Communicating over the Network

© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.0

Communicating over the Network

Network Fundamentals – Chapter 2

2© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

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


Network Structure

A network: the definition– Data or information networks capable of carrying many different

types of communications


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


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

http://www.diffen.com/difference/Hardware_vs_Software

http://www.diffen.com/difference/Hardware_vs_Software


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


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

http://www.youtube.com/watch?v=DGv77pcsBTg&feature=related

http://www.youtube.com/watch?v=DGv77pcsBTg&feature=related


Network Structure– Role of an intermediary device

• Provides connectivity and ensures data flows across network


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


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

http://www.youtube.com/watch?v=_6SSiNIzfGc

http://www.youtube.com/watch?v=_6SSiNIzfGc


Network Structure Network media Criteria for making a network me

dia 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

http://fcit.usf.edu/network/chap4/chap4.htm

http://fcit.usf.edu/network/chap4/chap4.htm

http://www.luxlink.com/faq/multi_or_single.htm




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.


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


Network Types The Internet

– The internet is defined as a global mesh of interconnected networks

– ISPs

http://www.onestopmalaysia.com/directory/internet/isp/


Network Topology

Star Topology Ring Topology Bus Topology Tree Topology Mesh Topology Hybrid Topology http://www.edrawsoft.com/Network-Topologies.php

http://compnetworking.about.com/od/networkdesign/a/topologies.htm

http://www.edrawsoft.com/Network-Topologies.php


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.


Network Types Network representations


Function of Protocol in Network Communication Protocols

– A protocol is a set of predetermined rules– used to facilitate communication over data networks


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


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

http://www.webopedia.com/TERM/S/standard.html

http://www.ansi.org/

http://www.itu.int/en/Pages/default.aspx

http://www.ieee.org/index.html

http://www.ietf.org/


Function of Protocol in Network Communication Protocols and how they interact Ethernet Local Talk Token Ring FDDI ATM http://www.edrawsoft.com/Network-Protocol.php

http://en.wikipedia.org/wiki/List_of_network_protocols

http://www.edrawsoft.com/Network-Protocol.php


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.


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


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


Layers with TCP/IP and OSI Model


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


Layers with TCP/IP and OSI Model The Communication Process


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 thesource 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.


Layer Description Protocols

Application Defines TCP/IP application protocols and how host programs interface with transport layer services to use the network.

HTTP, Telnet, FTP, TFTP, SNMP, DNS, SMTP, X Windows, other application protocols

TransportProvides communication session management between host computers. Defines the level of service and status of the connection used when transporting data.

TCP, UDP, RTP

InternetPackages 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


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.


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

PDU


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.


The process of sending and receiving messages

Using the proper terms for PDUs and the TCP/IP model, the process of sending the e-mail is as follows:

1. An end user, using an e-mail application, creates data. The application layer codes the data as e-mail 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 e-mail application. The message is successful.

Layers with TCP/IP and OSI Model


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


Layers with TCP/IP and OSI Model OSI


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


Addressing and Naming Schemes Labels in encapsulation headers are used to manage

communication in data networks.


Addressing and Naming Schemes Ethernet MAC Addresses, IP Addresses, and TCP/UDP

Port numbersLayer 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 e-mail 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 e-mail software on your computer).

Layer 7 addresses (e.g., a Web URL: www.google.com) are used by the Application layer programs.


Addressing and Naming Schemes Labels in encapsulation headers are used to manage

communication in data networks


Addressing and Naming Schemes Information in the encapsulation header is used to

identify the source and destination processes for data communication

Communicating over the Network

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