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the ppt describes about voip,its advantages and disadvantages.it also describes the protocols and the packet formats involved in a voip session .

the ppt describes about voip,its advantages and disadvantages.it also describes the protocols and the packet formats involved in a voip session .

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Transcript

  • 1. What is VOIP ?
    • VOIP - Voice over internet protocol
    • VOIP is the protocol used to transfer voice through packet switched networks
    • Voice-over-IP systems carry telephony signals as digital audio, typically reduced in data rate using speech data compression techniques, encapsulated in a data-packet stream over IP.
  • 2. VOIP modes of operation
    • pc to pc
    • pc to telephone
    • telephone to pc
    • telephone to telephone
  • 3. WHY VOIP ?
    • Cheaper calls
    • For a pc-to-pc call , the call is absolutely free
    • Merging of data/voice infrastructures
    • No worrying about cell phone coverage, roaming, or long distance charges.
    • Services like call forwarding, call waiting, voicemail, caller ID and more are available through your ip phone, usually at no extra charge.
  • 4. PROTOCOLS INVOLVED IN VOIP
    • SESSION ESTABLISHMENT :
    • * SIP [ session initiation protocol ]
    • * H.323
    • Protocols involved in transfer of data :
    • * RTP [ real time transport protocol ]
    • * RTCP [ real time transport control protocol ]
    • * UDP
    • * IP
  • 5. RTP
    • REAL TIME TRANSPORT PROTOCOL
    • Application layer protocol for transmitting realtime data (audio, video, ...)
    • Includes payload type identification, sequence numbering, timestamping, delivery monitoring
    • Mostly over UDP
    • Supports multicast & unicast
  • 6. Control Protocol - RTCP
    • RTP Control Protocol
    • Periodic transmission of control packets to all participants in the session
    • Main functions:
    • provide feedback on quality of data distribution
    • carries a persistent transport-level identifier for an RTP source (CNAME)
    • each participant sends control packets to all others which independently observe the number of participants
  • 7. SIP – Session Initiation Protocol
    • Developed by IETF since 1999
    • SIP is a text-based protocol similar to HTTP and
    • SMTP, for initiating interactive communication
    • sessions between users
    • SIP is an application-layer control (signalling)
    • protocol for creating, modifying and terminating
    • sessions with one or more participants
    • Sessions include Internet Multimedia
    • conferences, Internet Telephone calls and
    • Multimedia distribution
  • 8. ENCODING USED FOR VOIP
    • Bandwidth
    • Generally modest (64 kbps or less)
    • G.711 [ 64 Kbps ]
    • G.722 [ 48 – 64 Kbps ]
    • G.729 [ 8 Kbps ]
  • 9. PACKET FORMATS
  • 10.
    • VOIP PACKET FORMAT :
  • 11.
    • RTP header format :
  • 12. SIP REQUEST PACKET
    • FIELDS IN SIP REQUEST PACKET :
    • 1 . Method - method to be performed on the resource. Possible methods are Invite, Ack, Options, Bye, Cancel, Register
    • 2. request URI - A SIP URL or a general Uniform Resource Identifier, this is the user or service to which this request is being addressed.
    • 3.SIP version - The SIP version being used; this should be version 2.0
  • 13. METHODS IN SIP
    • INVITE [ for initiation of a session ]
    • ACK [ confirm final response ]
    • BYE [ terminates the call ]
    • CANCEL [ cancel searches and ringing ]
    • REGISTER [ register with location service]
  • 14. SIP packet format
    • Fields in a “SIP REQUEST” packet :
    • 1. SIP VERSION
    • 2.STATUS CODE - a 3-digit integer result code of the attempt to understand and satisfy the request.
    • 3.REASON PHRASE
  • 15. Status codes in SIP
    • 1xx Searching, ringing, queuing
    • 2xx Success
    • 3xx Forwarding
    • 4xx Client mistakes
    • 5xx Server failures
    • 6xx Busy, refuse, not available anywhere