Network Working Group D. Newman
INTERNET-DRAFT Data Communications
Expires in July 1999 January 1999
Benchmarking Terminology for Firewall Performance
<draft-ietf-bmwg-secperf-05.txt>
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1. Introduction ....................................................2
2. Existing definitions ............................................3
3. Term definitions ................................................3
3.1 Allowed traffic ..............................................3
3.2 Application proxy.............................................4
3.3 Authentication ...............................................4
3.4 Bit forwarding rate ..........................................5
3.5 Circuit proxy ................................................5
3.6 Concurrent connections .......................................6
3.7 Connection ...................................................7
3.8 Connection establishment .....................................8
3.9 Connection establishment time ................................9
3.10 Connection maintenance ......................................9
3.11 Conection overhead .........................................10
3.12 Connection teardown ........................................10
3.13 Connection teardown time ...................................11
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3.14 Data source ................................................11
3.15 Demilitarized zone .........................................12
3.16 Firewall ...................................................12
3.17 Goodput ....................................................13
3.18 Homed ......................................................13
3.19 Illegal traffic.............................................14
3.20 Logging ....................................................14
3.21 Network address translation ................................15
3.22 Packet filtering ...........................................15
3.23 Policy .....................................................16
3.24 Protected network ..........................................16
3.25 Proxy ......................................................17
3.26 Rejected traffic ...........................................17
3.27 Rule set ...................................................18
3.28 Security association .......................................18
3.29 Stateful packet filtering ..................................19
3.30 Tri-homed ..................................................19
3.31 Unit of transfer ...........................................20
3.32 Unprotected network ........................................20
3.33 User .......................................................21
4. Security considerations ...........................................21
5. References ........................................................22
6. Acknowledgments ...................................................22
7. Contact information ...............................................23
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
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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 1944 (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.
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.
Measurement units:
not applicable
Issues:
See also:
policy
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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.
Measurement units:
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) with restricted access MUST
require 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 MAY 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 SHOULD 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
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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.
Measurement units:
not applicable
Issues:
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). Any bit forwarding rate measurement MUST
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.
Units of measurement:
bits per second
Issues:
Allowed traffic vs. rejected traffic
See also:
allowed traffic
goodput
illegal traffic
rejected traffic
unit of transfer
3.5 Circuit proxy
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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).
Measurement units:
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 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.
Measurement units:
Concurrent connections
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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 MAY use TCP, but they don't have to. Other protocols such
as ATM also may 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
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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.
Measurement units:
concurrent connections
connections
connection establishment time
maximum number of concurrent connections
connection teardown time
Issues:
proxy-based 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
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.
Measurement units:
none
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See also:
connection
connection establishement time
connection maintenance
connection teardown
Issues:
none
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.
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.
Metric
Connection establishment time
Issues:
See also:
concurrent connections
connection
connection overhead
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
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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.
Measurement units:
maintenance traffic forwarding rate
See also:
connection
connection establishment time
connection teardown
connection teardown time
Issues:
none
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.
Measurement units:
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.
Measurement units:
none
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See also:
connection teardown time
Issues:
none
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.
Metric
Connection teardown time
Issues:
See also:
concurrent connections
connection
connection overhead
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.
Measurement units:
not applicable
Issues:
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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 WWW or FTP
servers) reside on a so-called DMZ network. To connect protected,
DMZ, and unprotected networks with one device, the device MUST have
at least three network interfaces.
Multiple firewalls MAY bound the DMZ. In this case, the firewalls
connecting the protected network with the DMZ and the DMZ with the
unprotected network MUST each have at least two network interfaces.
DMZ networks are sometimes called perimeter networks.
Measurement units:
not applicable
Issues:
Homed
See also:
unprotected network
protected 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 is deliberately not
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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.
Measurement units:
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:
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Firewalls MUST contain at least two logical interfaces. In network
topologies where a DMZ is used, the firewall 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
strongly discouraged for testing purposes because of the difficulty
in verifying that no leakage occurs between protected and unprotected
segments.
Measurement units:
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 may 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.
Measurement units:
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 MUST 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
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SHOULD attempt to log equivalent data when comparing different
DUT/SUTs.
Logging MAY take place on systems other than the DUT/SUT.
Measurement units:
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.
Measurement units:
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.
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Measurement units:
not applicable
Issues:
static versus 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.
Measurement units:
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.
Measurement units:
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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.
Measurement units:
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:
Firewalls MUST reject any 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.
Measurement units:
not applicable
Issues:
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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 MUST NOT apply equally to all
network interfaces; otherwise there would be no need for the
firewall. Therefore, a specific rule set MUST be 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 that testers measure only traffic forwarded or rejected by
the DUT/SUT, each rule set MUST include a rule denying all access
except for those packets allowed by the rule set.
Measurement units:
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, taken verbatim from RFC 1825, 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
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bit forwarding rate or UOTs per second MUST be taken after all
security associations have been established.
Measurement units:
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).
Measurement units:
not applicable
Issues:
See also:
applicaton proxy
packet filter
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.
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Measurement units:
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.
Measurement units:
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.
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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.
Measurement units:
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).
Measurement units:
not applicable
Issues:
See also:
data source
4. Security considerations
The primary goal of this memo is to describe terms used in
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INTERNET-DRAFT Firewall Performance Terminology January 1999
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--such as the recent Teardrop2 attack
involving a few packet fragments--may significantly degrade firewall
performance, or stop the firewall altogether. Further, the safeguards
in firewalls to guard against such attacks may have 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 must take
safeguards against such attacks into consideration. Specifically, the
same safeguards must be in place when comparing performance of
different firewall implementations.
5. References
Atkinson, R. "Security Architecture for the Internet Protocol." RFC
1825.
Bradner, S., editor. "Benchmarking Terminology for Network
Interconnection Devices." RFC 1242.
Bradner, S., and McQuaid, J. "Benchmarking Methodology for Network
Interconnect Devices." RFC 1944.
Mandeville, R. "Benchmarking Terminology for LAN Switching Devices."
RFC 2285.
Rekhter, Y., et al. "Address Allocation for Private Internets." RFC
1918.
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 (NSTL), Jim Hurd (NSTL), Dale Lancaster (Axent
Technologies), Robert Mandeville (European Network Laboratories),
Brent Melson (NSTL), Steve Platt (NSTL), Marcus Ranum (Network Flight
Recorder Inc.), Greg Shannon (Ascend Communications), Christoph
Schuba (Sun Microsystems), Rick Siebenaler (Cyberguard), and Greg
Smith (Check Point Software Technologies).
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INTERNET-DRAFT Firewall Performance Terminology January 1999
7. Contact information
David Newman
Data Communications magazine
3 Park Ave.
31st Floor
New York, NY 10016
USA
212-592-8256 voice
212-592-8265 fax
dnewman@data.com
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