VoIP Voice over Internet Protocol

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VoIPVoice over Internet Protocol

• Geh Chee WooiEE05811Section 1
• Semester 1, 2004

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Abstract

• Telephone has been one of the best but costly
  inventions of the 19th century. VoIP is the
  technology that emerged as a solution by
• method of integrating voice into these packets
  along with the data
• allows us to make telephone calls using a
  broadband Internet connection instead of a
  regular (or analog) phone line.
• attracting more and more attention as an
  alternative to or substitute for established
  telephony network technology

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Introduction

• VoIP
• (voice over IP - voice delivered using the
  Internet Protocol)
• introduced back in 1995
• been adopted universally as a reliable technology
  alternative by which voice is transmitted over a
  data network instead of a traditional voice
  network
• term used in IP telephony for a set of facilities
  for managing the delivery of voice information
  using the Internet Protocol (IP).
• sending voice information in digital form in
  discrete packets rather than in the traditional
  circuit-committed protocols of the public
  switched telephone network (PSTN)
• advantage of VoIP and Internet telephony is that
  it avoids the tolls charged by ordinary telephone
  service.

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VoIP Technologies

• Where it all started
• PSTN (Public Switched telephone network)
• It has been used for more than a century
• Uses circuit switching the circuits are switched
  in the intervening telephone exchanges to create
  a physical connection between the caller and the
  person being called for the duration of the call
• great advantage of this type of switching is that
  call quality is extremely high because a
  dedicated line is being devoted to the call
• major disadvantage is that this type of switching
  is expensive because it requires considerable
  capacity in the network as most of the time most
  of the capacity is not being used

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• Alternative packet switching
• traditionally it has been used for data networks
  connecting computers.
• data is divided up into small packets which are
  given identifying information and then sent over
  the network by a variety of different routes,
  before being reassembled at the end into the
  format of the original message.
• these networks do not use an elaborate system of
  switches or exchanges but a much simpler system
  of routers.
• great advantage very cost-effective, making much
  more intense use of the network, by routing
  packages along the least busy lines.
• in the past, not used for voice because the
  breaking up and reassembly of the packets would
  cause an unacceptable deterioration in quality,
  notably because of the variable delay in the
  packets.
• increasingly these delays can be engineered out
  and indeed systems can distinguish between
  packets that are voice and packets that are data
  and give priority to the former.

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Circuit switching versus packet switching

• Circuit switching
• Uses TDM
• Inflexible-does not allow inclusion of new
  services easily
• Data is switched
• Connection-oriented
• 64 Kbps in each direction
• Billing according to time and duration

• Packet switching
• Uses statistical multiplexing
• Flexible technology-allows new services to be
  integrated easily
• Data is routed
• Connectionless
• Variable length and can be compressed to 8 Kbps
• Billing according to usage

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The advantage of VoIP technology

• VoIP technology has several advantages over
  normal
• circuit switching telephone system.
• allows several phone calls to occupy the amount
  of space occupied by only one in circuit switched
  network.
• example, using PSTN, 10 minutes call will
  consumed full 10 minutes of transmission time at
  a cost of 128kbps, whereas with VoIP, the same
  length of call may occupied only 3.5 minutes of
  transmission time and at cost of 64kbps, leaving
  another 64kbps free for that 3.5 minutes and
  additional 128kbps for the remaining 6.5 minutes.
• can place several call at one time space used by
  single call in the PSTN system. This doesnt
  count the data compression which can reduce the
  transmission packet size.

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Flexibility

• We can make any call anytime and anywhere if we
  have broadband
• connectivity. Below are the three main VoIP
  service available today
• Analog Telephone Adapter (ATA)
• The most commonly used method to place calls for
  VoIP.
• The ATA is an analog to digital converter.
• It allows us to connect standard phone to our
  personal computer or internet to use with VoIP.
• Analog signals from traditional phone is
  converted to digital data for transmission over
  the internet.

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• IP Phones
• This phones is like normal phone with headset
  except it doesn't come with RJ-11 phone
  connectors.
• IP Phones will have USB connector or Rj-45
  Ethernet connector to connect the phones to our
  computer and a software for the PC.
• IP phones connect directly to the internet
  connection thru our PC.
• To make a call, all we need to do is hook up the
  PC to the internet and place a call by using the
  IP Phones.

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• 3. Computer to Computer
• This is the best way to use VoIP and it doesn't
  cost any single cent to make a phone call.
• All we need is a VoIP software such as Skype -
  the best and popular VoIP software available
  freely from the internet, and a headset to make a
  call.

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Price

• VoIP is much cheaper compared to PSTN
  communications.
• Local VoIP low as RM0.30 per call anywhere in the
  world
• IP phone to IP phone call are FREE!
• This is the biggest drawbacks of PSTN
  communications compared to VoIP.
• extra features to the VoIP telephony such as
• Caller Identity (Caller ID)
• Call Waiting
• Call transfer
• Repeat dialing
• Return Call
• Missed Call
• Three way calling

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VoIP Technical Issues

• Must be capable of transporting the VoIP packets
  correctly, and the devices must use compatible
  standards.
• Organizations evaluate VoIP as many things
• a PBX replacement
• free long distance
• a natural blending of voice and data
• a cost-saving (or cutting) technology
• The value of VoIP technology will vary with each
  customer site. Issues such as the state of the
  existing network or PBX as well as the amount of
  long-distance calling that occurs will affect
  VoIP value at an organizational level. Therefore,
  each site must individually evaluate the
  cost-effectiveness of VoIP technologies.

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VoIP Equipments

• VoIP equipment or devices can be classified in
  three general areas
• End stations (phones)
• Gateways and routers
• Controllers
• Each area has specific functions that it
  performs, and combined, they
• make up a complete system.

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VoIP Configuration
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1. End Stations

• There are two types of IP phones
• Hardware hardware phone is a physical device,
  similar to a standard phone, with a handset,
  dialpad, that differs in that it connects to an
  Ethernet network rather than a telephone network.
  IP phones contain all the hardware (and software)
  to digitize voice as well as setup and make call.
  
• Software only phones, or soft phones, use the
  PCs soundcard, CPU and network card as the
  phones hardware, and enable a PC to become an IP
  phone.

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2. Gateways and Routers

• Gateway
• connects the VoIP network to PSTN.
• connection enables users of IP-based systems to
  make and receive calls from the PSTN, like a
  traditional phone system.
• come with analog or digital interfaces to connect
  to the local telephone company.
• also do transcoding, or changing a signal from
  one codec version to another.
• Routers
• move the IP datagrams between networks along the
  path from source to destination.
• Theyre connection between a LAN and a WAN, the
  ability to ensure that high-priority traffic is
  handled correctly are very important. Since WAN
  speeds are generally much slower than LAN speeds,
  proper packet queuing and prioritization must
  occur to ensure good voice quality across the
  network.

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3. Controllers

• VoIP controllers (IP PBXs)
• manage the VoIP network.
• devices are responsible for configuring the IP
  phones, controlling what a user can do from a
  phone, enabling functions
• performing the functions that a traditional PBX
  would. IP PBX controllers are PC-based, running a
  standard OS with additional software to control
  the VoIP systems.
• can provide APIs to extend vendor-provided or
  user-written features and functionality.
• can be added to the network to provide
  functionality like voicemail, Automated Call
  Distribution, automated attendant, voice
  response-based applications and more.

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VoIP Implementation Issue

• When deploying a VoIP solution on a network, a
  great deal
• of design and verification work must be done to
  ensure a
• successful deployment. Factors such as
• current quality and reliability of the network
• the volume and quality of voice calling to be
  handled and the traffic flows must be fully
  understood.
• need for low latency between endpoints.
• Latency is comprised of four distinct components,
  three of which can be affected by the network
  design.
• Propagation delay
• Transport delay
• Packetization delay

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Propagation delay

• time a signal takes to travel from one end to the
  other end.
• The farther the signal must travel, the larger
  the propagation delay time
• Propagation delay is the signal travels close to
  the speed of light, and nothing (short of moving
  the endpoints closer) will affect it.

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Transport delay

• The time a signal takes to get through the
  devices in the network
• Example, routers, firewalls and slow/congested
  links.
• This time can be improved by reducing the router
  hops, increasing link bandwidth and other
  techniques.

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Packetization delay

• The time the codec takes to digitize and compress
  the signal and undo it at the far end .
• Using a faster codec can lower this time, (e.g.,
  G.711 instead of G.729), the tradeoff is higher
  bandwidth consumption (64 Kbps instead of 8
  Kbps).

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Jitter buffer delay

• amount of time the receiver holds the packets to
  control jitter.
• the receiver controls jitter buffer delay as it
  holds packets in order to manage playback
  regardless of the variation in arrival time of
  the packets.
• the larger the buffer, the smoother the playback
  but the greater the latency.
• The packetization and jitter buffer delay are
  constant for a call, however, transport delay may
  vary as the network may be congested or the
  queues may fill
• Latency higher than 150 ms begins to cause
  discomfort in the conversation as both parties
  begin to speak simultaneously and then collide,
  or begin to insert long pauses to ensure that the
  other speaker is finished (a walkie-talkie
  effect).

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Other VoIP Implementation Issues

• Call Volume
• important pieces of information in engineering a
  VoIP solution
• With this, along with a busy hour study on
  existing PBX trunks, decisions can be made as to
  how many trunks are needed and the bandwidth
  required to handle the call volume
• analysis of calls between locations will also
  provide data on toll charges that can be avoided
  by switching to VoIP.
• Network
• PSTN, reliability is 99.999.
• Data networks do not have this level of
  reliability. Power outages, server crashes,
  software failures, network congestion, and user
  error all contribute to network downtime
• Understanding and managing the traffic flows will
  be key to ensuring that VoIP traffic is not
  impacted by other applications in the network.
• The networks physical infrastructure also is key
  to ability to support VoIP, networks need to have
  sufficient bandwidth to handle the traffic.

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Infrastructure

• The physical infrastructure that needs to be
  addressed are
• Power
• Switching
• Routing
• Firewalls
• Quality of Services (QoS)
• bandwidth
• Power
• In a VoIP deployment, the IP phones need power,
  whether from a local power supply or over
  Ethernet in-line power.
• the IP PBX must remain powered, which can entail
  adding UPS systems in many places to keep
  switches and routers powered during an outage.

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• Switching
• Hubs create bottlenecks in a LAN, hence, replace
  hubs with switches, and a Layer 3 switch, for QoS
  mechanisms
• Other options are the ability to provide in-line
  power over the Ethernet ports via the built-in
  power supply system
• Routing
• Routers manage the traffic between networks
• either within the organization or to the outside
  world.
• have sufficient CPU power to run the QoS features
  needed to ensure VoIP traffic is managed
  correctly and have enough memory to queue
  traffic.
• Routers add latency to the traffic path to
  ensure that VoIP packets traverse as few router
  hops as possible.
• to reduce router hops, the traffic path should
  also be evaluated.
• Firewalls
• IP Firewalls pose a special problem to VoIP
  systems.
• Firewalls that are providing proxy services, such
  as NAT/PAT, can prevent VoIP calls from correctly
  being routed onto the network.
• introduce a delay in the traffic flow, increasing
  latency, as well as being a potential bottleneck
  if they are running close to or at capacity.
• (NAT Network Address Translation PAT Port
  Address Translation)

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• Quality of Service (QoS)
• QoS needs to be managed from end to end in the
  network The design
• should ensure proper bandwidth is available for
  the traffic flows.
• There are three techniques that can be used to
  improve network QoS.
• Controlling the networking environment
• provide a controlled networking environment in
  which the capacity can be pre-planned and
  adequate performance can be assumed.
• Using management tools to configure the network
  nodes, monitor performance, and manage capacity.
  Traffic can be prioritized which allows real-time
  traffic to be given precedence over non-critical
  traffic.
• Adding control protocols and mechanisms help
  avoid or alleviate the problems inherent in IP
  networks.
• The use of 802.1p/Q-aware switches enables the
  control and segregation of VoIP traffic from
  normal data traffic.
• RSVP, DiffServ and MPLS is an effective way to
  provide end-to-end traffic control for
  applications such as VoIP.

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• Bandwidth
• Good voice quality means proper amount of
  bandwidth
• Congested LANS or slow WAN links coupled with
  poor queuing techniques will result in high
  packet loss
• Ensuring that all segments in the LAN have
  sufficient capacity to handle the VoIP traffic,
  as well as ensuring that applications on the WAN
  do not saturate the links will go a long way to
  ensuring good VoIP call quality.
• VoIP Traffic Control
• controlling the amount and type of VoIP traffic
  on the network can make a big impact on the
  performance of the network and the call quality.
• Options such as the codec selection, silence
  suppression, jitter buffer size and speech packet
  size will all affect the utilization of the
  network.
• If the network is highly utilized or control is
  needed on the amount of VoIP traffic that is
  carried by the network, some form of admission
  control might be needed.

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Summary

• The Benefits Of Voice Over IP
• Businesses are rapidly to VoIP because there are
  compelling advantages.
• The most obviously, there are significant
  financial savings on running the network itself.
• Each network has its own value, that value is
  maximized when the two systems are consolidated.
• VoIP allows organisations to integrate telephone,
  fax, e-mail and other applications to capitalise
  on the benefits of unified messaging.
• VoIP technology can contribute to an effective
  knowledge management strategy.
• More choice of voice operators and tariff
  packages
• Cheaper services including possibility of 'free'
  calls
• New services such as conferencing
• Innovative services to be announced
• A compelling reason to subscribe to broadband

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• The future of VoIP
• There are two dimensions in which VoIP can be
  improved.
• One dimension is technology itself.
• high quality, big capacity, multi-functionality
• combination of this technology with other
  existing technologies.
• The next phase of VoIP services will be
  applications such as wireless unified messaging
• VoIP is a new technology that growing very fast.
  It is ideal for computer-based communications and
  at the same time bringing down the cost of
  multimedia transfer.

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Conclusion

• We stand today with VoIP something like where we
  stood with the Internet in the early 1990s. The
  speed of development and the widespread impacts
  of VoIP will be comparable to that of the
  Internet. VoIP is truly a disruptive technology
  that will pose many challenges.
• The year 2003 saw VoIP move from being a fringe
  interest of high tech enthusiasts to a concept
  central to the planning of all major
  telecommunications operators. The world  shall be
  hearing a great deal about VoIP in 2004 and other
  years to come in the technical media.