Communicating over the Network

Transcription

1 Communicating over the Network Network Fundamentals Chapter 2 Version 4.0 1

2 Network Structure The elements of communication 3 common elements of communication Message source people/electronic devices need to send msg The channel media that provides the pathway Message destination receives and interprets message 2

3 Network Structure A network: the definition Data or information networks capable of carrying many different types of communications 3

4 Network Structure How messages are communicated? Data is sent across a network in small chunks called segments - segmentation Adv+ Multiplexing Increased efficiency of network communications diff route 4

5 Network Structure The components of a network Either PC-PC or around globe Network components Hardware Device + media visible..? Software Services and process Run on networked devices 5

6 Network Structure End Devices and their Role in the Network End devices/host refers to a piece of equipment that is either the source or the destination of a message on a network. End devices form interface with human network & communications network Examples of hosts and end devices are as follows: Computers, including workstations, laptops, and servers connected to a network Network printers Voice over Internet Protocol (VoIP) phones Cameras on a network, including webcams and security cameras Handheld devices such as PDAs and handheld scanners Remote monitoring stations for weather observation 6

7 Network Structure End Devices and their Role in the Network End devices are the hosts that initiate communications Role of end devices: Client Request information / service Server hosts that are set up to store and share information/ services Both client and server use addresses to find each other. unique physical address 7

8 Network Structure Role of an intermediary device Provides connectivity and ensures data flows across network 8

9 Network Structure Role of an intermediary device Processes running on the intermediary network devices perform these functions: Regenerate and retransmit data signals Maintain information about what pathways exist through the network and internetwork Notify other devices of errors and communication failures Direct data along alternate pathways when there is a link failure Classify and direct messages according to quality of service (QoS) priorities Permit or deny the flow of data, based on security settings 9

10 Network Structure Network media Network media this is the channel over which a message travels Three main types: Encoding data converted to pattern of electrical, light or electromagnetic energy 10

11 Network Structure Network media Criteria for making a network media choice The distance the media can carry the signal Single mode vs multimode The environment in which the media works The bandwidth requirements for users The cost of installation The cost of connectors and compatible equipment 11

12 Network Types The size of the area covered The number of users connected The number and types of services available Local Area Networks (LANs) A network serving a home, building or campus is considered a Local Area Network (LAN) Local - computers were grouped geographically close together + same purpose in an organization. As technologies evolve - multibuilding campus. 12

13 Network Types Wide Area Networks (WANs) LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN) contract with a telecommunications service provider (TSP) to provide data lines between LANs 13

14 Network Types The Internet The internet is defined as a global mesh of interconnected networks ISPs 14

15 Network Topology Star Topology Ring Topology Bus Topology Tree Topology Mesh Topology Hybrid Topology 15

16 Network Types Network representations Network interface card (NIC): A NIC, or LAN adapter, provides the physical connection to the network at the PC or other host device. The media connecting the PC to the networking device plugs directly into the NIC. Each NIC has a unique physical address that identifies it on the LAN. Physical port: A physical port is a connector or outlet on a networking device where the media is connected to a host or other networking device. Interface: The term interface refers to how the device can allow two different networks to communicate. Routers connect to different networks, and the specialized NICs on routers are simply called interfaces. 16

17 Network Types Network representations 17

18 Function of Protocol in Network Communication Protocols A protocol is a set of predetermined rules used to facilitate communication over data networks 18

19 Function of Protocol in Network Communication Network protocols Network protocols are used to allow devices to communicate successfully The format of the message, such as how much data to put into each segment The way intermediary devices share information about the path to the destination The method to handle update messages between intermediary devices The process to initiate and terminate communications between hosts 19

20 Function of Protocol in Network Communication Protocol suites and industry standards A standard is a process or protocol that has been endorsed by the networking industry and ratified by a standards organization For example, Microsoft, Apple, and Linux operating systems each have a way to implement the TCP/IP protocol stack. Common protocols allows the users of different operating systems to have common access to network communication 20

21 Function of Protocol in Network Communication Protocols and how they interact Ethernet Local Talk Token Ring FDDI ATM 21

22 Function of Protocol in Network Communication Interaction of Protocols Hypertext Transfer Protocol (HTTP): HTTP is a common protocol that governs the way that a web server and a web client interact. HTTP defines the content and formatting of the requests and responses exchanged between the client and server. Both the client and the web server software implement HTTP as part of the application. The HTTP protocol relies on other protocols to govern how the messages are transported between client and server. Transport protocol: Transmission Control Protocol (TCP) is the transport protocol that manages the individual conversations between web servers and web clients. TCP divides the HTTP messages into smaller pieces, called segments, to be sent to the destination client. It is also responsible for controlling the size and rate at which messages are exchanged between the server and the client. Internetwork protocol: The most common internetwork protocol is Internet Protocol (IP). IP is responsible for taking the formatted segments from TCP, encapsulating them into packets, assigning the appropriate addresses, and selecting the best path to the destination host. Network access protocols: Network access protocols describe two primary functions: data-link management and the physical transmission of data on the media. Data-link management protocols take the packets from IP and format them to be transmitted over the media. The standards and protocols for the physical media govern how the signals are sent over the media and how they are interpreted by the receiving clients. 22

23 Function of Protocol in Network Communication Technology independent Protocols 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 Protocol in asking question raise hand different ways 23

24 Layers with TCP/IP and OSI Model The IT industry uses layered models to describe the complex process of network communication. Protocols for specific functions in the process are grouped by purpose into well defined layers. Benefits of using a layered model Benefits include Assists in protocol design Fosters competition Changes in one layer do not affect other layers Provides a common language 24

25 Layers with TCP/IP and OSI Model 25

26 Layers with TCP/IP and OSI Model TCP/IP Model 26

27 Layers with TCP/IP and OSI Model The Communication Process 27

28 Layers with TCP/IP and OSI Model A complete communication process includes these steps: 1. Creation of data at the application layer of the originating source end device. 2. Segmentation and encapsulation of data as it passes down the protocol stack in the source end device. 3. Generation of the data onto the media at the network access layer of the stack. 4. Transportation of the data through the internetwork, which consists of media and any intermediary devices. 5. Reception of the data at the network access layer of the destination end device. 6. Decapsulation and reassembly of the data as it passes up the stack in the destination device. 7. Passing this data to the destination application at the application layer of the destination end device. 28

29 Layer Description Protocols Application Transport Defines TCP/IP application protocols and how host programs interface with transport layer services to use the network. Provides communication session management between host computers. Defines the level of service and status of the connection used when transporting data. HTTP, Telnet, FTP, TFTP, SNMP, DNS, SMTP, X Windows, other application protocols TCP, UDP, RTP Internet Packages data into IP datagrams, which contain source and destination address information that is used to forward the datagrams between hosts and across networks. Performs routing of IP datagrams. IP, ICMP, ARP, RARP Network interface Specifies details of how data is physically sent through the network, including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire. Ethernet, Token Ring, FDDI, X.25, Frame Relay, RS-232, v.35 29

30 Layers with TCP/IP and OSI Model The process of adding control information as it passes through the layered model is called encapsulation. Decapsulation is the process of removing the extra information and sending only the original application data up to the destination application layer. Each layer adds control information at each step. The generic term for data at each level is protocol data unit (PDU), but a PDU is different at each layer. 30

31 Layers with TCP/IP and OSI Model Protocol data units (PDU) and encapsulation PDU 31

32 Layers with TCP/IP and OSI Model The process of sending and receiving messages TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent. 32

33 Layers with TCP/IP and OSI Model The process of sending and receiving messages Using the proper terms for PDUs and the TCP/IP model, the process of sending the is as follows: 1. An end user, using an application, creates data. The application layer codes the data as and sends the data to the transport layer. 2. The message is segmented, or broken into pieces, for transport. The transport layer adds control information in a header so that it can be assigned to the correct process and all segments put into proper order at the destination. The segment is sent down to the internetwork layer. 3. The internetwork layer adds IP addressing information in an IP header. The segment is now an addressed packet that can be handled by routers en route to the destination. The internetwork layer sends the packet down to the network access layer. 4. The network access layer creates an Ethernet frame with local network physical address information in the header. This enables the packet to get to the local router and out to the web. The frame also contains a trailer with error-checking information. After the frame is created, it is encoded into bits and sent onto the media to the destination. 5. At the destination host, the process is reversed. The frame is decapsulated to a packet, then to a segment, and then the transport layer puts all segments into the proper order. 6. When all data has arrived and is ready, it is sent to the application layer, and then the original application data goes to the receiver s application. The message is successful. 33

34 Layers with TCP/IP and OSI Model Protocol and reference models 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 34

35 Layers with TCP/IP and OSI Model OSI 35

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37 Layers with TCP/IP and OSI Model OSI and TCP/IP model 37

38 Addressing and Naming Schemes Labels in encapsulation headers are used to manage communication in data networks. 38

39 Addressing and Naming Schemes Ethernet MAC Addresses, IP Addresses, and TCP/UDP Port numbers Layer 2 addresses (e.g., Ethernet) are used to move messages to the correct end device. Layer 3 addresses (e.g., IP addresses) are used to move message between different parts of the network and to identify the correct end device. IP addresses have two parts: -the network (e.g., the IP number assigned to google.com) and -the specific computer within that part of the network (e.g., a specific web server or server within the Google network). Layer 4 addresses (e.g., TCP port numbers) are used to move the message to correct Application layer conversation at the end device (e.g., the Web browser or software on your computer). Layer 7 addresses (e.g., a Web URL: are used by the Application layer programs. 39

40 Addressing and Naming Schemes Labels in encapsulation headers are used to manage communication in data networks 40

41 Addressing and Naming Schemes Information in the encapsulation header is used to identify the source and destination processes for data communication 41

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