Benchmarking Methodology Working C. Davids
Group Illinois Institute of Technology
Internet-Draft V. Gurbani
Expires: September 13, 2012 Bell Laboratories, Alcatel-Lucent
S. Poretsky
Allot Communications
March 12, 2012
Terminology for Benchmarking Session Initiation Protocol (SIP)
Networking Devices
draft-ietf-bmwg-sip-bench-term-04
Abstract
This document provides a terminology for benchmarking SIP performance
in networking devices. 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 control plane and media plane. The
terms are intended for use in a companion methodology document for
complete performance characterization of a device in a variety of
conditions making it possible to compare performance of different
devices. It is critical to provide test setup parameters and a
methodology document for SIP performance benchmarking because SIP
allows a wide range of configuration and operational conditions that
can influence performance benchmark measurements. It is necessary to
have terminology and methodology standards to ensure that reported
benchmarks have consistent definition and were obtained following the
same procedures. Benchmarks can be applied to compare performance of
a variety of SIP networking devices.
Status of this Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on September 13, 2012.
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Copyright Notice
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Benchmarking Models . . . . . . . . . . . . . . . . . . . 7
3. Term Definitions . . . . . . . . . . . . . . . . . . . . . . . 13
3.1. Protocol Components . . . . . . . . . . . . . . . . . . . 13
3.1.1. Session . . . . . . . . . . . . . . . . . . . . . . . 13
3.1.2. Signaling Plane . . . . . . . . . . . . . . . . . . . 16
3.1.3. Media Plane . . . . . . . . . . . . . . . . . . . . . 16
3.1.4. Associated Media . . . . . . . . . . . . . . . . . . . 17
3.1.5. Overload . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.6. Session Attempt . . . . . . . . . . . . . . . . . . . 18
3.1.7. Established Session . . . . . . . . . . . . . . . . . 18
3.1.8. Invite-initiated Session (IS) . . . . . . . . . . . . 19
3.1.9. Non-INVITE-initiated Session (NS) . . . . . . . . . . 20
3.1.10. Session Attempt Failure . . . . . . . . . . . . . . . 20
3.1.11. Standing Sessions Count . . . . . . . . . . . . . . . 21
3.2. Test Components . . . . . . . . . . . . . . . . . . . . . 21
3.2.1. Emulated Agent . . . . . . . . . . . . . . . . . . . . 21
3.2.2. Signaling Server . . . . . . . . . . . . . . . . . . . 22
3.2.3. SIP-Aware Stateful Firewall . . . . . . . . . . . . . 22
3.2.4. SIP Transport Protocol . . . . . . . . . . . . . . . . 23
3.3. Test Setup Parameters . . . . . . . . . . . . . . . . . . 24
3.3.1. Session Attempt Rate . . . . . . . . . . . . . . . . . 24
3.3.2. IS Media Attempt Rate . . . . . . . . . . . . . . . . 24
3.3.3. Establishment Threshold Time . . . . . . . . . . . . . 25
3.3.4. Session Duration . . . . . . . . . . . . . . . . . . . 25
3.3.5. Media Packet Size . . . . . . . . . . . . . . . . . . 26
3.3.6. Media Offered Load . . . . . . . . . . . . . . . . . . 26
3.3.7. Media Session Hold Time . . . . . . . . . . . . . . . 27
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3.3.8. Loop Detection Option . . . . . . . . . . . . . . . . 27
3.3.9. Forking Option . . . . . . . . . . . . . . . . . . . . 28
3.4. Benchmarks . . . . . . . . . . . . . . . . . . . . . . . . 29
3.4.1. Registration Rate . . . . . . . . . . . . . . . . . . 29
3.4.2. Session Establishment Rate . . . . . . . . . . . . . . 29
3.4.3. Session Capacity . . . . . . . . . . . . . . . . . . . 30
3.4.4. Session Overload Capacity . . . . . . . . . . . . . . 31
3.4.5. Session Establishment Performance . . . . . . . . . . 31
3.4.6. Session Attempt Delay . . . . . . . . . . . . . . . . 32
3.4.7. IM Rate . . . . . . . . . . . . . . . . . . . . . . . 32
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
5. Security Considerations . . . . . . . . . . . . . . . . . . . 33
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 34
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.1. Normative References . . . . . . . . . . . . . . . . . . . 34
7.2. Informational References . . . . . . . . . . . . . . . . . 34
Appendix A. White Box Benchmarking Terminology . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35
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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].
Definitions are indexed and grouped together for ease of reference.
This document uses existing terminology defined in other BMWG work.
Examples include, but are not limited to:
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. 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 protocol.
2. Introduction
Service Providers are now planning Voice Over IP (VoIP) and
Multimedia network deployments using the IETF developed Session
Initiation Protocol (SIP) [RFC3261]. SIP is a signaling protocol
originally intended to be used for the dynamic establishment,
disconnection and modification of streams of media between end users.
As it has evolved it has been adopted for use in a growing number of
applications and features. Many of these result in the creation of a
media stream, but some do not. Instead, they create other services
tailored to the end-users' immediate needs or preferences. 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. The performance of end-user devices is outside the
scope of this document.
VoIP with SIP has led to the development of new networking devices
including SIP Server, Session Border Controllers (SBC), Back-to-back
user agents (B2BUA) and SIP-Aware Stateful Firewall. The mix of
voice and IP functions in these various devices has produced
inconsistencies in vendor reported performance metrics and has caused
confusion in the service provider community. SIP allows a wide range
of configuration and operational conditions that can influence
performance benchmark measurements. When the device under test
terminates or relays both media and signaling, for example, it is
important to be able to correlate a signaling measurement with the
media plane measurements to determine the system performance. As
devices and their functions proliferate, the need to have a
consistent set of metrics to compare their performance becomes
increasingly urgent. This document and its companion methodology
document [I-D.ietf-bmwg-sip-bench-meth] provide a set of black-box
benchmarks 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
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and to achieve comparable and repeatable results. This document
provides a common set of well-defined terms for Test Components, Test
Setup Parameters, and Benchmarks. All the benchmarks defined are
black-box measurements of the SIP Control (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 (control- plane)
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 (this is
referred to as the "Signaling Server".) The DUT MAY be a multi-
port SIP-to-switched network gateway implemented as a SIP UAC or
UAS.
o The DUT MAY have 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 Control Signaling in presence of Media
* The media performance is not benchmarked in this work item.
* It is RECOMMENDED that control plane benchmarks are 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 control
plane and media plane are treated as orthogonal to each other
in this document. While many devices support the creation of
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
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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; however, 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 as this may impact the
performance benchmarks. Any observable performance degradation
due to authentication is of interest to the SIP community.
Whether or not the REGISTER and INVITE requests are challenged is
a condition of test and will be recorded and reported.
o Re-INVITE requests are not considered in scope of this work item.
o Only session establishment is considered for the performance
benchmarks. Session disconnect is not considered in the scope of
this work item.
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
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.
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+--------+ Signaling request +--------+
| +----------------------------->| |
| Tester | | Tester |
| | 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
associated media.
+--------+ Signaling request +--------+
| +----------------------------->| |
| Tester | | DUT |
| EA | Response | |
| |<-----------------------------+ |
+--------+ +--------+
Figure 3: Baseline performance for DUT acting as a user agent server
without associated media
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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
with associated media
Figure 6 shows that the Tester acts as the initiating and responding
EA as the DUT/SUT forwards Session Attempts.
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+--------+ 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) |
| | 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) |
| | | | | |
+--------+ +--------+ +--------+
/|\ /|\
| 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|
| | | | | | | |
| | | | | | | |
+------+ +---+ +---+ +------+
/|\ /|\
| 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|
| | | | | | | |
| | | | | | | |
| |<========>| |<========>| |<========>| |
+------+ 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 | | |
--------|<-------------- | | |
| | | |
| | | |
| | | Media |
Established | |<=====>|
| | | |
| BYE | | |
--------+--------------> | | |
| | | |
Disconnecting | | |
| 200 OK | | |
--------|<-------------- | | |
| | | |
Figure 11: Basic SIP test topology
3. Term Definitions
3.1. Protocol Components
3.1.1. Session
Definition:
The combination of signaling and media messages and processes that
enable two or more participants to communicate.
Discussion:
SIP messages in the signaling plane can be used to create and
manage applications for one or more end users. SIP is often used
to create and manage media streams in support of applications. A
session always has a signaling component and may have a media
component. Therefore, a Session may be defined as signaling only
or a combination of signaling and media (c.f. Associated Media,
see Section 3.1.4). SIP includes definitions of a Call-ID, a
dialogue and a transaction that support this application. A
growing number of usages and applications do not require the
creation of associated media. The first such usage was the
REGISTER. Applications that use the MESSAGE and SUBSCRIBE/NOTIFY
methods also do not require SIP to manage media streams. The
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terminology Invite-initiated Session (IS) and Non-invite initiated
Session (NS) are used to distinguish between these different
usages.
A Session in the context of this document, is 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.
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, 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:
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N/A.
Issues:
None.
See Also:
Media Plane
Signaling Plane
Associated Media
Invite-initiated Session (IS)
Non-invite-initiated Session (NS)
|\
|
| \
sess.sig|
| \
|
| \
| o
| /
| / |
| /
| / |
| /
| / |
| /
| / | sess.medc
|/_____________________
/ /
/ |
/ /
sess.med / |
/_ _ _ _ _ _ _ _/
/
/
/
/
Figure 12: Application or session components
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3.1.2. Signaling Plane
Definition:
The control plane in which SIP messages [RFC3261] are exchanged
between SIP Agents [RFC3261] to establish a connection for media
exchange.
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 Signaling
Plane MUST include the Session Description Protocol (SDP).
The Signaling Plane for a single Session is represented by
session.sig.
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 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, video, whiteboard,
and instant messaging service. The media stream is described in
the SDP of the Signaling Plane.
The media for a single Session is represented by session.med. The
media control protocol is represented by session.medc.
Measurement Units:
N/A.
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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:
Any media protocol MAY be used.
For any session's signaling component, represented as session.sig,
there may be one or multiple associated media streams which are
represented be a vector array session.med[y], which is referred to
as the Associated Media.
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]. The distinction between an
overload condition and other failure scenarios is outside the
scope of this document which is blackbox testing.
Discussion:
Under overload conditions, all or a percentage of Session Attempts
will fail due to lack of resources. 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, overload issues will
be dominated by the number of signaling messages they can handle
in a unit time before their throughput starts to drop.
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For UA-type of network devices (e.g., gateways), overload must
necessarily include both the signaling traffic and media streams.
It is expected that the amount of signaling that a UA can handle
is inversely proportional to the amount of media streams currently
handled by that UA.
Measurement Units:
N/A.
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 Session for which the EA has sent the SIP INVITE or
SUBSCRIBE NOTIFY and has not yet received a message response from
the DUT/SUT.
Discussion:
The attempted session may be an IS or an NS. The Session Attempt
includes SIP INVITEs and SUBSCRIBE/NOTIFY messages. It also
includes all INVITEs that are rejected for lack of authentication
information.
Measurement Units:
N/A.
Issues:
None.
See Also:
Session
Session Attempt Rate
Invite-initiated Session
Non-Invite initiated Session
3.1.7. Established Session
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Definition:
A SIP session for which the EA acting as the UE/UA has received a
200 OK message from the DUT/SUT.
Discussion:
An Established Session MAY be type INVITE-Session (IS) or Non-
INVITE Session (NS).
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:
An IS is identified by the Call-ID, To-tag, and From-tag of the
SIP message that establishes the session. These three fields are
used to identify a SIP Dialog (RFC3261 [RFC3261]). An IS may have
Associated Media description in the SDP body. An IS may have
multiple Associated Media streams. 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).
Measurement Units:
N/A.
Issues:
None.
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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 messages in the
Signaling Plane that does not include an initial 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 from
the DUT/SUT 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.
Measurement Units:
Number of sessions
Issues:
None.
See Also:
Session Duration
Session Attempt Rate
Session Attempt Rate
3.2. Test Components
3.2.1. Emulated Agent
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Definition:
A device in 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 test topology that acts to create sessions between EAs
in the media plane. This device is either a DUT or component of a
SUT.
Discussion:
The DUT MUST be a 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 test topology that provides Denial-of-Service (DoS)
Protection to the Signaling and Media Planes for the EAs and
Signaling Server
Discussion:
The 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 as a SUT has no degradation to the measured 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.
See Also:
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3.3. Test Setup Parameters
3.3.1. Session Attempt Rate
Definition:
Configuration of the EA for the number of sessions that the EA
attempts to establish with the DUT/SUT over a specified time
interval.
Discussion:
The Session Attempt Rate can cause variation in performance
benchmark measurements. Since this is the number of sessions
configured on the Tester, some sessions may not be successfully
established on the DUT. A session 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 number of ISs with Associated Media to
be established at the DUT per continuous one- second time
intervals.
Discussion:
Note that a Media Session MUST be associated with an IS. In this
document we assume that there is a one to one correspondence
between IS session attempts and Media Session attempts. By
including this definition we leave open the possibility that there
may be an IS that does not include a media description. Also note
that 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. Variations in the Media Session
Attempt Rate might cause variations in performance benchmark
measurements. Some attempts might not result in successful
sessions established on the DUT.
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Measurement Units:
session attempts per second (saps)
Issues:
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
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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.
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;
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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.
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
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Definition:
An option that causes a Proxy to check for loops in the routing of
a SIP request before forwarding the request.
Discussion:
This is an optional process that a SIP proxy may employ; the
process is described under Proxy Behavior in RFC 3261 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.
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Issues:
None.
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.
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Sessions may be IS or NS or a mix of both and will be defined in
the particular test.
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.
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See Also:
Established Session
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. It is worth noting 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 Maximum Session Establishment Rate.
Measurement Units:
Seconds
Issues:
None.
See Also:
Maximum 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-03 (work in progress),
March 2011.
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
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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-07 (work in progress),
January 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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