Week 1 – Introduction to Networking
COMP90007 Internet Technologies
Lecturer: Semester 2, 2021
© University of Melbourne 2021
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Outline
Computer Networks
Different types of computer networks Protocols, Layers and Services
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Network vs Computer Network
Network:
An intricately connected system of things or people
An interconnected or intersecting configuration or system of components
Computer Network:
A collection of autonomous computers interconnected by a single technology
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Terminologies
Network device: e.g. PC, Phone, Router, Switch.
Server: Provider of a service. Accept requests from clients.
Client: A network device connecting to a server and requesting a service.
Packet: A message sent between two network devices.
IP address: A unique number identifying a network device.
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What are the Internet and the World Wide Web?
Is the Internet or WWW a computer network?
Simple answers:
The Internet is not a single network but a network of networks!
The WWW is a distributed
system that runs on top of the Internet
https://mountpeaks.wordpress.com/
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Uses of Computer Networks
Business and Personal Applications
Resourcesharing(e.g.,printer,scanner,files)
Access to information
Interactiveentertainment
E-commerce
SocialInteractions
Internet-of-Things
parking,smart-meter,vendingmachines
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Simple Client-Server Network
A network with two clients and one server
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Simple Client-Server Network
The client-server model involves requests and replies
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Differentiating Factors of Networks
Types of transmission technology Broadcast link
Broadcast networks have a single communication channel shared by all machines on a network.
Packets sent by any machine are received by all others. Intended recipients process the packet contents, others simply ignore it.
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Differentiating Factors of Networks
Types of transmission technology Point-to-point links
Datafromsendermachineisnotseenandprocessedby other machines.
Unicastingisthetermusedwherepoint-to-pointnetworks with a single sender and receiver pair can exchange data.
Point-to-pointnetworksconsistofmanyconnectionsbetween individual pairs of machines.
Multicasting
Transmissiontoasubsetofthemachines.
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Differentiating Factors of Networks
By Scale
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Differentiating Factors of Networks
By Topology Mesh
Fully mesh: each device has a dedicated point-to-point link to every other device.
Bus
All devices are attached to a shared medium.
Only a single device on the network can transmit at any point in time. Requires a negotiation mechanism to resolve transmission conflicts.
e.g. Ethernet is the most common bus network.
(b) bus
(a) mesh
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Differentiating Factors of Networks
By Topology Star
All devices are attached to a central device. Ring
Each device on the ring receives the data from the previous device and forwards it to the next device.
Requires access control to resolve propagation queuing.
e.g., Token ring.
hub
(c) star (d) ring
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What Makes the Internet Work
Protocols, Layers and Services
Protocol Hierarchies
Design of Layer Models
Connection-Oriented and Connectionless Services Services Primitives
Services and Protocols
Network Reference Models Open Systems Interconnect TCP/IP
Network Standards
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The Philosopher-Translator-Secretary Architecture
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Network Software: Protocol Hierarchies (1)
Layers,protocolsandinterfaces
Consider the network as a stack of layers
Each layer offers services to layers above it through interface
Protocol is an agreement between the communicating parties on how communication is to proceed
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Network Software: Protocol Hierarchies (2)
Information flow supporting the virtual communication in layer 5
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Services
Choice of service type has a corresponding impact on the reliability and quality of the service
Connection-Oriented vs. Connectionless
Connection-Oriented: connect, use, disconnect (similar to telephone service). Negotiation inherent in connection setup.
Connectionless: just send (similar to postal service).
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Connection-Oriented and Connectionless
Six different types of services
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Service Primitives
Primitives are a formal set of operations for services
The number and type of primitives depends on the nature of service – in general more complex services require more service primitives
Six service primitives for implementing a simple connection- oriented service
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Relationship of Services and Protocols
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Relationship of Services and Protocols
Service = set of primitives that a layer provides to a
layer above it
Provided through the interfaces between layers (service provider vs. service users)
Defines what operations the layer is prepared to perform on behalf of its users
Abstract: nothing about how these operations are implemented
Protocol = a set of rules governing the format and meaning of packets that are exchanged by peers within a layer
Packets sent between peer entities
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Next: Reference Models
The OSI Reference Model
The TCP/IP Reference Model
A Comparison of OSI and TCP/IP
A Critique of the OSI Model and Protocols A Critique of the TCP/IP Reference Model
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