Data Communication Network

1. Data Communication Network 333: DISCUSS THE FUNDAMENTALS OF NETWORKING

2. 333: DISCUSS THE FUNDAMENTALS OF NETWORKING • 1. Discuss networking concepts (20 hrs) • 2. Discuss hardware & software requirement to setup a Local Area Network (20 hrs)

3. 333.1: Discuss networking concepts • PERFORMANCE STANDARD • Given a scenario, identify correctly the hardware and services required for a Network • Objectives: • Define a Node/Host • Discuss functional & geographical relationship among nodes • Discuss services provided by a common carrier such as • Leased line • Switched line • Describe switching techniques • Circuit • Message • Packet • Discuss ISO/OSl reference model • Explain network communication protocols

4. SKILL AREA 331.1.3 Discuss services provided by a common carrier

5. Carriers • You can only install wires on your own property • Called your customer premises • To send signals between sites or to customers, you must use a carrier • Carriers transport data and voice traffic between customer premises, charging a price for their services • Receive rights of way from the government to lay wires and radio links Carrier Customer Premises

6. Computer network nodes • In data communication, a physical network node may either be a data circuit-terminating equipment (DCE) such as a modem, hub, bridge or switch or a data terminal equipment (DTE) such as a digital telephone handset, a printer or a host computer, for example a router, a workstation or a server.

7. Types of Traditional Telephone Circuits • Dial-Up Service (Any-to-Any) • Leased Lines • Point-to-point only • Cheaper for high volumes of use Switched Dial-Up Service Brunei Leased Line Miri

8. Dial-up • Uses POTS (Plain Old Telephone System) • Dial up networking technology provides PCs and other network devices access to a LAN or WAN via standard telephone lines. • Dial up Internet service providers offer subscription plans for home computer users. • Provides a low cost need based access. • Bandwidth 33.6 /56 Kbps. • Types of dial up services include V.34 and V.90 modem as well as Integrated Services Digital Network (ISDN). Dial up systems utilize special-purpose network protocols like Point-to-Point Protocol (PPP).

9. Dial-up • To use a dial up Internet connection, a client modem calls another modem located at the Internet Service Provider (ISP). The modems transfer network information over the telephone until one modem or the other disconnects. • When the popularity of the Internet exploded in the 1990s, dial up was the most common form of Internet access due mainly to its low cost to setup. However, the performance of dial up networking is relatively poor due to the limitations of traditional modem technology. V.90 modem dial up supports less than 56 Kbps bandwidth and ISDN handles approximately 128Kbps. • Many home users are currently replacing their dial up services with high-speed broadband technologies that operate at much higher speeds.

10. Dial-up

11. Leased Lines • A leased line connects two locations for private voice and/or data telecommunication service. • It is not a dedicated cable, a leased line is actually a reserved circuit between two points.  • Permanent telephone connection between two points • Organization ‘owns’ the leased line – not shared with anyone else. • Leased lines can span short or long distances. • Quality of service is assured • Line access is assured • Line is always active • Fixed monthly fee • Fees based on distance and speed of connection

12. Leased Line Service Switching Office Leased Lines May Pass Through Multiple Switches, Even Multiple Carriers Trunk Line Trunk Line Switching Office Switching Office Local Loop Local Loop Customer Premises A Customer Premises B

13. Leased Lines • Leased Lines are Circuits • Often goes through multiple switches and trunk lines • Looks to user like a simple direct link • Limited to point-to-point communication • Limits who you can talk to • Carriers offer leased lines at an attractive price per bit sent to keep high-volume customers Switch Trunk Line Leased Line

14. Leased Line Meshes • If you have several sites, you need a mesh of leased lines among sites Mesh Leased Line

15. Leased Line Speeds • Largest Demand is 56 kbps to a few Mbps • 56 kbps (sometimes 64 kbps) digital leased lines • DS0 signaling • T1 (1.544 Mbps) digital leased lines • 24 times effective capacity of 56 kbps • Only about 3-5 times cost of 56 kbps • DS1 signaling

16. Leased Line Speeds • Fractional T1 • Fraction of T1’s speed and price • Often 128, 256, 384 kbps • T3: is the next step • 44.7 Mbps in U.S. • Europe has E Series • E1: 2.048 Mbps • E3: 34 Mbps • SONET/SDH lines offer very high speeds • 156 Mbps, 622 Mbps, 2.5 Gbps, 10 Gbps

17. Advantages of Leased Line • Flexible level of connection based upon your business requirements • Synchronous service where upstream and downstream speeds are the same • Private network offers reduced security risks as it does not use the public network • Service Level Agreement provides peace of mind • Managed service

18. Firewalls on Leased Lines • Increased threats of Internet misuse has prompted companies to add firewalls to private leased lines to filter traffic coming into their network • The firewall filters traffic based on rules • Can block several types of attacks • Can monitor network traffic • Can not protect against virus attacks

19. Digital Subscriber Lines (DSLs) • Can Use Instead of Traditional Leased Lines • Less expensive • HDSL (High-Speed DSL) • Symmetrical: Same speed in each direction • HDSL: 768 kbps (Half a T1) on a single twisted pair • HDSL2: 1.544 Mbps (T1) on a single twisted pair

20. Digital Subscriber Line • Normal Leased Lines Used Data Grade Wires • High-quality, high-cost • Two pairs (one in each direction) • DSLs Normally Use Voice Grade Copper • Not designed for high-speed data • So sometimes works poorly • Usually one pair (ADSL, HDSL) • Sometimes two pairs (HDSL2)

21. Problems of Leased Lines • With many sites, meshes are expensive and difficult to manage • With N sites, N*(N-1)/2 leased lines for a mesh • May not need all links, but usually use many • User firm must handle switching and ongoing management • Expensive because this requires planning and the hiring, training, and retention of a WAN staff Sites Lines 5 10 10 45 25 300

22. T1 Leased Lines • Voice Requirements • Analog voice signal is encoded as a 64 kbps data stream • 8 bits per sample • 8,000 samples per second

23. T1 Leased Lines • T1 lines are designed to multiplex 24 voice channels of 64 kbps each • T1 lines use time division multiplexing (TDM) • Time is divided into 8,000 frames per second • One frame for each sampling period • Each frame is divided into 24 8-bit slots • One for each channel’s sample in that time period • (24 x 8) 192 bits • Plus one framing bit for 193 bits per frame

24. T1 Leased Lines • Speed Calculation • 193 bits per frame • 8,000 frames per second • 1.544 Mbps • Framing Bit • One per frame • 8,000 per second • Used to carry supervisory information (in groups of 12 or 24 framing bits)

25. PSDN PSDNs • Public Switched Data Networks • Designed for data rather than voice • Site-to-site switching is handled for you • You merely connect each site to the PSDN “cloud” (No need to know internal details)

26. PSDN PSDNs • Connect each site to the PSDN using one leased line • Only one leased line per site • With N sites, you only need N leased lines, not N* (N-1)/2 as with a full mesh 1 LeasedLine

27. PSDN PSDNs • Access Device Needed at Each Site • Connects each site to access line • Often a router • Sometimes a device specific to a particular PSDN Technology Access Device

28. PSDN PSDNs • Point of Presence (POP) • Place where you connect to the cloud • May be several in a city • May not have any POP close • Need leased line to POP • Separate from PSDN charges POP LeasedLine

29. PSDNs in Perspective • Simpler than Networks of Leased Lines • Less staffing • Fewer leased lines to support • Less Expensive than Networks of Leased Lines • Less staffing • PSDN prices are very low • PSDN is less expensive overall • PSDNs are replacing many leased line mesh networks

30. PSDN Circuit-Switched PSDNs • End-to-End Capacity is Guaranteed • If you need it, it is always there • When you don’t need it, you still pay for it • Expensive for data traffic, which usually has short bursts and long silences A bcd efg

31. Packet-Switched PSDNs • Messages are divided into small units called packets • Short packets load switches more effectively than fewer long messages

32. Packet-Switched PSDNs • Packet-Switched PSDNs Usually Operate at Layer 2 (Data Link Layer for Single Subnets) • Should be called frame-switched networks • Still called packet-switched networks

33. Packet Switched PSDNs • Packets are multiplexed on trunk lines • Cost of trunk lines is shared • Packet switching lowers transmission costs • Dominates PSDN service today Multiplexed Trunk Line

34. Packet Switched PSDNs: Virtual Circuits • All commercial packet switched PSDNs use virtual circuits • Eliminates forwarding decisions for individual packets • Reduces switching load, so reduces switching costs VirtualCircuit

35. Unreliable PSDNs • Most commercial PSDNs are Unreliable • (Only obsolete X.25 PSDN technology was reliable) • No error correction at each hop between switches • Reduces costs of switching • Note that both virtual circuits and unreliable service reduce switching costs

36. PSDN Cost Savings • Packet Switching • Reduces costs of transmission lines through multiplexing • Virtual Circuits • Reduces costs of switches because they do not have to make decisions for each frame • Unreliability • Reduces costs of switches because they do not have to do error correction

37. Question?