Voice over IP

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Voice over IP
AFNOG 2001 Accra Ghana 12 Mai 2001

• By
• Adiel AKPLOGAN
• CAFE Informatique S. A. - TOGO
• E-mail adiel_at_akplogan.net - Web
  http//www.akplogan.net

2
Topics

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

3
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

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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

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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.

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VoIP system model
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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?

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The two models in brief
H.323 SIP
Gatekeeper Gateway H.323 terminal MCU UAC (user agent Client) UAS (User agent server) SIP Terminal Proxy Redirect Server Location server
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Architecture
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Communication
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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.

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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.

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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)

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Voice packet routing and Delay

• Echo is generated toward the packet network from
  the telephone networkas 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.

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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 EM.
• Signaling from Router ? router
• Dial plan Mapper.
• Signaling from Router ?PABX
• Line seizure signaling.

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VoIP application

• In todays 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.

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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.

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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.

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VoIP application

• Example
• 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

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VoIP application
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VoIP

• Question?