Chapter 1 - An Introduction to Wireless Networks

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Oct 26, 2013 (3 years and 11 months ago)

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Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

Section

1
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©Neurolink Ltd, 2005

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Appendix A


Wired Network Basics

Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

Section

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©Neurolink Ltd, 2005

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Networking models


When discussing computer networking, most people now focus on two models. One model, the
Open Systems Interconnection model, presents a descriptive v
iew of networking. The other
model is the functioning TCP/IP (Transmission Control Protocol over Internet Protocol)
standard.


These models came from the need to increase flexibility. For years, operating system vendors’
proprietary rules defined computer

communications. Since the rules were so complex, the cost
of adding five new terminals or a new printer was high and flexibility low.


Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

Section

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©Neurolink Ltd, 2005

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Data Formatting

Session Handling

Routing

Local Signaling


Evolution


The resulting evolution separated the rules

or protocols into task specific areas: Local signaling,
Routing, Session, and Data Formatting. Stacking the protocols clarified their relationships to
each other, to the network, and to the participating computer systems.


Since the Data Formatting protoc
ols know nothing of the communications process, they rely on
the Session protocols to support communications including Routing. The chosen Session
protocol relies on the selected Routing protocols to identify each flow of communication from
network to netw
ork. Local signaling protocols set the rules for carrying the data internal of the
network.


The extra benefit of this stacking or layering of protocols is that programmers can focus on one
layer of the stack at a time.

Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

Section

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©Neurolink Ltd, 2005

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Tasks



TCP/
IP




OSI

Data Formatting

Process

7 Application

6 Presentation

Session

Host
-
to
-
Host

5 Session

4 Transport

Routing

Internetwork

3 Network

Local Signaling

Network Interface

2 Data Link

1 Physical


Stacks Compared


This was the basis for the two models i
n use today: the Transmission Control Protocol over
Internet Protocol or TCP/IP model and the Open System Interconnection or OSI model.


A guideline for protocol stacks is that the lower layers are more hardware focused and the higher
layers are more softw
are oriented. The Routing layer performs its functions in computers, routers
and devices that act as routers. Local signaling works through network interface cards, hubs (in
their various forms), and switches.


Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

Section

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©Neurolink Ltd, 2005

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LAN


Local Area Networks (LAN) support w
orkgroup communication. Members of the workgroup
may communicate with destinations inside or outside the workgroup. The devices inside the
workgroup are often computers, printers, servers, and the supporting switches.

Some networks
are using wired or wirel
ess hubs, to connect interactive users’ computers to the workgroup
switches.


Up to the last few years, a workgroup has been bordered with routing
-
based device. In that
scenario, each workgroup is a different subnet and requires a different router interfac
e.


As technology evolved, switches, with their VLAN capabilities, have pushed routers back from
the workgroup users to connecting multiple workgroups at each router interface.



NOTE: Many specialists agree on a workgroup design guideline of 80% of the
traffic between
devices in the same workgroup.

Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

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©Neurolink Ltd, 2005

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Ethernet


FDDI


Token Ring/802.5


802.3





LAN Protocols


Different local signaling protocols have supported workgroup and LAN communication over the
years. The most used LAN protocols are: Ethernet, FDDI (
Fiber Distributed Data Interface), and
the IEEE (
Institute of Electrical and Electronics Engineers
) protocols 802.3 (similar to Ethernet)
and 802.5 (Token Ring).


With advances in technology, most managers have migrated to Ethernet LANs. With current
speed
s of 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps, managers can mix and match the speeds as
needed to work with the organization’s networked systems.

Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

Section

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©Neurolink Ltd, 2005

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WAN


Until switches and VLANs became part of networks, Wide Area Networks (WANs) were used to
interconne
ct LANs inside an organization’s network. Now a WAN connects organizational
locations.


The service provider is usually the only one to know the details of what happens in a WAN. The
result is that WANs are drawn as clouds with routers at their edges. The

connecting point for
LAN

to
-
WAN is a router.


Routers use different signaling protocols on the WAN interfaces than those the LAN interfaces.
The WAN protocols include PPP (Point to Point Protocol
), SONET (Synchronous Optical
Network), Frame Relay, X.25, a
nd ATM (Asynchronous Transfer Mode).


WAN are not necessarily “wide”. They can cover an extended campus, a metropolitan area, a
county or parish, a state, a country, or even a planet.


Section 1: An Introduction to Wireless Networks


Building, Deploying, and Securing Wireless LANs

Section

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©Neurolink Ltd, 2005

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TCP/IP Protocols


The Transmission Control Protocol over Interne
t Protocol (TCP/IP) suite is the de

facto standard
in today’s networks. The component protocols fit into three layers that sit atop the Network
Interface Layer.


The Network Interface Layer protocol header includes a two
-
byte identification of the Internet

layer protocol it is carrying.


The Internet Protocol header contains a single byte to identify the protocol it is carrying.


The Host
-
to
-
Host layer protocol header has two two
-
byte identifiers. One identifies the Process
layer’s application port number.

The other specifies the client side port number. Combining the
port number with its matching IP address sets the socket identification for that end of the
conversation.