draft-ietf-bliss-shared-appearances-10.txt   draft-ietf-bliss-shared-appearances-11.txt 
BLISS A. Johnston, Ed. BLISS A. Johnston, Ed.
Internet-Draft Avaya Internet-Draft Avaya
Updates: 3261, 4235 (if approved) M. Soroushnejad Updates: 3261, 4235 (if approved) M. Soroushnejad
Intended status: Standards Track V. Venkataramanan Intended status: Standards Track V. Venkataramanan
Expires: November 5, 2012 Sylantro Systems Corp Expires: December 10, 2012 Sylantro Systems Corp
May 4, 2012 June 8, 2012
Shared Appearances of a Session Initiation Protocol (SIP) Address of Shared Appearances of a Session Initiation Protocol (SIP) Address of
Record (AOR) Record (AOR)
draft-ietf-bliss-shared-appearances-10 draft-ietf-bliss-shared-appearances-11
Abstract Abstract
This document describes the requirements and implementation of a This document describes the requirements and implementation of a
group telephony feature commonly known as Bridged Line Appearance group telephony feature commonly known as Bridged Line Appearance
(BLA) or Multiple Line Appearance (MLA), or Shared Call/Line (BLA) or Multiple Line Appearance (MLA), or Shared Call/Line
Appearance (SCA). When implemented using the Session Initiation Appearance (SCA). When implemented using the Session Initiation
Protocol (SIP), it is referred to as shared appearances of an Address Protocol (SIP), it is referred to as shared appearances of an Address
of Record (AOR) since SIP does not have the concept of lines. This of Record (AOR) since SIP does not have the concept of lines. This
feature is commonly offered in IP Centrex services and IP-PBX feature is commonly offered in IP Centrex services and IP-PBX
offerings and is likely to be implemented on SIP IP telephones and offerings and is likely to be implemented on SIP IP telephones and
SIP feature servers used in a business environment. This feature SIP feature servers used in a business environment. This feature
allows several user agents (UAs) to share a common AOR, learn about allows several user agents (UAs) to share a common AOR, learn about
calls placed and received by other UAs in the group, and pick up or calls placed and received by other UAs in the group, and pick up or
join calls within the group. This document discusses use cases, join calls within the group. This document discusses use cases,
lists requirements and defines extensions to implement this feature. lists requirements and defines extensions to implement this feature.
This specification updates RFC3261 and RFC4235.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 5, 2012. This Internet-Draft will expire on December 10, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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4.2. Implementation . . . . . . . . . . . . . . . . . . . . . 9 4.2. Implementation . . . . . . . . . . . . . . . . . . . . . 9
5. Normative Description . . . . . . . . . . . . . . . . . . . . 11 5. Normative Description . . . . . . . . . . . . . . . . . . . . 11
5.1. Elements . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1. Elements . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Shared Appearance Dialog Package Extensions . . . . . . . 12 5.2. Shared Appearance Dialog Package Extensions . . . . . . . 12
5.2.1. The <appearance> element . . . . . . . . . . . . . . . 12 5.2.1. The <appearance> element . . . . . . . . . . . . . . . 12
5.2.2. The <exclusive> element . . . . . . . . . . . . . . . 12 5.2.2. The <exclusive> element . . . . . . . . . . . . . . . 12
5.2.3. The <joined-dialog> element . . . . . . . . . . . . . 13 5.2.3. The <joined-dialog> element . . . . . . . . . . . . . 13
5.2.4. The <replaced-dialog> element . . . . . . . . . . . . 14 5.2.4. The <replaced-dialog> element . . . . . . . . . . . . 14
5.3. Shared Appearance User Agents . . . . . . . . . . . . . . 14 5.3. Shared Appearance User Agents . . . . . . . . . . . . . . 14
5.3.1. Appearance Numbers and Call Context . . . . . . . . . 17 5.3.1. Appearance Numbers and Call Context . . . . . . . . . 17
5.3.2. Appearance Numbers and Call Control . . . . . . . . . 17 5.3.2. Appearance Numbers and Call Control . . . . . . . . . 18
5.3.3. Appearance Numbers and Transfer . . . . . . . . . . . 18 5.3.3. Appearance Numbers and Transfer . . . . . . . . . . . 18
5.4. Appearance Agent . . . . . . . . . . . . . . . . . . . . 19 5.4. Appearance Agent . . . . . . . . . . . . . . . . . . . . 19
6. XML Schema Definition . . . . . . . . . . . . . . . . . . . . 21 6. XML Schema Definition . . . . . . . . . . . . . . . . . . . . 21
7. Alert-Info Appearance Parameter Definition . . . . . . . . . . 23 7. Alert-Info Appearance Parameter Definition . . . . . . . . . . 23
8. User Interface Considerations . . . . . . . . . . . . . . . . 24 8. User Interface Considerations . . . . . . . . . . . . . . . . 24
8.1. Appearance Number Rendering . . . . . . . . . . . . . . . 24 8.1. Appearance Number Rendering . . . . . . . . . . . . . . . 24
8.1.1. Single Appearance UAs . . . . . . . . . . . . . . . . 24 8.1.1. Single Appearance UAs . . . . . . . . . . . . . . . . 24
8.1.2. Dual Appearance UAs . . . . . . . . . . . . . . . . . 24 8.1.2. Dual Appearance UAs . . . . . . . . . . . . . . . . . 24
8.1.3. Shared Appearance UAs with Fixed Appearance Number . . 25 8.1.3. Shared Appearance UAs with Fixed Appearance Number . . 25
8.1.4. Shared Appearance UAs with Variable Appearance 8.1.4. Shared Appearance UAs with Variable Appearance
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11.10. Joining or Bridging an Appearance . . . . . . . . . . . . 55 11.10. Joining or Bridging an Appearance . . . . . . . . . . . . 55
11.11. Appearance Allocation - Loss of Appearance . . . . . . . 58 11.11. Appearance Allocation - Loss of Appearance . . . . . . . 58
11.12. Appearance Seizure Contention Race Condition . . . . . . 59 11.12. Appearance Seizure Contention Race Condition . . . . . . 59
11.13. Appearance Agent Subscription to UAs . . . . . . . . . . 60 11.13. Appearance Agent Subscription to UAs . . . . . . . . . . 60
11.14. Appearance Pickup Race Condition Failure . . . . . . . . 62 11.14. Appearance Pickup Race Condition Failure . . . . . . . . 62
11.15. Appearance Seizure Incoming/Outgoing Contention Race 11.15. Appearance Seizure Incoming/Outgoing Contention Race
Condition . . . . . . . . . . . . . . . . . . . . . . . . 65 Condition . . . . . . . . . . . . . . . . . . . . . . . . 65
12. Security Considerations . . . . . . . . . . . . . . . . . . . 66 12. Security Considerations . . . . . . . . . . . . . . . . . . . 66
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66
13.1. SIP Event Package Parameter: shared . . . . . . . . . . . 66 13.1. SIP Event Package Parameter: shared . . . . . . . . . . . 66
13.2. URN Sub-Namespace Registration: sa-dialog-info . . . . . 67 13.2. SIP Alert-Info Header Field Parameter: appearance . . . . 66
13.3. XML Schema Registration . . . . . . . . . . . . . . . . . 67 13.3. URN Sub-Namespace Registration: sa-dialog-info . . . . . 67
13.4. XML Schema Registration . . . . . . . . . . . . . . . . . 68
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 68 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 68
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 68 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 69
15.1. Normative References . . . . . . . . . . . . . . . . . . 68 15.1. Normative References . . . . . . . . . . . . . . . . . . 69
15.2. Informative References . . . . . . . . . . . . . . . . . 69 15.2. Informative References . . . . . . . . . . . . . . . . . 70
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 70
1. Introduction 1. Introduction
The feature and functionality requirements for SIP user agents (UAs) The feature and functionality requirements for SIP user agents (UAs)
supporting business telephony applications differ greatly from basic supporting business telephony applications differ greatly from basic
SIP user agents, both in terms of services and end user experience. SIP user agents, both in terms of services and end user experience.
In addition to basic SIP support [RFC3261], many of the services in a In addition to basic SIP support [RFC3261], many of the services in a
business environment require the support for SIP extensions such as business environment require the support for SIP extensions such as
REFER [RFC3515], SUBSCRIBE/NOTIFY primitives REFER [RFC3515], SUBSCRIBE/NOTIFY primitives
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5.3. Shared Appearance User Agents 5.3. Shared Appearance User Agents
User Agents that support the Shared Appearance feature MUST support User Agents that support the Shared Appearance feature MUST support
the dialog state package [RFC4235] with the shared appearance the dialog state package [RFC4235] with the shared appearance
extensions and the 'shared' dialog event package parameter defined in extensions and the 'shared' dialog event package parameter defined in
Section 13. Section 13.
User Agents MUST support the dialog package extensions in Section 5.2 User Agents MUST support the dialog package extensions in Section 5.2
along with SUBSCRIBE and NOTIFY [I-D.ietf-sipcore-rfc3265bis] and along with SUBSCRIBE and NOTIFY [I-D.ietf-sipcore-rfc3265bis] and
PUBLISH [RFC3903]. SUBSCRIBE, NOTIFY, and PUBLISH requests for the PUBLISH [RFC3903]. SUBSCRIBE, NOTIFY, and PUBLISH requests for the
dialog event package MUST include the 'shared' Event header field dialog event package include the 'shared' Event header field
parameter. parameter as required by this specification.
The presence of the 'shared' Event package parameter tells the The presence of the 'shared' Event package parameter tells the
Appearance Agent that this UA supports this specification. Appearance Agent that the UA supports this specification.
Upon initialization, the UA MUST subscribe to the dialog event Upon initialization, the UA MUST subscribe to the dialog event
package of the AOR and refresh the subscription per the SIP Events package of the AOR and refresh the subscription per the SIP Events
Framework. If the SUBSCRIBE request fails, then no Appearance Agent Framework. If the SUBSCRIBE request fails, then no Appearance Agent
may be present and this feature is not active for this AOR. The UA may be present and this feature is not active for this AOR. The UA
MAY periodically retry the subscription to see if conditions have MAY periodically retry the subscription to see if conditions have
changed at intervals no shorter than 4 hours. changed at intervals no shorter than 4 hours.
Four hours was chosen to limit the subscription test to 6 per day Four hours was chosen to limit the subscription test to 6 per day
per UA. Increading this interval would reduce this failure per UA. Increading this interval would reduce this failure
traffic but take longer for a newly activated Appearance Agent to traffic but take longer for a newly activated Appearance Agent to
be discovered. be discovered.
UAs can also use the presence of the 'shared' dialog event package
parameter in NOTIFYs to discover the presence of an Appearance Agent
for the AOR.
User Agents which implement the shared appearances feature and call User Agents which implement the shared appearances feature and call
pickup, joining and bridging MUST support sending an INVITE with pickup, joining and bridging MUST support sending an INVITE with
Replaces [RFC3891] or Join [RFC3911]. The User Agent Client needs to Replaces [RFC3891] or Join [RFC3911]. The User Agent Client needs to
include the to-tag and from-tag information in the Replaces or Join include the to-tag and from-tag information in the Replaces or Join
header so that the correct dialog will be matched by the User Agent header so that the correct dialog will be matched by the User Agent
Server per the rules in RFC 3891 and RFC 3911. Server per the rules in RFC 3891 and RFC 3911.
All User Agents which implement the shared appearances feature and All User Agents which implement the shared appearances feature and
support INVITE MUST support receiving an INVITE with a Replaces support INVITE MUST support receiving an INVITE with a Replaces
[RFC3891] or a Join [RFC3911] header field. [RFC3891] or a Join [RFC3911] header field.
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header field. As a result, the Appearance Agent will have reused the header field. As a result, the Appearance Agent will have reused the
appearance number of the dialog with Carol, and this appearance appearance number of the dialog with Carol, and this appearance
number will continue to be used after the dialog with Carol has been number will continue to be used after the dialog with Carol has been
terminated. terminated.
5.4. Appearance Agent 5.4. Appearance Agent
An Appearance Agent defined in this specification MUST implement a An Appearance Agent defined in this specification MUST implement a
dialog package state agent for the UAs registered against the AOR. dialog package state agent for the UAs registered against the AOR.
The Appearance Agent MUST support the appearance dialog package The Appearance Agent MUST support the appearance dialog package
extensions defined in Section 5.2. The Appearance Agent MUST support extensions defined in Section 5.2 and use the 'shared' event
publications and subscriptions for this event package. parameter. The Appearance Agent MUST support publications and
subscriptions for this event package.
The Appearance Agent MUST have a way of discovering the state of all The Appearance Agent MUST have a way of discovering the state of all
dialogs associated with the AOR. If this information is not dialogs associated with the AOR. If this information is not
available from a call stateful proxy or B2BUA, the Appearance Agent available from a call stateful proxy or B2BUA, the Appearance Agent
MAY use the registration event package [RFC3680] to learn of UAs MAY use the registration event package [RFC3680] to learn of UAs
associated with the AOR and MAY subscribe to their dialog event associated with the AOR and MAY subscribe to their dialog event
state. Also, an Appearance Agent MAY subscribe to a UAs dialog event state. Also, an Appearance Agent MAY subscribe to a UAs dialog event
state in order to reconstruct state. As a result, the registrar MUST state in order to reconstruct state. As a result, the registrar MUST
support the registration event package. Dialog package notifications support the registration event package. Dialog package notifications
are recommended by RFC 4235 to "only contain information on the are recommended by RFC 4235 to "only contain information on the
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for an incoming INVITE with a Join or Replaces header field. For for an incoming INVITE with a Join or Replaces header field. For
this case, the appearance number should match the appearance number this case, the appearance number should match the appearance number
of the dialog being joined or replaced. If the INVITE Replaces or of the dialog being joined or replaced. If the INVITE Replaces or
Join comes from outside the appearance group, the Appearance Agent Join comes from outside the appearance group, the Appearance Agent
will include a <joined-dialog> or <replaced-dialog> element in the will include a <joined-dialog> or <replaced-dialog> element in the
NOTIFY containing the dialog information from the Replaces or Joined NOTIFY containing the dialog information from the Replaces or Joined
header field. header field.
The Appearance Agent MUST be able to communicate with the forking The Appearance Agent MUST be able to communicate with the forking
proxy to learn about incoming calls and also to pass the appearance proxy to learn about incoming calls and also to pass the appearance
number to the proxy to insert in the Alert-Info header field. number to the proxy, or otherwise ensure the Alert-Info header field
is included in the INVITE with the appropriate appearance number.
Note that UAs need to be able to handle incoming INVITEs without Note that UAs need to be able to handle incoming INVITEs without
an appearance number assigned. This could be caused by a failure an appearance number assigned. This could be caused by a failure
of the Appearance Agent or other error condition. Although the of the Appearance Agent or other error condition. Although the
proper rendering of the INVITE may not be possible, this is better proper rendering of the INVITE may not be possible, this is better
than ignoring or failing the INVITE. than ignoring or failing the INVITE.
An Appearance Agent SHOULD assign an appearance number to an outgoing An Appearance Agent SHOULD assign an appearance number to an outgoing
dialog if a PUBLISH has not been received selecting/seizing a dialog if a PUBLISH has not been received selecting/seizing a
particular appearance number. particular appearance number.
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appearance AOR sip:HelpDesk@example.com. Bob REGISTERs using contact appearance AOR sip:HelpDesk@example.com. Bob REGISTERs using contact
sip:bob@ua2.example.com. Alice REGISTERs with contact sip:bob@ua2.example.com. Alice REGISTERs with contact
sip:alice@ua1.example.com. sip:alice@ua1.example.com.
User Agents for Alice and Bob subscribe to the dialog package for the User Agents for Alice and Bob subscribe to the dialog package for the
appearance AOR and publish dialog state to the Appearance Agent. appearance AOR and publish dialog state to the Appearance Agent.
Message exchanges between the Registrar, Appearance Agent, Alice, and Message exchanges between the Registrar, Appearance Agent, Alice, and
Bob are shown below. The call flow examples below do not show the Bob are shown below. The call flow examples below do not show the
authentication of subscriptions, publications, and notifications. It authentication of subscriptions, publications, and notifications. It
should be noted that for security purposes, all publications and should be noted that for security purposes, all publications and
subscriptions must be authorized before the SUBSCRIBE is accepted. subscriptions must be authorized before they are accepted.
Also note that registrations and subscriptions must all be refreshed Also note that registrations and subscriptions must all be refreshed
by Alice at intervals determined by the expiration intervals returned by Alice at intervals determined by the expiration intervals returned
by the Registrar or Appearance Agent. by the Registrar or Appearance Agent.
Registrar Appearance Agent Alice Bob Registrar Appearance Agent Alice Bob
| | | | | | | |
| | | | | | | |
|<--------------------------- REGISTER F1<| | |<--------------------------- REGISTER F1<| |
| | | | | | | |
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13.1. SIP Event Package Parameter: shared 13.1. SIP Event Package Parameter: shared
This specification defines a new event parameter 'shared' for the This specification defines a new event parameter 'shared' for the
Dialog Package. When used in a NOTIFY, it indicates that the Dialog Package. When used in a NOTIFY, it indicates that the
notifier supports the shared appearance feature. When used in a notifier supports the shared appearance feature. When used in a
PUBLISH, it indicates that the publisher has explicit appearance PUBLISH, it indicates that the publisher has explicit appearance
information contained in the message body. If not present in a information contained in the message body. If not present in a
PUBLISH, the Appearance Agent MAY assign an appearance number to any PUBLISH, the Appearance Agent MAY assign an appearance number to any
new dialogs in the message body. new dialogs in the message body.
13.2. URN Sub-Namespace Registration: sa-dialog-info 13.2. SIP Alert-Info Header Field Parameter: appearance
This document defines the 'appearance' parameter to the Alert-Info
header in the SIP Parameters registry.
Predefined
Header Field Parameter Name Values Reference
---------------------- --------------- --------- ---------
Alert-Info appearance No [RFC3261]
13.3. URN Sub-Namespace Registration: sa-dialog-info
This section registers a new XML namespace per the procedures This section registers a new XML namespace per the procedures
in [RFC3688]. in [RFC3688].
URI: urn:ietf:params:xml:ns:sa-dialog-info. URI: urn:ietf:params:xml:ns:sa-dialog-info.
Registrant Contact: IETF BLISS working group, <bliss@ietf.org>, Registrant Contact: IETF BLISS working group, <bliss@ietf.org>,
Alan Johnston <alan.b.johnston@gmail.com> Alan Johnston <alan.b.johnston@gmail.com>
XML: XML:
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN" <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"> "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"> <html xmlns="http://www.w3.org/1999/xhtml">
<head> <head>
<meta http-equiv="content-type" <meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/> content="text/html;charset=iso-8859-1"/>
<title>Shared Appearance Dialog Information Namespace</title> <title>Shared Appearance Dialog Information Namespace</title>
</head> </head>
<body> <body>
<h1>Namespace for Shared Appearance Dialog Information</h1> <h1>Namespace for Shared Appearance Dialog Information</h1>
<h2>urn:ietf:params:xml:ns:dialog-info</h2> <h2>urn:ietf:params:xml:ns:sa-dialog-info</h2>
<p>See <a href="ftp://ftp.rfc-editor.org/in-notes/rfcXXXX.txt"> <p>See <a href="ftp://ftp.rfc-editor.org/in-notes/rfcXXXX.txt">
RFCXXXX</a>.</p> RFCXXXX</a>.</p>
</body> </body>
</html> </html>
END END
13.3. XML Schema Registration 13.4. XML Schema Registration
This section registers an XML schema per the procedures in This section registers an XML schema per the procedures in
[RFC3688]. [RFC3688].
URI: urn:ietf:params:xml:schesa:sa-dialog-info. URI: urn:ietf:params:xml:schesa:sa-dialog-info.
Registrant Contact: IETF BLISS working group, <bliss@ietf.org>, Registrant Contact: IETF BLISS working group, <bliss@ietf.org>,
Alan Johnston <alan.b.johnston@gmail.com> Alan Johnston <alan.b.johnston@gmail.com>
The XML for this schema can be found in Section 6. The XML for this schema can be found in Section 6.
14. Acknowledgements 14. Acknowledgements
The following individuals were part of the shared appearance Design The following individuals were part of the shared appearance Design
team and have provided input and text to the document (in team and have provided input and text to the document (in
alphabetical order): alphabetical order):
Martin Dolly, Andrew Hutton, Raj Jain, Fernando Lombardo, Derek Martin Dolly, Andrew Hutton, Raj Jain, Fernando Lombardo, Derek
MacDonald, Bill Mitchell, Michael Procter, Theo Zowzouvillys. MacDonald, Bill Mitchell, Michael Procter, Theo Zourzouvillys.
Thanks to Chris Boulton for helping with the XML schema. Thanks to Chris Boulton for helping with the XML schema.
Much of the material has been drawn from previous work by Mohsen Much of the material has been drawn from previous work by Mohsen
Soroushnejad, Venkatesh Venkataramanan, Paul Pepper and Anil Kumar, Soroushnejad, Venkatesh Venkataramanan, Paul Pepper and Anil Kumar,
who in turn received assistance from: who in turn received assistance from:
Kent Fritz, John Weald, and Sunil Veluvali of Sylantro Systems, Steve Kent Fritz, John Weald, and Sunil Veluvali of Sylantro Systems, Steve
Towlson, and Michael Procter of Citel Technologies, Rob Harder and Towlson, and Michael Procter of Citel Technologies, Rob Harder and
Hong Chen of Polycom Inc, John Elwell, J D Smith of Siemens Hong Chen of Polycom Inc, John Elwell, J D Smith of Siemens
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