Convergence and Switching in Telecom Networks

1. Lecture 11 Convergence

2. 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

3. 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

4. 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

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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

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

22. 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

23. 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

24. 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

25. 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

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

27. 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

28. 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

29. Call Center Connections to Internet

30. IP-Based Telephone Systems

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