[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 1.128b, available from
https://tools.ietf.org/tools/rfcmarkup/