easy accessible voice gateway between mbone and isdn/pstn networks linqing liu and torsten braun...
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Easy Accessible Voice Gateway between Mbone and ISDN/PSTN Networks
Linqing Liu and Torsten Braun
Institute of Computer Science and Applied Mathematics
University of Berne[liu|braun]@iam.unibe.ch
2-3 April, 2001 The 2nd IP-Telephony Workshop
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Outline Introduction Scenario Main functionalities Structure Audio forwarding and support unit Gateway control unit Usage and some sample snapshots Gateway administration Limitation and future work
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Introduction IP based telephony is booming with low cost long-
distance calls. IP telephony is convenient to set up conference without
the need of expensive Multipoint Control Unit (MCU). Related work:
-ISDN4Linux-Mbone2Tel-AudioGate in MECCANO project
Architecture and implementation of an easy accessible voice gateway between MBONE and ISDN with
integration of existing component from public domain software.
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Scenario
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Conference scenario
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Main functionalities Display available multicast session list via
HTML/WML pages, keyword searchable. User registration/creating new session via
HTML/WML. Get session contact information via
HTML/WML/SMS/Email. “Click-to-dial” for existing gateway users. Gateway administration/configuration via
HTML.
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Processing client request
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Main structure
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Audio forwarding and support unit
Responsible for converting audio data between Mbone and ISDN/PSTN networks, listening to existing Mbone sessions and announcing new sessions over the Mbone
Try to use existing software in public domain as components for audio forwarding and support unit:
-Using AudioGate in MECCANO project as audio
forwarding component.-Using mSD as daemon to listen Mbone session
information.-Using mAnnouncer to send out SDP file over
Mbone for new session announcement.
AudioGate functionalities
Calling users can be authenticated based upon their Calling Line Identification (CLI)
Allow to assign a full name to each of these numbers for presentation in the Mbone Sesion.
Provide a simple (easily configurable) voice menu for prompting callers for a conference selection.
Conferences can either be explicitly selected through the voice menu or callers can automatically be put into a particular conference.
Imposes no artificial limits on the number of simultaneous calls it can handle. The only practical limit is the number of B channels that are available. Support one or more ISDN BRI boards.
Supports up to nine simultaneous conferences.
Can be configured to use any number of ISDN Multiple Subscriber Numbering (MSN). Some of them can be directly mapped into a conference while others may first lead into a voice menu.
Supports muting/unmuting callers using Dual-Tone Multi-Frequency (DTMF) for control. The initial status for the callers can be configured in the AudioGate initialization file.
All codecs and transmission modes (particularly including redundancy coding) supported by Robust Audio Tool (RAT) are supported by AudioGate.
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Gateway control unit Main component to achieve easy
accessibility. Provide user registration via HTML/WML web
pages with selectable Mbone session list. Create new Mbone session via HTML/WML. Enable user calling participant via
HTML/WML(“click-to-dial”). Gateway administration/configuration via
HTML.
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Gateway control unit(cont.)
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Display Session Information and User Registration Transform mSD cache files to
HTML/WML pages. Generate HTML/WML page
according to keywords inputted by users, together with registration form.
Provide gateway contact information after user registration.
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Screen snapshot after inputting “TV” as searching keyword
Display gateway contact information
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Create New Sessions via HTML/WML Generate SDP files via HTML/WML
interfaces in compliance with SDP, MALLOC, SAP requirements.
Announce the new sessions via mAnnouncer.
Display new session information in HTML/WML pages and send the new session information to email/SMS.
Support “click-to-dial” by utilizing the relevant functionality from AudioGate.
Snapshot for creating a new session with WAP mobile phone
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Gateway Administration Gateway configuration via HTML
interface with system administrator authentication.
Gateway accounting mechanism via parsing AudioGate log files.
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Snapshot for gateway administration
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Limitations and future works Implemented in Linux PC with ISDN BRI board. One ISDN board support two lines. Limited slots for ISDN boards. AudioGate supports nine sessions
simultaneously. Future works:
-To develop a mechanism for seamless service without interrupting existing users.-To support AudioGate Mbus interface in future versions.