1. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice HallChapter Four 1 Business Data Communications Chapter Four Components of a Local Area Network

2. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 2 Primary Learning Objectives Identify key components that compose a local area network (LAN) Understand the meaning of “topology” Describe selected LAN physical components Describe selected LAN logical components Identify common LAN devices Explain Standard versus Fast Ethernet Define metered versus site licensing Understand LAN design considerations

3. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 3 Local Area Network (LAN) Components Are physical and logical Physical or hardware elements include: NICs, servers, clients, printers, cables, hubs, switches, routers Logical or software elements include: Network operating systems, client operating systems, device drivers, monitoring and troubleshooting tools Logical elements also incorporate documented procedures

4. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 4 Local Area Network (LAN) Components Both physical and logical elements need to be installed, configured, and maintained Once implemented, elements must be monitored Monitoring may reveal that troubleshooting is required: To troubleshoot is to evaluate the causes of a problem so as to take corrective measures Troubleshooting tools can be hardware, software, a combination of these, or documented procedures

5. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 5 Local Area Network (LAN) Components - Hardware

6. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 6 Local Area Network (LAN) Components - Software

7. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 7 Topology A topology: Is an additional LAN characteristic Is both logical and physical Refers to the way that pieces of a network are physically connected Determines how network-connected devices access the physical network Three common topologies are: Star Ring Bus

8. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 8 Topology – Star A traditional star topology has a central controlling device Other networked devices connect to the central device using point-to-point circuits The central device is usually a mainframe or mini- computer Devices connecting to the mainframe/mini-computer are referred to as terminals A star can centralize network resources and management, but can also be a single point of failure

9. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 9 Topology – Standard Star

10. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 10 Topology – Ring Developed by IBM IBM also developed the Token Ring Protocol, later formalized as the 802.5 by the IEEE Uses a single cable such that a closed loop is created, hence the term “ring” Circling the ring, in one direction, is a token: Used by networked devices that need to communicate Either free or busy Performs well in networks with heavy traffic Not widely implemented due to cost and complexity

11. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 11 Topology – Ring

12. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 12 Topology – Bus Uses a central cable, but does not form a closed loop Conceptually more like a pipeline along which network communications travel Uses a broadcast mechanism Data packets placed on the bus go to all devices on the bus The bus topology most commonly uses the IEEE 802.3 Ethernet protocol 802.3, a contention-based protocol using CSMA/CD In a network with high traffic volume a standard bus using 802.3 can lack efficiency

13. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 13 Topology – Bus

14. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 14 LAN Physical Components The Physical components of a LAN’s hardware include: Network Interface Cards (NICs) Media Servers Clients Hubs Switches Routers

15. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 15 LAN Physical Components -- Network Interface Card When selecting a NIC, certain features must be evaluated: Bus width Cache Direct memory access Bus mastering Throughput Auto-sensing capability NICs have a physical address, expressed hexadecimally for Ethernet cards: 08:00:5A:28:E4:F8 The 1 st six digits identify the manufacturer; the last six, the card serial number

16. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 16 LAN Physical Components -- Network Interface Card Internal NICs are plugged into an expansion slot on the computer’s motherboard The PCI slots on this Intel motherboard could be used for an internal NIC PCI Slots in White

17. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 17 LAN Physical Components -- Media “Media” is plural, “medium” is singular and refers to a specific type of physical circuit In LANs, the most common medium is unshielded twisted wire Pair, or UTP UTP is categorized from CAT 1, lowest quality, to CAT 7, highest quality The higher category number the greater the throughput capacity CAT 5, a popular UTP choice, supports speeds from 10 Mbps to 100 Mbps LAN wiring most often runs from the networked device to a wiring closet

18. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 18 LAN Physical Components – Servers Servers generally control and manage networked resources in a LAN Depending on use, key server elements include: Primary memory or RAM Cache NIC capacity Processor; speed as well as number must be considered Hard Drive; capacity as well as speed must be considered Operating system Degree of fault tolerance: mirroring versus duplexing Server farms play an important role in today’s society

19. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 19 LAN Physical Components – Servers

20. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 20 LAN Physical Components – Servers

21. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 21 LAN Physical Components – Servers

22. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 22 LAN Physical Components – Clients Clients connect users to the network A client could be a desktop computer, a powerful workstation, a cell phone, a personal digital assistant, or any number of other networkable devices Like servers, clients require a NIC Clients require an operating system appropriate to the way they are to be used: Modern client operating systems incorporate “network aware” capability, and can be configured in a peer-to-peer network Most LANs configure clients in a client/server model

23. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 23 LAN Physical Components – Clients

24. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 24 LAN Devices Two devices particularly associated with LANs are switches and routers Switches: Create Point-to-point circuits between themselves and their connected devices Have largely replaced hubs in modern Ethernet LANs Are less expensive than routers, and have displaced but not eliminated routers, causing routers to be pushed to the edge of the network Are capable, based on the switch, of multilayer support for the data link and/or network layers

25. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 25 LAN Devices A Cisco 3550 Series Switch Note that the ports offer different speed capacities: 10 Mbps 100 Mbps 1000 Mbps

26. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 26 LAN Devices Routers: Function at the network layer of the OSI and TCP/IP models Are capable of connecting different logical networks Are required for different logical networks to communicate with each other Are more expensive than switches Use routing tables that are updated either manually, or automatically through software Do not broadcast packets

27. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 27 LAN Devices A Cisco 12410 series router

28. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 28 Standard versus Fast Ethernet The underlying Ethernet 802.3 architecture has not changed What has changed: The types of devices used within an Ethernet LAN (switches instead of hubs) The diameter an Ethernet LAN can be configured for (250 meters versus 2,500 meters) Switches can be used in a hierarchy: Faster, more expensive switches at the top Slower, less expensive switches at the bottom For Fast Ethernet, 100BaseX has been the market winner

29. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 29 Standard versus Fast Ethernet Standard Ethernet LANs have a limit of 2,500 meters, due to the physics of how packets are transmitted on UTP

30. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 30 Standard versus Fast Ethernet If the segment length is too long, errors result.

31. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 31 Standard versus Fast Ethernet

32. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 32 Standard versus Fast Ethernet An Ethernet switching hierarchy This type of hierarchy allows network planners to leverage capacity based on need, resulting in cost savings

33. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 33 Metered Licensing versus Site Licensing In a business, two common forms of licensing are metered licensing and site licensing Licensing is a critical issue in the network, legally and ethically Licensing policies should be part of any business’s documented network procedures Licensing documentation is often used in audits, both internal and external to the business

34. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 34 Metered Licensing versus Site Licensing With a metered license: The business buys a limited number of licenses for a given application Software maintains a count of the number of licenses As users login to use the application, the metered license counter is incremented When the maximum value is reached, new users will be denied access to the application, until an already logged-in user terminates his or her session If the metered value is too small, user frustration results If the metered value is too large, cost inefficiency results

35. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 35 Metered Licensing versus Site Licensing With a site license: The business is buying a licensing right to use an application for the entire organization, covering the entire site For an application used by a majority of staff, clients, or general users, a site license can offer cost savings An application that is rarely used, or used only by a few, is a questionable candidate for site licensing

36. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 36 LAN Design Considerations There is no one solution that is right for all businesses Designing a LAN solution requires answering numerous questions: What is the budget? What applications must be supported? What staff is available or required? What are the security issues? What scale is the network for? What are the facility requirements? What areas of the network are most vulnerable? What documentation is available or required?

37. Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 37 In Summary LAN Components are either physical, logical, or both A LAN has a topology Common elements within a LAN include media, servers, clients, NICs, switches, and routers Most LANs use a form of Ethernet Newer forms of Ethernet have not changed Ethernet's underlying architecture LAN licensing is an important legal and ethical issue LAN design must be driven by a business’s specific requirements