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

2

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

2-3 April, 2001 The 2nd IP-Telephony Workshop

3

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.

2-3 April, 2001 The 2nd IP-Telephony Workshop

4

Scenario

2-3 April, 2001 The 2nd IP-Telephony Workshop

5

Conference scenario

2-3 April, 2001 The 2nd IP-Telephony Workshop

6

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.

2-3 April, 2001 The 2nd IP-Telephony Workshop

7

Processing client request

2-3 April, 2001 The 2nd IP-Telephony Workshop

8

Main structure

2-3 April, 2001 The 2nd IP-Telephony Workshop

9

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.

2-3 April, 2001 The 2nd IP-Telephony Workshop

11

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.

2-3 April, 2001 The 2nd IP-Telephony Workshop

12

Gateway control unit(cont.)

2-3 April, 2001 The 2nd IP-Telephony Workshop

13

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.

2-3 April, 2001 The 2nd IP-Telephony Workshop

14

Screen snapshot after inputting “TV” as searching keyword

Display gateway contact information

2-3 April, 2001 The 2nd IP-Telephony Workshop

16

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

2-3 April, 2001 The 2nd IP-Telephony Workshop

18

Gateway Administration Gateway configuration via HTML

interface with system administrator authentication.

Gateway accounting mechanism via parsing AudioGate log files.

2-3 April, 2001 The 2nd IP-Telephony Workshop

19

Snapshot for gateway administration

2-3 April, 2001 The 2nd IP-Telephony Workshop

20

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.