RFC2647

Network Working Group D. Newman Request for Comments: 2647 Data Communications Category: Informational August 1999

       Benchmarking Terminology for Firewall Performance

Status of this Memo

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1999). All Rights Reserved.

Introduction

This document defines terms used in measuring the performance of firewalls. It extends the terminology already used for benchmarking routers and switches with definitions specific to firewalls.

Forwarding rate and connection-oriented measurements are the primary metrics used in this document.

Why do we need firewall performance measurements? First, despite the rapid rise in firewall deployment, there is no standard method of performance measurement. Second, implementations vary widely, making it difficult to do direct performance comparisons. Finally, more and more organizations are deploying firewalls on internal networks operating at relatively high speeds, while most firewall implementations remain optimized for use over relatively low-speed wide-area connections. As a result, users are often unsure whether the products they buy will stand up to relatively heavy loads.

Existing definitions

This document uses the conceptual framework established in RFCs 1242 and 2544 (for routers) and RFC 2285 (for switches). The router and switch documents contain discussions of several terms relevant to benchmarking the performance of firewalls. Readers should consult the router and switch documents before making use of this document.

This document uses the definition format described in RFC 1242, Section 2. The sections in each definition are: definition, discussion, measurement units (optional), issues (optional), and cross-references.

Term definitions

Allowed traffic

Definition:

 Packets forwarded as a result of the rule set of the device under
 test/system under test (DUT/SUT).

Discussion:

 Firewalls typically are configured to forward only those packets
 explicitly permitted in the rule set. Forwarded packets must be
 included in calculating the bit forwarding rate or maximum bit
 forwarding rate of the DUT/SUT. All other packets must not be
 included in bit forwarding rate calculations.

 This document assumes 1:1 correspondence of allowed traffic offered
 to the DUT/SUT and forwarded by the DUT/SUT. There are cases where
 the DUT/SUT may forward more traffic than it is offered; for
 example, the DUT/SUT may act as a mail exploder or a multicast
 server. Any attempt to benchmark forwarding rates of such traffic
 must include a description of how much traffic the tester expects
 to be forwarded.

Unit of measurement:

 not applicable

Issues:

See also:

 policy
 rule set

Application proxy

Definition:

 A proxy service that is set up and torn down in response to a
 client request, rather than existing on a static basis.

Discussion:

 Circuit proxies always forward packets containing a given port
 number if that port number is permitted by the rule set.
 Application proxies, in contrast, forward packets only once a
 connection has been established using some known protocol. When the
 connection closes, a firewall using applicaton proxies rejects
 individual packets, even if they contain port numbers allowed by a
 rule set.

Unit of measurement:

 not applicable

Issues:

 circuit proxy
 rule sets

See also:

 allowed traffic
 circuit proxy
 proxy
 rejected traffic
 rule set

Authentication

Definition:

 The process of verifying that a user requesting a network resource
 is who he, she, or it claims to be, and vice versa.

Discussion:

 Trust is a critical concept in network security. Any network
 resource (such as a file server or printer) typically requires
 authentication before granting access.

 Authentication takes many forms, including but not limited to IP
 addresses; TCP or UDP port numbers; passwords; external token
 authentication cards; and biometric identification such as
 signature, speech, or retina recognition systems.

 The entity being authenticated might be the client machine (for
 example, by proving that a given IP source address really is that
 address, and not a rogue machine spoofing that address) or a user
 (by proving that the user really is who he, she, or it claims to
 be).  Servers might also authenticate themselves to clients.

 Testers should be aware that in an increasingly mobile society,
 authentication based on machine-specific criteria such as an IP
 address or port number is not equivalent to verifying that a given
 individual is making an access request. At this writing systems
 that verify the identity of users are typically external to the
 firewall, and may introduce additional latency to the overall SUT.

Unit of measurement:

 not applicable

Issues:

See also:

 user

Bit forwarding rate

Definition:

 The number of bits per second of allowed traffic a DUT/SUT can be
 observed to transmit to the correct destination interface(s) in
 response to a specified offered load.

Discussion:

 This definition differs substantially from section 3.17 of RFC 1242
 and section 3.6.1 of RFC 2285.

 Unlike both RFCs 1242 and 2285, this definition introduces the
 notion of different classes of traffic: allowed, illegal, and
 rejected (see definitions for each term). For benchmarking
 purposes, it is assumed that bit forwarding rate measurements
 include only allowed traffic.

 Unlike RFC 1242, there is no reference to lost or retransmitted
 data.  Forwarding rate is assumed to be a goodput measurement, in
 that only data successfully forwarded to the destination interface
 is measured.  Bit forwarding rate must be measured in relation to
 the offered load.  Bit forwarding rate may be measured with
 differed load levels, traffic orientation, and traffic
 distribution.

 Unlike RFC 2285, this measurement counts bits per second rather
 than frames per second. Testers interested in frame (or frame-like)
 measurements should use units of transfer.

Unit of measurement:

 bits per second

Issues:

 Allowed traffic vs. rejected traffic

See also:

 allowed traffic
 goodput
 illegal traffic
 rejected traffic
 unit of transfer

Circuit proxy

Definition:

 A proxy service that statically defines which traffic will be
 forwarded.

Discussion:

 The key difference between application and circuit proxies is that
 the latter are static and thus will always set up a connection if
 the DUT/SUT's rule set allows it. For example, if a firewall's rule
 set permits ftp connections, a circuit proxy will always forward
 traffic on TCP port 20 (ftp-data) even if no control connection was
 first established on TCP port 21 (ftp-control).

Unit of measurement:

 not applicable

Issues:

 application proxy
 rule sets

See also:

 allowed traffic
 application proxy
 proxy
 rejected traffic
 rule set

Concurrent connections

Definition:

 The aggregate number of simultaneous connections between hosts
 across the DUT/SUT, or between hosts and the DUT/SUT.

Discussion:

 The number of concurrent connections a firewall can support is just
 as important a metric for some users as maximum bit forwarding
 rate.

 While "connection" describes only a state and not necessarily the
 transfer of data, concurrency assumes that all existing connections
 are in fact capable of transferring data. If a data cannot be sent
 over a connection, that connection should not be counted toward the
 number of concurrent connections.

 Further, this definition assumes that the ability (or lack thereof)
 to transfer data on a given connection is solely the responsibility
 of the DUT/SUT. For example, a TCP connection that a DUT/SUT has

 left in a FIN_WAIT_2 state clearly should not be counted. But
 another connection that has temporarily stopped transferring data
 because some external device has restricted the flow of data is not
 necessarily defunct. The tester should take measures to isolate
 changes in connection state to those effected by the DUT/SUT.

Unit of measurement:

 Concurrent connections
 Maximum number of concurrent connections

Issues:

See also:

 connections
 connection establishment time
 connection overhead

Connection

Definition:

 A state in which two hosts, or a host and the DUT/SUT, agree to
 exchange data using a known protocol.

Discussion:

 A connection is an abstraction describing an agreement between two
 nodes: One agrees to send data and the other agrees to receive it.

 Connections might use TCP, but they don't have to. Other protocols
 such as ATM also might be used, either instead of or in addition to
 TCP connections.

 What constitutes a connection depends on the application. For a
 native ATM application, connections and virtual circuits may be
 synonymous. For TCP/IP applications on ATM networks (where multiple
 TCP connections may ride over a single ATM virtual circuit), the
 number of TCP connections may be the most important consideration.

 Additionally, in some cases firewalls may handle a mixture of
 native TCP and native ATM connections. In this situation, the
 wrappers around user data will differ. The most meaningful metric
 describes what an end-user will see.

 Data connections describe state, not data transfer. The existence
 of a connection does not imply that data travels on that connection
 at any given time, although if data cannot be forwarded on a
 previously established connection that connection should not be
 considered in any aggregrate connection count (see concurrent
 connections).

 A firewall's architecture dictates where a connection terminates.
 In the case of application or circuit proxy firewalls, a connection
 terminates at the DUT/SUT. But firewalls using packet filtering or
 stateful packet filtering designs act only as passthrough devices,
 in that they reside between two connection endpoints. Regardless of
 firewall architecture, the number of data connections is still
 relevant, since all firewalls perform some form of connection
 maintenance; at the  very least, all check connection requests
 against their rule sets.

 Further, note that connection is not an atomic unit of measurement
 in that it does not describe the various steps involved in
 connection setup, maintenance, and teardown. Testers may wish to
 take separate measurements of each of these components.

 When benchmarking firewall performance, it's important to identify
 the connection establishment and teardown procedures, as these must
 not be included when measuring steady-state forwarding rates.
 Further, forwarding rates must be measured only after any security
 associations have been established.

 Though it seems paradoxical, connectionless protocols such as UDP
 may also involve connections, at least for the purposes of firewall
 performance measurement. For example, one host may send UDP packets
 to another across a firewall. If the destination host is listening
 on the correct UDP port, it receives the UDP packets. For the
 purposes of firewall performance measurement, this is considered a
 connection.

Unit of measurement:

 concurrent connections
 connection
 connection establishment time
 maximum number of concurrent connections
 connection teardown time

Issues:

 application proxy vs. stateful packet filtering
 TCP/IP vs. ATM

 connection-oriented vs. connectionless

See also:

 data source
 concurrent connections
 connection establishment

 connection establishment time
 connection teardown
 connection teardown time

Connection establishment

Definition:

 The data exchanged between hosts, or between a host and the
 DUT/SUT, to initiate a connection.

Discussion:

 Connection-oriented protocols like TCP have a proscribed
 handshaking procedure when launching a connection. When
 benchmarking firewall performance, it is import to identify this
 handshaking procedure so that it is not included in measurements of
 bit forwarding rate or UOTs per second.

 Testers may also be interested in measurements of connection
 establishment time through or with a given DUT/SUT.

Unit of measurement:

 not applicable

See also:

 connection
 connection establishement time
 connection maintenance
 connection teardown

Issues:

 not applicable

Connection establishment time

Definition:

 The length of time needed for two hosts, or a host and the DUT/SUT,
 to agree to set up a connection using a known protocol.

Discussion:

 Each connection-oriented protocol has its own defined mechanisms
 for setting up a connection. For purposes of benchmarking firewall
 performance, this shall be the interval between receipt of the
 first bit of the first octet of the packet carrying a connection
 establishment request on a DUT/SUT interface until transmission of
 the last bit of the last octet of the last packet of the connection
 setup traffic headed in the opposite direction.

 This definition applies only to connection-oriented protocols such
 as TCP. For connectionless protocols such as UDP, the notion of
 connection establishment time is not meaningful.

Unit of measurement:

 Connection establishment time

Issues:

See also:

 concurrent connections
 connection
 connection maintenance

3.10 Connection maintenance

Definition:

 The data exchanged between hosts, or between a host and the
 DUT/SUT, to ensure a connection is kept alive.

Discussion:

 Some implementations of TCP and other connection-oriented protocols
 use "keep-alive" data to maintain a connection during periods where
 no user data is exchanged.

 When benchmarking firewall performance, it is useful to identfy
 connection maintenance traffic as distinct from UOTs per second.
 Given that maintenance traffic may be characterized by short bursts
 at periodical intervals, it may not be possible to describe a
 steady-state forwarding rate for maintenance traffic. One possible
 approach is to identify the quantity of maintenance traffic, in
 bytes or bits, over a given interval, and divide through to derive
 a measurement of maintenance traffic forwarding rate.

Unit of measurement:

 maintenance traffic
 forwarding rate

See also:

 connection
 connection establishment time
 connection teardown
 connection teardown time

Issues:

 not applicable

3.11 Connection overhead

Definition:

 The degradation in bit forwarding rate, if any, observed as a
 result of the addition of one connection between two hosts through
 the DUT/SUT, or the addition of one connection from a host to the
 DUT/SUT.

Discussion:

 The memory cost of connection establishment and maintenance is
 highly implementation-specific. This metric is intended to describe
 that cost in a method visible outside the firewall.

 It may also be desirable to invert this metric to show the
 performance improvement as a result of tearing down one connection.

Unit of measurement:

 bit forwarding rate

Issues:

3.12 Connection teardown

Definition:

 The data exchanged between hosts, or between a host and the
 DUT/SUT, to close a connection.

Discussion:

 Connection-oriented protocols like TCP follow a stated procedure
 when ending a connection. When benchmarking firewall performance,
 it is important to identify the teardown procedure so that it is
 not included in measurements of bit forwarding rate or UOTs per
 second.

 Testers may also be interested in measurements of connection
 teardown time through or with a given DUT/SUT.

Unit of measurement:

 not applicable

See also:

 connection teardown time

Issues:

 not applicable

3.13 Connection teardown time

Definition:

 The length of time needed for two hosts, or a host and the DUT/SUT,
 to agree to tear down a connection using a known protocol.

Discussion:

 Each connection-oriented protocol has its own defined mechanisms
 for dropping a connection. For purposes of benchmarking firewall
 performance, this shall be the interval between receipt of the
 first bit of the first octet of the packet carrying a connection
 teardown request on a DUT/SUT interface until transmission of the
 last bit of the last octet of the last packet of the connection
 teardown traffic headed in the opposite direction.

 This definition applies only to connection-oriented protocols such
 as TCP. For connectionless protocols such as UDP, the notion of
 connection teardown time is not meaningful.

Unit of measurement:

 Connection teardown time

Issues:

See also:

 concurrent connections
 connection
 connection maintenance

3.14 Data source

Definition:

 A host capable of generating traffic to the DUT/SUT.

Discussion:

 One data source may emulate multiple users or hosts. In addition,
 one data source may offer traffic to multiple network interfaces on
 the DUT/SUT.

 The term "data source" is deliberately independent of any number of
 users. It is useful to think of data sources simply as traffic
 generators, without any correlation to any given number of users.

Unit of measurement:

 not applicable

Issues:

 user

See also:

 connection
 user

3.15 Demilitarized zone

Definition:

 A network segment or segments located between protected and
 unprotected networks.

Discussion:

 As an extra security measure, networks may be designed such that
 protected and unprotected segments are never directly connected.
 Instead, firewalls (and possibly public resources such as HTTP or
 FTP servers) reside on a so-called DMZ network.

 DMZ networks are sometimes called perimeter networks.

Unit of measurement:

 not applicable

Issues:

 Homed

See also:

 protected network
 unprotected network

3.16 Firewall

Definition:

 A device or group of devices that enforces an access control policy
 between networks.

Discussion:

 While there are many different ways to accomplish it, all firewalls
 do the same thing: control access between networks.

 The most common configuration involves a firewall connecting two
 segments (one protected and one unprotected), but this is not the
 only possible configuration. Many firewalls support tri-homing,
 allowing use of a DMZ network. It is possible for a firewall to
 accommodate more than three interfaces, each attached to a
 different network segment.

 The criteria by which access are controlled are not specified here.
 Typically this has been done using network- or transport-layer
 criteria (such as IP subnet or TCP port number), but there is no

 reason this must always be so. A growing number of firewalls are
 controlling access at the application layer, using user
 identification as the criterion. And firewalls for ATM networks may
 control access based on data link-layer criteria.

Unit of measurement:

 not applicable

Issues:

See also:

 DMZ
 tri-homed
 user

3.17 Goodput

Definition:

 The number of bits per unit of time forwarded to the correct
 destination interface of the DUT/SUT, minus any bits lost or
 retransmitted.

Discussion:

 Firewalls are generally insensitive to packet loss in the network.
 As such, measurements of gross bit forwarding rates are not
 meaningful since (in the case of proxy-based and stateful packet
 filtering firewalls) a receiving endpoint directly attached to a
 DUT/SUT would not receive any data dropped by the DUT/SUT.

 The type of traffic lost or retransmitted is protocol-dependent.
 TCP and ATM, for example, request different types  of
 retransmissions.  Testers must observe retransmitted data for the
 protocol in use, and subtract this quantity from measurements of
 gross bit forwarding rate.

Unit of measurement:

 bits per second

Issues:

 allowed vs. rejected traffic

See also:

 allowed traffic
 bit forwarding rate
 rejected traffic

3.18 Homed

Definition:

 The number of logical interfaces a DUT/SUT contains.

Discussion:

 Firewalls typically contain at least two logical interfaces. In
 network topologies where a DMZ is used, the firewall usually
 contains at least three interfaces and is said to be tri-homed.
 Additional interfaces would make a firewall quad-homed, quint-
 homed, and so on.

 It is theoretically possible for a firewall to contain one physical
 interface and multiple logical interfaces. This configuration is
 discouraged for testing purposes because of the difficulty in
 verifying that no leakage occurs between protected and unprotected
 segments.

Unit of measurement:

 not applicable

Issues:

See also:

 tri-homed

3.19 Illegal traffic

Definition:

 Packets specified for rejection in the rule set of the DUT/SUT.

Discussion:

 A buggy or misconfigured firewall might forward packets even though
 its rule set specifies that these packets be dropped. Illegal
 traffic differs from rejected traffic in that it describes all
 traffic specified for rejection by the rule set, while rejected
 traffic specifies only those packets actually dropped by the
 DUT/SUT.

Unit of measurement:

 not applicable

Issues:

See also:

 accepted traffic
 policy
 rejected traffic
 rule set

3.20 Logging

Definition:

 The recording of user requests made to the firewall.

Discussion:

 Firewalls typically log all requests they handle, both allowed and
 rejected. For many firewall designs, logging requires a significant
 amount of processing overhead, especially when complex rule sets
 are in use.

 The type and amount of data logged varies by implementation.
 Testers may find it desirable to log equivalent data when comparing
 different DUT/SUTs.

 Some systems allow logging to take place on systems other than the
 DUT/SUT.

Unit of measurement:

 not applicable

Issues:

 rule sets

See also:

 allowed traffic
 connection
 rejected traffic

3.21 Network address translation

Definition:

 A method of mapping one or more private, reserved IP addresses to
 one or more public IP addresses.

Discussion:

 In the interest of conserving the IPv4 address space, RFC 1918
 proposed the use of certain private (reserved) blocks of IP
 addresses. Connections to public networks are made by use of a
 device that translates one or more RFC 1918 addresses to one or
 more public addresses--a network address translator (NAT).

 The use of private addressing also introduces a security benefit in
 that RFC 1918 addresses are not visible to hosts on the public
 Internet.

 Some NAT implementations are computationally intensive, and may
 affect bit forwarding rate.

Unit of measurement:

 not applicable

Issues:

See also:

3.22 Packet filtering

Definition:

 The process of controlling access by examining packets based on the
 content of packet headers.

Discussion:

 Packet-filtering devices forward or deny packets based on
 information in each packet's header, such as IP address or TCP port
 number. A packet-filtering firewall uses a rule set to determine
 which traffic should be forwarded and which should be blocked.

Unit of measurement:

 not applicable

Issues:

 static vs. stateful packet filtering

See also:

 application proxy
 circuit proxy
 proxy
 rule set
 stateful packet filtering

3.23 Policy

Definition:

 A document defining acceptable access to protected, DMZ, and
 unprotected networks.

Discussion:

 Security policies generally do not spell out specific
 configurations for firewalls; rather, they set general guidelines
 for what is and is not acceptable network access.

 The actual mechanism for controlling access is usually the rule set
 implemented in the DUT/SUT.

Unit of measurement:

 not applicable

Issues:

See also:

 rule set

3.24 Protected network

Definition:

 A network segment or segments to which access is controlled by the
 DUT/SUT.

Discussion:

 Firewalls are intended to prevent unauthorized access either to or
 from the protected network. Depending on the configuration
 specified by the policy and rule set, the DUT/SUT may allow hosts
 on the protected segment to act as clients for servers on either
 the DMZ or the unprotected network, or both.

 Protected networks are often called "internal networks." That term
 is not used here because firewalls increasingly are deployed within
 an organization, where all segments are by definition internal.

Unit of measurement:

not applicable

Issues:

See also:

 demilitarized zone (DMZ)
 unprotected network
 policy
 rule set
 unprotected network

3.25 Proxy

Definition:

 A request for a connection made on behalf of a host.

Discussion:

 Proxy-based firewalls do not allow direct connections between
 hosts.  Instead, two connections are established: one between the
 client host and the DUT/SUT, and another between the DUT/SUT and
 server host.

 As with packet-filtering firewalls, proxy-based devices use a rule
 set to determine which traffic should be forwarded and which should
 be rejected.

 There are two types of proxies: application proxies and circuit
 proxies.

Unit of measurement:

 not applicable

Issues:

 application

See also:

 application proxy
 circuit proxy
 packet filtering
 stateful packet filtering

3.26 Rejected traffic

Definition:

 Packets dropped as a result of the rule set of the DUT/SUT.

Discussion:

 For purposes of benchmarking firewall performance, it is expected
 that firewalls will reject all traffic not explicitly permitted in
 the rule set. Dropped packets must not be included in calculating
 the bit forwarding rate or maximum bit forwarding rate of the
 DUT/SUT.

Unit of measurement:

 not applicable

Issues:

See also:

 allowed traffic
 illegal traffic
 policy
 rule set

3.27 Rule set

Definition:

 The collection of access control rules that determines which
 packets the DUT/SUT will forward and which it will reject.

Discussion:

 Rule sets control access to and from the network interfaces of the

 DUT/SUT. By definition, rule sets do not apply equally to all
 network interfaces; otherwise there would be no need for the
 firewall. For benchmarking purposes, a specific rule set is
 typically applied to each network interface in the DUT/SUT.

 The tester must describe the complete contents of the rule set of
 each DUT/SUT.

 To ensure measurements reflect only traffic forwarded by the
 DUT/SUT, testers are encouraged to include a rule denying all
 access except for those packets allowed by the rule set.

Unit of measurement:

 not applicable

Issues:

See also:

 allowed traffic
 demilitarized zone (DMZ)
 illegal traffic
 policy
 protected network
 rejected traffic
 unprotected network

3.28 Security association

Definition:

 The set of security information relating to a given network
 connection or set of connections.

Discussion:

 This definition covers the relationship between policy and
 connections. Security associations (SAs) are typically set up
 during connection establishment, and they may be reiterated or
 revoked during a connection.

 For purposes of benchmarking firewall performance, measurements of
 bit forwarding rate or UOTs per second must be taken after all
 security associations have been established.

Unit of measurement:

 not applicable

See also:

 connection
 connection establishment
 policy
 rule set

3.29 Stateful packet filtering

Definition:

 The process of forwarding or rejecting traffic based on the
 contents of a state table maintained by a firewall.

Discussion:

 Packet filtering and proxy firewalls are essentially static, in
 that they always forward or reject packets based on the contents of
 the rule set.

 In contrast, devices using stateful packet filtering will only
 forward packets if they correspond with state information
 maintained by the device about each connection. For example, a
 stateful packet filtering device will reject a packet on port 20
 (ftp-data) if no connection has been established over the ftp
 control port (usually port 21).

Unit of measurement:

 not applicable

Issues:

See also:

 applicaton proxy
 packet filtering
 proxy

3.30 Tri-homed

Definition:

 A firewall with three network interfaces.

Discussion:

 Tri-homed firewalls connect three network segments with different
 network addresses. Typically, these would be protected, DMZ, and
 unprotected segments.

 A tri-homed firewall may offer some security advantages over
 firewalls with two interfaces. An attacker on an unprotected
 network may compromise hosts on the DMZ but still not reach any
 hosts on the protected network.

Unit of measurement:

 not applicable

Issues:

 Usually the differentiator between one segment and another is its
 IP address. However, firewalls may connect different networks of
 other types, such as ATM or Netware segments.

See also:

 homed

3.31 Unit of transfer

Definition:

 A discrete collection of bytes comprising at least one header and
 optional user data.

Discussion:

 This metric is intended for use in describing steady-state
 forwarding rate of the DUT/SUT.

 The unit of transfer (UOT) definition is deliberately left open to
 interpretation, allowing the broadest possible application.
 Examples of UOTs include TCP segments, IP packets, Ethernet frames,
 and ATM cells.

 While the definition is deliberately broad, its interpretation must
 not be. The tester must describe what type of UOT will be offered
 to the DUT/SUT, and must offer these UOTs at a consistent rate.
 Traffic measurement must begin after all connection establishment
 routines complete and before any connection completion routine
 begins.  Further, measurements must begin after any security
 associations (SAs) are established and before any SA is revoked.

 Testers also must compare only like UOTs. It is not appropriate,
 for example, to compare forwarding rates by offering 1,500-byte
 Ethernet UOTs to one DUT/SUT and 53-byte ATM cells to another.

Unit of measurement:

 Units of transfer
 Units of transfer per second

Issues:

See also:

 bit forwarding rate
 connection

3.32 Unprotected network

Definition:

 A network segment or segments to which access is not controlled by
 the DUT/SUT.

Discussion:

 Firewalls are deployed between protected and unprotected segments.
 The unprotected network is not protected by the DUT/SUT.

 Note that a DUT/SUT's policy may specify hosts on an unprotected
 network. For example, a user on a protected network may be
 permitted to access an FTP server on an unprotected network. But
 the DUT/SUT cannot control access between hosts on the unprotected
 network.

Unit of measurement:

 not applicable

Issues:

See also:

 demilitarized zone (DMZ)
 policy
 protected network
 rule set

3.33 User

Definition:

 A person or process requesting access to resources protected by the
 DUT/SUT.

Discussion:

 "User" is a problematic term in the context of firewall performance
 testing, for several reasons. First, a user may in fact be a
 process or processes requesting services through the DUT/SUT.
 Second, different "user" requests may require radically different
 amounts of DUT/SUT resources. Third, traffic profiles vary widely
 from one organization to another, making it difficult to
 characterize the load offered by a typical user.

 For these reasons, testers should not attempt to measure DUT/SUT
 performance in terms of users supported. Instead, testers should
 describe performance in terms of maximum bit forwarding rate and
 maximum number of connections sustained. Further, testers should
 use the term "data source" rather than user to describe traffic
 generator(s).

Unit of measurement:

 not applicable

Issues:

See also:

 data source

Security Considerations

The primary goal of this memo is to describe terms used in benchmarking firewall performance. However, readers should be aware that there is some overlap between performance and security issues. Specifically, the optimal configuration for firewall performance may not be the most secure, and vice-versa.

Further, certain forms of attack may degrade performance. One common form of denial-of-service (DoS) attack bombards a firewall with so much rejected traffic that it cannot forward allowed traffic. DoS attacks do not always involve heavy loads; by definition, DoS describes any state in which a firewall is offered rejected traffic that prohibits it from forwarding some or all allowed traffic. Even a small amount of traffic may significantly degrade firewall performance, or stop the firewall altogether. Further, the safeguards in firewalls to guard against such attacks may have a significant negative impact on performance.

Since the library of attacks is constantly expanding, no attempt is made here to define specific attacks that may affect performance. Nonetheless, any reasonable performance benchmark should take into

consideration safeguards against such attacks. Specifically, the same safeguards should be in place when comparing performance of different firewall implementations.

References

Bradner, S., Ed., "Benchmarking Terminology for Network

       Interconnection Devices", RFC 1242, July 1991.

Bradner, S. and J. McQuaid, "Benchmarking Methodology for Network

       Interconnect Devices", RFC 2544, March 1999.

Mandeville, R., "Benchmarking Terminology for LAN Switching Devices",

       RFC 2285, February 1998.

Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. and E. Lear,

       "Address Allocation for Private Internets", BCP 5, RFC 1918,
       February 1996.

Acknowledgments

The author wishes to thank the IETF Benchmarking Working Group for agreeing to review this document. Several other persons offered valuable contributions and critiques during this project: Ted Doty (Internet Security Systems), Kevin Dubray (Ironbridge Networks), Helen Holzbaur, Dale Lancaster, Robert Mandeville, Brent Melson (NSTL), Steve Platt (NSTL), Marcus Ranum (Network Flight Recorder), Greg Shannon, Christoph Schuba (Sun Microsystems), Rick Siebenaler, and Greg Smith (Check Point Software Technologies).

Contact Information

David Newman Data Communications magazine 3 Park Ave. 31st Floor New York, NY 10016 USA

Phone: 212-592-8256 Fax: 212-592-8265 EMail: [email protected]

Full Copyright Statement

Copyright (C) The Internet Society (1999). All Rights Reserved.

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