程序代做CS代考 Week 1 – Introduction to Networking – cscodehelp代写

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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