rfc2647.txt

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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.

Table of Contents

   1. Introduction...................................................2
   2. Existing definitions...........................................2
   3. Term definitions...............................................3
   3.1 Allowed traffic...............................................3
   3.2 Application proxy.............................................3
   3.3 Authentication................................................4
   3.4 Bit forwarding rate...........................................5
   3.5 Circuit proxy.................................................6
   3.6 Concurrent connections........................................6
   3.7 Connection....................................................7
   3.8 Connection establishment......................................9
   3.9 Connection establishment time.................................9
   3.10 Connection maintenance......................................10
   3.11 Conection overhead..........................................11
   3.12 Connection teardown.........................................11
   3.13 Connection teardown time....................................12
   3.14 Data source.................................................12
   3.15 Demilitarized zone..........................................13
   3.16 Firewall....................................................13
   3.17 Goodput.....................................................14
   3.18 Homed.......................................................15
   3.19 Illegal traffic.............................................15
   3.20 Logging.....................................................16
   3.21 Network address translation.................................16
   3.22 Packet filtering............................................17
   3.23 Policy......................................................17
   3.24 Protected network...........................................18
   3.25 Proxy.......................................................19
   3.26 Rejected traffic............................................19



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   3.27 Rule set....................................................20
   3.28 Security association........................................20
   3.29 Stateful packet filtering...................................21
   3.30 Tri-homed...................................................22
   3.31 Unit of transfer............................................22
   3.32 Unprotected network.........................................23
   3.33 User........................................................23
   4. Security considerations.......................................24
   5. References....................................................25
   6. Acknowledgments...............................................25
   7. Contact Information...........................................25
   8. Full Copyright Statement......................................26

1. 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.

2. 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.







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3. Term definitions

3.1 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

3.2 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.





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   Unit of measurement:
     not applicable

   Issues:
     circuit proxy
     rule sets

   See also:
     allowed traffic
     circuit proxy
     proxy
     rejected traffic
     rule set

3.3 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:




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   See also:
     user

3.4 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







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3.5 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

3.6 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



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     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

3.7 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).



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     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





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     connection establishment time
     connection teardown
     connection teardown time

3.8 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

3.9 Connection establishment time