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Versions: 00 01 02 draft-ietf-opsec-routing-capabilities

OPSEC Working Group                                              Y. Zhao
Internet-Draft                                                   F. Miao
Intended status: Informational                       Huawei Technologies
Expires: March 17, 2007                                        R. Callon
                                                        Juniper Networks
                                                      September 13, 2006


              Routing Control Plane Security Capabilities
              draft-zhao-opsec-routing-capabilities-02.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The document lists the security capabilities needed for the routing
   control plane of an IP infrastructure to support the practices
   defined in Operational Security Current Practices.  In particular
   this includes capabilities for route filtering and for authentication
   of routing protocol packets.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Threat model . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Format and Definition of Capabilities  . . . . . . . . . .  3
     1.3.  Packet Filtering versus Route Filtering  . . . . . . . . .  4
   2.  Route Filtering Capabilities . . . . . . . . . . . . . . . . .  5
     2.1.  General Route Filtering Capabilities . . . . . . . . . . .  5
       2.1.1.  Ability to Filter Inbound or Outbound Routes . . . . .  5
       2.1.2.  Ability to Filter Routes by Prefix . . . . . . . . . .  6
     2.2.  Route Filtering of Exterior Gateway Protocol . . . . . . .  6
       2.2.1.  Ability to Filter Routes by Route Attributes . . . . .  6
       2.2.2.  Ability to Filter Routing Update by TTL  . . . . . . .  7
       2.2.3.  Ability to Limit the Number of Routes from a Peer  . .  8
       2.2.4.  Ability to Limit the Length of Prefixes  . . . . . . .  9
       2.2.5.  Ability to Cooperate in Outbound Route Filtering . . .  9
     2.3.  Route Filtering of Interior Gateway Protocols  . . . . . . 10
       2.3.1.  Route Filtering Within an IGP Area . . . . . . . . . . 10
       2.3.2.  Route Filtering Between IGP Areas  . . . . . . . . . . 10
     2.4.  Route Filtering during Redistribution  . . . . . . . . . . 11
   3.  Route Authentication Capabilities  . . . . . . . . . . . . . . 12
     3.1.  Ability to configure an authentication mechanism . . . . . 12
     3.2.  Ability to support authentication key chains . . . . . . . 12
   4.  Ability to Damp Route Flap . . . . . . . . . . . . . . . . . . 13
   5.  Performance and Prioritization . . . . . . . . . . . . . . . . 14
     5.1.  Ensure Resources for Management Functions  . . . . . . . . 14
     5.2.  Ensure Resources for Routing Functions . . . . . . . . . . 15
     5.3.  Limit Resources used by IP Multicast . . . . . . . . . . . 16
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
   Intellectual Property and Copyright Statements . . . . . . . . . . 20
















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1.  Introduction

   This document is defined in the context of Operation Security
   Framework [12] and Operation Security Current Practice [13].

   The Framework for Operation Security Framework outlines the effort of
   the IETF OPSEC working group.  This includes producing a series of
   drafts to codify knowledge gained through operational experience
   about capabilities that are needed to securely deploy and operate
   managed network elements providing transit services at the data link
   and network layers.

   This document lists the security capabilities needed for the routing
   control plane of IP infrastructure to support the practices defined
   in Operational Security Current Practices.  In particular this
   includes capabilities for route filtering and for authentication of
   routing protocol packets.

   Note that this document lists capabilities that can reasonably be
   expected to be currently deployed in the context of existing
   standards.  Extensions to existing protocol standards and development
   of new protocol standards are outside of the scope of this effort.
   The preferred capabilities needed for securing the routing
   infrastructure may evolve over time.

   There will be other capabilities which are needed to fully secure a
   router infrastructure.  For example, network management of devices
   must be secured in order to prevent unauthorized access to or denial
   of service to the device Network Management Access Security
   Capabilities [15].  The reader should refer to Operation Security
   Framework for a more complete list of documents describing
   operational capabilities for network and link layer devices
   supporting IP Network Infrastructure.

   Operational Security Current Practices defines the goals, motivation,
   scope, definitions, intended audience, threat model, potential
   attacks and give justifications for each of the practices.

1.1.  Threat model

   The capabilities listed in this document are intended to aid in
   preventing or mitigating the threats outlined in Operation Security
   Framework and Current Practices.

1.2.  Format and Definition of Capabilities

   Each individual capability will be defined using the four elements,
   "Capability", "Supported Practices", "Current Implementations", and



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   "Considerations", as explained in section 1.7 of Operation Security
   Framework.

1.3.  Packet Filtering versus Route Filtering

   It is useful to make a distinction between Packet Filtering versus
   Route Filtering.

   The term "packet filter" is used to refer to the filter that a router
   applies to network layer packets passing through or destined to it.
   In general packet filters are based on contents of the network (IP)
   and transport (TCP,UDP) layers, and are mostly stateless, in the
   sense that whether or not a filter applies to a particular packet is
   a function of that packet (including the contents of IP and transport
   layer headers, size of packet, incoming interface, and similar
   characteristics), but does not depend upon the contents of other
   packets which might be part of the same stream (and thus which may
   also be forwarded by the same router).  One common minor exception to
   the "stateless" nature of packet filters is that packets that match a
   particular filter may be counted and/or rate limited (the act of
   counting therefore represents a very simple "state" associated with
   the filter).

   Because of the simplicity and stateless nature of packet filters,
   they can typically be implemented with very high performance.  It is
   not unusual for them to be implemented on line cards and to perform
   at or near full line rate.  For this reason they are very useful to
   counter very high bandwidth attacks, such as large DDoS attacks.

   Packet filtering capabilities are outside of the scope of this
   document.  A detailed description of packet filtering capabilities
   can be found in "Filtering Capabilities for IP Network
   Infrastructure" [14].

   The Term "route filter" is used to refer to filters that routers
   apply to the content of routing protocol packets that they are either
   sending or receiving.  Typically these therefore occur at the
   application layer (although which route filters are applied to a
   particular packet may be a function of network layer information,
   such as what interface the packet is received on, or the source
   address for the packet -- indicating the system that transmitted the
   packet).

   Route filters are typically implemented in some sort of processor.
   In many cases the total bandwidth which can be received by the
   processor is considerably less than the sum of the rate that packets
   may be received on all interfaces to a router.  Therefore in general
   route filters cannot handle the same bandwidth as packet filters.



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   Route filters are however very useful in that they can be applied to
   the contents of routing packets.


2.  Route Filtering Capabilities

2.1.  General Route Filtering Capabilities

2.1.1.  Ability to Filter Inbound or Outbound Routes

   Capability.

      The device provides the ability to filter which routes may be
      received in routing protocols (with BGP [10], and with RIP [7] and
      other distance vector routing protocols), as well as the ability
      to filter which routes are announced into each routing protocol.

   Supported Practices.

      See section 2.4.2 of Current Practices.

      It is a beneficial practice to configure routing filters in both
      directions, which will counter potential misconfiguration in each
      side of peers.  Also, incoming route filters will prevent a
      deliberate attacker to inject invalid routing information.

   Current Implementations.

      The unicast routing protocols used with IP can be classified into
      path vector routing protocols (such as BGP), distance vector
      protocols (such as RIP) and link state protocols (such as OSPF [4]
      and IS-IS [1]).  Because of difference of protocol mechanism,
      route filters will affect them in different ways.

      Take BGP for example, an implementation may check a received route
      against inbound filters to determine whether to install it into
      the overall route table or not.  Also, it will restrict the routes
      which will go out to neighbors against outbound route filters.

      However, as to link state protocols, such as OSPF, a router
      maintains a topology database and exchanges link state information
      with neighbors.  Since route filters do not influence the link
      state database, route filters will only affect which routes are
      advertised into the routing protocol.  That is to say, only
      inbound route filters are effective on link state protocols.

      Most of the routing protocols support methods to configure route
      filters which permit or deny learning or advertising of specific



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      routes.

   Considerations.

      None.

2.1.2.  Ability to Filter Routes by Prefix

   Capability.

      The device supports filtering routes based on prefix.

   Supported Practices.

      See section 2.4.2 of Current Practices.

   Current Implementations.

      The filter may include a list of specific prefixes to be accepted
      or rejected.  The filter may alternately include a list of
      prefixes, such that more specific (longer) prefixes which are
      included in the more inclusive (shorter) prefix are accepted,
      rejected, or summarized into the shorter prefix.

   Considerations.

      Operators may wish to ignore advertisements for routes to
      specially used addresses, such as private addresses, reserved
      addresses and multicast addresses, etc.  The up-to-date allocation
      of IPv4 address space can be found in INTERNET PROTOCOL V4 ADDRESS
      SPACE [18].

2.2.  Route Filtering of Exterior Gateway Protocol

   An exterior gateway protocol is used to exchange external routing
   information between different autonomous systems.  Since BGP is the
   actual standard, this section mainly depicts special routing filter
   capabilities of BGP.

2.2.1.  Ability to Filter Routes by Route Attributes

   Capability.

      The device supports filtering routing updates by route attributes.

   Supported Practices.





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      See RFC3013 [8] and section 3.2 of RFC2196 [3] and section 2.4.2
      of Current Practices.

   Current Implementations.

      In comparison with other routing protocol, BGP defines various
      path attributes to describe characteristics of routes.  Besides
      filtering by specific prefixes, BGP could also use some path
      attributes to precisely filter routes to determine whether a route
      is accepted from or sent to a neighboring router.

      These filters may be based upon any combination of route
      attributes, such as:

      *  Restrictions on the Content of AS_PATH.  Restrictions on the
         contents of the AS PATH are frequently used: for example, the
         received AS_PATH may be checked to ensure the sending AS is
         actually contained in the received AS_PATH.

      *  Restrictions on Communities.  Implementations could filter
         received routes based on the set of communities RFC1997 [2] or
         extended communities RFC4360 [11].

   Considerations.

      None.

2.2.2.  Ability to Filter Routing Update by TTL

   Capability.

      The device should provide a means to filter route packets based on
      the value of the TTL field in the IPv4 header or the Hop-Limit
      field in the IPv6 header.

      Note that "Filtering Capabilities for IP Network Infrastructure"
      Filtering Capabilities specifies:

      Capability.

         The filtering mechanism supports filtering based on the
         value(s) of any portion of the protocol headers for IP, ICMP,
         UDP and TCP.

      The ability to filter based on TTL is therefore a packet filtering
      capability which is already implicitly covered by the capabilities
      listed in Filtering Capabilities.  Since this capability is
      particularly important for BGP, we felt that it is worth



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      mentioning here.

   Supported Practices.

      See Current Practices section 2.4.2 and RFC3682 [9].

   Current Implementations.

      Most current BGP implementations support this capability to
      protect BGP sessions.

   Considerations.

      There will be situations in which the distance to the neighboring
      router is more than one hop away.  This for example is common for
      I-BGP.

2.2.3.  Ability to Limit the Number of Routes from a Peer

   Capability.

      The device should provide a means to configure the maximum number
      of routes (prefixes) to accept from a peer.

   Supported Practices.

      Both routing policy misconfiguration and a deliberate attack from
      a peer may cause too many routes to be sent to a peer which may
      exhaust memory resources of the router, introduce routing
      instability into the overall routing table, or both.  Therefore,
      operators may want to restrict the amount of routes received from
      a particular peer router through a maximum prefix limitation
      approach.

   Current Implementations.

      Most BGP implementations support this capability.  If too many
      routes are sent, then the router may reset the BGP session or may
      reject excess routes.  In either case the device may log the
      failure event (at a minimum), or shut down the BGP session.

   Considerations.

      Operators must be cognizant of the need to allow for valid swings
      in routing announcements between themselves, and as such should
      always set the max-prefix limit to some agreed upon number plus a
      sane amount for overhead to allow for these necessary announcement
      swings.  Individual implementations amongst ISPs are unique, and



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      depending on equipment supplier(s) different implementation
      options are available.  Most equipment vendors offer
      implementation options ranging from just logging excessive
      prefixes being received to automatically shutting down the
      session.  If the option of reestablishing a session after some
      pre-configured idle timeout has been reached is available, it
      should be understood that automatically reestablishing the session
      may continuously introduce instability into the overall routing
      table if a policy misconfiguration on the adjacent neighbor is
      causing the condition.  If a serious misconfiguration on a peering
      neighbor has occurred then automatically shutting down the session
      and leaving it shut down until being manually cleared is perhaps
      best and allows for operator intervention to correct as needed.

2.2.4.  Ability to Limit the Length of Prefixes

   Capability.

      The device has the capability to allow filtering route updates by
      prefix length.

   Supported Practices.

      Some large ISPs declare in their peer BGP policies that they will
      not accept the announcements whose prefix length is longer than a
      specific threshold.

   Current Implementations.

      Most BGP implementations support this capability.

   Considerations.

      None.

2.2.5.  Ability to Cooperate in Outbound Route Filtering

   Capability.

      A device provides the capability to allow operators to configure
      whether "Outbound Route Filtering"/ORF [17] are accepted from or
      sent to other peer routers.

   Supported Practices

      "Outbound Route Filtering" defines a BGP mechanism to reduce the
      number of BGP updates between BGP peers.  It will conserve the
      resource in both sides of peers, since the BGP speaker will not



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      generate updates that will be filtered and the neighbor router
      will not process them as well.  A router with limited resource may
      need this feature to prevent overfull routes from peers.

   Current Implementations.

      ORF may be based on prefix, path attributes.  Currently, most
      implementations support prefix-based ORF.

   Considerations.

      None.

2.3.  Route Filtering of Interior Gateway Protocols

   This section describes route filtering as it may be applied to OSPF
   and IS-IS when used as the interior gateway protocol (Internal
   Gateway Protocol or "IGP") used within a routing domain.  Route
   filtering with RIP is TBD.


2.3.1.  Route Filtering Within an IGP Area

   A critical design principle of OSPF and IS-IS is that each router
   within an area has the same view of the topology, thereby allowing
   consistent routes to be computed by all routers within the area.  For
   this reason, all properly authenticated (if applicable) routing
   topology advertisements (Link State Advertisements or LSAs in OSPF,
   or Link State Packets or LSPs in IS-IS) are flooded unchanged
   throughout the area.  Route filtering within an OSPF or IS-IS area is
   therefore not appropriate.

2.3.2.  Route Filtering Between IGP Areas

   Capability.

      The device provides the capability to allow the network operator
      to configure route filters which restrict which routes (ie,
      address prefixes) are advertised into areas from outside of the
      area (ie, from other OSPF or IS-IS areas).

   Supported Practices.

      See Current Practices section 2.4.2.

   Current Implementations.

      TBD.




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   Considerations

      If filters are used which restrict the passing of routes between
      IGP areas, then this may result in some addresses being
      unreachable from some other areas within the same routing domain.

      It is normal when passing routes into the backbone area (area
      O.0.0.0 in OSPF, or the level 2 backbone in IS-IS) for routes to
      be summarized, in the sense that multiple more specific (longer)
      address prefixes that are reachable in an area may be summarized
      into a smaller number of less specific (shorter) address prefixes.
      This provides important scaling improvements, but is generally not
      primarily intended to aid in security and is therefore outside of
      the scope of this document.

2.4.  Route Filtering during Redistribution

   Capability.

      The device provides a means to filter routes when distributing
      them between routing protocols or between routing protocol
      processes running in the single device.

   Supported Practices.

      Route redistribution bridges between different route domains and
      improves the flexibility of routing system.  This allows for the
      transmission of reachable destinations learned in one protocol
      through another protocol.  However, without careful consideration
      it may lead to looping or black holes as well.

      Filters always needed when routes redistributing between IGP and
      BGP.  For example, it is unfeasible to inject all internet routes
      from BGP to IGPs, since IGPs are not able to deal with such a
      large number of routes.

   Current Implementations.

      Most implementations allow applying a filter based on a prefix
      list to control redistribution.

   Considerations

      TBD.







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3.  Route Authentication Capabilities

3.1.  Ability to configure an authentication mechanism

   Capabilities.

      The device has one or more methods to allow the routing protocol
      to be configured an authentication mechanism (authentication keys
      and authentication algorithms).

   Supported Practices.

      See Current Practices section 2.4.2.

   Current Implementations.

      RFC2385 [5] is deployed widely in BGP.  Other routing protocols,
      such as OSPF, adopt similar technology.

   Consideration.

      In most of current implementations, neither the authentication
      mechanism nor key can be negotiated.  An operator has to configure
      it manually, which will affect scalability.

      To the date of writing this draft, MD5 is the only cryptographic
      hash function used in route authentication.  However, recent
      research revealed weakness of MD5, which means stronger algorithms
      are necessary.

3.2.  Ability to support authentication key chains

   Capabilities.

      The device provides a key chain mechanism to update authentication
      keys of routing protocols.

   Supported Practices.

      Using a fixed authentication key is vulnerable to a compromise.  A
      key chain is a series of keys which will be used in configured
      time intervals.  A device can transit keys based on system time
      and configured key chain.  In this way, it reduces possibility of
      leakage of an authentication key.

   Current Implementations.





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      This mechanism could be implemented in most routing protocols.
      Different vendors provide this feature in different routing
      protocols, such as RIP, OSPF and BGP.

   Consideration.

      None.


4.  Ability to Damp Route Flap

   Capability.

      The device provides the capability to damp route flaps.

   Supported Practices.

      The function to damp route flaps may enhance the stability of
      routing system and minimize the influence of flapping.  It is
      useful to counter against some DoS attacks.

   Current Implementations.

      BGP RFD (Route Flap Damping) RFC2439 [6] defined the primary
      mechanism in BGP to mitigate the influence caused by flapping.
      Most of current BGP implementations support this capability.

      Other routing protocols may be vulnerable to route flaps as well.
      Some vendors introduce SPF (shortest path first) algorithm timers
      in OSPF to control parameters, such as the amount of minimal time
      between consecutive SPF calculations, which may be used to
      mitigate excessive resource exhaustion caused by link flaps.

   Consideration.

      MAO [19] described a flaw of current BGP RFD standard RFC2439,
      which shows that route flap damping could suppress relatively
      stable routes and affect routing convergence.

      Since none of vendors has corrected his BGP implementation,
      RIPE378 [20] proposes that, with the current implementations of
      BGP flap damping, the application of flap damping in ISP networks
      is not recommended.








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5.  Performance and Prioritization

5.1.  Ensure Resources for Management Functions

   Capability.

      This capability specifies that device implementations ensure that
      at least a certain minimum sufficient level of resources are
      available for management functions.  This may include resources at
      ingress to the device, on egress from the device, for internal
      transmission, and processing.  This may include at least protocols
      used for configuration, monitoring, configuration backup, logging,
      time synchronization, and authentication.

   Supported Practices.

      Certain attacks (and normal operation) can cause resource
      saturation such as link congestion, memory exhaustion or CPU
      overload.  In these cases it is important that resources be
      available for management functions in order to ensure that
      operators have the tools needed to recover from the attack.

   Current Implementations.

      How this is implemented depend upon the details of the device.
      There are a variety of ways that this may be ensured such as
      prioritizing management functions in comparison with other
      functions performed by the device, providing separate queues for
      management traffic, use of operating systems or other methods that
      partition resources between processes or functions, and so on.

   Consideration.

      Imagine a service provider with 1,000,000 DSL subscribers, most of
      whom have no firewall protection.  Imagine that a large portion of
      these subscribers machines were infected with a new worm that
      enabled them to be used in coordinated fashion as part of large
      denial of service attack that involved flooding.  It is entirely
      possible that such an attack could in some cases cause processor
      saturation or other internal resource saturation on routers
      causing the routers to become unmanageable.  A DoS attack against
      hosts could therefore become a DoS attack against the network.

      Guarantee of resources within an individual device is not a
      panacea.  Control packets may not make it across a saturated link.
      This requirement simply says that the device should ensure
      resources for management functions within its scope of control
      (e.g., ingress, egress, internal transit, processing).  To the



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      extent that this is done across an entire network, the overall
      effect will be to ensure that the network remains manageable.

5.2.  Ensure Resources for Routing Functions

   Capability.

      This capability specifies that a device implementation ensures at
      least a certain minimum sufficient level of resources are
      available for routing protocol functions.  This may include
      resources at ingress to the device, on egress from the device, for
      internal transmission, and processing.  This may include at least
      protocols used for routing protocol operation, including resources
      used for routing HELLO packets for BGP, IS-IS, and OSPF.

   Supported Practices.

      Certain attacks (and normal operation) can cause resource
      saturation such as link congestion, memory exhaustion or CPU
      overload.  In these cases it is important that resources be
      available for the operation of routing protocols in order to
      ensure that the network continues to operate (for example, that
      routes can be computed in order to allow management traffic to be
      delivered).  For many routing protocols the loss of HELLO packets
      can cause the protocol to drop adjacencies and/or to send out
      additional routing packets, potentially destabilizing the routing
      protocol and/or adding to whatever congestion may be causing the
      problem.

   Current Implementations.

      How this is implemented depend upon the details of the device.
      There are a variety of ways that this may be ensured such as
      prioritizing routing functions in comparison with other functions
      performed by the device, providing separate queues for routing
      traffic, use of operating systems or other methods that partition
      resources between processes or functions, and so on.

   Consideration.

      If routing HELLO packets are not prioritized, then it is possible
      during DoS attacks or during severe network congestion for routing
      protocols to drop HELLO packets, causing routing adjacencies to be
      lost.  This in turn can cause overall failure of a network.  A DoS
      attack against hosts can therefore become a DoS attack against the
      network.





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      Guaranteeing resources within routers is not a panacea.  Routing
      packets may not make it across a saturated link (thus for example
      it may also be desirable to prioritize routing packets for
      transmission across link layer devices such as Ethernet switches).
      This requirement simply says that the device should prioritize
      routing functions within its scope of control (e.g., ingress,
      egress, internal transit, processing).  To the extent that this is
      done across an entire network, the overall effect will be to
      ensure that the network continues to operate.

5.3.  Limit Resources used by IP Multicast

   Capability.

      This capability specifies that some mechanism(s) is provided to
      allow the control plane resources used by IP multicast, including
      processing and memory, to be limited to some level which is less
      than 100% of the total available processing and memory.  In some
      cases the maximum limit of resources used by multicast may be
      configurable.  Routers may also provide a mechanism(s) to allow
      the amount of link bandwidth consumed by IP multicast on any
      particular link to be limited to some level which is less than
      100% of total available bandwidth on that link.

   Supported Practices.

      IP multicast has characteristics which may potentially impact the
      availability of IP networks.  In particular, IP multicast requires
      that routers perform control plane processing and maintain state
      in response to data plane traffic.  Also, the use of multicast
      implies that a single packet input into the network can result in
      a large number of packets being delivered throughout the network.
      Also, it is possible in some situations for a multicast traffic to
      *both* enter a loop, and also be delivered to some destinations
      (implying that many copies of the same packet could be delivered).

   Current Implementations.

      TBD

   Consideration.

      If the amount of resources used by multicast are not limited, then
      it is possible during an attack for multicast to consume
      potentially as much as 100% of available memory, processing, or
      bandwidth resources, thereby causing network problems.





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6.  Security Considerations

   Security is the subject matter of this entire document.  This
   document lists device capabilities intended to improve the ability of
   the network to withstand security threats.  Operational Security
   Current Practices defines the threat model and practices, and lists
   justifications for each practice.


7.  Acknowledgements

   The authors gratefully acknowledge the contributions of Ron Bonica,
   Ted Seely, Pat Cain, George Jones, and Russ White etc for their
   contributed texts, useful comments and suggestions.


8.  References

8.1.  Normative References

   [1]   Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual
         environments", RFC 1195, December 1990.

   [2]   Chandrasekeran, R., Traina, P., and T. Li, "BGP Communities
         Attribute", RFC 1997, August 1996.

   [3]   Fraser, B., "Site Security Handbook", RFC 2196, September 1997.

   [4]   Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

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

   [6]   Villamizar, C., Chandra, R., and R. Govindan, "BGP Route Flap
         Damping", RFC 2439, November 1998.

   [7]   Malkin, G., "RIP Version 2", STD 56, RFC 2453, November 1998.

   [8]   Killalea, T., "Recommended Internet Service Provider Security
         Services and Procedures", BCP 46, RFC 3013, November 2000.

   [9]   Gill, V., Heasley, J., and D. Meyer, "The Generalized TTL
         Security Mechanism (GTSM)", RFC 3682, February 2004.

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

   [11]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended



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         Communities Attribute", RFC 4360, February 2006.

8.2.  Informative References

   [12]  Jones, G., "Framework for Operational Security Capabilities for
         IP Network  Infrastructure", draft-ietf-opsec-framework-03
         (work in progress), July 2006.

   [13]  Kaeo, M., "Operational Security Current Practices",
         draft-ietf-opsec-current-practices-07 (work in progress),
         August 2006.

   [14]  Morrow, C., "Filtering and Rate Limiting Capabilities for IP
         Network Infrastructure", draft-ietf-opsec-filter-caps-03 (work
         in progress), September 2006.

   [15]  Bonica, R. and S. Ahmed, "Network Management Access Security
         Capabilities", draft-ietf-opsec-nmasc-00 (work in progress),
         March 2006.

   [16]  Callon, R. and G. Jones, "Miscellaneous Capabilities for IP
         Network Infrastructure", draft-ietf-opsec-misc-cap-00 (work in
         progress), February 2006.

   [17]  Chen, E. and Y. Rekhter, "Outbound Route Filtering Capability
         for BGP-4", draft-ietf-idr-route-filter-15 (work in progress),
         July 2006.

   [18]  IANA, "INTERNET PROTOCOL V4 ADDRESS SPACE", 2006.

   [19]  Mao, Z., Govindan, R., Varghese, G., and R. Katz, "Route Flap
         Damping Exacerbates Internet Routing Convergence", 2002.

   [20]  RIPE, "Recommendations on Route-flap Damping", May 2006.


Authors' Addresses

   Zhao Ye
   Huawei Technologies
   No. 3, Xinxi Rd
   Shangdi Information Industry Base
   Haidian District, Beijing  100085
   P. R. China

   Email: ye.zhao_ietf@hotmail.com





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   Miao Fuyou
   Huawei Technologies
   No. 3, Xinxi Rd
   Shangdi Information Industry Base
   Haidian District, Beijing  100085
   P. R. China

   Phone: +86 10 8288 2008
   Email: miaofy@huawei.com


   Ross W. Callon
   Juniper Networks
   10 Technology Park Drive
   Shangdi Information Industry Base
   Westford, MA  01886
   USA

   Email: rcallon@juniper.net
































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Full Copyright Statement

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