Transcript Chapter Four

Business Data Communications
Chapter Four
Components of a
Local Area Network
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
Chapter Four
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Primary Learning Objectives
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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
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Local Area Network (LAN)
Components
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Are physical and logical
Physical or hardware elements include:
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Logical or software elements include:
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NICs, servers, clients, printers, cables, hubs, switches,
routers
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
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Local Area Network (LAN)
Components
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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:
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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
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Local Area Network (LAN)
Components - Hardware
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Local Area Network (LAN)
Components - Software
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Topology
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A topology:
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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:
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Star
Ring
Bus
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Topology – Star
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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 minicomputer
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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
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Topology – Standard Star
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Topology – Ring
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Developed by IBM
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Uses a single cable such that a closed loop is created,
hence the term “ring”
Circling the ring, in one direction, is a token:
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IBM also developed the Token Ring Protocol, later
formalized as the 802.5 by the IEEE
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
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Topology – Ring
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Topology – Bus
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Uses a central cable, but does not form a closed loop
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Uses a broadcast mechanism
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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
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Conceptually more like a pipeline along which network
communications travel
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
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Topology – Bus
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LAN Physical Components
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The Physical components of a LAN’s hardware include:
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Network Interface Cards (NICs)
Media
Servers
Clients
Hubs
Switches
Routers
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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LAN Physical Components -Network Interface Card
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When selecting a NIC, certain features must be evaluated:
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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
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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
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LAN Physical Components -Network Interface Card
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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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
PCI Slots in
White
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LAN Physical Components -Media
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“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
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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
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LAN Physical Components –
Servers
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Servers generally control and manage networked
resources in a LAN
Depending on use, key server elements include:
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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
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LAN Physical Components –
Servers
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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LAN Physical Components –
Servers
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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LAN Physical Components –
Servers
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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LAN Physical Components –
Clients
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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:
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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
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LAN Physical Components –
Clients
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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LAN Devices
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Two devices particularly associated with LANs are switches
and routers
Switches:
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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
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LAN Devices
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A Cisco 3550 Series Switch
Note that the ports offer
different speed capacities:
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10 Mbps
100 Mbps
1000 Mbps
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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LAN Devices
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Routers:
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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
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LAN Devices
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A Cisco 12410 series router
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Standard versus
Fast Ethernet
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The underlying Ethernet 802.3 architecture has not
changed
What has changed:
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Switches can be used in a hierarchy:
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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)
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
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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
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Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Standard versus
Fast Ethernet
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If the segment length is too long, errors result.
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Standard versus Fast Ethernet
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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Standard versus
Fast Ethernet
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An Ethernet
switching hierarchy
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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
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Metered Licensing versus
Site Licensing
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In a business, two common forms of licensing are
metered licensing and site licensing
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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
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Metered Licensing versus
Site Licensing
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With a metered license:
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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
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Metered Licensing versus
Site Licensing
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With a site license:
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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
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LAN Design
Considerations
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There is no one solution that is right for all businesses
Designing a LAN solution requires answering numerous
questions:
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What
What
What
What
What
What
What
What
is the budget?
applications must be supported?
staff is available or required?
are the security issues?
scale is the network for?
are the facility requirements?
areas of the network are most vulnerable?
documentation is available or required?
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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In Summary
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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
Business Data Communications, by Allen Dooley, (c) 2005 Pearson Prentice Hall
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