Understanding Local Area Networks: Basics and Implementation, Slides of Network security

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Introduction to Local Area Networks

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What is a Local Area Network?

• A local area network is a network whose

size is not large. For example, the size may

be a room, a department, a company, a

campus, etc.

• A network that covers a place that is city-

wide is called a “metropolitan network.”

• A network that spans states or countries is

called a “wide area network.”

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Why We Study Local Area Networks?

• You are using local area networks (e.g., Ethernets, wireless LANs, NFS, MW’s neighborhood, etc.) everyday and everywhere.
• You better know them well.
• This course is aimed to be self-contained. If you have taken “計網概” course, that is good. If not, that is still OK. We will spend the first four weeks on the basics that are covered in “計網概”.
• After taking this course, you will have hand-on experiences of using and configuring a switch.

How Is a Local Area Network

Implemented?

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A computer network is used to transfer a piece of

data from one node (traffic source) to any other

node (traffic destination).

source

destination

data

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source

destination

A computer network also needs protocols so that different nodes can talk to and work with each other to finish a job.

data

Hey, you send

too fast!

Hey, your 3rd data is lost.

Error control protocols

Congestion control protocols 1-

Protocol Layering Is Used To Manage

Complex Protocols

The ISO OSI seven-layer reference model 1-

The Internet TCP/IP Protocol Stack

transport

application

network

physical

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Why You Study Computer Networks

As A Student?

• Learn how computer networks work today
  • As numerous protocols are emerging and fading out rapidly, understanding protocol principles is far more important than knowing protocol details.
  • E.g., instead of memorizing how frequently routers exchange their “hello” messages and when to declare a router is dead in RIP, it is more important to understand why doing this protocol allows a router to detect that its neighboring router is dead.

Why We Study Computer Networks

As An Engineer?

Try to achieve the following ideal goals:

• A user’s data can be transferred from one node to any other node reliably, in-sequence, and spontaneously.
• A network’s resources (e.g., bandwidth) can be efficiently and fully utilized to reduce the operation costs.

However, sometimes these goals are conflicting, which makes achieving these goals at the same time very hard! 1-

Welcome to the Internet! Internet’s topology

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