💾 Archived View for gemini.bortzmeyer.org › rfc-mirror › rfc2647.txt captured on 2024-05-26 at 17:24:22.
⬅️ Previous capture (2021-11-30)
-=-=-=-=-=-=-
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
Newman Informational [Page 1]
RFC 2647 Firewall Performance Terminology August 1999
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.
Newman Informational [Page 2]
RFC 2647 Firewall Performance Terminology August 1999
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.
Newman Informational [Page 3]
RFC 2647 Firewall Performance Terminology August 1999
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:
Newman Informational [Page 4]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 5]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 6]
RFC 2647 Firewall Performance Terminology August 1999
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).
Newman Informational [Page 7]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 8]
RFC 2647 Firewall Performance Terminology August 1999
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
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.
Newman Informational [Page 9]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 10]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 11]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 12]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 13]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 14]
RFC 2647 Firewall Performance Terminology August 1999
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:
Newman Informational [Page 15]
RFC 2647 Firewall Performance Terminology August 1999
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).
Newman Informational [Page 16]
RFC 2647 Firewall Performance Terminology August 1999
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.
Newman Informational [Page 17]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 18]
RFC 2647 Firewall Performance Terminology August 1999
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:
Newman Informational [Page 19]
RFC 2647 Firewall Performance Terminology August 1999
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.
Newman Informational [Page 20]
RFC 2647 Firewall Performance Terminology August 1999
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
Newman Informational [Page 21]
RFC 2647 Firewall Performance Terminology August 1999
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.
Newman Informational [Page 22]
RFC 2647 Firewall Performance Terminology August 1999
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.
Newman Informational [Page 23]
RFC 2647 Firewall Performance Terminology August 1999
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
4. 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
Newman Informational [Page 24]
RFC 2647 Firewall Performance Terminology August 1999
consideration safeguards against such attacks. Specifically, the same
safeguards should be in place when comparing performance of different
firewall implementations.
5. 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.
6. 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).
7. 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: dnewman@data.com
Newman Informational [Page 25]
RFC 2647 Firewall Performance Terminology August 1999
8. Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Newman Informational [Page 26]