Benchmarking Methodology Working Group C. Davids
Internet-Draft Illinois Institute of Technology
Expires: April 25, 2013 V. Gurbani
Bell Laboratories,
Alcatel-Lucent
S. Poretsky
Allot Communications
October 22, 2012
Terminology for Benchmarking Session Initiation Protocol (SIP)
Networking Devices
draft-ietf-bmwg-sip-bench-term-05
Abstract
This document provides a terminology for benchmarking the SIP
performance of networking devices. The term performance in this
context means the capacity of the device- or system-under-test to
process SIP messages. Terms are included for test components, test
setup parameters, and performance benchmark metrics for black-box
benchmarking of SIP networking devices. The performance benchmark
metrics are obtained for the SIP signaling plane only. The terms are
intended for use in a companion methodology document for
characterizing the performance of a SIP networking device under a
variety of conditions. The intent of the two documents is to enable
a comparison of the capacity of SIP networking devices. Test setup
parameters and a methodology document are necessary because SIP
allows a wide range of configuration and operational conditions that
can influence performance benchmark measurements. A standard
terminology and methodology will ensure that benchmarks have
consistent definition and were obtained following the same
procedures.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 25, 2013.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Benchmarking Models . . . . . . . . . . . . . . . . . . . 9
3. Term Definitions . . . . . . . . . . . . . . . . . . . . . . . 14
3.1. Protocol Components . . . . . . . . . . . . . . . . . . . 14
3.1.1. Session . . . . . . . . . . . . . . . . . . . . . . . 14
3.1.2. Signaling Plane . . . . . . . . . . . . . . . . . . . 17
3.1.3. Media Plane . . . . . . . . . . . . . . . . . . . . . 18
3.1.4. Associated Media . . . . . . . . . . . . . . . . . . . 18
3.1.5. Overload . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.6. Session Attempt . . . . . . . . . . . . . . . . . . . 20
3.1.7. Established Session . . . . . . . . . . . . . . . . . 20
3.1.8. Invite-initiated Session (IS) . . . . . . . . . . . . 21
3.1.9. Non-INVITE-initiated Session (NS) . . . . . . . . . . 22
3.1.10. Session Attempt Failure . . . . . . . . . . . . . . . 22
3.1.11. Standing Sessions Count . . . . . . . . . . . . . . . 23
3.2. Test Components . . . . . . . . . . . . . . . . . . . . . 23
3.2.1. Emulated Agent . . . . . . . . . . . . . . . . . . . . 24
3.2.2. Signaling Server . . . . . . . . . . . . . . . . . . . 24
3.2.3. SIP-Aware Stateful Firewall . . . . . . . . . . . . . 24
3.2.4. SIP Transport Protocol . . . . . . . . . . . . . . . . 25
3.3. Test Setup Parameters . . . . . . . . . . . . . . . . . . 26
3.3.1. Session Attempt Rate . . . . . . . . . . . . . . . . . 26
3.3.2. IS Media Attempt Rate . . . . . . . . . . . . . . . . 26
3.3.3. Establishment Threshold Time . . . . . . . . . . . . . 27
3.3.4. Session Duration . . . . . . . . . . . . . . . . . . . 27
3.3.5. Media Packet Size . . . . . . . . . . . . . . . . . . 28
3.3.6. Media Offered Load . . . . . . . . . . . . . . . . . . 28
3.3.7. Media Session Hold Time . . . . . . . . . . . . . . . 29
3.3.8. Loop Detection Option . . . . . . . . . . . . . . . . 29
3.3.9. Forking Option . . . . . . . . . . . . . . . . . . . . 30
3.4. Benchmarks . . . . . . . . . . . . . . . . . . . . . . . . 31
3.4.1. Registration Rate . . . . . . . . . . . . . . . . . . 31
3.4.2. Session Establishment Rate . . . . . . . . . . . . . . 31
3.4.3. Session Capacity . . . . . . . . . . . . . . . . . . . 32
3.4.4. Session Overload Capacity . . . . . . . . . . . . . . 33
3.4.5. Session Establishment Performance . . . . . . . . . . 33
3.4.6. Session Attempt Delay . . . . . . . . . . . . . . . . 34
3.4.7. IM Rate . . . . . . . . . . . . . . . . . . . . . . . 34
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
5. Security Considerations . . . . . . . . . . . . . . . . . . . 35
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 36
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.1. Normative References . . . . . . . . . . . . . . . . . . . 36
7.2. Informational References . . . . . . . . . . . . . . . . . 36
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Appendix A. White Box Benchmarking Terminology . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
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1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC2119
[RFC2119]. RFC 2119 defines the use of these key words to help make
the intent of standards track documents as clear as possible. While
this document uses these keywords, this document is not a standards
track document. The term Throughput is defined in RFC2544 [RFC2544].
For the sake of clarity and continuity, this document adopts the
template for definitions set out in Section 2 of RFC 1242 [RFC1242].
The terms Device Under Test (DUT) and System Under Test (SUT) are
defined in the following BMWG documents:
Device Under Test (DUT) (c.f., Section 3.1.1 RFC 2285 [RFC2285]).
System Under Test (SUT) (c.f., Section 3.1.2, RFC 2285 [RFC2285]).
Many commonly used SIP terms in this document are defined in RFC 3261
[RFC3261]. For convenience the most important of these are
reproduced below. Use of these terms in this document is consistent
with their corresponding definition in [RFC3261].
o Call Stateful: A proxy is call stateful if it retains state for a
dialog from the initiating INVITE to the terminating BYE request.
A call stateful proxy is always transaction stateful, but the
converse is not necessarily true.
o Stateful Proxy: A logical entity that maintains the client and
server transaction state machines defined by this specification
during the processing of a request, also known as a transaction
stateful proxy. The behavior of a stateful proxy is further
defined in Section 16 of RFC 3261 [RFC3261] . A transaction
stateful proxy is not the same as a call stateful proxy.
o Stateless Proxy: A logical entity that does not maintain the
client or server transaction state machines defined in this
specification when it processes requests. A stateless proxy
forwards every request it receives downstream and every response
it receives upstream.
o Back-to-back User Agent: A back-to-back user agent (B2BUA) is a
logical entity that receives a request and processes it as a user
agent server (UAS). In order to determine how the request should
be answered, it acts as a user agent client (UAC) and generates
requests. Unlike a proxy server, it maintains dialog state and
must participate in all requests sent on the dialogs it has
established. Since it is a concatenation of a UAC and a UAS, no
explicit definitions are needed for its behavior.
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o Loop: A request that arrives at a proxy, is forwarded, and later
arrives back at the same proxy. When it arrives the second time,
its Request-URI is identical to the first time, and other header
fields that affect proxy operation are unchanged, so that the
proxy will make the same processing decision on the request it
made the first time. Looped requests are errors, and the
procedures for detecting them and handling them are described by
the SIP protocol[RFC3261] and also by RFC 5393
2. Introduction
Service Providers and IT Organizations deliver Voice Over IP (VoIP)
and Multimedia network services based on the IETF Session Initiation
Protocol (SIP) [RFC3261]. SIP is a signaling protocol originally
intended to be used to dynamically establish, disconnect and modify
streams of media between end users. As it has evolved it has been
adopted for use in a growing number of services and applications.
Many of these result in the creation of a media session, but some do
not. Examples of this latter group include text messaging and
subscription services. The set of benchmarking terms provided in
this document is intended for use with any SIP-enabled device
performing SIP functions in the interior of the network, whether or
not these result in the creation of media sessions. The performance
of end-user devices is outside the scope of this document.
A number of networking devices have been developed to support SIP-
based VoIP services. These include SIP Servers, Session Border
Controllers (SBC), Back-to-back User Agents (B2BUA), and SIP-Aware
Stateful Firewalls. These devices contain a mix of voice and IP
functions whose performance may be reported using metrics defined by
the equipment manufacturer or vendor. The Service Provider or IT
Organization seeking to compare the performance of such devices will
not be able to do so using these vendor-specific metrics, whose
conditions of test and algorithms for collection are often
unspecified. SIP functional elements and the devices that include
them can be configured many different ways and can be organized into
various topologies. These configuration and topological choices
impact the value of any chosen signaling benchmark. Unless these
conditions-of-test are defined, a true comparison of performance
metrics will not be possible. Some SIP-enabled network devices
terminate or relay media as well as signaling. The processing of
media by the device impacts the signaling performance. As a result,
the conditions-of-test must include information as to whether or not
the device under test processes media and if the device does process
media, a description of the media handled and the manner in which it
is handled. This document and its companion methodology document
[I-D.ietf-bmwg-sip-bench-meth] provide a set of black-box benchmarks
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for describing and comparing the performance of devices that
incorporate the SIP User Agent Client and Server functions and that
operate in the network's core.
The definition of SIP performance benchmarks necessarily includes
definitions of Test Setup Parameters and a test methodology. These
enable the Tester to perform benchmarking tests on different devices
and to achieve comparable results. This document provides a common
set of definitions for Test Components, Test Setup Parameters, and
Benchmarks. All the benchmarks defined are black-box measurements of
the SIP signaling plane. The Test Setup Parameters and Benchmarks
defined in this document are intended for use with the companion
Methodology document. Benchmarks of internal DUT characteristics
(also known as white-box benchmarks) such as Session Attempt Arrival
Rate, which is measured at the DUT, are described in Appendix A to
allow additional characterization of DUT behavior with different
distribution models.
2.1. Scope
The scope of this work item is summarized as follows:
o This terminology document describes SIP signaling performance
benchmarks for black-box measurements of SIP networking devices.
Stress and debug scenarios are not addressed in this work item.
o The DUT must be an RFC 3261 capable network equipment. This may
be a Registrar, Redirect Server, Stateless Proxy or Stateful
Proxy. A DUT MAY also include a B2BUA, SBC functionality. The
DUT MAY be a multi-port SIP-to-switched network gateway
implemented as a SIP UAC or UAS.
o The DUT MAY include an internal SIP Application Level Gateway
(ALG), firewall, and/or a Network Address Translator (NAT). This
is referred to as the "SIP Aware Stateful Firewall."
o The DUT or SUT MUST NOT be end user equipment, such as personal
digital assistant, a computer-based client, or a user terminal.
o The Tester acts as multiple "Emulated Agents" (EA) that initiate
(or respond to) SIP messages as session endpoints and source (or
receive) associated media for established connections.
o SIP Signaling in presence of Media
* The media performance is not benchmarked in this work item.
* It is RECOMMENDED that SIP signaling plane benchmarks be
performed with media present, but this is optional.
* The SIP INVITE requests MUST include the SDP body.
* The type of DUT dictates whether the associated media streams
traverse the DUT or SUT. Both scenarios are within the scope
of this work item.
* SIP is frequently used to create media streams; the signaling
plane and media plane are treated as orthogonal to each other
in this document. While many devices support the creation of
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media streams, benchmarks that measure the performance of these
streams are outside the scope of this document and its
companion methodology document [I-D.ietf-bmwg-sip-bench-meth].
Tests may be performed with or without the creation of media
streams. The presence or absence of media streams MUST be
noted as a condition of the test as the performance of SIP
devices may vary accordingly. Even if the media is used during
benchmarking, only the SIP performance will be benchmarked, not
the media performance or quality.
o Both INVITE and non-INVITE scenarios (such as Instant Messages or
IM) are addressed in this document. However, benchmarking SIP
presence is not a part of this work item.
o Different transport mechanisms -- such as UDP, TCP, SCTP, or TLS
-- may be used. The specific transport mechanism MUST be noted as
a condition of the test as the performance of SIP devices may vary
accordingly.
o Looping and forking options are also considered since they impact
processing at SIP proxies.
o REGISTER and INVITE requests may be challenged or remain
unchallenged for authentication purpose. Whether or not the
REGISTER and INVITE requests are challenged is a condition of test
which will be recorded along with other such parameters which may
impact the SIP performance of the device or system under test.
o Re-INVITE requests are not considered in scope of this work item
since the benchmarks for INVITEs are based on the dialog created
by the INVITE and not on the transactions that take place within
that dialog.
o Only session establishment is considered for the performance
benchmarks. Session disconnect is not considered in the scope of
this work item. This is because our goal is to determine the
maximum throughput of the device or system under test, that is the
number of simultaneous SIP sessions that the device or system can
support. It is true that there are BYE requests being created
during the test process. These transactions do contribute to the
load on the device or system under test and thus are accounted for
in the metric we derive. We do not seek a separate metric for the
number of BYE transactions a device or system can support.
o SIP Overload [I-D.ietf-soc-overload-design] is within the scope of
this work item. We test to failure and then can continue to
observe and record the behavior of the system after failures are
recorded. The cause of failure is not within the scope of this
work. We note the failure and may continue to test until a
different failure or condition is encountered. Considerations on
how to handle overload are deferred to work progressing in the SOC
working group [I-D.ietf-soc-overload-control]. Vendors are, of
course, free to implement their specific overload control behavior
as the expected test outcome if it is different from the IETF
recommendations. However, such behavior MUST be documented and
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interpreted appropriately across multiple vendor implementations.
This will make it more meaningful to compare the performance of
different SIP overload implementations.
o IMS-specific scenarios are not considered, but test cases can be
applied with 3GPP-specific SIP signaling and the P-CSCF as a DUT.
2.2. Benchmarking Models
This section shows ten models to be used when benchmarking SIP
performance of a networking device. Figure 1 shows shows the
configuration needed to benchmark the tester itself. This model will
be used to establish the limitations of the test apparatus.
+--------+ Signaling request +--------+
| +----------------------------->| |
| Tester | | Tester |
| EA | Signaling response | EA |
| |<-----------------------------+ |
+--------+ +--------+
/|\ /|\
| Media |
+=========================================+
Figure 1: Baseline performance of the Emulated Agent without a DUT
present
Figure 2 shows the DUT playing the role of a user agent client (UAC),
initiating requests and absorbing responses. This model can be used
to baseline the performance of the DUT acting as an UAC without
associated media.
+--------+ Signaling request +--------+
| +----------------------------->| |
| DUT | | Tester |
| | Signaling response | EA |
| |<-----------------------------+ |
+--------+ +--------+
Figure 2: Baseline performance for DUT acting as a user agent client
without associated media
Figure 3 shows the DUT plays the role of a user agent server (UAS),
absorbing the requests and sending responses. This model can be used
as a baseline performance for the DUT acting as a UAS without
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associated media.
+--------+ Signaling request +--------+
| +----------------------------->| |
| Tester | | DUT |
| EA | Response | |
| |<-----------------------------+ |
+--------+ +--------+
Figure 3: Baseline performance for DUT acting as a user agent server
without associated media
Figure 4 shows the DUT plays the role of a user agent client (UAC),
initiating requests and absorbing responses. This model can be used
as a baseline performance for the DUT acting as a UAC with associated
media.
+--------+ Signaling request +--------+
| +----------------------------->| |
| DUT | | Tester |
| | Signaling response | (EA) |
| |<-----------------------------+ |
| |<============ Media =========>| |
+--------+ +--------+
Figure 4: Baseline performance for DUT acting as a user agent client
with associated media
Figure 5 shows the DUT plays the role of a user agent server (UAS),
absorbing the requests and sending responses. This model can be used
as a baseline performance for the DUT acting as a UAS with associated
media.
+--------+ Signaling request +--------+
| +----------------------------->| |
| Tester | | DUT |
| (EA) | Response | |
| |<-----------------------------+ |
| |<============ Media =========>| |
+--------+ +--------+
Figure 5: Baseline performance for DUT acting as a user agent server
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with associated media
Figure 6 shows that the Tester acts as the initiating and responding
EA as the DUT/SUT forwards Session Attempts.
+--------+ Session +--------+ Session +--------+
| | Attempt | | Attempt | |
| |<------------+ |<------------+ |
| | | | | |
| | Response | | Response | |
| Tester +------------>| DUT +------------>| Tester |
| (EA) | | | | (EA) |
| | | | | |
+--------+ +--------+ +--------+
Figure 6: DUT/SUT performance benchmark for session establishment
without media
Figure 7 is used when performing those same benchmarks with
Associated Media traversing the DUT/SUT.
+--------+ Session +--------+ Session +--------+
| | Attempt | | Attempt | |
| |<------------+ |<------------+ |
| | | | | |
| | Response | | Response | |
| Tester +------------>| DUT +------------>| Tester |
| (EA) | | | | (EA) |
| | Media | | Media | |
| |<===========>| |<===========>| |
+--------+ +--------+ +--------+
Figure 7: DUT/SUT performance benchmark for session establishment
with media traversing the DUT
Figure 8 is to be used when performing those same benchmarks with
Associated Media, but the media does not traverse the DUT/SUT.
Again, the benchmarking of the media is not within the scope of this
work item. The SIP control signaling is benchmarked in the presence
of Associated Media to determine if the SDP body of the signaling and
the handling of media impacts the performance of the DUT/SUT.
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+--------+ Session +--------+ Session +--------+
| | Attempt | | Attempt | |
| |<------------+ |<------------+ |
| | | | | |
| | Response | | Response | |
| Tester +------------>| DUT +------------>| Tester |
| (EA) | | | | (EA) |
| | | | | |
+--------+ +--------+ +--------+
/|\ /|\
| Media |
+=============================================+
Figure 8: DUT/SUT performance benchmark for session establishment
with media external to the DUT
Figure 9 is used when performing benchmarks that require one or more
intermediaries to be in the signaling path. The intent is to gather
benchmarking statistics with a series of DUTs in place. In this
topology, the media is delivered end-to-end and does not traverse the
DUT.
SUT
------------------^^^^^^^^-------------
/ \
+------+ Session +---+ Session +---+ Session +------+
| | Attempt | | Attempt | | Attempt | |
| |<---------+ |<---------+ |<---------+ |
| | | | | | | |
| | Response | | Response | | Response | |
|Tester+--------->|DUT+--------->|DUT|--------->|Tester|
| (EA) | | | | | | (EA) |
| | | | | | | |
+------+ +---+ +---+ +------+
/|\ /|\
| Media |
+=============================================+
Figure 9: DUT/SUT performance benchmark for session establishment
with multiple DUTs and end-to-end media
Figure 10 is used when performing benchmarks that require one or more
intermediaries to be in the signaling path. The intent is to gather
benchmarking statistics with a series of DUTs in place. In this
topology, the media is delivered hop-by-hop through each DUT.
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SUT
-----------------^^^^^^^^-------------
/ \
+------+ Session +---+ Session +---+ Session +------+
| | Attempt | | Attempt | | Attempt | |
| |<---------+ |<---------+ |<---------+ |
| | | | | | | |
| | Response | | Response | | Response | |
|Tester+--------->|DUT+--------->|DUT|--------->|Tester|
| (EA) | | | | | | (EA) |
| | | | | | | |
| |<========>| |<========>| |<========>| |
+------+ Media +---+ Media +---+ Media +------+
Figure 10: DUT/SUT performance benchmark for session establishment
with multiple DUTs and hop- by-hop media
Figure 11 illustrates the SIP signaling for an Established Session.
The Tester acts as the EAs and initiates a Session Attempt with the
DUT/SUT. When the Emulated Agent (EA) receives a 200 OK from the
DUT/SUT that session is considered to be an Established Session. The
illustration indicates three states of the session bring created by
the EA - Attempting, Established, and Disconnecting. Sessions can be
one of two type: Invite-Initiated Session (IS) or Non-Invite
Initiated Session (NS). Failure for the DUT/SUT to successfully
respond within the Establishment Threshold Time is considered a
Session Attempt Failure. SIP Invite messages MUST include the SDP
body to specify the Associated Media. Use of Associated Media, to be
sourced from the EA, is optional. When Associated Media is used, it
may traverse the DUT/SUT depending upon the type of DUT/SUT. The
Associated Media is shown in Figure 11 as "Media" connected to media
ports M1 and M2 on the EA. After the EA sends a BYE, the session
disconnects. Performance test cases for session disconnects are not
considered in this work item (the BYE request is shown for
completeness.)
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EA DUT/SUT M1 M2
| | | |
| INVITE | | |
---------+-------------->| | |
| | | |
Attempting | | |
| 200 OK | | |
---------+<--------------| | |
| ACK | | |
|-------------->| | |
| | | |
| | | |
| | | Media |
Established | |<=====>|
| | | |
| BYE | | |
--------+--------------> | | |
| | | |
Disconnecting | | |
| 200 OK | | |
--------|<-------------- | | |
| | | |
Figure 11: Invite-initiated Session States
3. Term Definitions
3.1. Protocol Components
3.1.1. Session
Definition:
The combination of signaling and media messages and processes that
support a SIP-based service.
Discussion:
SIP messages are used to create and manage services for end users.
Often, these services include the creation of media streams that
are defined in the SDP body of a SIP message and carried in RTP
protocol data units. However, SIP messages can also be used to
create Instant Message services and subscription services, and
such services are not associated with media streams. SIP reserves
the term "session" to describe services that are analogous to
telephone calls on a circuit switched network. SIP reserves the
term "dialog" to refer to a signaling-only relationship between
User Agent peers. SIP reserves the term "transaction" to refer to
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the brief communication between a client and a server that lasts
only until the final response to the SIP request. None of these
terms describes the entity whose performance we want to benchmark.
For example, the MESSAGE request does not create a dialog and can
be sent either within or outside of a dialog. It is not
associated with media, but it resembles a phone call in its
dependence on human rather than machine initiated responses. The
SUBSCRIBE method does create a dialog between the originating end-
user and the subscription service. It too is not associated with
a media session. In light of these observations we have extended
the term "session" to include SIP-based services that are not
initiated by INVITE requests and that do not have associated
media. In this extended definition, a session always has a
signaling component and may also have a media component. Thus, a
session can be defined as signaling-only or a combination of
signaling and media. We define the term "Associated Media", see
Section 3.1.4, to describe the situation in which media is
associated with a SIP dialog. The terminology "Invite-initiated
Session" (IS) Section 3.1.8 and "Non-invite-Initiated Session"
(NS) (add xref target="NS") are used to distinguish between these
two types of session. An Invite-initiated Session is a session as
defined in SIP. The performance of a device or system that
supports Invite-initiated Sessions that do not create media
sessions, "Invite-initiated Sessions without Associated Media",
can be measured and is of interest for comparison and as a
limiting case. The REGISTER request can be considered to be a
"Non-invite-initiated Session without Associated Media." A
separate set of benchmarks is provided for REGISTER requests since
most implementations of SIP-based services require this request
and since a registrar may be a device under test.
A Session in the context of this document, can be considered to be
a vector with three components:
1. A component in the signaling plane (SIP messages), sess.sig;
2. A media component in the media plane (RTP and SRTP streams for
example), sess.med (which may be null);
3. A control component in the media plane (RTCP messages for
example), sess.medc (which may be null).
An IS is expected to have non-null sess.sig and sess.med
components. The use of control protocols in the media component
is media dependent, thus the expected presence or absence of
sess.medc is media dependent and test-case dependent. An NS is
expected to have a non-null sess.sig component, but null sess.med
and sess.medc components.
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Packets in the Signaling Plane and Media Plane will be handled by
different processes within the DUT. They will take different
paths within a SUT. These different processes and paths may
produce variations in performance. The terminology and benchmarks
defined in this document and the methodology for their use are
designed to enable us to compare performance of the DUT/SUT with
reference to the type of SIP-supported application it is handling.
Note that one or more sessions can simultaneously exist between
any participants. This can be the case, for example, when the EA
sets up both an IM and a voice call through the DUT/SUT. These
sessions are represented as an array session[x].
Sessions will be represented as a vector array with three
components, as follows:
session->
session[x].sig, the signaling component
session[x].medc[y], the media control component (e.g. RTCP)
session[x].med[y], an array of associated media streams (e.g.
RTP, SRTP, RTSP, MSRP). This media component may consist of zero
or more media streams.
Figure 12 models the vectors of the session.
Measurement Units:
N/A.
Issues:
None.
See Also:
Media Plane
Signaling Plane
Associated Media
Invite-initiated Session (IS)
Non-invite-initiated Session (NS)
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|\
|
| \
sess.sig|
| \
|
| \
| o
| /
| / |
| /
| / |
| /
| / |
| /
| / | sess.medc
|/_____________________
/ /
/ |
/ /
sess.med / |
/_ _ _ _ _ _ _ _/
/
/
/
/
Figure 12: Session components
3.1.2. Signaling Plane
Definition:
The plane in which SIP messages [RFC3261] are exchanged between
SIP Agents [RFC3261].
Discussion:
SIP messages are used to establish sessions in several ways:
directly between two User Agents [RFC3261], through a Proxy Server
[RFC3261], or through a series of Proxy Servers. The Session
Description Protocol is included in the Signaling Plane. (SDP).
The Signaling Plane for a single Session is represented by
session.sig.
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Measurement Units:
N/A.
Issues:
None.
See Also:
Media Plane
EAs
3.1.3. Media Plane
Definition:
The data plane in which one or more media streams and their
associated media control protocols are exchanged between User
Agents after a media connection has been created by the exchange
of signaling messages in the Signaling Plane.
Discussion:
Media may also be known as the "bearer channel". The Media Plane
MUST include the media control protocol, if one is used, and the
media stream(s). Examples of media are audio and video. The
media streams are described in the SDP of the Signaling Plane.
The media for a single Session is represented by session.med. The
media control protocol for a single media description is
represented by session.medc.
Measurement Units:
N/A.
Issues:
None.
See Also:
Signaling Plane
3.1.4. Associated Media
Definition:
Media that corresponds to an 'm' line in the SDP payload of the
Signaling Plane.
Discussion:
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Any media protocol MAY be used.
For any session's signaling component, session.sig, there may be
zero, one, or multiple associated media streams. When there are
multiple media streams, these are represented be a vector array
session.med[y]. When there are multiple media streams there will
be multiple media control protocol descriptions as well. They are
represented by a vector array session.medc[y].
Measurement Units:
N/A.
Issues:
None.
3.1.5. Overload
Definition:
Overload is defined as the state where a SIP server does not have
sufficient resources to process all incoming SIP messages
[I-D.ietf-soc-overload-design].
Discussion:
The distinction between an overload condition and other failure
scenarios is outside the scope of black box testing and of this
document. Under overload conditions, all or a percentage of
Session Attempts will fail due to lack of resources. In black box
testing the cause of the failure is not explored. The fact that a
failure occurred for whatever reason, will trigger the tester to
reduce the offered load, as described in the companion methodology
document, [I-D.ietf-bmwg-sip-bench-meth]. SIP server resources
may include CPU processing capacity, network bandwidth, input/
output queues, or disk resources. Any combination of resources
may be fully utilized when a SIP server (the DUT/SUT) is in the
overload condition. For proxy-only type of devices, it is
expected that the proxy will be driven into overload based on the
delivery rate of signaling requests.
For UA-type of network devices such as gateways, it is expected
that the UA will be driven into overload based on the volume of
media streams it is processing.
Measurement Units:
N/A.
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Issues:
The issue of overload in SIP networks is currently a topic of
discussion in the SIPPING WG. The normal response to an overload
stimulus -- sending a 503 response -- is considered inadequate and
new response codes and behaviors may be specified in the future.
From the perspective of this document, all these responses will be
considered to be failures. There is thus no dependency between
this document and the ongoing work on the treatment of overload
failure.
3.1.6. Session Attempt
Definition:
A SIP request sent by the EA that has not received a final
response.
Discussion:
The attempted session may be Invite Initiated or Non-invite
Initiated. When counting the number of session attempts we
include all INVITEs that are rejected for lack of authentication
information. The EA needs to record the total number of session
attempts including those attempts that are routinely rejected by a
proxy that requires the UA to authenticate itself. The EA is
provisioned to deliver a specific number of session attempts per
second. But the EA must also count the actual number of session
attempts per given tie interval.
Measurement Units:
N/A.
Issues:
None.
See Also:
Session
Session Attempt Rate
Invite-initiated Session
Non-Invite initiated Session
3.1.7. Established Session
Definition:
A SIP session for which the EA acting as the UE/UA has received a
200 OK message.
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Discussion:
An Established Session MAY be Invite Initiated or Non-invite
Initiated.
Measurement Units:
N/A.
Issues:
None.
See Also:
Invite-initiated Session
Session Attempting State
Session Disconnecting State
3.1.8. Invite-initiated Session (IS)
Definition:
A Session that is created by an exchange of messages in the
Signaling Plane, the first of which is a SIP INVITE request.
Discussion:
When an IS becomes an Established Session its signaling component
is identified by the SIP dialog parameter values, Call-ID, To-tag,
and From-tag (RFC3261 [RFC3261]). An IS may have zero, one or
multiple Associated Media descriptions in the SDP body. The
inclusion of media is test case dependent. An IS is successfully
established if the following two conditions are met:
1. Sess.sig is established by the end of Establishment Threshold
Time (c.f. Section 3.3.3), and
2. If a media session is described in the SDP body of the
signaling message, then the media session is established by
the end of Establishment Threshold Time (c.f. Section 3.3.3).
An SBC or B2BUA may receive media from a calling or called
party before a signaling dialog is established and certainly
before a confirmed dialog is established. The EA can be built
in such a way that it does not send early media or it needs to
include a parameter that indicates when it will send media.
This parameter must be included in the list of test setup
parameters in Section 5.1 of [I-D.ietf-bmwg-sip-bench-meth]
Measurement Units:
N/A.
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Issues:
None.
See Also:
Session
Non-Invite initiated Session
Associated Media
3.1.9. Non-INVITE-initiated Session (NS)
Definition:
A session that is created by an exchange of SIP messages in the
Signaling Plane the first of which is not a SIP INVITE message.
Discussion:
An NS is successfully established if the Session Attempt via a
non- INVITE request results in the EA receiving a 2xx reply before
the expiration of the Establishment Threshold timer (c.f.,
Section 3.3.3). An example of a NS is a session created by the
SUBSCRIBE request.
Measurement Units:
N/A.
Issues:
None.
See Also:
Session
Invite-initiated Session
3.1.10. Session Attempt Failure
Definition:
A session attempt that does not result in an Established Session.
Discussion:
The session attempt failure may be indicated by the following
observations at the EA:
1. Receipt of a SIP 4xx, 5xx, or 6xx class response to a Session
Attempt.
2. The lack of any received SIP response to a Session Attempt
within the Establishment Threshold Time (c.f. Section 3.3.3).
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Measurement Units:
N/A.
Issues:
None.
See Also:
Session Attempt
3.1.11. Standing Sessions Count
Definition:
The number of Sessions currently established on the DUT/SUT at any
instant.
Discussion:
The number of Standing Sessions is influenced by the Session
Duration and the Session Attempt Rate. Benchmarks MUST be
reported with the maximum and average Standing Sessions for the
DUT/SUT for the duration of the test. In order to determine the
maximum and average Standing Sessions on the DUT/SUT for the
duration of the test it is necessary to make periodic measurements
of the number of Standing Sessions on the DUT/SUT. The
recommended value for the measurement period is 1 second. Since
we cannot directly poll the DUT/SUT, we take the number of
standing sessions on the DUT/SUT to be the number of distinct
calls as measured by the number of distinct Call-IDs that the EA
is processing at the time of measurement. The EA must make that
count available for viewing ad recording.
Measurement Units:
Number of sessions
Issues:
None.
See Also:
Session Duration
Session Attempt Rate
Session Attempt Rate
Emulated Agent
3.2. Test Components
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3.2.1. Emulated Agent
Definition:
A device in the test topology that initiates/responds to SIP
messages as one or more session endpoints and, wherever
applicable, sources/receives Associated Media for Established
Sessions.
Discussion:
The EA functions in the Signaling and Media Planes. The Tester
may act as multiple EAs.
Measurement Units:
N/A
Issues:
None.
See Also:
Media Plane
Signaling Plane
Established Session
Associated Media
3.2.2. Signaling Server
Definition:
Device in the test topology that acts to create sessions between
EAs. This device is either a DUT or a component of a SUT.
Discussion:
The DUT MUST be an RFC 3261 capable network equipment such as a
Registrar, Redirect Server, User Agent Server, Stateless Proxy, or
Stateful Proxy. A DUT MAY also include B2BUA or SBC.
Measurement Units:
NA
Issues:
None.
See Also:
Signaling Plane
3.2.3. SIP-Aware Stateful Firewall
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Definition:
Device in the test topology that provides protection against
various types of security threats to which the Signaling and Media
Planes of the EAs and Signaling Server are vulnerable.
Discussion:
Threats may include Denial-of-Service, theft of service and misuse
of service.he SIP-Aware Stateful Firewall MAY be an internal
component or function of the Session Server. The SIP-Aware
Stateful Firewall MAY be a standalone device. If it is a
standalone device it MUST be paired with a Signaling Server. If
it is a standalone device it MUST be benchmarked as part of a SUT.
SIP-Aware Stateful Firewalls MAY include Network Address
Translation (NAT) functionality. Ideally, the inclusion of the
SIP-Aware Stateful Firewall in the SUT does not lower the measured
values of the performance benchmarks.
Measurement Units:
N/A
Issues:
None.
See Also:
3.2.4. SIP Transport Protocol
Definition:
The protocol used for transport of the Signaling Plane messages.
Discussion:
Performance benchmarks may vary for the same SIP networking device
depending upon whether TCP, UDP, TLS, SCTP, or another transport
layer protocol is used. For this reason it MAY be necessary to
measure the SIP Performance Benchmarks using these various
transport protocols. Performance Benchmarks MUST report the SIP
Transport Protocol used to obtain the benchmark results.
Measurement Units:
TCP,UDP, SCTP, TLS over TCP, TLS over UDP, or TLS over SCTP
Issues:
None.
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See Also:
3.3. Test Setup Parameters
3.3.1. Session Attempt Rate
Definition:
Configuration of the EA for the number of sessions per second that
the EA attempts to establish using the services of the DUT/SUT.
Discussion:
The Session Attempt Rate is the number of sessions per second that
the EA sends toward the DUT/SUT. Some of the sessions attempted
may not result in a session being established. A session in this
case may be either an IS or an NS.
Measurement Units:
Session attempts per second
Issues:
None.
See Also:
Session
Session Attempt
3.3.2. IS Media Attempt Rate
Definition:
Configuration on the EA for the rate, measured in sessions per
second, at which the EA attempts to establish INVITE-initiated
sessions with Associated Media, using the services of the DUT/SUT.
Discussion:
An IS is not required to include a media description. The IS
Media Attempt Rate defines the number of media sessions we are
trying to create, not the number of media sessions that are
actually created. Some attempts might not result in successful
sessions established on the DUT.
Measurement Units:
session attempts per second (saps)
Issues:
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None.
See Also:
IS
3.3.3. Establishment Threshold Time
Definition:
Configuration of the EA for representing the amount of time that
an EA will wait before declaring a Session Attempt Failure.
Discussion:
This time duration is test dependent.
It is RECOMMENDED that the Establishment Threshold Time value be
set to Timer B (for ISs) or Timer F (for NSs) as specified in RFC
3261, Table 4 [RFC3261]. Following the default value of T1
(500ms) specified in the table and a constant multiplier of 64
gives a value of 32 seconds for this timer (i.e., 500ms * 64 =
32s).
Measurement Units:
seconds
Issues:
None.
See Also:
session establishment failure
3.3.4. Session Duration
Definition:
Configuration of the EA that represents the amount of time that
the SIP dialog is intended to exist between the two EAs associated
with the test.
Discussion:
The time at which the BYE is sent will control the Session
Duration
Normally the Session Duration will be the same as the Media
Session Hold Time. However, it is possible that the dialog
established between the two EAs can support different media
sessions at different points in time. Providing both parameters
allows the testing agency to explore this possibility.
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Measurement Units:
seconds
Issues:
None.
See Also:
Media Session Hold Time
3.3.5. Media Packet Size
Definition:
Configuration on the EA for a fixed size of packets used for media
streams.
Discussion:
For a single benchmark test, all sessions use the same size packet
for media streams. The size of packets can cause variation in
performance benchmark measurements.
Measurement Units:
bytes
Issues:
None.
See Also:
3.3.6. Media Offered Load
Definition:
Configuration of the EA for the constant rate of Associated Media
traffic offered by the EA to the DUT/SUT for one or more
Established Sessions of type IS.
Discussion:
The Media Offered Load to be used for a test MUST be reported with
three components:
1. per Associated Media stream;
2. per IS;
3. aggregate.
For a single benchmark test, all sessions use the same Media
Offered Load per Media Stream. There may be multiple Associated
Media streams per IS. The aggregate is the sum of all Associated
Media for all IS.
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Measurement Units:
packets per second (pps)
Issues:
None.
See Also:
Established Session
Invite Initiated Session
Associated Media
3.3.7. Media Session Hold Time
Definition:
Parameter configured at the EA, that represents the amount of time
that the Associated Media for an Established Session of type IS
will last.
Discussion:
The Associated Media streams may be bi-directional or uni-
directional as indicated in the test methodology.
Normally the Media Session Hold Time will be the same as the
Session Duration. However, it is possible that the dialog
established between the two EAs can support different media
sessions at different points in time. Providing both parameters
allows the testing agency to explore this possibility.
Measurement Units:
seconds
Issues:
None.
See Also:
Associated Media
Established Session
Invite-initiated Session (IS)
3.3.8. Loop Detection Option
Definition:
An option that causes a Proxy to check for loops in the routing of
a SIP request before forwarding the request.
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Discussion:
This is an optional process that a SIP proxy may employ; the
process is described under Proxy Behavior in RFC 3261 [RFC3261] in
Section 16.3 Request Validation and that section also contains
suggestions as to how the option could be implemented. Any
procedure to detect loops will use processor cycles and hence
could impact the performance of a proxy.
Measurement Units:
NA
Issues:
None.
See Also:
3.3.9. Forking Option
Definition:
An option that enables a Proxy to fork requests to more than one
destination.
Discussion:
This is an process that a SIP proxy may employ to find the UAS.
The option is described under Proxy Behavior in RFC 3261 in
Section 16.1. A proxy that uses forking must maintain state
information and this will use processor cycles and memory. Thus
the use of this option could impact the performance of a proxy and
different implementations could produce different impacts.
SIP supports serial or parallel forking. When performing a test,
the type of forking mode MUST be indicated.
Measurement Units:
The number of endpoints that will receive the forked invitation.
A value of 1 indicates that the request is destined to only one
endpoint, a value of 2 indicates that the request is forked to two
endpoints, and so on. This is an integer value ranging between 1
and N inclusive, where N is the maximum number of endpoints to
which the invitation is sent.
Type of forking used, namely parallel or serial.
Issues:
None.
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See Also:
3.4. Benchmarks
3.4.1. Registration Rate
Definition:
The maximum number of registrations that can be successfully
completed by the DUT/SUT in a given time period without
registration failures in that time period.
Discussion:
This benchmark is obtained with zero failure in which 100% of the
registrations attempted by the EA are successfully completed by
the DUT/SUT. The registration rate provisioned on the Emulated
Agent is raised and lowered as described in the algorithm in the
companion methodology draft [I-D.ietf-bmwg-sip-bench-meth] until a
traffic load consisting of registrations at the given attempt rate
over the sustained period of time identified by T in the algorithm
completes without failure.
Measurement Units:
registrations per second (rps)
Issues:
None.
See Also:
3.4.2. Session Establishment Rate
Definition:
The maximum number of sessions that can be successfully completed
by the DUT/SUT in a given time period without session
establishment failures in that time period.
Discussion:
This benchmark is obtained with zero failure in which 100% of the
sessions attempted by the Emulated Agent are successfully
completed by the DUT/SUT. The session attempt rate provisioned on
the EA is raised and lowered as described in the algorithm in the
accompanying methodology document, until a traffic load at the
given attempt rate over the sustained period of time identified by
T in the algorithm completes without any failed session attempts.
Sessions may be IS or NS or a mix of both and will be defined in
the particular test.
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Measurement Units:
sessions per second (sps)
Issues:
None.
See Also:
Invite-initiated Sessions
Non-INVITE initiated Sessions
Session Attempt Rate
3.4.3. Session Capacity
Definition:
The maximum value of Standing Sessions Count achieved by the DUT/
SUT during a time period T in which the EA is sending session
establishment messages at the Session Establishment Rate.
Discussion:
Sessions may be IS or NS. If they are IS they can be with or
without media. When benchmarking Session Capacity for sessions
with media it is required that these sessions be permanently
established (i.e., they remain active for the duration of the
test.) This can be achieved by causing the EA not to send a BYE
for the duration of the testing. In the signaling plane, this
requirement means that the dialog lasts as long as the test lasts.
When media is present, the Media Session Hold Time MUST be set to
infinity so that sessions remain established for the duration of
the test. If the DUT/SUT is dialog-stateful, then we expect its
performance will be impacted by setting Media Session Hold Time to
infinity, since the DUT/SUT will need to allocate resources to
process and store the state information. The report of the
Session Capacity must include the Session Establishment Rate at
which it was measured.
Measurement Units:
sessions
Issues:
None.
See Also:
Established Session
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Session Attempt Rate
Session Attempt Failure
3.4.4. Session Overload Capacity
Definition:
The maximum number of Established Sessions that can exist
simultaneously on the DUT/SUT until it stops responding to Session
Attempts.
Discussion:
Session Overload Capacity is measured after the Session Capacity
is measured. The Session Overload Capacity is greater than or
equal to the Session Capacity. When benchmarking Session Overload
Capacity, continue to offer Session Attempts to the DUT/SUT after
the first Session Attempt Failure occurs and measure Established
Sessions until no there is no SIP message response for the
duration of the Establishment Threshold. Note that the Session
Establishment Performance is expected to decrease after the first
Session Attempt Failure occurs.
Units:
Sessions
Issues:
None.
See Also:
Overload
Session Capacity
Session Attempt Failure
3.4.5. Session Establishment Performance
Definition:
The percent of Session Attempts that become Established Sessions
over the duration of a benchmarking test.
Discussion:
Session Establishment Performance is a benchmark to indicate
session establishment success for the duration of a test. The
duration for measuring this benchmark is to be specified in the
Methodology. The Session Duration SHOULD be configured to
infinity so that sessions remain established for the entire test
duration.
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Session Establishment Performance is calculated as shown in the
following equation:
Session Establishment = Total Established Sessions
Performance --------------------------
Total Session Attempts
Session Establishment Performance may be monitored real-time
during a benchmarking test. However, the reporting benchmark MUST
be based on the total measurements for the test duration.
Measurement Units:
Percent (%)
Issues:
None.
See Also:
Established Session
Session Attempt
3.4.6. Session Attempt Delay
Definition:
The average time measured at the EA for a Session Attempt to
result in an Established Session.
Discussion:
Time is measured from when the EA sends the first INVITE for the
call-ID in the case of an IS. Time is measured from when the EA
sends the first non-INVITE message in the case of an NS. Session
Attempt Delay MUST be measured for every established session to
calculate the average. Session Attempt Delay MUST be measured at
the Session Establishment Rate.
Measurement Units:
Seconds
Issues:
None.
See Also:
Session Establishment Rate
3.4.7. IM Rate
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Definition:
Maximum number of IM messages completed by the DUT/SUT.
Discussion:
For a UAS, the definition of success is the receipt of an IM
request and the subsequent sending of a final response.
For a UAC, the definition of success is the sending of an IM
request and the receipt of a final response to it. For a proxy,
the definition of success is as follows:
A. the number of IM requests it receives from the upstream client
MUST be equal to the number of IM requests it sent to the
downstream server; and
B. the number of IM responses it receives from the downstream
server MUST be equal to the number of IM requests sent to the
downstream server; and
C. the number of IM responses it sends to the upstream client
MUST be equal to the number of IM requests it received from
the upstream client.
Measurement Units:
IM messages per second
Issues:
None.
See Also:
4. IANA Considerations
This document requires no IANA considerations.
5. Security Considerations
Documents of this type do not directly affect the security of
Internet or corporate networks as long as benchmarking is not
performed on devices or systems connected to production networks.
Security threats and how to counter these in SIP and the media layer
is discussed in RFC3261 [RFC3261], RFC 3550 [RFC3550], RFC3711
[RFC3711] and various other drafts. This document attempts to
formalize a set of common terminology for benchmarking SIP networks.
Packets with unintended and/or unauthorized DSCP or IP precedence
values may present security issues. Determining the security
consequences of such packets is out of scope for this document.
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6. Acknowledgments
The authors would like to thank Keith Drage, Cullen Jennings, Daryl
Malas, Al Morton, and Henning Schulzrinne for invaluable
contributions to this document.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[I-D.ietf-bmwg-sip-bench-meth]
Davids, C., Gurbani, V., and S. Poretsky, "Methodology for
Benchmarking SIP Networking Devices",
draft-ietf-bmwg-sip-bench-meth-04 (work in progress),
March 2012.
7.2. Informational References
[RFC2285] Mandeville, R., "Benchmarking Terminology for LAN
Switching Devices", RFC 2285, February 1998.
[RFC1242] Bradner, S., "Benchmarking terminology for network
interconnection devices", RFC 1242, July 1991.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[I-D.ietf-soc-overload-design]
Hilt, V., Noel, E., Shen, C., and A. Abdelal, "Design
Considerations for Session Initiation Protocol (SIP)
Overload Control", draft-ietf-soc-overload-design-08 (work
Davids, et al. Expires April 25, 2013 [Page 36]
Internet-Draft SIP Benchmarking Terminology October 2012
in progress), July 2011.
[I-D.ietf-soc-overload-control]
Gurbani, V., Hilt, V., and H. Schulzrinne, "Session
Initiation Protocol (SIP) Overload Control",
draft-ietf-soc-overload-control-10 (work in progress),
October 2012.
Appendix A. White Box Benchmarking Terminology
Session Attempt Arrival Rate
Definition:
The number of Session Attempts received at the DUT/SUT over a
specified time period.
Discussion:
Sessions Attempts are indicated by the arrival of SIP INVITES OR
SUBSCRIBE NOTIFY messages. Session Attempts Arrival Rate
distribution can be any model selected by the user of this
document. It is important when comparing benchmarks of different
devices that same distribution model was used. Common
distributions are expected to be Uniform and Poisson.
Measurement Units:
Session attempts/sec
Issues:
None.
See Also:
Session Attempt
Authors' Addresses
Carol Davids
Illinois Institute of Technology
201 East Loop Road
Wheaton, IL 60187
USA
Phone: +1 630 682 6024
Email: davids@iit.edu
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Vijay K. Gurbani
Bell Laboratories, Alcatel-Lucent
1960 Lucent Lane
Rm 9C-533
Naperville, IL 60566
USA
Phone: +1 630 224 0216
Email: vkg@bell-labs.com
Scott Poretsky
Allot Communications
300 TradeCenter, Suite 4680
Woburn, MA 08101
USA
Phone: +1 508 309 2179
Email: sporetsky@allot.com
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