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VoWLAN : The Voice over WLAN

VoWLAN : The Voice over WLAN. Maxime Staszewski. Fall 2008 - CS 484: Network Concept. Agenda. Brief overwiew of VoWLAN WLAN: Security issue (Virtual Private Network) VoIP : Voice Digitization /Compression IPv6 Session Initiation Protocol (SIP) Conclusion.

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VoWLAN : The Voice over WLAN

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  1. VoWLAN: The Voice over WLAN Maxime Staszewski Fall 2008 - CS 484: Network Concept

  2. Agenda Briefoverwiew of VoWLAN WLAN: Security issue (Virtual Private Network) VoIP: Voice Digitization/Compression IPv6 Session Initiation Protocol (SIP) Conclusion

  3. BriefOverwiew of VoWLAN • VoIP over WLAN • Low-cost communication costs • Addmobility of phone terminals • No permanent connectionbetween the twosides • transmits information according to the status of network congestion • Slight degradation of communication compared to a fixed line • Convergence data/voice • Require802.11 set by the IEEE

  4. VirtualPrivate Network (VPN) • Virtual: connects two “physical” networks (WLANs) by an untrusted link (Internet) • Private: only computers on both sides of the VPN can "see" the data. • Tunneling Protocol: a protocol allowing data from one end of the VPN to another to be secured by encryption algorithms.

  5. VirtualPrivate Network (VPN) • VPN client: the component allowing to encrypt and decrypt data on the user side (client) • VPN server: the component encrypting and decrypting the data on the other side of the organization

  6. Virtual Private Network

  7. Point-to-point tunneling protocol (PPTP) • Protocol of PPP encapsulation over IP designed by Microsoft • Allow to set the virtual private networks (VPNs) over a public network. • The protocol opens two channels of communication between the client and server: • a channel control for the management of the bond (TCP connection) • a channel carrying data traffic of private network (Protocol Generic Routing Encapsulation)

  8. Internet Protocol Security (IPsec) • Set of protocols (Layer 3 of OSI model) using algorithms allowing the transport of secured data over an IP network • The purpose of this protocol: authenticate and encrypt the data • The stream can only be understood by the final recipient (encryption) • Modification of data through intermediaries may not be possible (integrity).

  9. Speech digitizationmethods • Waveform coders: utilize algorithms to produce an output that approximates the input waveform • Vocoding: digitize a compact description of the voice spectrum in several frequency bands.

  10. Waveformcoders • Use an algorithm to produce an output that approximates the input waveform • Two processes are required to perform digitizing of an analog signal: • Sampling: this discretizes the signal in time • Quantizing: this discretizes the signal in amplitude

  11. Pulse Code Modulation (PCM) • An uncompressed sampling technique of an analog signal

  12. IPv6 (Internet Protocol version 6) • Successor of IPv4 • Ensures QoS better than IPv4 • availability, reliability, timeliness • uses QoS with the help classification and marking of IP packets to make the VoIP infrastructure sure • provides a traffic-class field (8 bits) in the IPv6 header. • has a 20-bit flow label.

  13. IPv6 (Internet Protocol version 6)

  14. Session Initiation Protocol (SIP) • Open standard protocol of management sessions often used in telecommunications normalized by IETF • Most common for Internet telephony (VoIP) since 2007 • Takes the best aspects of the H.323 protocol. • Handles authentication and location of multiple participants • Responsible for negotiating on the types of media used by the different participants in encapsulating SDP messages (Session Description Protocol).

  15. Session Initiation Protocol (SIP) • The basic methods are: • INVITE allows a client to request a new session • ACK confirms the establishment of the session • CANCEL cancels INVITES in abeyance • BYE ends a session in progress • The answer codes are similar to HTTP: • 100 TRYING • 200 OK • 404 not found

  16. Session Initiation Protocol (SIP) • The development of SIP is based on three elements: • The User Agents designate the agents found in SIP phones • The Registrar is a server that handles REGISTER requests sent by the User Agent to report their current location • A SIP Proxy serves as an intermediary between User Agents who do not know their respective locations (IP address).

  17. Session Initiation Protocol (SIP) • Proxy Server SIP Call Flow

  18. Conclusion • Potential market growth • Some problems: • Interferences • Quality of voice call • … • Many opportunities • Main competitor; DECT

  19. ThankYou • For • Your Attention

  20. Questions?

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