draft-ietf-opsec-filter-caps-02.txt   draft-ietf-opsec-filter-caps-03.txt 
None. C. Morrow None. C. Morrow
Internet-Draft UUNET Technologies Internet-Draft UUNET Technologies
Expires: September 25, 2006 G. Jones Intended status: Informational G. Jones
The MITRE Corporation Expires: March 5, 2007 The MITRE Corporation
March 24, 2006 V. Manral
IP Infusion
September 1, 2006
Filtering and Rate Limiting Capabilities for IP Network Infrastructure Filtering and Rate Limiting Capabilities for IP Network Infrastructure
draft-ietf-opsec-filter-caps-02 draft-ietf-opsec-filter-caps-03
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
[I-D.ietf-opsec-current-practices] lists operator practices related [I-D.ietf-opsec-current-practices] lists operator practices related
to securing networks. This document lists filtering and rate to securing networks. This document lists filtering and rate
limiting capabilities needed to support those practices. limiting capabilities needed to support those practices.
Capabilities are limited to filtering and rate limiting packets as Capabilities are limited to filtering and rate limiting packets as
they enter or leave the device. Route filters and service specific they enter or leave the device. Route filters and service specific
filters (e.g. SNMP, telnet) are not addressed. filters (e.g. SNMP, telnet) are not addressed.
Capabilities are defined without reference to specific technologies. Capabilities are defined without reference to specific technologies.
This is done to leave room for deployment of new technologies that This is done to leave room for deployment of new technologies that
implement the capability. Each capability cites the practices it implement the capability. Each capability cites the practices it
supports. Current implementations that support the capability are supports. Current implementations that support the capability are
cited. Special considerations are discussed as appropriate listing cited. Special considerations are discussed as appropriate listing
operational and resource constraints, limitations of current operational and resource constraints, limitations of current
implementations, tradeoffs, etc. implementations, trade-offs, etc.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Packet Selction for Managemnet and Data Plane Controls . . . . 6 2. Packet Selection for Management and Data Plane Controls . . . 6
3. Packet Selection Criteria . . . . . . . . . . . . . . . . . . 7 3. Packet Selection Criteria . . . . . . . . . . . . . . . . . . 7
3.1. Select Traffic on All Interfaces . . . . . . . . . . . . . 7 3.1. Select Traffic on All Interfaces . . . . . . . . . . . . . 7
3.2. Select Traffic To the Device . . . . . . . . . . . . . . . 7 3.2. Select Traffic To the Device . . . . . . . . . . . . . . . 7
3.3. Select Transit Traffic . . . . . . . . . . . . . . . . . . 8 3.3. Select Transit Traffic . . . . . . . . . . . . . . . . . . 8
3.4. Select Inbound and/or Outbound . . . . . . . . . . . . . . 8 3.4. Select Inbound and/or Outbound . . . . . . . . . . . . . . 9
3.5. Select by Protocols . . . . . . . . . . . . . . . . . . . 9 3.5. Select by Protocols . . . . . . . . . . . . . . . . . . . 9
3.6. Select by Addresses . . . . . . . . . . . . . . . . . . . 9 3.6. Select by Addresses . . . . . . . . . . . . . . . . . . . 10
3.7. Select by Protocol Header Fields . . . . . . . . . . . . . 10 3.7. Select by Protocol Header Fields . . . . . . . . . . . . . 10
4. Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4. Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Specify Filter Actions . . . . . . . . . . . . . . . . . . 12 4.1. Specify Filter Actions . . . . . . . . . . . . . . . . . . 12
4.2. Specify Rate Limits . . . . . . . . . . . . . . . . . . . 12 4.2. Specify Rate Limits . . . . . . . . . . . . . . . . . . . 13
4.3. Specify Log Actions . . . . . . . . . . . . . . . . . . . 13 4.3. Specify Log Actions . . . . . . . . . . . . . . . . . . . 13
4.4. Specify Log Granularity . . . . . . . . . . . . . . . . . 14 4.4. Specify Log Granularity . . . . . . . . . . . . . . . . . 14
4.5. Ability to Display Filter Counters . . . . . . . . . . . . 14 4.5. Ability to Display Filter Counters . . . . . . . . . . . . 15
5. Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5. Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1. Ability to Display Filter Counters per Filter 5.1. Filter Counters Displayed Per Application . . . . . . . . 16
Application . . . . . . . . . . . . . . . . . . . . . . . 16
5.2. Ability to Reset Filter Counters . . . . . . . . . . . . . 16 5.2. Ability to Reset Filter Counters . . . . . . . . . . . . . 16
5.3. Filter Hits are Accurately Counted . . . . . . . . . . . . 17 5.3. Filter Hits are Counted . . . . . . . . . . . . . . . . . 17
5.4. Filter Counters are Accurate . . . . . . . . . . . . . . . 17 5.4. Filter Counters are Accurate . . . . . . . . . . . . . . . 18
6. Minimal Performance Degradation . . . . . . . . . . . . . . . 19 6. Minimal Performance Degradation . . . . . . . . . . . . . . . 19
7. Additional Operational Practices . . . . . . . . . . . . . . . 21 7. Additional Operational Practices . . . . . . . . . . . . . . . 21
7.1. Profile Current Traffic . . . . . . . . . . . . . . . . . 21 7.1. Profile Current Traffic . . . . . . . . . . . . . . . . . 21
7.2. Block Malicious Packets . . . . . . . . . . . . . . . . . 21 7.2. Block Malicious Packets . . . . . . . . . . . . . . . . . 21
7.3. Limit Sources of Management . . . . . . . . . . . . . . . 21 7.3. Limit Sources of Management . . . . . . . . . . . . . . . 21
7.4. Select Traffic To the Device . . . . . . . . . . . . . . . 21 7.4. Respond to Incidents Based on Accurate Data . . . . . . . 21
7.5. Select Transit Traffic . . . . . . . . . . . . . . . . . . 22 7.5. Implement Filters Where Necessary . . . . . . . . . . . . 22
7.6. Select Traffic Inbound and/or Outbound . . . . . . . . . . 22 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
7.7. Select Traffic by Protocol . . . . . . . . . . . . . . . . 22
7.8. Select Traffic by Addresses . . . . . . . . . . . . . . . 22
7.9. Select Traffic by Protocol Header Field . . . . . . . . . 22
7.10. Specify Filter Actions . . . . . . . . . . . . . . . . . . 22
7.11. Specify Rate Limits . . . . . . . . . . . . . . . . . . . 22
7.12. Specify Log Actions . . . . . . . . . . . . . . . . . . . 23
7.13. Log Granularity . . . . . . . . . . . . . . . . . . . . . 23
7.14. Display Filter Counters . . . . . . . . . . . . . . . . . 23
7.15. Counters . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.16. Ability to Reset Filter Counters . . . . . . . . . . . . . 23
7.17. Filter Hits are Accurately Counted . . . . . . . . . . . . 23
7.18. Filter Hits are Accurate . . . . . . . . . . . . . . . . . 23
7.19. Minimal Performance Degredation . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. Non-normative References . . . . . . . . . . . . . . . . . . . 24 9. Non-normative References . . . . . . . . . . . . . . . . . . . 24
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 25 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
Intellectual Property and Copyright Statements . . . . . . . . . . 27 Intellectual Property and Copyright Statements . . . . . . . . . . 27
1. Introduction 1. Introduction
This document is defined in the context of [I-D.ietf-opsec-current- This document is defined in the context of
practices]. [I-D.ietf-opsec-current-practices] defines the goals, [I-D.ietf-opsec-current-practices].
motivation, scope, definitions, intended audience,threat model, [I-D.ietf-opsec-current-practices] defines the goals, motivation,
potential attacks and give justifications for each of the practices. scope, definitions, intended audience, threat model, potential
Many of the capabilities listed here refine or add to capabilities attacks and give justifications for each of the practices. Many of
listed in [RFC3871]. the capabilities listed here refine or add to capabilities listed in
[RFC3871].
Also see [I-D.lewis-infrastructure-security] for a useful description Also see [I-D.lewis-infrastructure-security] for a useful description
of techniques for protecting infrastructure devices, including the of techniques for protecting infrastructure devices, including the
use of filtering. use of filtering.
1.1. Threat Model 1.1. Threat Model
Threats in today's networked environment range from simple packet Threats in today's networked environment range from simple packet
floods with overwhelming bandwidth toward a leaf network to subtle floods with overwhelming bandwidth toward a leaf network to subtle
attacks aimed at subverting known vulnerabilities in existing attacks aimed at subverting known vulnerabilities in existing
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o Considerations (caveats, resource issues, protocol issues, etc.) o Considerations (caveats, resource issues, protocol issues, etc.)
The Capability section describes a feature to be supported by the The Capability section describes a feature to be supported by the
device. The Supported Practice section cites practices described in device. The Supported Practice section cites practices described in
[I-D.ietf-opsec-current-practices] that are supported by this [I-D.ietf-opsec-current-practices] that are supported by this
capability. The Current Implementation section is intended to give capability. The Current Implementation section is intended to give
examples of implementations of the capability, citing technology and examples of implementations of the capability, citing technology and
standards current at the time of writing. It is expected that the standards current at the time of writing. It is expected that the
choice of features to implement the capabilities will change over choice of features to implement the capabilities will change over
time. The Considerations section lists operational and resource time. The Considerations section lists operational and resource
constraints, limitations of current implementations, tradeoffs, etc. constraints, limitations of current implementations, trade-offs, etc.
2. Packet Selction for Managemnet and Data Plane Controls 2. Packet Selection for Management and Data Plane Controls
In this document section Section 3 describes a number of criteria for In this document Section 3 describes a number of criteria for
performing packet selection. It is assumed in this document that performing packet selection. It is assumed in this document that
o all of these criteria can be used to select packets for both o all of these criteria can be used to select packets for both
filtering and rate limiting packets, filtering and rate limiting packets,
o management plane controls can be implemented by applying these o management plane controls can be implemented by applying these
criteria to filter/rate limit traffic destined for the device criteria to filter/rate limit traffic destined for the device
itself, itself,
o data plane controls can be implemented by applying these criteria o data plane controls can be implemented by applying these criteria
to filter/rate limit traffic destined through the device to filter/rate limit traffic destined through the device
o multiple packet selection criteria can be used to select a single
set of packets for filtering action
3. Packet Selection Criteria 3. Packet Selection Criteria
This section lists packet selection criteria that can be applied to This section lists packet selection criteria that can be applied to
both filtering and rate limiting. both filtering and rate limiting.
3.1. Select Traffic on All Interfaces 3.1. Select Traffic on All Interfaces
Capability. Capability.
The device provides a means to filter IP packets on any interface The device provides a means to filter IP packets on any interface
implementing IP. implementing IP.
Supported Practices. Supported Practices.
* Data Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.1)
* Management Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.2)
* Profile Current Traffic (Section 7.1) * Profile Current Traffic (Section 7.1)
* Block Malicious Packets (Section 7.2) * Block Malicious Packets (Section 7.2)
* Limit Sources of Management ([I-D.ietf-opsec-current-
practices], Section 2.8.2)
Current Implementations. Current Implementations.
Many devices currently implement access control lists or filters Many devices currently implement access control lists or filters
that allow filtering based on protocol and/or source/destination that allow filtering based on protocol and/or source/destination
address and or source/destination port and allow these filters to address and or source/destination port and allow these filters to
be applied to interfaces. be applied to interfaces.
Considerations. Considerations.
None. None.
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3.2. Select Traffic To the Device 3.2. Select Traffic To the Device
Capability. Capability.
It is possible to apply the filtering mechanism to traffic that is It is possible to apply the filtering mechanism to traffic that is
addressed directly to the device via any of its interfaces - addressed directly to the device via any of its interfaces -
including loopback interfaces. including loopback interfaces.
Supported Practices. Supported Practices.
* Select Traffic To the Device (Section 7.4) * Management Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.2)
Current Implementations. Current Implementations.
Many devices currently implement access control lists or filters Many devices currently implement access control lists or filters
that allow filtering based on protocol and/or source/destination that allow filtering based on protocol and/or source/destination
address and or source/destination port and allow these filters to address and or source/destination port and allow these filters to
be applied to services offered by the device. be applied to services offered by the device.
Examples of this might include filters that permit only BGP from Examples of this might include filters that permit only BGP from
peers and SNMP and SSH from an authorized management segment and peers and SNMP and SSH from an authorized management segment and
directed to the device itself, while dropping all other traffic directed to the device itself, while dropping all other traffic
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3.3. Select Transit Traffic 3.3. Select Transit Traffic
Capability. Capability.
It is possible to apply the filtering mechanism to traffic that It is possible to apply the filtering mechanism to traffic that
will transit the device via any of its interfaces. will transit the device via any of its interfaces.
Supported Practices. Supported Practices.
* Select Transit Traffic (Section 7.5) * Data Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.1)
Current Implementations. Current Implementations.
Many devices currently implement access control lists or filters Many devices currently implement access control lists or filters
that allow filtering based on protocol and/or source/destination that allow filtering based on protocol and/or source/destination
address and or source/destination port and allow these filters to address and or source/destination port and allow these filters to
be applied to the interfaces on the device in order to protect be applied to the interfaces on the device in order to protect
assets attached to the network. assets attached to the network.
Examples of this may include filtering all traffic save SMTP Examples of this may include filtering all traffic save SMTP
(tcp/25) destined to a mail server. A common use of this today (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 would also be denying all traffic to a destination which has been
determined to be hostile. determined to be hostile.
Considerations. Considerations.
None. This allows the operator to apply filters that protect the
networks and assets surrounding the device from attacks and
unauthorized access.
3.4. Select Inbound and/or Outbound 3.4. Select Inbound and/or Outbound
Capability. Capability.
It is possible to filter both incoming and outgoing traffic on any It is possible to filter both incoming and outgoing traffic on any
interface. interface.
Supported Practices. Supported Practices.
* Select Inbound and/or Outbound Traffic (Section 7.6) * Data Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.1)
* Management Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.2)
Current Implementations. Current Implementations.
It might be desirable on a border router, for example, to apply an It might be desirable on a border router, for example, to apply an
egress filter outbound on the interface that connects a site to egress filter outbound on the interface that connects a site to
its external ISP to drop outbound traffic that does not have a its external ISP to drop outbound traffic that does not have a
valid internal source address. Inbound, it might be desirable to valid internal source address. Inbound, it might be desirable to
apply a filter that blocks all traffic from a site that is known apply a filter that blocks all traffic from a site that is known
to forward or originate large amounts of junk mail. to forward or originate large amounts of junk mail.
Considerations. Considerations.
None. This allows flexibility in applying filters at the place that
makes the most sense. It allows invalid or malicious traffic to
be dropped as close to the source as possible with the least
impact on other traffic transiting the interface(s) in question.
3.5. Select by Protocols 3.5. Select by Protocols
Capability. Capability.
The device provides a means to filter traffic based on the value The device provides a means to filter traffic based on the value
of the protocol field in the IP header. of the protocol field in the IP header.
Supported Practices. Supported Practices.
* Select by Protocols(Section 7.7) * Data Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.1)
* Management Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.2)
Current Implementations. Current Implementations.
Some denial of service attacks are based on the ability to flood Some denial of service attacks are based on the ability to flood
the victim with ICMP traffic. One quick way (admittedly with some the victim with ICMP traffic. One quick way (admittedly with some
negative side effects) to mitigate the effects of such attacks is negative side effects) to mitigate the effects of such attacks is
to drop all ICMP traffic headed toward the victim. to drop all ICMP traffic headed toward the victim.
Considerations. Considerations.
None. Being able to filter on protocol is necessary to allow
implementation of policy, secure operations and for support of
incident response. Filtering all traffic to a destination host is
not often possible, business requirements will dictate that
critical traffic be permitted if at all possible.
3.6. Select by Addresses 3.6. Select by Addresses
Capability. Capability.
The device is able to control the flow of traffic based on source The device is able to control the flow of traffic based on source
and/or destination IP address or blocks of addresses such as and/or destination IP address or blocks of addresses such as
Classless Inter-Domain Routing (CIDR) blocks. Classless Inter-Domain Routing (CIDR) blocks.
Supported Practices. Supported Practices.
* Select by Addresses(Section 7.8) * Data Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.1)
* Management Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.2)
Current Implementations. Current Implementations.
One example of the use of address based filtering is to implement One example of the use of address based filtering is to implement
ingress filtering per [RFC2827] ingress filtering per [RFC2827]
Considerations. Considerations.
None. The capability to filter on addresses and address blocks is a
fundamental tool for establishing boundaries between different
networks.
3.7. Select by Protocol Header Fields 3.7. Select by Protocol Header Fields
Capability. Capability.
The filtering mechanism supports filtering based on the value(s) The filtering mechanism supports filtering based on the value(s)
of any portion of the protocol headers for IP, ICMP, UDP and TCP. of any portion of the protocol headers for IP, ICMP, UDP and TCP
It supports filtering of all other protocols supported at layer 3 by specifying fields by name (e.g., "protocol = ICMP") rather than
and 4. It supports filtering based on the headers of higher level bit- offset/length/numeric value (e.g., 72:8 = 1).
protocols. It is possible to specify fields by name (e.g.,
"protocol = ICMP") rather than bit- offset/length/numeric value It supports arbitrary header-based filtering (possibly using bit-
(e.g., 72:8 = 1). offset/length/value) of all other protocols.
Supported Practices. Supported Practices.
* Select by Protocol Header Field(Section 7.9) * Data Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.1)
* Management Plane Filtering ([I-D.ietf-opsec-current-practices],
Section 2.7.2)
Current Implementations. Current Implementations.
This capability implies that it is possible to filter based on TCP 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 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 ICMP type and code fields. One common example is to reject
"inbound" TCP connection attempts (TCP, SYN bit set+ACK bit clear "inbound" TCP connection attempts (TCP, SYN bit set+ACK bit clear
or SYN bit set+ACK,FIN and RST bits clear). Another common or SYN bit set+ACK,FIN and RST bits clear). Another common
example is the ability to control what services are allowed in/out example is the ability to control what services are allowed in/out
of a network. It may be desirable to only allow inbound of a network. It may be desirable to only allow inbound
connections on port 80 (HTTP) and 443 (HTTPS) to a network hosting connections on port 80 (HTTP) and 443 (HTTPS) to a network hosting
web servers. web servers.
Supporting arbitrary offset/length/value filtering allows
filtering of unknown (possibly new) protocols, e.g. filtering RTP
even when the device itself does not support RTP.
Considerations. Considerations.
None. Being able to filter on portions of the header is necessary to
allow implementation of policy, secure operations, and support
incident response.
4. Actions 4. Actions
4.1. Specify Filter Actions 4.1. Specify Filter Actions
Capability. Capability.
The device provides a mechanism to allow the specification of the The device provides a mechanism to allow the specification of the
action to be taken when a filter rule matches. Actions include action to be taken when a filter rule matches. Actions include
"permit" (allow the traffic), "reject" (drop with appropriate "permit" (allow the traffic), "reject" (drop with appropriate
notification to sender), and "drop" (drop with no notification to notification to sender), and "drop" (drop with no notification to
sender). sender).
Supported Practices. Supported Practices.
* Specify Filter Actions(Section 7.10) * Access Control([I-D.ietf-opsec-current-practices], Section
2.3.3)
* Data Origin Authentication ([I-D.ietf-opsec-current-practices],
Section 2.3.3)
Current Implementations. Current Implementations.
Assume that your management devices for deployed networking Assume that your management devices for deployed networking
devices live on several subnets, use several protocols, and are devices live on several subnets, use several protocols, and are
controlled by several different parts of your organization. There controlled by several different parts of your organization. There
might exist a reason to have disparate policies for access to the might exist a reason to have disparate policies for access to the
devices from these parts of the organization. devices from these parts of the organization.
Actions such as "permit", "deny", "drop" are essential in defining Actions such as "permit", "reject", and "drop" are essential in
the security policy for the services offered by the network defining the security policy for the services offered by the
devices. network devices.
Considerations. Considerations.
While silently dropping traffic without sending notification may While silently dropping traffic without sending notification may
be the correct action in security terms, consideration should be be the correct action in security terms, consideration should be
given to operational implications. See [RFC3360] for given to operational implications. See [RFC3360] for
consideration of potential problems caused by sending consideration of potential problems caused by sending
inappropriate TCP Resets. inappropriate TCP Resets.
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. syslog messages). For this reason
it might be desirable to rate-limit notifications.
4.2. Specify Rate Limits 4.2. Specify Rate Limits
Capability. Capability.
The device provides a mechanism to allow the specification of the The device provides a mechanism to allow the specification of the
action to be taken when a rate limiting filter rule matches. The action to be taken when a rate limiting filter rule matches. The
actions include "transmit" (permit the traffic because it's below actions include "transmit" (permit the traffic because it's below
the specified limit), "limit" (limit traffic because it exceeds the specified limit), "limit" (limit traffic because it exceeds
the specified limit). Limits should be applicable by both bits the specified limit). Limits should be applicable by both bits
per second and packets per timeframe (possible timeframes might per second and packets per timeframe (possible timeframes might
include second, minute, hour). Limits should able to be placed in include second, minute, hour). Limits should able to be placed in
both inbound and outbound directions. both inbound and outbound directions.
Supported Practices. Supported Practices.
* Specify Rate Limits (Section 7.11) * Denial of Service Tracking/Tracing with Rate Limiting
([I-D.ietf-opsec-current-practices], Section 2.8.4)
Current Implementations. Current Implementations.
Assume that your management devices for deployed networking Assume that your management devices for deployed networking
devices live on several subnets, use several protocols, and are devices live on several subnets, use several protocols, and are
controlled by several different parts of your organization. There controlled by several different parts of your organization. There
might exist a reason to have disparate policies for access to the might exist a reason to have disparate policies for access to the
devices from these parts of the organization with respect to devices from these parts of the organization with respect to
priority access to these services. Rate Limits may be used to priority access to these services. Rate Limits may be used to
enforce these prioritizations. enforce these prioritizations.
Considerations. 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 While silently dropping traffic without sending notification may
be the correct action in security terms, consideration should be be the correct action in security terms, consideration should be
given to operational implications. See [RFC3360] for given to operational implications. See [RFC3360] for
consideration of potential problems caused by sending consideration of potential problems caused by sending
inappropriate TCP Resets. inappropriate TCP Resets.
4.3. Specify Log Actions 4.3. Specify Log Actions
Capability. Capability.
It is possible to log all filter actions. The logging capability It is possible to log all filter actions. The logging capability
is able to capture at least the following data: is able to capture at least the following data:
* permit/deny/drop status * permit/reject/drop status
* source and destination IP address * source and destination IP address
* source and destination ports (if applicable to the protocol) * source and destination ports (if applicable to the protocol)
* which network element received the packet (interface, MAC * which network element received or was sending the packet
address or other layer 2 information that identifies the (interface, MAC address or other layer 2 information that
previous hop source of the packet). identifies the previous hop source of the packet).
Supported Practices. Supported Practices.
* Log exceptions ([I-D.ietf-opsec-current-practices], Section * Logging Security Practices([I-D.ietf-opsec-current-practices],
2.7.2) Section 2.6.2)
* Log Actions (Section 7.12)
Current Implementations. Current Implementations.
Actions such as "permit", "deny", "drop" are essential in defining Actions such as "permit", "reject", "drop" are essential in
the security policy for the services offered by the network defining the security policy for the services offered by the
devices. Auditing the frequency, sources and destinations of network devices. Auditing the frequency, sources and destinations
these attempts is essential for tracking ongoing issues today. of these attempts is essential for tracking ongoing issues today.
Considerations. Considerations.
Logging can be burdensome to the network device, at no time should Logging can be burdensome to the network device, at no time should
logging cause performance degradation to the device or services logging cause performance degradation to the device or services
offered on the device. 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 4.4. Specify Log Granularity
Capability. Capability.
It is possible to enable/disable logging on a per rule basis. It is possible to enable/disable logging on a per rule basis.
Supported Practices. Supported Practices.
* Log Granularity (Section 7.13) * Logging Security Practices([I-D.ietf-opsec-current-practices],
Section 2.6.2)
Current Implementations. Current Implementations.
If a filter is defined that has several rules, and one of the If a filter is defined that has several rules, and one of the
rules denies telnet (tcp/23) connections, then it should be rules denies telnet (tcp/23) connections, then it should be
possible to specify that only matches on the rule that denies possible to specify that only matches on the rule that denies
telnet should generate a log message. telnet should generate a log message.
Considerations. Considerations.
None. 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 4.5. Ability to Display Filter Counters
Capability. Capability.
The device provides a mechanism to display filter counters. The device provides a mechanism to display filter counters.
Supported Practices. Supported Practices.
* Display Filter Counters (Section 7.14) * Profile Current Traffic (Section 7.1)
* Respond to Incidents Based on Accurate Data (Section 7.4)
Current Implementations. Current Implementations.
Assume there is a router with four interfaces. One is an up-link Assume there is a router with four interfaces. One is an up-link
to an ISP providing routes to the Internet. The other three to an ISP providing routes to the Internet. The other three
connect to separate internal networks. Assume that a host on one connect to separate internal networks. Assume that a host on one
of the internal networks has been compromised by a hacker and is of the internal networks has been compromised by a hacker and is
sending traffic with bogus source addresses. In such a situation, sending traffic with bogus source addresses. In such a situation,
it might be desirable to apply ingress filters to each of the it might be desirable to apply ingress filters to each of the
internal interfaces. Once the filters are in place, the counters internal interfaces. Once the filters are in place, the counters
can be examined to determine the source (inbound interface) of the can be examined to determine the source (inbound interface) of the
bogus packets. bogus packets.
Considerations. Considerations.
None. None.
5. Counters 5. Counters
5.1. Ability to Display Filter Counters per Filter Application 5.1. Filter Counters Displayed Per Application
Capability. Capability.
If it is possible for a filter to be applied more than once at the 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 same time, then the device provides a mechanism to display filter
counters per filter application. counters per filter application.
Supported Practices. Supported Practices.
* Counters (Section 7.15) * Profile Current Traffic (Section 7.1)
* Respond to Incidents Based on Accurate Data (Section 7.4)
Current Implementations. Current Implementations.
One way to implement this capability would be to have the counter One way to implement this capability would be to have the counter
display mechanism show the interface (or other entity) to which display mechanism show the interface (or other entity) to which
the filter has been applied, along with the name (or other the filter has been applied, along with the name (or other
designator) for the filter. For example if a filter named designator) for the filter. For example if a filter named
"desktop_outbound" applied two different interfaces, say, "desktop_outbound" applied two different interfaces, say,
"ethernet0" and "ethernet1", the display should indicate something "ethernet0" and "ethernet1", the display should indicate something
like "matches of filter 'desktop_outbound' on ethernet0 ..." and like "matches of filter 'desktop_outbound' on ethernet0 ..." and
"matches of filter 'desktop_outbound' on ethernet1 ..." "matches of filter 'desktop_outbound' on ethernet1 ..."
Considerations. Considerations.
None. 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 5.2. Ability to Reset Filter Counters
Capability. Capability.
It is possible to reset counters to zero on a per filter basis. It is possible to reset counters to zero on a per filter basis.
Supported Practices.
* Profile Current Traffic (Section 7.1)
* Respond to Incidents Based on Accurate Data (Section 7.4)
Current Implementations.
For the purposes of this capability it would be acceptable for the For the purposes of this capability it would be acceptable for the
system to maintain two counters: an "absolute counter", C[now], system to maintain two counters: an "absolute counter", C[now],
and a "reset" counter, C[reset]. The absolute counter would and a "reset" counter, C[reset]. The absolute counter would
maintain counts that increase monotonically until they wrap or maintain counts that increase monotonically until they wrap or
overflow the counter. The reset counter would receive a copy of overflow the counter. The reset counter would receive a copy of
the current value of the absolute counter when the reset function the current value of the absolute counter when the reset function
was issued for that counter. Functions that display or retrieve was issued for that counter. Functions that display or retrieve
the counter could then display the delta (C[now] - C[reset]). the counter could then display the delta (C[now] - C[reset]).
Supported Practices. Considerations.
* Reset Counters (Section 7.16)
Current Implementations.
Assume that filter counters are being used to detect internal Assume that filter counters are being used to detect internal
hosts that are infected with a new worm. Once it is believed that 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 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 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 to reset the filter counters to zero and see if traffic indicative
of the worm has ceased. of the worm has ceased.
Considerations. 5.3. Filter Hits are Counted
None.
5.3. Filter Hits are Accurately Counted
Capability. Capability.
The device supplies a facility for accurately counting all filter The device supplies a facility for counting all filter matches.
matches.
Supported Practices. Supported Practices.
* Filter Hits are Accurately Counted (Section 7.17) * Profile Current Traffic (Section 7.1)
* Respond to Incidents Based on Accurate Data (Section 7.4)
Current Implementations. Current Implementations.
Assume, for example, that a ISP network implements anti-spoofing Assume, for example, that a ISP network implements anti-spoofing
egress filters (see [RFC2827]) on interfaces of its edge routers egress filters (see [RFC2827]) on interfaces of its edge routers
that support single-homed stub networks. Counters could enable that support single-homed stub networks. Counters could enable
the ISP to detect cases where large numbers of spoofed packets are the ISP to detect cases where large numbers of spoofed packets are
being sent. This may indicate that the customer is performing being sent. This may indicate that the customer is performing
potentially malicious actions (possibly in violation of the ISPs potentially malicious actions (possibly in violation of the ISPs
Acceptable Use Policy), or that system(s) on the customers network Acceptable Use Policy), or that system(s) on the customers network
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Capability. Capability.
Filter counters are accurate. They reflect the actual number of Filter counters are accurate. They reflect the actual number of
matching packets since the last counter reset. Filter counters matching packets since the last counter reset. Filter counters
are be capable of holding up to 2^32 - 1 values without are be capable of holding up to 2^32 - 1 values without
overflowing and should be capable of holding up to 2^64 - 1 overflowing and should be capable of holding up to 2^64 - 1
values. values.
Supported Practices. Supported Practices.
* Filter Hits are Accurately (Section 7.18) * Respond to Incidents Based on Accurate Data (Section 7.4)
Current Implementations. Current Implementations.
If N packets matching a filter are sent to/through a device, then If N packets matching a filter are sent to/through a device, then
the counter should show N matches. the counter should show N matches.
Considerations. Considerations.
None. None.
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performance degradation. This specifically applies to stateless performance degradation. This specifically applies to stateless
packet filtering operating on layer 3 (IP) and layer 4 (TCP or packet filtering operating on layer 3 (IP) and layer 4 (TCP or
UDP) headers, as well as normal packet forwarding information such UDP) headers, as well as normal packet forwarding information such
as incoming and outgoing interfaces. as incoming and outgoing interfaces.
The device is able to apply stateless packet filters on ALL The device is able to apply stateless packet filters on ALL
interfaces (up to the total number of interfaces attached to the interfaces (up to the total number of interfaces attached to the
device) simultaneously and with multiple filters per interface device) simultaneously and with multiple filters per interface
(e.g., inbound and outbound). (e.g., inbound and outbound).
The filtering of traffic destined to interfaces on the device,
including the loopback interface, should not degrade performance
significantly.
Supported Practices. Supported Practices.
* Minimal Performance Degradation (Section 7.19) * Implement Filters Where Necessary (Section 7.5)
Current Implementations. Current Implementations.
Another way of stating the capability is that filter performance Another way of stating the capability is that filter performance
should not be the limiting factor in device throughput. If a should not be the limiting factor in device throughput. If a
device is capable of forwarding 30Mb/sec without filtering, then device is capable of forwarding 30Mb/sec without filtering, then
it should be able to forward the same amount with filtering in it should be able to forward the same amount with filtering in
place. place.
Considerations. Considerations.
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box to crash". At the other end would be a throughput loss of box to crash". At the other end would be a throughput loss of
less than one percent with tens of thousands of filters applied. less than one percent with tens of thousands of filters applied.
The level of performance degradation that is acceptable will have The level of performance degradation that is acceptable will have
to be determined by the operator. to be determined by the operator.
Repeatable test data showing filter performance impact would be Repeatable test data showing filter performance impact would be
very useful in evaluating this capability. Tests should include very useful in evaluating this capability. Tests should include
such information as packet size, packet rate, number of interfaces such information as packet size, packet rate, number of interfaces
tested (source/destination), types of interfaces, routing table tested (source/destination), types of interfaces, routing table
size, routing protocols in use, frequency of routing updates, etc. size, routing protocols in use, frequency of routing updates, etc.
This capability does not address stateful filtering, filtering This capability does not address stateful filtering, filtering
above layer 4 headers or other more advanced types of filtering above layer 4 headers or other more advanced types of filtering
that may be important in certain operational environments. that may be important in certain operational environments.
Finally, if key infrastructure devices crash or experience severe Finally, if key infrastructure devices crash or experience severe
performance degradation when filtering under heavy load, or even performance degradation when filtering under heavy load, or even
have the reputation of doing so, it is likely that security have the reputation of doing so, it is likely that security
personnel will be forbidden, by policy, from using filtering in personnel will be forbidden, by policy, from using filtering in
ways that would otherwise be appropriate for fear that it might ways that would otherwise be appropriate for fear that it might
cause unnecessary service disruption. cause unnecessary service disruption.
7. Additional Operational Practices 7. Additional Operational Practices
This section describes practices not covered in [I-D.ietf-opsec- This section describes practices not covered in
current-practices]. They are included here to provide justification [I-D.ietf-opsec-current-practices]. They are included here to
for capabilities that reference them. provide justification for capabilities that reference them.
7.1. Profile Current Traffic 7.1. Profile Current Traffic
This capability allows a network operator to monitor traffic across This capability allows a network operator to monitor traffic across
an active interface in the network at a minimal level. This helps to an active interface in the network at a minimal level. This helps to
determine probable cause for interface or network problems. determine probable cause for interface or network problems.
The ability to separate and distinguish traffic at a layer-3 or The ability to separate and distinguish traffic at a layer-3 or
layer-4 level allows the operator to characterize beyond simple layer-4 level allows the operator to characterize beyond simple
interface counters the traffic in question. This is critical because interface counters the traffic in question. This is critical because
skipping to change at page 21, line 46 skipping to change at page 21, line 46
Management of a network should be limited to only trusted hosts. Management of a network should be limited to only trusted hosts.
This implies that the network elements will be able to limit access This implies that the network elements will be able to limit access
to management functions to these trusted hosts. to management functions to these trusted hosts.
Currently operators will limit access to the management functions on Currently operators will limit access to the management functions on
a network device to only the hosts that are trusted to perform that a network device to only the hosts that are trusted to perform that
function. This allows separation of critical functions and function. This allows separation of critical functions and
protection of those functions on the network devices. protection of those functions on the network devices.
7.4. Select Traffic To the Device 7.4. Respond to Incidents Based on Accurate Data
This allows the operator to apply filters that protect the device
itself from attacks and unauthorized access.
7.5. Select Transit Traffic
This allows the operator to apply filters that protect the networks
and assets surrounding the device from attacks and unauthorized
access.
7.6. Select Traffic Inbound and/or Outbound
This allows flexibility in applying filters at the place that makes
the most sense. It allows invalid or malicious traffic to be dropped
as close to the source as possible with the least impact on other
traffic transiting the interface(s) in question.
7.7. Select Traffic by Protocol
Being able to filter on protocol is necessary to allow implementation
of policy, secure operations and for support of incident response.
Filtering all traffic to a destination host is not often possible,
business requirements will dictate that critical traffic be permitted
if at all possible.
7.8. Select Traffic by Addresses
The capability to filter on addresses and address blocks is a
fundamental tool for establishing boundaries between different
networks.
7.9. Select Traffic by Protocol Header Field
Being able to filter on portions of the header is necessary to allow
implementation of policy, secure operations, and support incident
response.
7.10. Specify Filter Actions
This capability is essential to the use of filters to enforce policy.
With a defined filter classification of some traffic and no action
defined there is little use for the filter, actions must be included
in order to provide the requisite security.
7.11. Specify Rate Limits
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.
7.12. Specify Log Actions
Logging is essential for auditing, incident response, and operations
7.13. Log Granularity
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.
7.14. Display Filter Counters
Information that is collected is not useful unless it can be
displayed.
7.15. Counters
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.
7.16. Ability to Reset Filter Counters
This allows operators to get a current picture of the traffic
matching particular rules/filters.
7.17. Filter Hits are Accurately Counted
Accurate counting of filter rule matches is important because it Accurate counting of filter rule matches is important because it
shows the frequency of attempts to violate policy. This enables shows the frequency of attempts to violate policy. Inaccurate data
resources to be focused on areas of greatest need. 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
7.18. Filter Hits are Accurate focused on areas of greatest need.
Inaccurate data can not be relied on as the basis for action. Under-
reported data can conceal the magnitude of a problem.
7.19. Minimal Performance Degredation 7.5. Implement Filters Where Necessary
This enables the implementation of filters on whichever services are This enables the implementation of filters on whichever services are
necessary. To the extent that filtering causes degradation, it may necessary. To the extent that filtering causes degradation, it may
not be possible to apply filters that implement the appropriate not be possible to apply filters that implement the appropriate
policies. policies.
8. Security Considerations 8. Security Considerations
General General
Security is the subject matter of this entire memo. The Security is the subject matter of this entire memo. The
capabilities listed cite practices in [I-D.ietf-opsec-current- capabilities listed cite practices in
practices] that they are intended to support. [I-D.ietf-opsec- [I-D.ietf-opsec-current-practices] that they are intended to
current-practices] defines the threat model, practices and lists support. [I-D.ietf-opsec-current-practices] defines the threat
justifications for each practice. model, practices and lists justifications for each practice.
9. Non-normative References 9. Non-normative References
[I-D.ietf-opsec-current-practices] [I-D.ietf-opsec-current-practices]
Kaeo, M., "Operational Security Current Practices", Kaeo, M., "Operational Security Current Practices",
draft-ietf-opsec-current-practices-04 (work in progress), draft-ietf-opsec-current-practices-06 (work in progress),
June 2006. July 2006.
[I-D.lewis-infrastructure-security] [I-D.lewis-infrastructure-security]
Lewis, D., "Service Provider Infrastructure Security", Lewis, D., "Service Provider Infrastructure Security",
draft-lewis-infrastructure-security-00 (work in progress), draft-lewis-infrastructure-security-00 (work in progress),
June 2006. June 2006.
[I-D.savola-rtgwg-backbone-attacks] [I-D.savola-rtgwg-backbone-attacks]
Savola, P., "Backbone Infrastructure Attacks and Savola, P., "Backbone Infrastructure Attacks and
Protections", draft-savola-rtgwg-backbone-attacks-01 (work Protections", draft-savola-rtgwg-backbone-attacks-02 (work
in progress), June 2006. in progress), July 2006.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000. Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, [RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828,
May 2000. May 2000.
[RFC3360] Floyd, S., "Inappropriate TCP Resets Considered Harmful", [RFC3360] Floyd, S., "Inappropriate TCP Resets Considered Harmful",
BCP 60, RFC 3360, August 2002. BCP 60, RFC 3360, August 2002.
[RFC3871] Jones, G., "Operational Security Requirements for Large [RFC3871] Jones, G., "Operational Security Requirements for Large
Internet Service Provider (ISP) IP Network Internet Service Provider (ISP) IP Network
Infrastructure", RFC 3871, September 2004. Infrastructure", RFC 3871, September 2004.
Appendix A. Acknowledgments Appendix A. Acknowledgments
The editors gratefully acknowledges the contributions of: The authors gratefully acknowledge the contributions of:
o The MITRE Corporation for supporting development of this document. o The MITRE Corporation for supporting development of this document.
NOTE: The editor's affiliation with The MITRE Corporation is NOTE: The editor's affiliation with The MITRE Corporation is
provided for identification purposes only, and is not intended to provided for identification purposes only, and is not intended to
convey or imply MITRE's concurrence with, or support for, the convey or imply MITRE's concurrence with, or support for, the
positions, opinions or viewpoints expressed by the editor. positions, opinions or viewpoints expressed by the editor.
Authors' Addresses Authors' Addresses
Christopher L. Morrow Christopher L. Morrow
skipping to change at page 27, line 5 skipping to change at page 26, line 25
George M. Jones George M. Jones
The MITRE Corporation The MITRE Corporation
7515 Colshire Drive, M/S WEST 7515 Colshire Drive, M/S WEST
McLean, Virginia 22102-7508 McLean, Virginia 22102-7508
U.S.A. U.S.A.
Phone: +1 703 488 9740 Phone: +1 703 488 9740
Email: gmjones@mitre.org Email: gmjones@mitre.org
Intellectual Property Statement 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
Full Copyright Statement
Copyright (C) The Internet Society (2006).
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 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 The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights 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 might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
skipping to change at page 27, line 29 skipping to change at page 27, line 45
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
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rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Disclaimer of Validity
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 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.
Copyright Statement
Copyright (C) The Internet Society (2006). 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.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is provided by the IETF
Internet Society. Administrative Support Activity (IASA).
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