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University of education township campus lahore, Pakistan

Lecture 02

Introduction of Internet, Building Blocks

Internet Architecture and Protocols, University of education township campus lahore, Pakistan

Internet Architecture and Protocols

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Introduction

Computer Network:

“An interconnected collection of autonomous/independent computers that are capable of exchanging information”

Two computers are said to be interconnected if they are able to exchange information

The most elementary network consists of two computers communicating over a cable

The old model of a single computer serving all of the organization’s computational needs has now been replaced by one in which a large number of separate but interconnected computers do the job. These systems are called computer networks.

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Introduction

Uses of computer networks

Computer Networks are everywhere

↗ Email↗ World Wide Web,↗ Video Conferencing↗ File Transfer↗ Collaborative Virtual Environments↗ Remote control of robots and machines↗ Distributed Programs and Applications↗ Hacking↗ Banking↗ Internet telephone . . . . . . . . . . etc

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Introduction

Why Do We Need Computer Networks

We need computer networks for

↗Sharing of resources ↗Sharing of data ↗Sharing of ideas

So, a computer network

Eliminates the geographical constraints, improve communications and more than one person can work on a single job.

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Components of a Computer Network

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Classification of Computer Networks

Computer networks are classified by many factors:

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Roles of a computer in a Network

↗ Server:

They provide network resources

↗ Client:

They use but not provide network resources

↗ Peer:

They both use and provide network resources

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Network Architectures

↗ Server based Networks

↗ Peer Networks

↗ Hybrid Networks

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Network Architectures

Server based Networks

↗Server based networks are defined by the presence of servers on the network and are responsible for security and administration↗All the resources are with server↗Clients request services, such as file storage and printing and servers deliver them↗Server computers typically are more powerful than client computers

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Network Architectures

Advantages:↗ Security↗ Centralized control↗ Central file storage↗ Central backup↗ Ability to pool available resources↗ Share expensive equipment↗ Optimized faster dedicated servers↗ Easy manageability

Disadvantages:

↗ Expensive dedicated hardware↗ Network OS and software are expensive↗ Network administration required

Pooling is a resource management term that refers to the grouping together of resources (assets, equipment, personnel, effort, etc.) for the purposes of maximizing advantage and/or minimizing risk to the users. The term is used in many disciplines.

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Network Architectures

Peer networks

↗Peer networks are defined by the lack of central control over the network↗There are no servers in peer networks↗Peer networks are organized into workgroups↗These are used for small networks

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Network Architectures

Advantages:

↗ No extra investment in hardware and software↗ Easy setup, Low cost↗ No network administrator required↗ Ability of user to control sharing

Disadvantages:

↗ Additional loads on computer because of resource sharing↗ Lack of central organization↗ No central point for file storage↗ Weak and intrusive security↗ Each user must administrate its own computer

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Network Architectures

Hybrid networks

↗Hybrid networks have all three types of computers operating on them and generally have active domains and workgroups↗This means that while most shared resources are located on servers, network users still have access to any resources being shared by peers in the workgroup

Advantages :

↗The advantages of server based networking as well as of peer based networking↗Ability of users and network administrator to control security based on the importance of the shared resource

Disadvantages :

↗They share the disadvantages of server based as well as peer based networking

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Two Basic Network Structures

Workgroups vs Domains

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Two Basic Network Structures

↗ A domain is a logical grouping of networked computers that share a centralized database which contains user accounts and security information for the domain

↗ A domain is a specific name given to a LAN that includes one or more Servers (Domain Controllers)

↗ Advantage, you have a dedicated server to log/track all users and shares via Active Directory, disadvantage is the cost and maintenance required to keep this configuration running

↗ A workgroup is a logical grouping of networked computers that share resources

↗ A workgroup has not dedicated server(s) to track users and such, it's all done via each client machine on the LAN, this includes shared objects and user logons

↗ Advantage, cheaper to run and maintain as you only need two machines running in the same workgroup to be called a workgroup , disadvantage no centralize management and security

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Network Building Blocks

A network can be defined/build recursively as:

↗Two or more nodes connected by a link

↗When we have more than two nodes, we need intermediate devices to connect them

↗Circular nodes (switches) implement the network Squared nodes (hosts) use the network

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Network Building Blocks

↗ Two or more networks connected by one or more nodes; internetworks

↗ Circular nodes (router or gateway) interconnects the networksA cloud denotes “any type of independent network”

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Network Building Blocks

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Network Building Blocks

Nodes

↗Hosts: general-purpose computers↗Switches: typically special-purpose hardware↗Routers : connecting networks

Links

↗Copper wire with electronic signaling↗Glass fiber with optical signaling↗Wireless with electromagnetic (radio, infrared, microwave) signaling

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Network Building Blocks

Switching Strategies

Circuit switching: ↗carry bit streams↗establishes a dedicated circuit↗links reserved for use by communication channel↗send/receive bit stream at constant rate↗example: original telephone network

Packet switching:↗store-and-forward messages↗operates on discrete blocks of data↗utilizes resources dynamically according to traffic demand↗send/receive messages at variable rate↗example: Internet

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Network Building Blocks

Hosts are directly or indirectly connected to each other

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Network Building Blocks

Address: byte-string that identifies a node

↗ Usually unique

Routing: forwarding decisions

↗ Process of determining how to forward messages to the

destination node based on its address

Types of addresses

↗ unicast: node-specific

↗ broadcast: all nodes on a network

↗ multicast: some subset of nodes on a network

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Network Building Blocks

↗ A network can be constructed from nesting of networks

↗ An address is required for each node that is reachable on the network

↗ Address is used to route messages toward appropriate destination

Enough ???

↗ A network is delivering packets among a collection of computers

↗ How application processes communicate in a meaningful way?

↗ Hide network complexity by implementing the common services

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Network Building Blocks

↗ Turn host-to-host connectivity into process-to-process

communication, making the communication meaningful

Host Host

Application

Host

Application

Host Host

Channel

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Network Building Blocks