Transcript Voice over IP

Voice over IP
AFNOG 2001 Accra – Ghana
12 Mai 2001
By:
Adiel AKPLOGAN
CAFE Informatique S. A. - TOGO
E-mail: [email protected] - Web: http://www.akplogan.net
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 Multiservice 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
LAN
Voice Agent
PABX
Voice Agent
IP Network
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
Gatekeeper
Gateway
H.323 terminal
MCU
SIP
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.
– Two application:
 International
 Call
Communication
center
– 30 local worker.
– Tele-marketing for America and Canadian company
– Data scramble for foreign company
VoIP application
Architecture du Réseau CAFEnet
CISCO 3661
10 FXS ports
2 FXO ports
Mail
INTERNET
DNS
Router/firewall
RWeb Hosting Network/ SMS/ FAX/Real Audio
CACHE
Real Audio Producer
Local Usage
Multimedia and Audio Production
Net2Phone
IPmax
VPN Server
Call Center
By Adiel AKPLOGAN
adiel@ak plogan.net
VoIP

Question?