applied.

   We propose to introduce an identification of interfaces within BGP
   Flowspec.  All interfaces may be associated to one or more group-
   identifiers and a BGP Flowspec rule may also be associated with one
   or more group-identifiers including a filtering direction
   (input/output/both) , so the FlowSpec rule will be applied only on
   interfaces belonging the the group identifier included in the BGP
   FlowSpec update.

   Considering figure 2, we can imagine the following design :

   o  Internet customer interfaces are associated with group-identifier

   o  VPN customer interfaces are associated with group-identifier 2.

   o  All customer interfaces are associated with group-identifier 3.

   o  Peer interfaces are associated with group-identifier 4.

   o  Transit interfaces are associated with group-identifier 5.

   o  All external provider interfaces are associated with group-
      identifier 6.

   o  All interfaces are associated with group-identifier 7.

   If the service provider wants to deploy a specific inbound filtering
   on external provider interfaces only, the provider can send the BGP
   flow specification using group-identifier 6 and including inbound

3.  Interface-set extended community

   This document proposes a new BGP extended community called "flow spec
   interface-set".  This new BGP extended community is part of

   The Global Administrator field of this community MUST be set to the
   ASN of the originating router.  The Local Administrator field is
   encoded as follows :

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     0   1   2   3   4   5   6   7
   | O | I |  Group Identifier     :
   : Group Identifier  (cont.)     |

   The flags are :

   o  O : if set, the flow specification rule MUST be applied in
      outbound direction to the interface set referenced by the
      following group-identifier.

   o  I : if set, the flow specification rule MUST be applied in input
      direction to the interface set referenced by the following group-

   Both flags can be set at the same time in the interface-set extended
   community leading to flow rule to be applied in both directions.  An
   interface-set extended community with both flags set to zero MUST be
   treated as an error and as consequence, the FlowSpec update MUST be

   Thr Group Identifier is coded as a 14-bit number (values goes from 0
   to 16383).

   Multiple instances of the interface-set community may be present in a
   BGP update.  This may appear if the flow rule need to be applied to
   multiple set of interfaces.

   Multiple instances of the community in a BGP update MUST be
   interpreted as a "OR" operation : if a BGP update contains two
   interface-set communities with group ID 1 and group ID 2, the filter
   would need to be installed on interfaces belonging to Group ID 1 or
   Group ID 2.

4.  Security Considerations

   Managing permanent Access Control List by using BGP Flowspec as
   described in Section 1.2 helps in saving roll out time of such ACL.
   However some ACL especially at network boundary are critical for the
   network security and loosing the ACL configuration may lead to
   network open for attackers.

   By design, BGP flowspec rules are ephemeral : the flow rule exists in
   the router while the BGP session is UP and the BGP path for the rule
   is valid.  We can imagine a scenario where a Service Provider is

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   managing the network boundary ACLs by using only FlowSpec.  In this
   scenario, if , for example, an attacker succeed to make the internal
   BGP session of a router to be down , it can open all boundary ACLs on
   the node, as flowspec rules will disappear due to the BGP session

   In reality, the chance for such attack to occur is low, as boundary
   ACLs should protect the BGP session from being attacked.

   In order to complement the BGP flowspec solution is such deployment
   scenario and provides security against such attack, a service
   provider may activate Long lived Graceful Restart
   [I-D.uttaro-idr-bgp-persistence] on the BGP session owning Flowspec
   address family.  So in case of BGP session to be down, the BGP paths
   of Flowspec rules would be retained and the flowspec action will be

5.  Acknowledgements

   Authors would like to thanks Wim Hendrickx for his valuable comments.

6.  IANA Considerations

   This document requests a new sub-type from the "TRANSITIVE FOUR-OCTET
   registry.  The sub-type name shall be 'Flow spec interface-set'.

7.  Normative References

              Uttaro, J., Chen, E., Decraene, B., and J. Scudder,
              "Support for Long-lived BGP Graceful Restart", draft-
              uttaro-idr-bgp-persistence-03 (work in progress), November

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

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, August 2009.

Authors' Addresses

   Stephane Litkowski


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   Adam Simpson
   Alcatel Lucent


   Keyur Patel


   Jeff Haas
   Juniper Networks


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