VoWLAN: The Voice over WLAN Maxime Staszewski Fall 2008 – CS 484:

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

Brief Overwiew of VoWLAN VoIP over WLAN Low-cost communication costs Add mobility of phone terminals No permanent connection between the two sides transmits information according to the status of network congestion Slight degradation of communication compared to a fixed line Convergence data/voice Require 802.11 set by the IEEE

Virtual Private 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.

Virtual Private 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

Virtual Private Network

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)

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).

Speech digitization methods 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.

Waveform coders 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

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

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.

IPv6 (Internet Protocol version 6)

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).

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

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).

Session Initiation Protocol (SIP) Proxy Server SIP Call Flow

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

Thank You For Your Attention

Questions?