[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09

None.                                                          C. Morrow
Internet-Draft                                        UUNET Technologies
Intended status: Best Current                                   G. Jones
Practice                                                    Port111 Labs
Expires: January 6, 2008                                       V. Manral
                                                             IP Infusion
                                                            July 5, 2007


 Filtering and Rate Limiting Capabilities for IP Network Infrastructure
                    draft-ietf-opsec-filter-caps-09

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on January 6, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).











Morrow, et al.           Expires January 6, 2008                [Page 1]

Internet-Draft           Filtering Capabilities                July 2007


Abstract

   [RFC4778] lists operator practices related to securing networks.
   This document lists filtering and rate limiting capabilities needed
   to support those practices.  Capabilities are limited to filtering
   and rate limiting packets as they enter or leave the device.  Route
   filters and service specific filters (e.g.  SNMP, telnet) are not
   addressed.

   Capabilities are defined without reference to specific technologies.
   This is done to leave room for deployment of new technologies that
   implement the capability.  Each capability cites the practices it
   supports.  Current implementations that support the capability are
   cited.  Special considerations are discussed as appropriate listing
   operational and resource constraints, limitations of current
   implementations, trade-offs, etc.



































Morrow, et al.           Expires January 6, 2008                [Page 2]

Internet-Draft           Filtering Capabilities                July 2007


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Threat Model . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Format . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Traffic Types, Rules and Filters . . . . . . . . . . . . . . .  6
   3.  Packet Selection Criteria  . . . . . . . . . . . . . . . . . .  8
     3.1.  Select Traffic on ANY Interface  . . . . . . . . . . . . .  8
     3.2.  Select Traffic on ALL Interfaces . . . . . . . . . . . . .  8
     3.3.  Select Traffic To the Device . . . . . . . . . . . . . . .  9
     3.4.  Select Transit Traffic . . . . . . . . . . . . . . . . . . 10
     3.5.  Select Inbound and/or Outbound . . . . . . . . . . . . . . 11
     3.6.  Select by Address, Protocol or Protocol Header Fields  . . 12
   4.  Actions  . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     4.1.  Specify Filter Actions . . . . . . . . . . . . . . . . . . 14
     4.2.  Specify Rate Limits  . . . . . . . . . . . . . . . . . . . 15
     4.3.  Specify Log Actions  . . . . . . . . . . . . . . . . . . . 15
     4.4.  Specify Log Granularity  . . . . . . . . . . . . . . . . . 16
     4.5.  Ability to Display Filter Counters . . . . . . . . . . . . 17
   5.  Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     5.1.  Filter Counters Displayed Per Application  . . . . . . . . 18
     5.2.  Ability to Reset Filter Counters . . . . . . . . . . . . . 18
     5.3.  Filter Hits are Counted  . . . . . . . . . . . . . . . . . 19
     5.4.  Filter Counters are Accurate . . . . . . . . . . . . . . . 20
   6.  Minimal Performance Degradation  . . . . . . . . . . . . . . . 21
   7.  Additional Operational Practices . . . . . . . . . . . . . . . 23
     7.1.  Profile Current Traffic  . . . . . . . . . . . . . . . . . 23
     7.2.  Block Malicious Packets  . . . . . . . . . . . . . . . . . 23
     7.3.  Limit Sources of Management  . . . . . . . . . . . . . . . 23
     7.4.  Respond to Incidents Based on Accurate Data  . . . . . . . 23
     7.5.  Implement Filters Where Necessary  . . . . . . . . . . . . 24
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 25
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     10.1. NormativeReferences  . . . . . . . . . . . . . . . . . . . 27
     10.2. Informational References . . . . . . . . . . . . . . . . . 27
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 28
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
   Intellectual Property and Copyright Statements . . . . . . . . . . 30











Morrow, et al.           Expires January 6, 2008                [Page 3]

Internet-Draft           Filtering Capabilities                July 2007


1.  Introduction

   This document is defined in the context of [RFC4778].  [RFC4778]
   defines the goals, motivation, scope, definitions, intended audience,
   threat model, potential attacks and gives justifications for each of
   the practices.  Many of the capabilities listed here refine or add to
   capabilities listed in [RFC3871].

   Also see [I-D.lewis-infrastructure-security] for a useful description
   of techniques for protecting infrastructure devices, including the
   use of filtering.

1.1.  Threat Model

   Threats in today's networked environment range from simple packet
   floods with overwhelming bandwidth toward a leaf network to subtle
   attacks aimed at subverting known vulnerabilities in existing
   applications.  The target of the attack may be the networking device
   or links inside the provider core.

   Networks must have the ability to mitigate attacks in order to limit
   these threats.  These mitigation steps could include routing updates,
   traffic filters, and routing filters.  It is possible that the
   mitigation steps might have to affect transit traffic as well as
   traffic destined to the device on which the mitigation steps are
   activated.

   The scope of the threat includes simply denying services to an
   individual customer on one side of the scale to exploiting a newly
   discovered protocol vulnerability which affects the entire provider
   core.  The obvious risk to the business requires mitigation
   capabilities which can span this range of threats.

   Also see [I-D.savola-rtgwg-backbone-attacks] for a list of attacks on
   backbone devices and counter measures.

1.2.  Definitions

   Terms are used as defined in [RFC2828].  The following definitions
   are intended to add clarification specific the context and threat
   model assumed in this document.

   Threat: An indication of impending danger or harm to the network or
   its parts.  This could be formed from the projected loss of revenue
   to the business.  Additionally, it could be formed from the increased
   cost to the business caused by the event.  The increased costs could
   come from the need for more interfaces, more bandwidth, more
   personnel to support the increased size or complexity, etc.



Morrow, et al.           Expires January 6, 2008                [Page 4]

Internet-Draft           Filtering Capabilities                July 2007


   Risk: The possibility of suffering harm or loss of network services
   due to a threat.

   Attack: Typically this is a form of flood of packets to or through a
   network.  This could also be a much smaller stream of packets created
   with the intent of exploiting a vulnerability in the infrastructure
   of the network.

   Asset: Either a customer, network device or network link.  Any of
   these could be assets from a business perspective.

1.3.  Format

   Each capability has the following subsections:

   o  Capability (what)

   o  Supported Practices (why)

   o  Current Implementations (how)

   o  Considerations (caveats, resource issues, protocol issues, etc.)

   The Capability section describes a feature to be supported by the
   device.  The Supported Practice section cites practices described in
   [RFC4778] that are supported by this capability.  The Current
   Implementation section is intended to give examples of
   implementations of the capability, citing technology and standards
   current at the time of writing.  It is expected that the choice of
   features to implement the capabilities will change over time.  The
   Considerations section lists operational and resource constraints,
   limitations of current implementations, trade-offs, etc.



















Morrow, et al.           Expires January 6, 2008                [Page 5]

Internet-Draft           Filtering Capabilities                July 2007


2.  Traffic Types, Rules and Filters

   This document describes capabilities that enable routers to filter
   transit, control and management traffic.

   Transit traffic is traffic that passes through a router, but does not
   otherwise impact the behavior of that router.  Routers filter transit
   traffic by applying "filters" to interfaces.  For any given
   interface, a filter can be applied to inbound traffic, outbound
   traffic or both.

   Control and management traffic either originates on the router or is
   destined for the router.  Routers filter control and management
   traffic by applying one or more filters to all of their interfaces,
   as an aggregate.  Aggregation permits the router to select any
   control packet, regardless of the interface upon which it arrives.
   So, the router can enforce a filter like the one that follows: "The
   router will accept only 1mbps of telnet traffic, regardless of the
   interface(s) upon which that traffic arrives."

   A "Filter" is a list of one or more rules that may be applied as a
   group.

   A rule consists of the following:

   o  selection criteria

   o  actions

   Selection criteria identify the packets that will be impacted by this
   rule.  Section 3 of this document describes selection criteria in
   detail.

   Actions define treatment that will be afforded to packets meeting the
   selection criteria.  An action can include the following:

   o  forwarding treatment

   o  logging treatment

   o  accounting treatment

   Forwarding behaviors include the following:

   o  accept

   o  accept but rate limit




Morrow, et al.           Expires January 6, 2008                [Page 6]

Internet-Draft           Filtering Capabilities                July 2007


   o  reject (discard and emit ICMP message)

   o  silently discard

   Section 4 describes actions in detail.  Section 5 describes counter
   actions in detail.













































Morrow, et al.           Expires January 6, 2008                [Page 7]

Internet-Draft           Filtering Capabilities                July 2007


3.  Packet Selection Criteria

   This section lists packet selection criteria that can be applied to
   both filtering and rate limiting.

3.1.  Select Traffic on ANY Interface

   Capability.

      The device provides a means to select IP packets on any individual
      interface implementing IP.

   Supported Practices.

      *  Security Practices for Device Management ([RFC4778], Section
         2.2.2)

      *  Security Practices for Data Path ([RFC4778], Section 2.3.2)

      *  Security Practices for Software Upgrades and Configuration
         Integrity/Validation ([RFC4778], Section 2.5.2)

      *  Data Plane Filtering ([RFC4778], Section 2.7.1)

      *  Management Plane Filtering ([RFC4778], Section 2.7.2)

      *  Profile Current Traffic (Section 7.1)

      *  Block Malicious Packets (Section 7.2)

   Current Implementations.

      Many devices currently implement access control lists or filters
      that allow filtering based on protocol and/or source/destination
      address and/or source/destination port and allow these filters to
      be applied to interfaces.

   Considerations.

      This allows implementation of policies such as "Allow no more than
      1Mb/s of ingress ICMP traffic on interface FOO".

3.2.  Select Traffic on ALL Interfaces








Morrow, et al.           Expires January 6, 2008                [Page 8]

Internet-Draft           Filtering Capabilities                July 2007


   Capability.

      The device provides a means to select IP packets on any interface
      implementing IP.  The mechanism should support a shorthand
      notation representing all interfaces on the router.

   Supported Practices.

      *  Security Practices for Device Management ([RFC4778], Section
         2.2.2)

      *  Security Practices for Data Path ([RFC4778], Section 2.3.2)

      *  Security Practices for Software Upgrades and Configuration
         Integrity/Validation ([RFC4778], Section 2.5.2)

      *  Data Plane Filtering ([RFC4778], Section 2.7.1)

      *  Management Plane Filtering ([RFC4778], Section 2.7.2)

      *  Profile Current Traffic (Section 7.1)

      *  Block Malicious Packets (Section 7.2)

   Current Implementations.

      Many devices currently implement access control lists or filters
      that allow filtering based on protocol and/or source/destination
      address and/or source/destination port and allow these filters to
      be applied to all interfaces.

   Considerations.

      This allows implementation of policies such as "Allow no more than
      1Mb/s of ingress ICMP traffic combined on all interfaces on the
      device".

3.3.  Select Traffic To the Device

   Capability.

      It is possible to select traffic that is addressed directly to the
      device via any of its interfaces - including loopback interfaces.
      The mechanism should support a shorthand notation representing all
      interfaces on that router.






Morrow, et al.           Expires January 6, 2008                [Page 9]

Internet-Draft           Filtering Capabilities                July 2007


   Supported Practices.

      *  Security Practices for Device Management ([RFC4778], Section
         2.2.2)

      *  Security Practices for Software Upgrades and Configuration
         Integrity/Validation ([RFC4778], Section 2.5.2)

      *  Management Plane Filtering ([RFC4778], Section 2.7.2)

   Current Implementations.

      Many devices currently implement access control lists or filters
      that allow filtering based on protocol and/or source/destination
      address and/or source/destination port and allow these filters to
      be applied to services offered by the device.

      Examples of this might include filters that permit only BGP from
      peers and SNMP and SSH from an authorized management segment and
      directed to the device itself, while dropping all other traffic
      addressed to the device.

   Considerations.

      None.

3.4.  Select Transit Traffic

   Capability.

      It is possible to select traffic that will transit the device via
      any of its interfaces.  The mechanism should support a shorthand
      notation representing traffic not addressed to any of the routers
      interfaces.

   Supported Practices.

      *  Security Practices for Data Path ([RFC4778], Section 2.3.2)

      *  Data Plane Filtering ([RFC4778], Section 2.7.1)

   Current Implementations.

      Many devices currently implement access control lists or filters
      that allow filtering based on protocol and/or source/destination
      address and/or source/destination port and allow these filters to
      be applied to the interfaces on the device in order to protect
      assets attached to the network.



Morrow, et al.           Expires January 6, 2008               [Page 10]

Internet-Draft           Filtering Capabilities                July 2007


      Examples of this may include filtering all traffic save SMTP
      (tcp/25) destined to a mail server.  A common use of this today
      would also be denying all traffic to a destination which has been
      determined to be hostile.

   Considerations.

      This allows the operator to apply filters that protect the
      networks and assets surrounding the device from attacks and
      unauthorized access.

3.5.  Select Inbound and/or Outbound

   Capability.

      It is possible to select both incoming and outgoing traffic on any
      interface.

   Supported Practices.

      *  Security Practices for Device Management ([RFC4778], Section
         2.2.2)

      *  Security Practices for Data Path ([RFC4778], Section 2.3.2)

      *  Security Practices for Software Upgrades and Configuration
         Integrity/Validation ([RFC4778], Section 2.5.2)

      *  Data Plane Filtering ([RFC4778], Section 2.7.1)

      *  Management Plane Filtering ([RFC4778], Section 2.7.2)

   Current Implementations.

      It might be desirable on a border router, for example, to apply an
      egress filter on the interface that connects a site to its
      external ISP to drop outbound traffic that does not have a valid
      internal source address.  Inbound, it might be desirable to apply
      a filter that blocks all traffic from a site that is known to
      forward or originate large amounts of junk mail.

   Considerations.

      This allows flexibility in applying filters at the place that
      makes the most sense.  It allows traffic judged to be invalid or
      malicious to be dropped as close to the source as possible with
      the least impact on other traffic transiting the interface(s) in
      question.



Morrow, et al.           Expires January 6, 2008               [Page 11]

Internet-Draft           Filtering Capabilities                July 2007


3.6.  Select by Address, Protocol or Protocol Header Fields

   Capability.

      The device supports selection based on:

      *  source IP address

      *  destination IP address

      *  source port

      *  destination port

      *  protocol ID

      *  TCP flags (SYN, ACK, RST)

      *  DiffServ Code Point (DSCP)

      *  the value(s) of any portion of the protocol headers for IP,
         ICMP, UDP and TCP by specifying fields by name (e.g., "protocol
         = ICMP") rather than bit- offset/length/numeric value (e.g.,
         72:8 = 1).

      *  Arbitrary header-based selection (possibly using bit-offset/
         length/value) of all other protocols.

   Supported Practices.

      *  Security Practices for Device Management ([RFC4778], Section
         2.2.2)

      *  Security Practices for Data Path ([RFC4778], Section 2.3.2)

      *  Security Practices for Software Upgrades and Configuration
         Integrity/Validation ([RFC4778], Section 2.5.2)

      *  Data Plane Filtering ([RFC4778], Section 2.7.1)

      *  Management Plane Filtering ([RFC4778], Section 2.7.2)

   Current Implementations.

      This capability implies that it is possible to filter based on TCP
      or UDP port numbers, TCP flags such as SYN, ACK and RST bits, and
      ICMP type and code fields.  One common example is to reject
      "inbound" TCP connection attempts (TCP, SYN bit set+ACK bit clear



Morrow, et al.           Expires January 6, 2008               [Page 12]

Internet-Draft           Filtering Capabilities                July 2007


      or SYN bit set+ACK,FIN and RST bits clear).  Another common
      example is the ability to control what services are allowed in/out
      of a network.  It may be desirable to only allow inbound
      connections on port 80 (HTTP) and 443 (HTTPS) to a network hosting
      web servers.

      Some denial of service attacks are based on the ability to flood
      the victim with ICMP traffic.  One quick way to mitigate the
      effects of such attacks is to drop all ICMP traffic headed toward
      the victim.  It should be noted ([RFC2923]) that one possibly
      negative implication of filtering all ICMP traffic towards a
      victim is that legitimate functions which rely upon successful
      delivery of ICMP messages to the victim (e.g., ICMP unreachables,
      Type-3 messages) will not be received by the victim.

      Supporting arbitrary offset/length/value selection allows
      filtering of unknown (possibly new) protocols, e.g. filtering RTP
      even when the device itself does not support RTP.

   Considerations.

      The capability to filter on addresses, address blocks and
      protocols is a fundamental tool for establishing boundaries
      between different networks.

      Being able to filter on portions of the header is necessary to
      allow implementation of policy, secure operations, and support
      incident response.























Morrow, et al.           Expires January 6, 2008               [Page 13]

Internet-Draft           Filtering Capabilities                July 2007


4.  Actions

4.1.  Specify Filter Actions

   Capability.

      The device provides a mechanism through which operators can
      specify a forwarding action to be taken when the selection
      criteria is met.  Forwarding actions include the following:

      *  permit (allow the datagram)

      *  discard (silently discard the datagram)

      *  reject (discard the datagram and send a notification to its
         originator)

   Supported Practices.

      *  Data Origin Authentication ([RFC4778], Section 2.3.3)

   Current Implementations.

      Assume that your management devices for deployed networking
      devices live on several subnets, use several protocols, and are
      controlled by several different parts of your organization.  There
      might exist a reason to have disparate policies for access to the
      devices from these parts of the organization.

      Actions such as "permit", "reject", and "drop" are essential in
      defining the security policy for the services offered by the
      network devices.

   Considerations.

      While silently dropping traffic without sending notification may
      be the correct action in security terms, consideration should be
      given to operational implications.  See [RFC3360] for
      consideration of potential problems caused by sending
      inappropriate TCP Resets, for instance.

      Also note that it might be possible for an attacker to effect a
      denial of service attack by causing too many rejection
      notifications to be sent (e.g. via syslog messages).  For this
      reason it might be desirable to rate-limit notifications.






Morrow, et al.           Expires January 6, 2008               [Page 14]

Internet-Draft           Filtering Capabilities                July 2007


4.2.  Specify Rate Limits

   Capability.

      The device provides a mechanism to allow the specification of the
      action to be taken when a rate limiting filter matches.  The
      actions include "transmit" (permit the traffic because it's below
      the specified limit), "limit" (limit traffic because it exceeds
      the specified limit).  Limits should be applicable by both bits
      per second and packets per time-frame (possible time-frames might
      include second, minute, hour).  Limits should able to be placed in
      both inbound and outbound directions.

   Supported Practices.

      *  Denial of Service Tracking/Tracing with Rate Limiting
         ([RFC4778], Section 2.8.4)

   Current Implementations.

      Assume that your management devices for deployed networking
      devices live on several subnets, use several protocols, and are
      controlled by several different parts of your organization.  There
      might exist a reason to have disparate policies for access to the
      devices from these parts of the organization with respect to
      priority access to these services.  Rate Limits may be used to
      enforce these prioritizations.

   Considerations.

      This capability allows a filter to be used to rate limit a portion
      of traffic through or to a device.  It maybe desirable to limit
      SNMP (UDP/161) traffic to a device, but not deny it completely.
      Similarly, one might want to implement ICMP filters toward an
      external network instead of discarding all ICMP traffic.

      While silently dropping traffic without sending notification may
      be the correct action in security terms, consideration should be
      given to operational implications.  See [RFC3360] for
      consideration of potential problems caused by sending
      inappropriate TCP Resets, for instance.

4.3.  Specify Log Actions








Morrow, et al.           Expires January 6, 2008               [Page 15]

Internet-Draft           Filtering Capabilities                July 2007


   Capability.

      It is possible to log all filter actions.  The logging capability
      is able to capture at least the following data:

      *  permit/reject/drop status

      *  source and destination IP address

      *  source and destination ports (if applicable to the protocol)

      *  which network element received or was sending the packet
         (interface, MAC address or other layer 2 information that
         identifies the previous hop source of the packet).

   Supported Practices.

      *  Logging Security Practices([RFC4778], Section 2.6.2)

   Current Implementations.

      Actions such as "permit", "reject", "drop" are essential in
      defining the security policy for the services offered by the
      network devices.  Auditing the frequency, sources and destinations
      of these attempts is essential for tracking ongoing issues today.

   Considerations.

      Logging can be burdensome to the network device, at no time should
      logging cause performance degradation to the device or services
      offered on the device.

      Also note logging itself can be rate limited so as to not cause
      performance degradation of the device or the network(in case of
      syslog or other similar network logging mechanism.

4.4.  Specify Log Granularity

   Capability.

      The device provides a mechanism through which operators can
      enable/disable logging on a per rule basis.

   Supported Practices.

      *  Logging Security Practices([RFC4778], Section 2.6.2)





Morrow, et al.           Expires January 6, 2008               [Page 16]

Internet-Draft           Filtering Capabilities                July 2007


   Current Implementations.

      If a filter is defined that has several rules, and one of the
      rules specifies an action that denies telnet (tcp/23) connections,
      then it should be possible to specify that only matches on the
      rule that denies telnet should generate a log message.

   Considerations.

      The ability to tune the granularity of logging allows the operator
      to log the information that is desired and only the information
      that is desired.  Without this capability, it is possible that
      extra data (or none at all) would be logged, making it more
      difficult to find relevant information.

4.5.  Ability to Display Filter Counters

   Capability.

      The device provides a mechanism to display filter counters.

   Supported Practices.

      *  Profile Current Traffic (Section 7.1)

      *  Respond to Incidents Based on Accurate Data (Section 7.4)

   Current Implementations.

      Assume there is a router with four interfaces.  One is an up-link
      to an ISP providing routes to the Internet.  The other three
      connect to separate internal networks.  Assume that a host on one
      of the internal networks has been compromised by a hacker and is
      sending traffic with bogus source addresses.  In such a situation,
      it might be desirable to apply ingress filters to each of the
      internal interfaces.  Once the filters are in place, the counters
      can be examined to determine the source (inbound interface) of the
      bogus packets.

   Considerations.

      None.









Morrow, et al.           Expires January 6, 2008               [Page 17]

Internet-Draft           Filtering Capabilities                July 2007


5.  Counters

5.1.  Filter Counters Displayed Per Application

   Capability.

      If it is possible for a filter to be applied more than once at the
      same time, then the device provides a mechanism to display filter
      counters per filter application.

   Supported Practices.

      *  Profile Current Traffic (Section 7.1)

      *  Respond to Incidents Based on Accurate Data (Section 7.4)

   Current Implementations.

      One way to implement this capability would be to have the counter
      display mechanism show the interface (or other entity) to which
      the filter has been applied, along with the name (or other
      designator) for the filter.  For example if a filter named
      "desktop_outbound" is applied to two different interfaces, say,
      "ethernet0" and "ethernet1", the display should indicate something
      like "matches of filter 'desktop_outbound' on ethernet0 ..." and
      "matches of filter 'desktop_outbound' on ethernet1 ..."

   Considerations.

      It may make sense to apply the same filter definition
      simultaneously more than one time (to different interfaces, etc.).
      If so, it would be much more useful to know which instance of a
      filter is matching than to know that some instance was matching
      somewhere.

5.2.  Ability to Reset Filter Counters

   Capability.

      It is possible to reset individual counters to zero.

   Supported Practices.

      *  Profile Current Traffic (Section 7.1)

      *  Respond to Incidents Based on Accurate Data (Section 7.4)





Morrow, et al.           Expires January 6, 2008               [Page 18]

Internet-Draft           Filtering Capabilities                July 2007


   Current Implementations.

      For the purposes of this capability it would be acceptable for the
      system to maintain two counters: an "absolute counter", C[now],
      and a "reset" counter, C[reset].  The absolute counter would
      maintain counts that increase monotonically until they wrap or
      overflow the counter.  The reset counter would receive a copy of
      the current value of the absolute counter when the reset function
      was issued for that counter.  Functions that display or retrieve
      the counter could then display the delta (C[now] - C[reset]).

   Considerations.

      Assume that filter counters are being used to detect internal
      hosts that are infected with a new worm.  Once it is believed that
      all infected hosts have been cleaned up and the worm removed, the
      next step would be to verify that.  One way of doing so would be
      to reset the filter counters to zero and see if traffic indicative
      of the worm has ceased.

5.3.  Filter Hits are Counted

   Capability.

      The device supplies a facility for counting all filter matches.

   Supported Practices.

      *  Profile Current Traffic (Section 7.1)

      *  Respond to Incidents Based on Accurate Data (Section 7.4)

   Current Implementations.

      Assume, for example, that a ISP network implements anti-spoofing
      egress filters (see [RFC2827]) on interfaces of its edge routers
      that support single-homed stub networks.  Counters could enable
      the ISP to detect cases where large numbers of spoofed packets are
      being sent.  This may indicate that the customer is performing
      potentially malicious actions (possibly in violation of the ISPs
      Acceptable Use Policy), or that system(s) on the customers network
      have been "owned" by hackers and are being (mis)used to launch
      attacks.

   Considerations.

      None.




Morrow, et al.           Expires January 6, 2008               [Page 19]

Internet-Draft           Filtering Capabilities                July 2007


5.4.  Filter Counters are Accurate

   Capability.

      Filter counters are accurate.  They reflect the actual number of
      matching packets since the last counter reset.  Filter counters
      are be capable of holding up to 2^32 - 1 values without
      overflowing and should be capable of holding up to 2^64 - 1
      values.

   Supported Practices.

      *  Respond to Incidents Based on Accurate Data (Section 7.4)

   Current Implementations.

      If N packets matching a filter are sent to/through a device, then
      the counter should show N matches.

   Considerations.

      None.





























Morrow, et al.           Expires January 6, 2008               [Page 20]

Internet-Draft           Filtering Capabilities                July 2007


6.  Minimal Performance Degradation

   Capability.

      The device provides a means to filter packets without significant
      performance degradation.  This specifically applies to stateless
      packet filtering operating on layer 3 (IP) and layer 4 (TCP or
      UDP) headers, as well as normal packet forwarding information such
      as incoming and outgoing interfaces.

      The device is able to apply stateless packet filters on ALL
      interfaces (up to the total number of interfaces attached to the
      device) simultaneously and with multiple filters per interface
      (e.g., inbound and outbound).

   Supported Practices.

      *  Implement Filters Where Necessary (Section 7.5)

   Current Implementations.

      Another way of stating the capability is that filter performance
      should not be the limiting factor in device throughput.  If a
      device is capable of forwarding 30Mb/sec without filtering, then
      it should be able to forward the same amount with filtering in
      place.

   Considerations.

      The definition of "significant" is subjective.  At one end of the
      spectrum it might mean "the application of filters may cause the
      box to crash".  At the other end would be a throughput loss of
      less than one percent with tens of thousands of filters applied.
      The level of performance degradation that is acceptable will have
      to be determined by the operator.

      Repeatable test data showing filter performance impact would be
      very useful in evaluating this capability.  Tests should include
      such information as packet size, packet rate, number of interfaces
      tested (source/destination), types of interfaces, routing table
      size, routing protocols in use, frequency of routing updates, etc.
      This capability does not address stateful filtering, filtering
      above layer 4 headers or other more advanced types of filtering
      that may be important in certain operational environments.
      Finally, if key infrastructure devices crash or experience severe
      performance degradation when filtering under heavy load, or even
      have the reputation of doing so, it is likely that security
      personnel will be forbidden, by policy, from using filtering in



Morrow, et al.           Expires January 6, 2008               [Page 21]

Internet-Draft           Filtering Capabilities                July 2007


      ways that would otherwise be appropriate for fear that it might
      cause unnecessary service disruption.

















































Morrow, et al.           Expires January 6, 2008               [Page 22]

Internet-Draft           Filtering Capabilities                July 2007


7.  Additional Operational Practices

   This section describes practices not covered in [RFC4778].  They are
   included here to provide justification for capabilities that
   reference them.

7.1.  Profile Current Traffic

   This capability allows a network operator to monitor traffic across
   an active interface in the network at a minimal level.  This helps to
   determine probable cause for interface or network problems.

   The ability to separate and distinguish traffic at a layer-3 or
   layer-4 level allows the operator to characterize beyond simple
   interface counters the traffic in question.  This is critical because
   often the operator has no tools available for protocol analysis aside
   from interface filters.

7.2.  Block Malicious Packets

   Blocking or limiting traffic deemed to be malicious is a key
   component of application of any security policy's implementation.
   Clearly it is critical to be able to implement a security policy on a
   network.

   Malicious packets could potentially be defined by any part of,
   atleast, the layer-3 or layer-4 headers of the IP packet.  The
   ability to classify or select traffic based on these criteria and
   take some action based on that classification is critical to
   operations of a network.

7.3.  Limit Sources of Management

   Management of a network should be limited to only trusted hosts.
   This implies that the network elements will be able to limit access
   to management functions to these trusted hosts.

   Currently operators will limit access to the management functions on
   a network device to only the hosts that are trusted to perform that
   function.  This allows separation of critical functions and
   protection of those functions on the network devices.

7.4.  Respond to Incidents Based on Accurate Data

   Accurate counting of filter matches is important because it shows the
   frequency of attempts to violate policy.  Inaccurate data can not be
   relied on as the basis for action.  Under-reported data can conceal
   the magnitude of a problem.  This enables resources to be focused on



Morrow, et al.           Expires January 6, 2008               [Page 23]

Internet-Draft           Filtering Capabilities                July 2007


   areas of greatest need.

7.5.  Implement Filters Where Necessary

   This enables the implementation of filters on whichever services are
   necessary.  To the extent that filtering causes degradation, it may
   not be possible to apply filters that implement the appropriate
   policies.











































Morrow, et al.           Expires January 6, 2008               [Page 24]

Internet-Draft           Filtering Capabilities                July 2007


8.  Security Considerations

   General
      Security is the subject matter of this entire memo.  The
      capabilities listed cite practices in [RFC4778] that they are
      intended to support.  [RFC4778] defines the threat model,
      practices and lists justifications for each practice.












































Morrow, et al.           Expires January 6, 2008               [Page 25]

Internet-Draft           Filtering Capabilities                July 2007


9.  IANA Considerations

   This document has no actions for IANA.
















































Morrow, et al.           Expires January 6, 2008               [Page 26]

Internet-Draft           Filtering Capabilities                July 2007


10.  References

10.1.  NormativeReferences

   [RFC2828]  Shirey, R., "Internet Security Glossary", RFC 2828,
              May 2000.

10.2.  Informational References

   [I-D.lewis-infrastructure-security]
              Lewis, D., "Service Provider Infrastructure Security",
              draft-lewis-infrastructure-security-00 (work in progress),
              June 2006.

   [I-D.savola-rtgwg-backbone-attacks]
              Savola, P., "Backbone Infrastructure Attacks and
              Protections", draft-savola-rtgwg-backbone-attacks-03 (work
              in progress), January 2007.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.

   [RFC2923]  Lahey, K., "TCP Problems with Path MTU Discovery",
              RFC 2923, September 2000.

   [RFC3360]  Floyd, S., "Inappropriate TCP Resets Considered Harmful",
              BCP 60, RFC 3360, August 2002.

   [RFC3871]  Jones, G., "Operational Security Requirements for Large
              Internet Service Provider (ISP) IP Network
              Infrastructure", RFC 3871, September 2004.

   [RFC4778]  Kaeo, M., "Operational Security Current Practices in
              Internet Service Provider Environments", RFC 4778,
              January 2007.















Morrow, et al.           Expires January 6, 2008               [Page 27]

Internet-Draft           Filtering Capabilities                July 2007


Appendix A.  Acknowledgments

   The authors gratefully acknowledge the contributions of:

   o  Merike Kaeo for help aligning these capabilities with supported
      practices













































Morrow, et al.           Expires January 6, 2008               [Page 28]

Internet-Draft           Filtering Capabilities                July 2007


Authors' Addresses

   Christopher L. Morrow
   UUNET Technologies
   21830 UUNet Way
   Ashburn, Virginia  21047
   U.S.A.

   Phone: +1 703 886 3823
   Email: chris@uu.net


   George M. Jones
   Port111 Labs

   Phone: +1 703 488 9740
   Email: gmj3871@pobox.com


   Vishwas Manral
   IP Infusion
   Ground Floor, 5th Cross Road, Off 8th Main Road
   Bangalore,   52
   India

   Phone: +91-80-4113-1268
   Email: vishwas@ipinfusion.com
























Morrow, et al.           Expires January 6, 2008               [Page 29]

Internet-Draft           Filtering Capabilities                July 2007


Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





Morrow, et al.           Expires January 6, 2008               [Page 30]


Html markup produced by rfcmarkup 1.111, available from https://tools.ietf.org/tools/rfcmarkup/