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Transcript
Objectives Communicating over the Network Network Fundamentals – Chapter 2 Describe the structure of a network, including the devices and media that are necessary for successful communications. Explain the function of protocols in network communications. Explain the advantages of using a layered model to describe network functionality. Describe the role of each layer in two recognized network models: The TCP/IP model and the OSI model. Describe the importance of addressing and naming schemes in network communications. 2 Network Structure Network Structure Network Data is sent across a network in small “chunks” called segments Multiple computers connected together via a communications system Enables multiplexing – interleaving many conversations together over a single link 3 common elements of communication – message source – the channel – message destination 3 Network Structure End Devices Computers: work stations, laptops, servers, web servers Network components – hardware the physical components, devices and media – software programs, operating systems, services, etc. 4 Network printers VoIP phones Security cameras Mobile handheld devices End devices are also called hosts. A host device is either the source or destination of a message transmitted over the network. 5 Each host requires a network address. Copyright © 2001, Cisco Systems, Inc. All rights reserved. Printed in USA. Presentation_ID.scr 6 1 Intermediary Devices Network Media Role of an Intermediary Device The Network Media connects the devices together and provides a path over which the signals can travel –Provides connectivity for End Devices and ensures data flows across the network Copper cables – UTP, coaxial cable. Electrical signals Optical fibre cable. Laser signals. Network Access Devices (Hubs, switches, and wireless access points) Wireless media. Electro-magnetic signals. Internetworking Devices (routers) Communication Servers and Modems Security Devices (firewalls) 7 Local Area Networks (LANs) 8 Wide Area Networks (WANs) A network serving a home, building or campus is considered a Local Area Network (LAN) LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN) Covers a limited area, owned and administered by a single organization Organizations usually lease WAN services from a Service Provider 9 Internets and Intranets 10 Data Network Symbols An internetwork is a connection of individual networks, sometimes abbreviated to internet The Internet is a global mesh of public networks An intranet is a collection of interconnected private networks owned by one organization and only accessible to its employees 11 Copyright © 2001, Cisco Systems, Inc. All rights reserved. Printed in USA. Presentation_ID.scr 12 2 Function of Protocols in Network Communication A protocol is a set of predetermined rules The Interaction of Protocols When accessing a Web server, you are using a number of different protocols Network protocols are used to enable devices to communicate successfully A protocol suite is a set of protocols designed to work together, e.g. TCP/IP Industry standard a process or protocol that has been endorsed by the networking industry and ratified by a standards organization 13 14 Technology Independent Protocols Layered Network Models Many diverse types of devices can communicate using the same sets of protocols. This is because protocols specify network functionality, not the underlying technology to support this functionality. Using a layered model helps in the design of complex multi-use, multi-vendor networks Benefits include – assists in protocol design – fosters competition between vendors – changes in one layer do not affect other layers – provides a common language There are two important models – ISO Reference Model – a seven-layered model – TCP/IP Protocol Model – a four layered model 15 Layers with TCP/IP and OSI Model 16 The TCP/IP Model A protocol model provides a model that closely matches the structure of a particular protocol suite. A reference model provides a common reference for maintaining consistency within all types of network protocols and services. 17 Copyright © 2001, Cisco Systems, Inc. All rights reserved. Printed in USA. Presentation_ID.scr 18 3 The Communication Process Protocol data units (PDU) and Encapsulation Creation of data at the application layer of the originating source end device Segmentation and encapsulation of data as it passes down the protocol stack in the source end device Generation of the data onto the media at the network t k access layer l off the th stack t k 19 20 The OSI Layered Model Protocol data units (PDU) and Encapsulation 7. Application Provide access to network services for users. 6. Presentation Common data representation 5. Session Manage dialogues 4 Transport 4. Segment/reassemble the data. 3. Network Routing between networks 2. Data Link Exchanges frames between connected devices 1. Physical Bit transmission on the media 21 Comparison of TCP/IP and OSI Models 22 Encapsulation Headers Each PDU header contains information about the Source and Destination Transport Port number Network Host machine IP address Datalink Ethernet MAC address 23 Copyright © 2001, Cisco Systems, Inc. All rights reserved. Printed in USA. Presentation_ID.scr 24 4 Addressing and Naming Schemes Ethernet MAC Addresses, IP Addresses, and TCP/UDP Port numbers Addressing Schemes Transport Port number 80 Network IP address 209.165.202.130 Datalink MAC address 00-0C-76-6D-7E-AF 25 26 Port Numbers Summary 27 Copyright © 2001, Cisco Systems, Inc. All rights reserved. Printed in USA. Presentation_ID.scr 28 5