Network Designs and Cabling

1. Network Designs and Cabling Organizational Communications and Technologies Prithvi N. Rao H. John Heinz III School of Public Policy and Management Carnegie Mellon University

2. Readings Traditional Wide Area Networks(Stallings and van Slyke) Chapter 7 Local Area Networks (Stallings and van Slyke) Chapter 9

3. Objectives • Identify the differences of centralized vs distributed computing • Describe the three basic functions of any network • List two network design principles • Discuss the strengths of client/server network systems

4. Objectives • Discuss the strengths of peer-to-peer network systems • Describe two different media plant specifications

5. Token Ring Cabling • Explosion of personal computers has changed the way organizations process information • De-centralization created a number of problems for MIS managers • Sharing of information more difficult • Difficult to access corporate application files • Difficult to access common peripheral devices

6. Token Ring Cabling • Centralized mainframes • One central processing device • Single file system • Facility to control peripherals • Single communications mechanism • PC networks • Many processing units • Many file systems • Many peripherals • Many communications mecahism

7. Stand-Alone Computers Printer Sales Data Billing Data Customer Service Data Planning

8. Token Ring Cabling • Result was localized processing or distributed processing • Has both advantages and disadvantages over centralized processing

9. Advantages of Distributed Processing • Networks can be grown incrementally by adding additional workstations as needed • Localized processing allows some users to run computationally intensive applications without affecting the performance of other users • PC technology is widely known and well accepted • Vast library of application software for PC systems

10. Disadvantages of Distributed Processing • Lack of central file storage systems to store commonly accessible data and application files • Lack of communication facility to support sharing of peripherals • Operating a PC may require more skill • Employee skill level must increase

11. Local Area Networks (LAN) • LANs developed to restore lost functionality of centralized mainframes • Allowed connection of independent desktop computers together • LAN geographical range is small with reasonably high data rates of transfer

12. Local Area Networks (LAN) • LAN provides physical connection between independent computing devices • LAN provides logical connection including • Handshaking • Flow control • Error detection

13. Local Area Networks (LAN) • LANs offer benefits of sharing application data and peripherals among users • Greatly reduced cost • Incrementally expand network • Three basic functions of any network • File transfer • Remote program execution • Virtual terminal services

14. Local Area Networks (LAN) All other network applications (peripheral sharing) can be accomplished using one of these three basic functions. Example: Shared printing is a file transfer operation to another computer where it is printed

15. Token Ring File Server Node Shared printer Node Node Print Server Node Node

16. LAN Design Principles • Client – Server LANs define one computer as the master station or LAN Server and other computers are LAN clients • Clients depend on server for services • Central server contains • Central file system • Communication facility or NOS software • Centralized authority to manage network

17. LAN Strengths • Central file system • Communication can be efficiently managed by central server • Server can act to police the network traffic of clients • Client communication software is simple

18. LAN Weaknesses • Single point of failure: no server implies no network • All communication must involve server • Even local conversation between clients • Network operating system may be overly complex Example of NOS is Novell Netware

19. Peer-to-Peer • Peer-to-peer networks treat all computers on network as equal peers • All computers responsible for communication requirements of LAN • All computers are masters and manage communication amongst workstations • No single server to manage LAN

20. Peer-to-Peer Shared printer Shared disk storage Host Host Peer Host Host

21. Peer-to-Peer Strengths • No single point of failure for communication on the network • More flexibility for storing distributed data and sharing remote peripherals • Availability of more application programming interfaces that facilitate development of network-based distributed applications

22. Peer-to-Peer Weaknesses • Host software must be more self-sufficient requiring it to be more complex than client software • Absence of central monitor to manage network communication • Lack of authority mechanism to resolve contention issues that may arise during operation TCP/IP are an example of peer-to-peer networks

23. Interface Requirements • Each computer must contain a Network Interface Card (NIC) that physically attaches to the internal bus of the computer • NICs come in different types, speeds and price ranges • NICs handle the actual sending and receiving of data between computers that are communicating

24. NIC Functions • Physically attaching the computer to the network • Framing the data for transmission as digital signals • Decoding received signals and converting it back to data • Error detection (usually with CRC) and retransmission

25. NIC Configuration Items • I/O address • IRQ address • DMA channel • ROM and RAM addressing

26. Configuration Issues: Problems and Solutions • Problem right after installation of NIC card • NIC card failure • IRQ conflict • Solution is to reconfigure the IRQ to a different value • Software as well as hardware may need to be reconfigured • Problem is lobe media failure • Solution is to check cable and connectors and replace parts

27. Configuration Issues: Problems and Solutions • Problem • Node address is not unique • Solution • Another NIC card on the LAN has the same address as your card. Replace the card for a different one from your vendor • Problem • Insufficient memory for NOS or application program to run

28. Configuration Issues: Problems and Solutions • Solution • Adjust drivers to use alternative memory (higher) • Problem • DMA failure • Some NIC cards do not support DMA • Solution • Reconfigure NIC to alternative DMA channel • Disable DMA or disable memory cache addressing on NIC

29. Configuration Issues:Problems and Solutions • Problem • Hang’s up when accessing the server • Bad driver or speed related problem • Solution • Bad driver requires replacement from vendor software CD • Place driver on a different place on disk • Problem • PC is running too fast for NIC

30. Configuration Issues: Problems and Solutions • Solution • Upgrade NIC • Slow down PC by inserting wait-states inside CMOS setup • Problem • Invalid path, No xxxx file found means that some configuration files cannot be found • Solution • Set up NOS software to point to the files

31. Media • Two types of media used in networking systems • Bounded • unbounded • Bounded • Signal is contained within bounds of media in the cable • Unbounded • Signal travels in the absence of a cable outside bounds of physical media

32. Bounded Media • Coaxial cable • Twisted pair cable • Fiber optic cable

33. Unbounded Media • Satellite transmission • Infrared • Radio Frequency • Microwave • Laser

34. Twisted Pair • Two kinds • Shielded (STP) • Unshielded (UTP) • Twisted pair used to construct token ring LANs and 10Base-t (T for twisted pair) • Connects terminals (STP) • Voice communication and wiring telephone networks • Least expensive and does not require special skills to instal • Already exists mostly

35. Twisted Pair • Various grades of cable • Level 1 used for telephone connections • Level 5 used to support high speed LAN

36. Fiber Optic Cable Profile • Transmits light rather than electrical signals • FDDI is one example (Fiber Distributed Data Interface) • Token passing LAN protocol • Popular for long distance carriers • Little need to regenerate signal midway • Advantage over traditional cabling that have much shorter distances of propagation before signal must be regenerated • Large bandwidth so large movements of data possible

37. Fiber Optic Cable Profile • Advantages over traditional cabling • Immune from crosstalk • Immune from noise as a result of electro-magnetic interference (EMI) or radio frequency interference (RFI) Fiber is typically used as a backbone media connecting LANs together since the cost of the media and special skills to install it may prohibit its use to each workstation (for now)

38. Coaxial Cable • Two kinds • Thick • Thin • Generally used to construct • BUS Ethernet LAN • ARCNET LAN • Broadband LAN Coaxial cable can extend long distances and has a high level of immunity to electrical interference (thicknet more so than thinnet cable)

39. Cable Plant Specifications • Vendors provide specifications for layout of cable plant • IBM cable plant • AT&T premises distribution scheme • Both use a HUB and SPOKE approach • Hubs are placed in wiring closets • Spokes branch out to each workstation • Hubs are connected by a backbone

40. Design Considerations • Important to lay out wiring plan, install and test • Can use a simulator to assist in prediction of behavior of network • Existing cable layouts must be carefully examined to satisfy requirements due to cost of replacement • Cost of materials is usually less than 10% of total • Labor which can be 90% of total Might as well install expensive cable?

41. Radio Frequency (RF) LAN • Gaining popularity • No need for expensive cable plant installation and maintenance • Easier to modify, expand and dismantled • RF technology uses different spectrum to microwave • Cannot travel as far as microwave • Particularly useful for LAN • Wireless devices are getting more popular • Unanswered issues regarding assignment of spectrum ranges, security and reliability of transmission

42. Radio Frequency (RF) LAN Radio frequency Communications Controller Workstations with RF NICs

43. Summary • LANs follow two design principles • Clients or servers • Equal peers • Services include • File management • Print and communications services • Peer-to-peer can act as servers without being configured as such • Media can be greatest expense and source of failure

44. Summary • Two media types available • Bounded (twisted pair, coaxial cable, fiber optic cable) • Unbounded (satellite, microwave, radio frequency)