Chapter 8 Wide Are Networking (WAN)

1. Chapter 8Wide Are Networking (WAN) • Concepts • Packetizing • Multiplexing • Switching • Transmissions • Services • Selection

2. Packetizing • Organize a group of bits in a predetermined & structure format • Include user’s data, overhead or management information for error-free transmission • Packets, frames, cells, blocks, data units

3. Multiplexing • Frequency division multiplexing (FDM) • Time division multiplexing (TDM) • Statistical time division multiplexing (STDM) • Wavelength division multiplexing (WDM) • No interoperation between different manufacturers

4. Frequency Division Multiplexing • Use different frequencies for multiple input signals • Use guardbands (take space, not efficiency) • Transmit data and voice simultaneously over phone line • Data over voice (DOV) unit with PBX for college campus, not for PSTN

5. Time Division Multiplexing • 100% bandwidth available for a portion of the time • Use buffer memory & central clock for flow control (polling) • Composite message frame • Simple, not efficiency

6. Statistical Time Division Multiplexing • Efficiency • No idle time • No padded blanks or null characters in composite message blocks • Dynamically allocating time to terminals • Higher cost • Buffer • Processing power for control information (source terminal, bytes of data, & data compression)

7. Wavelength Division Multiplexing • Use different wavelengths of light • Long-distance fiber optic network

8. WAN Switching • Packet switching network • Circuit switching network

9. Packet Switching • Packet-switched network • Public data network (PDN) • Packet assembler/disassembler (PAD) • Stand-alone devices • Combined with modems or multiplexers • Location: end-user or entry point of packet switched data network • Equipment: DSEs (data-switching exchanges) or PSEs (packet-switching exchanges) • Every user having the same transmission rate

10. Packet Switched Services • Connectionless • Global address (source & destination) • Datagram (address with user data) • Unreliable (no error detection or flow control) • Connection-oriented: virtual circuits • Reliable packet network (ACK/NAK) • Call set-up packets, message-bearing packets, & clear request packet

11. Circuit Switching • Circuit switched network • Use circuit without source & destination address

12. WAN Networking Transmission • Local Loop • Plain old telephone service (POTS) • Integrated service digital network (ISDN) • Asymmetric digital subscriber line (ADSL) • Cable TV • Boradband • T1 • SONET

13. ISDN • A switched digital services for delivering voice, video, and data at same time • Types • Basic rate interface (BRI): 2B+D ( 2 Bearer channels of 64 kbps & 1 Delta or Data channel of 16 kbps) • Primary rate interface (PRI): 23B+D • Applications use ISDN terminal adapter • Single user-to-office or Internet connection • Office-to-office connection

14. ADSL • Use POTS at higher frequencies • Use frequency division multiplexing: (upstream & downstream) • Internet & voice at same time • Types • Very high speed digital subscriber line (VDSL) • Rate-adaptive digital subscriber line (RADSL) • Symmetric digital subscriber line (SDSL) • Application: access Internet using POTS & ADSL units

15. Cable TV Problems for WAN • Downstream only infrastructure • Remedy methods • Upstream using POTS • Modify cable architecture to upstream & downstream

16. T-1 • High-capacity digital transmission over voice channel • 1.544 Mbps bandwidth • 24 64-Kbps channels (DS-0 circuit) • T1 multiplexers • Application • Leased line or private line for business

17. T-1 Digital Services • Digital service hierarchy or DS standards • DS-0 : 64Kbps • DS-1: T-1uses four copper wires (two twisted pair) • DS-2: T-2 • DS-3: T-3 uses optical fiber media • DS-4: T-4

18. SONET • Optical transmission services: • For failure tolerance & reliable data delivery • Metropolitan area only • Expensive • Applications • Broadband ISDN • High-definition television

19. WAN Services • X.25 • Frame relay • Switched multimegabit data service (SMDS) • Cell relay - ATM • Broadband ISDN

20. X.25 • CCITT standard for the interface between DTE and packet-switched network • Point-to-point error checking or hop-by-hop error checking • Technology • Packet assembler/disassembler (PAD) • X.25 switches

21. Frame Relay • Error detection & correction • Point-to-point error detection (discard ) • End-to-end error correction • Frame: variable length • Pro: high through put with low delay for data only • Con: no guaranteed time delivery (not for voice & video)

22. Frame Relay • Technology • Frame relay or frame assembler/disassembler (FRAD or FAD) or frame relay access devices • Frame relay switch • Application: inter-LAN traffic

23. Switched Multimegabit Data Service - SMDS • Connectionless network service • Use SONET (T-3) • Fixed-length cells of data • Broadcast • Only MCI for long distance

24. Cell Relay - ATM • Cell • fixed length (53 octects) • 48 for data and 5 for control information • Predictable delivery time for voice and video • Technology • ATM network interface cards • ATM hub • ATM enterprise switch • ATM gateway switches or ATM access switches • ATM LAM emulation

25. WAN Selection Criteria • Data traffic patterns • Business objectives

26. Assignment • Review chapter 8 • Read chapter 9