Voice over IP

By:

Adiel AKPLOGAN

CAFE Informatique S. A. - TOGO

E-mail: adiel@akplogan.net - Web: http://www.akplogan.net

AFNOG 2001 Accra – Ghana

12 Mai 2001

Topics

Definition Standard Requirement QoS Application CAFEnet S.A. (Togo) exemple

Introduction Concern about reduction of communication

coast. Voice, Fax and Data integration become a challenge and priority for many network manager.

Telecommunication deregulation and Multi-service access network development allow this challenge to be achieve.

Today voice over packet network (ATM, Frame Relay and IP) is the one most growing aspect of Multi-service access network

VoIP System Model

Voice and signaling transmission using packet network (IP)

ITU standard for signaling Model– H.323 ( ITU )- Packet-based Multimedia

communication system. SIP (IETF) – Session initiation protocol The voice system resulting from these

two standard follow a common Model

VoIP System Model

A packet voice system like VoIP follow this model.– A packet network (Internet in most case)– Voice agent at edge of the cloud. Convert

voice information from it traditional telephony form to a suitable form for packet transmission.

– the packet are send to another voice agent at the call destination.

VoIP system model

IP Network

LAN

PABX

Voice Agent

Voice Agent

Voice Agent

Voice Agent

VoIP System Model

Two issue from the previous diagram

– Voice coding: Voice Packet, Packet Voice

– Signaling: who is called and where is the called party on the network?

The two models in brief

H.323 SIPGatekeeper

Gateway

H.323 terminal

MCU

UAC (user agent Client)

UAS (User agent server)

SIP Terminal

Proxy

Redirect Server

Location server

Architecture

Communication

VoIP Addressing

As Internet communication is based on IP address (layer 2), every equipment that want to communicate should have an IP address. For VoiP, the voice interface appear as additional IP host.

Translation of dial digits from the PBX to an IP host address is performed by the dial plan mapper. The destination telephone number, or some portion of the number, is mapped to the destination IP address.

Voice packet routing and Delay

VoIP take advantage of all strong and sophisticate routing protocols of IP (including best route calculation…)

But due to the way IP packets are send through the network, the big challenge is the Latency or delay that cause echo and talker overlap.

Voice packet routing and Delay

Source of delay include:– Accumulation delay: caused by need to collect a

frame of voice samples to be processed by the voice coder (from some microsecond to many milliseconds.

– Algorithmic Delay: caused by specific voice encoding delay.

– Processing delay: result from the two previous delay plus collecting the sample in to packet for transmission.

– Network delay: Processing that occurs as packets are sent across a network.(from protocol, medium, and buffer use to remove packet jitter on the receive side)

Voice packet routing and Delay

– Echo: is generated toward the packet network from the telephone network…as it always greater than 50 ms, it is not acceptable for good audition.

– Jitter: is the variable inter-packet timing cause by the fact that packets do not all cross the network at the same speed.

– Lost packet: Under peak load and congestion, voice frame are dropped at the same rate as data frame.

VoIP Signaling

Three distinct area:– Signaling from PABX router

Network seize the PABZ with any of the signaling used to seize a trunk (as the local network appear to the BABX as a trunk) – FXS or E&M.

– Signaling from Router router Dial plan Mapper.

– Signaling from Router PABX Line seizure signaling.

VoIP application

In today’s networking, there are several attractive alternatives both to conventional public telephony and to leased lines. Among the most interesting are networking technologies based on a different kind of voice transmission, called packet voice and in our case Voice over IP.

VoIP can be used in two broad context differentiated by geography or by the type of users to be served.

VoIP application

Within a national administration or telephony jurisdiction, – to support its own voice calling among its

own sites. – to support the activities of a single company

— to connect two or more company locations in multiple countries —

– to connect public calls within a company, the packet voice provider is technically providing a local or national telephone service and is subject to regulation as such.

VoIP application

Between different administration or telephony jurisdiction – to connect public calls between countries,

the packet voice provider is subject to the national regulations in the countries involved and also to any treaty provisions for international calling to which any of the countries served are signatories.

Be aware of the valid law applicable in your country until setting up VoIP application to avoid any inconvenience.

VoIP application

Example: CAFE Informatique & Telecommunications S.A.CAFE Informatique & Telecommunications S.A.

– Two application: International Communication Call center

– 30 local worker.– Tele-marketing for America and Canadian company– Data scramble for foreign company

VoIP application

RWeb Hosting Network/ SMS/ FAX/Real Audio

CISCO 366110 FXS ports2 FXO ports

Call Center

Mail

INTERNETDNS

CACHE

Router/firewall

Multimedia and Audio Production

VPN Server

Architecture du Réseau CAFEnet

By Adiel AKPLOGANadiel@akplogan.net

Real Audio Producer

Net2Phone IPmax

Local Usage

VoIP

Question?