Computer Communication and the Internet

1. 11 Computer Communication and the Internet

2. Alphanumeric Codes • The ASCII Code • American Standard Code for Information Interchange (ASCII) • 7-bit code used for representing alphanumeric symbols with a distinctive code word. • Developed for purpose of coding binary data. • ASCII-7 • Adopted international standard.

3. Alphanumeric Codes • The EBCDIC Code • Extended Binary-Coded Decimal Interchange Code (EBCDIC) • 8-bit alphanumeric code. • The Baudot Code • Alphanumeric code based on five binary values.

4. Alphanumeric Codes • The Gray Code • Numeric code representing decimal values 0 to 9. • Based on relationship that only one bit in a binary word changes for each binary step.

5. Computer Communication • Asynchronous system • Transmit and receive clocks free-run at approximately same speed. • Synchronous system • Both sender and receiver exactly synchronized to same clock frequency.

6. Computer Communication • Universal Serial Bus (USB) Port • Universal high-speed serial communications interface. • See Table 11-2: The USB Wire Colors and Functions

7. Table 11-2 The USB Wire Colors and Functions

8. Computer Communication • IEEE 1394 • High-speed serial connection for computers and peripherals; developed by Apple (FireWire).

9. Computer Communication • RS-232 Standard • Older serial data communications follows standard (RS-232 C). • Means of interfacing computer with modem. • Defined signal levels and different lines used.

10. Computer Communication • RS-232 Line Descriptions • Ground pins • Data signal pins • Handshaking pins • Equipment ready pins

11. Computer Communication • RS-232 Line Descriptions • Signal detect pin • Ring indicator pin • Other pins • See Table 11-3: Overview of Current Serial Computer Communication Standards

12. Table 11-3 Overview of Current Serial Computer Communication Standards

13. Computer Communication • RS-422, RS-485 • Uses differential technique that provides significant improvement in performance and greater distances and capacity to support higher data rates. • Supports multidrop applications. • See Table 11-4: Standard Computer Bus Interfaces

14. Table 11-4 Standard Computer Bus Interfaces

15. Table 11-4 (continued) Standard Computer Bus Interfaces

16. Local-Area Networks • Local-Area Network (LAN) • Local computer • Personal microcomputer-type system. • LANs defined in terms of topology (architecture) used to interconnect networking equipment and protocol for accessing network.

17. Local-Area Networks • Local-Area Network (LAN) • Carrier sense multiple access with collision detection (CSMA/CD) • Bus and star topologies; token passing; token-ring topology.

18. Local-Area Networks • Ethernet LAN • Baseband CSMA/CD protocol local area network system. • Capability for detecting data collisions (collision detection). • Ethernet protocol provides information regarding source and destination addresses.

19. Assembling a LAN • The Office LAN Example • If network hardware and software properly set up, all computers will be able to access server, printer, other computers. • See Table 11-5: Common Numerics for LAN Cabling

20. Table 11-5 Common Numerics for LAN Cabling

21. Assembling a LAN • Assembling a Building LAN • Network where multiple LANs within a building are connected together.

22. LAN Interconnection • Metropolitan area networks (MANs) • Two or more LANs linked together within limited geographical area. • Wide-area network (WAN) • Two or more LANs linked together over wide geographical area.

23. LAN Interconnection • Open systems interconnection (OSI) reference model • Developed by International Organization for Standardization (ISO).

24. LAN Interconnection • Interconnecting LANs • Switch • Routers • Gateways

25. Internet • Internet Protocol (IP) Addressing • Unique address that tells on which network the computer is located. • Assigned by Internet Assigned Numbers Authority (IANA). • See Table 11-6: The Three Classes of IP Networks

26. Table 11-6 The Three Classes of IP Networks

27. IP Telephony • IP telephony (voice-over IP) • Telephone system for computer networks. • Technologies comparable to private branch exchange (PBX) telephone systems while maintaining flexibility of computer networks.

28. Interfacing the Networks • Modem Technologies • To transmit data via a phone requires conversion of a signal within 300- to 3400-Hz range; conversion provided by a modem. • Cable Modems • High-bandwidth network to deliver high-speed, two-way data.

29. Interfacing the Networks • Integrated Services Digital Network • Data communications link for both voice and data using a set of standardized interfaces.

30. Interfacing the Networks • xDSL Modems • High-speed internet access technology. • DSL • Digital subscriber line. • Uses copper telephone lines for carrying data. • See Table 11-7: xDSL Services and Their Projected Data Rates

31. Table 11-7 xDSL Services and Their Projected Data Rates

32. Troubleshooting • Common maintenance situation for larger LAN installations is to set up a help desk. • OSI model to troubleshoot. • Problems with unshielded twisted-pair wiring • Pairs become crossed or split up; wrong kind of connector used.

33. Troubleshooting • Keep good-quality wiring diagrams of network installation.