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Business Data Communications. Chapter Four Components of a Local Area Network. Primary Learning Objectives. Identify key components that compose a local area network (LAN) Understand the meaning of “topology” Describe selected LAN physical components - PowerPoint PPT Presentation
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Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 1
Business Data Communications
Chapter Four
Components of a Local Area Network
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
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
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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 5
Local Area Network (LAN) Components - Hardware
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 6
Local Area Network (LAN) Components - Software
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
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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 9
Topology – Standard Star
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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 11
Topology – Ring
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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 13
Topology – Bus
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
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 1st six digits identify the manufacturer; the last six, the card serial number
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
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
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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 19
LAN Physical Components –Servers
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 20
LAN Physical Components –Servers
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 21
LAN Physical Components –Servers
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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 23
LAN Physical Components –Clients
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
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
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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 27
LAN Devices
A Cisco 12410 series router
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
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
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.
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall Chapter Four 31
Standard versus Fast Ethernet
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
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
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
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
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?
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