Lecture 11 Convergence Switching Circuit Switching designed to

Lecture 11 Convergence

Switching • Circuit Switching – designed to support voice network – set up a complete path before connecting calls – path saved for entire duration of call • Packet Switching – only uses network capacity when data to be transported – data broken into packets, multiple computers share same path

Circuit Switching • Based on voice traffic • Today data traffic increasing • Not necessary to reserve entire path for a connection when sending data • Waste of capacity when adding up silences on the circuit

Packet Switching • Internet Protocol does not save a path in the network for the entire duration of the call • During pauses and silences, conversations from multiple sources are transmitted over shared facilities • These variable lengths of data are called packets

Increases in Data Traffic • Caused by: – Internet usage from individual homes – increased email usage

IP-Based Networks • Will increasingly be built due to: – increased level of data traffic – increased demand for VPNs • VPNs are managed by carriers that provide links between corporate sites, and between corporate sites and their customers • Will dramatically change the design and structure of the public network

Structure of Telecom Networks • Is changing – Increases in competition • causes lower long distance prices • lower profit margins on long-distance • may disappear • Less costly to build due to increases in efficiency in equipment and multiplexing

Overlay Networks • Separate network for a particular service covering most of the same geographical locations as the basic telephone network, but operating independently • Elimination of these is a cost saver • Run on their own equipment • Everything duplicated when you have an overlay network

Technical Advances • Leading to improvements in IP networks: – improvements in switching routers – faster digital signal processors or DSPs – dense wavelength division multiplexing – lower, cost, programmable switches – new protocols improving the quality of voice and video over packet networks

Switching Routers • Enhance the quality of voice and video carried on IP networks – establish a path in network for high priority services such as voice and video – addressing stored on silicon cards – multi-protocol label switching enable router to process calls faster

Digital Signal Processors • DSPs are special purpose micro-processors • execute instructions • good at performing small number of repetitive tasks such as: – converting analog voice into digital – compressing voice – packetizing voice

Voice Compression • Key capability of DSPs • uses mathematical algorithms to make voice smaller so it can be sent at lower speeds

DWDM • Fiber optic multiplexing technique • Enable one strand of fiber to carry up to 96 channels of data • Makes networks faster and lower in cost to construct – need fewer amplifiers to boost signal – need less fiber – need fewer multiplexers

Programmable Switches • Non-proprietary telephone switches • Work with enhanced services in the public switched network – calling card services – debit cards – voice messaging – fax services – international callback

Programmable Switches • Connect central office switches with enhanced services • Can transport calls • Cost less than traditional central office switches • Costly switching programmed into router • Can be used to aggregate calls

Converged Networks • Free calling over the Internet – proprietary software – soundcard – headset, microphone, or telephone plugged into computer • H. 323 – standard way for users to make voice calls from PCs connected the Internet

Calls from PCs to the Telephones • Carriers include: – IDT – Delta Three • • offer long distance to consumers from PC or phone software available from the IDT Web site users abroad can make calls to US 10 -15 cents p/min users place local call to IDT switch, voice translated to digital, compresses, packetized, routed over Internet

Calls over Internet to Telephones • Carriers: IDT, ATT Worldnet, Delta Three – sell service routed from customer’s phones to Internet – customers dial a local telephone number and PIN number – local telephone provider routes call to the Internet Telephony Service Provider (ITSP) POP – – digitized, compressed, packetized routed over the Internet deconverted to analog billing tracked

Carriers with Facilities • Constructing new networks too expensive • Switches are now connected to networks • Carriers with switches buy exclusive access to fiber optic channels – Indefeasible Right to Use (IRU) – carrier purchases the rights to a set number of fiber strands from owners of fiber network

Converged Networks • • Calls over Internet from PC to telephones Calls over the Internet from telephones Carriers with their own facilities Data-only networks using IP and ATM

Applications for Convergence • Prepaid Debit Cards • Document Sharing • VPNs between corporate sites, E-commerce – Security issues – – tunneling network-based address filtering authentication authorization

Tunneling • Way to provide security on VPNs • VPNs are shared services: security an issue – traffic from multiple organizations carried on same transportation media – tunnels surround customer packets with an extra header on each packet to provide security – encryption also important component to tunneling

Tunneling • A local area network term – Means: • to temporarily change the destination of a packet • to traverse one or more routers that are unable to route to the real destination

Network Based Address Filtering • Alternative to tunneling • Address contains security information • Software looks up information contained in IP address to accept or reject information • Frequently used on security software located in organizations’ premises

Authentication • Authorizes you as the individual you claim to be on the system • CHAP popular authentication protocol – Challenge Handshake Authentication Protocol • Every time a remote user attempts to log onto the VPN the remote computer will be challenged by the security server • Remote computer responds with value calculated by CHAP software

Authorization • Ability to allow or deny an individual access to databases or services • Done – by the carrier – again at the customer site

Voice and Data Using IP on Dedicate Lines • VPN can be created by leasing dedicated lines • IP used on these dedicated lines to send email, data, voice • Requires use of: • security software • routers • multiplexers

Connecting Phone Systems to IP Networks • Used to connect two or more locations • Accomplished by connecting existing phone system to on-site routers – to send voice and fax over spare capacity in VPN or private lines using IP – voice digitized, packetized, compress then formatted for phone system, packets reordered, and decompressed

Call Center Connections to Internet

IP-Based Telephone Systems

Summary • IP for voice telephony still in its infancy • most voice traffic still carried of circuitswitched public networks • Voice over IP expected to grow • Being deployed by corporations for internal calling domestically and internationally • Sales today done on wholesale level