VOIP

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VOIP

• (Voice Over IP)
• Yonca Cumurcu
• Koray
  Kurt

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Today, we will deal with

• What is VoIP?
• Ways of using VoIP?
• What is PSTN?
• Which protocols are used?
• What are the Challanges?
• Advantages of the VoIP usage?
• Which companies produce VoIP software?
• VoIP prices?
• VoIP in Turkey and legal issues?

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What is VoIP?

• VoIP allows you to make telephone calls
• using a computer network, over a data network
  like the Internet
• VoIP uses the internet as its medium to send
  voice.
• For our purposes we will restrict it to mean
  voice communications among 2 or more computers.

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What is VoIP?

• Voice Calls are transmitted
• over Packet Switched
• Network instead of Public
• Switched Telephone
• Networks (PSTN)

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What is PSTN?

• PSTN is abbreveation of Public Switched Telephone
  Network.
• A network of fixed-line analog telephone system
• Is now entirely digital
• Includes not only fixed telephones but also
  mobile phones.

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What is PSTN?

• Two types of PSTN
• POTS(Plain Old Telephone Service)analog acoustic
  signal transformed to (similar) analog electrical
  signal. (ANALOG Telephony)
• ISDN(Integrated Services Digital Network)
  transforming analog acoustic or electric signal
  to digital values.(DIGITAL Telephony)

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Ways Of Using VoIP

• PC to PC
• PC to Phone
• Phone to PC
• Phone to Phone

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Scenario 1 PC to PC

• Need a PC with sound card
• IP Telephony software(softphone) Skype, Gtalk,
  VoIP Stunt, ...
• Video optional

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Scenario 2 PC to Phone
Need a gateway that connects IP network to phone
network
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Scenario 3 Phone to Phone

• Need more gateways that connect IP network to
  phone
• networks
• The IP network could be dedicated intra-net or
  the
• Internet.
• The phone networks could be intra-company PBXs or
• the carrier switches

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Illustration of Gateway
AT-RG613TX Gateway, 3 x 10/100TX LAN, 2 x FXS, 1
x 100TX WAN port
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Which Protocols are Required for VoIP?

• UDP (User Datagram Protocol)
• RTP (Real-Time Transport Protocol)
• SIP( Session Initiation Protocol)
• H323

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UDP Protocol

• Available in transport layer
• Enable the transmission of information between
  the correct processes (or applications) on host
  computers.
• UDP protocol is commonly used in transport layer
  as an alternative to TCP protocol.

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UDP Protocol

• UDP
• Connectionless protocol
• Unreliable
• No sequence numbers

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UDP Protocol
Source port Identifies the higher layer process
which originated the data. Destination port
Identifies with higher layer process to which
data is being transmitted. Length The length
in octets of the UDP data and payload (minimum
8). Checksum Optional field supporting error
detection.
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RTP Protocol

• provides end-to-end delivery services for data
  with real-time characteristics (audio and video)
• includes payload type identification, sequence
  numbering, and timestamping
• supports mixers and translators

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RTP Protocol

• translator coding transformation

• mixer mixing several audio streams into a
  single audio stream

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SIP Protocol

• SIP is a application layer control simple
  signalling protocol for VoIP implementations
• SIP not only for VoIP, but in general for
  multimedia communication
• eg audio / video conferencing,
  server-based or p2p
• provides the market with fast operation,
  flexibility, scalability and multiservice
  support.

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SIP Protocol

• provides its own reliability mechanism
• creates, modifies and terminates sessions which
  are internet multimedia conferences, Internet
  telephone calls and multimedia distribution with
  one or more participants.
• well-known port number 5060
• support for instant messaging
• format similar to HTTP

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SIP Protocol

• SIP works as follows
• Callers and callees are identified by SIP
  addresses
• a caller first locates the appropriate server and
  then sends a SIP request
• a SIP request may be redirected or may trigger a
  chain of new SIP requests by proxies
• Users can register their location(s) with SIP
  servers
• SIP messages can be transmitted either over TCP
  or UDP

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SIP Protocol

• Request Messages
• The format of the Request packet

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SIP Protocol

• Methods Command
• - Invite Initiate Call
• - Ack Confirm Final Response
• -Bye Terminate and Transfer Call
• - Cancel Cancel Searches and Ringing
• -Options Features Support by Other Side
• - RegisterRegister with Location Service

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SIP Protocol

• Response Message
• The format of the Response message

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SIP Protocol
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H323 Protocol

• H323 Prtocol is a ITU-T standard (International
  Telecommunications Union)
• framework for multimedia communication
• allow multimedia transmission through an
  unreliable packet-based network

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H323 Protocol

• H323 includes
• Call signaling H.225
• Media control H.245
• Audio coding G.711, G.722, G.723, G.728, G.729
  (G.711 is most used, G.729 is most quality
  enhanced)
• Video coding H.261, H263
• Data sharing T.120
• Media transport RTP, RTCP

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H323 Architecture

• - H323 Terminal
• Gateway
• Gatekeeper
• Multipoint Control Units (MCU)

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VoIP Challenges

• Packet loss
• Latency
• Jitter
• Echo
• Reliability
• Firewalls

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VoIP Challenges

• VoIP implementations face problems dealing with
  latency , echo and jitter
• Echo waving of voice
• Latency Changing in delivery time between voice
  packets
• Jitter Changing in delivery order of voice
  packets

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VoIP Challenges

• Connection Problems
• problems behind NAT between peers.
• Echo and jitter occurs because of packet loss.
• Internet stability problems can cause reliability
  problems and this discourages voip usage.
• routing VoIP traffic through firewalls blocks
  voice packets transmission.

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Advantages of VoIP

• What are the esssential factors that encourages
  people to use VoIP?

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Advantages of VoIP

• Cost of equipment and deployement
• Low price in leased-line(home phone)
• Portability
• Flexibility
• Versatility
• Interconnectivity
• Time to market

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VoIP Producers

• ITSP Internet Telecommunication Service Provider
  which provides VoIP softwares
• Most popular VoIP software and also the producers
  are MSN, SKYPE

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VoIP in TURKEY

• Most popular producers in Turkey are
• Superonline
• Borusan Telekom
• Koçnet
• Sabanci Telekom
• Turk Telekom

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Sample Estimated Price
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VoIP Prices

• Generally,
• Producers get approximately 2-3 membership fee
  monthly .
• From Soft to Soft is free
• From Soft to PSDN is cheaper than 80
• eg Calling to USA with Turk Telekom is 0.12 YTL,
  however Calling with VoIP Stunt is 0.3 YTL

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VoIP usage area in Turkey and Legal Issues

• Cellphone usage cost in Turkey is very high
• Until the half of the last year it was a confused
  concept and alsoTürk Telekom did not reach the
  necessary judgement.
• Today, it is legalized to some degree.
• However, Türk Telekom brought these producers to
  justice by esteeming this service as illegal.

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VoIP usage area in Turkey and Legal Issues

• Judgement come out in favour of the producers.
• However, Türk Telekom can cut the ISS lines and
  stop the activities of any voip firms without the
  judgement decision.
• Since, the Türk Telekom has voice monopoly,
  domination on VoIP firms are increased legally or
  illegaly.

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In Conlusion,

• We can criticise Türk Telekom because of these
  immoral attitudes.
• We can criticise the government because of the
  latency of these legal arrangements.
• We can criticise VoIP firms because of the
  nonconstructed infrastructure
• However, it is the unchangable fact that VoIP
  revolution will dominate the all
  telecommunication world several ten years more

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References

• 1) http//en.wikipedia.org/wiki/Voip
• 2) http//www.erlang.com/protocols.html
• 3) http//www.pusulanet.com.tr/voipurun.htm
• 4) http//www.voip.gen.tr/
• 5) http//siptutorial.blogspot.com/
• 6) http//www.linecube.com/rates/compare/

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QUESTIONS?
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• Q1) Is it possible to use voip solutions in wifi
  enabled cellphones?
• A1) Yes , it is possible. In many cellphone
  operating systems there are many softphone
  applications which enables voip usage. For
  example, SJPhone is an application deployed for
  Windows mobile 2005 OS

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• Q2) Is it possible to call the PC from the phone
  is used in daily life?
• A2) YES. It is possible by using DID. By the help
  of the special numbers which are assigned by the
  daily phone network to voip network, it is
  possible to provide the transition. However it
  can not be used in Turkey because it is illegal.
  This transmission is also called number of
  portability. (DID Number)

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• Q3 What do you think about the differences in
  price between PSDN and VoIP?
• A3 Voip networks uses IP networks and over these
  networks voice packages are transferred. Internet
  can be used in terms of IP network. So, there is
  no need to additional investment. However, PSTNs
  performs communication over the TDM and ATM
  networks which have high cost. So, cost advantage
  between them is very high and it explains the
  difference in cost.