Characteristics of communication system:Delivery, accuracy, timeliness, and jitter. Delivery. The system must deliver data to the correct destination. Data must be

received by the intended device or user and only by that device or user.

Accuracy. The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.

Timeliness. The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery is called real-time transmission.

Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets.

Network StructureWhere communication begins?

Communication begins with a message, or information, that must be sent from one individual or device to another.

People exchange ideas using many different communication methods. All of these methods have three elements in common.

• message source

• the channel

• message destination

Network Structurehow messages are communicated?

A better approach of message communication is to divide the data into smaller, more manageable pieces to send over the network. This division of the data stream into smaller pieces is called segmentation.

Data is sent across a network in small “chunks” called segments

Network Structure The components of a network The path that a message takes from source to destination can be as simple as a

single cable connecting one computer to another or as complex as a network that literally spans the globe.

– Network components are build up of:

– hardware and software.

– Devices and media are the physical elements or hardware of the network.

– Services and processes are the communication programs, called software, that run on the networked devices.

Network Structure

What are the END Devices and their Role in the Network?

The network devices that people are most familiar with are called end devices. These devices form the interface between the human network and the underlying communication network. Some examples of end devices are:

Computers (work stations, laptops, file servers, web servers)

Network printers

VoIP phones

Security cameras

Mobile handheld devices (such as wireless barcode scanners, PDAs)

Servers are hosts that have software installed that enables them to provide information and services, like e-mail or web pages, to other hosts on the network.

Clients are hosts that have software installed that enables them to request and display the information obtained from the server.

Network Structure– End devices form interface with human network & communications

network

– Role of end devices :

• client

• server

• both client and server

Network Structure

What are the role of an intermediary device in a data network?

Networks rely on intermediary devices to provide connectivity and to work behind the scenes to ensure that data flows across the network.

These devices connect the individual hosts to the network and can connect multiple individual networks to form an internetwork.

Examples of intermediary network devices are:

Network Access Devices (Hubs, switches, and wireless access points)

Internetworking Devices (routers)

Communication Servers and Modems

Security Devices (firewalls)

Network StructureRole of an intermediary device

• provides connectivity and ensures data flows across network

Network Structure network media and criteria for making a network media choice

Communication across a network is carried on a medium. The medium provides the channel over which the message travels from source to destination.

Network media

this is the channel over which a message travels

Network Types

The Local Area Networks (LANs)

A network serving a home, building or campus is considered a Local Area Network (LAN)

Networks infrastructures can vary greatly in terms of:The size of the area coveredThe number of users connectedThe number and types of services available

Network Types The Wide Area Networks (WANs)

- LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN)

Network Types Define the Internet

The internet is defined as a

global mesh of interconnected networks

Network TypesThe network representations

Network Interfaces

In addition to these representations, specialized terminology is used when discussing how each of these devices and media connect to each other. Important terms to remember are:

Network Interface Card - 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.

Physical Port - A connector or outlet on a networking device where the media is connected to a host or other networking device.

Interface - Specialized ports on an internetworking device that connect to individual networks. Because routers are used to interconnect networks, the ports on a router are referred to network interface

Function of Protocol in Network Communication

A protocol is a set of predetermined rules

All communication, whether face-to-face or over a network, is governed by predetermined rules called protocols.

These protocols are specific to the characteristics of the conversation.

Function of Protocol in Network Communication

The network protocols

Network protocols are used to allow devices to communicate successfully

Function of Protocol in Network Communication

Describe 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, such as the Institute of Electrical and Electronics Engineers (IEEE) or the Internet Engineering Task Force (IETF).

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

Layers with TCP/IP and OSI Model Describe the Communication Process

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

As application data is passed down the protocol stack on its way to be transmitted across the network media, various protocols add information to it at each level. This is commonly known as the encapsulation process.

The form that a piece of data takes at any layer is called a Protocol Data Unit (PDU). During encapsulation, each succeeding layer encapsulates the PDU that it receives from the layer above in accordance with the protocol being used.

Layers with TCP/IP and OSI Model Explain 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.

Addressing and Naming Schemes how labels in encapsulation headers are used to manage

communication in data networks?

Layers with TCP/IP and OSI ModelThe Open Systems Interconnection reference model is a layered, abstract representation created as a guideline for network protocol design.

The OSI model divides the networking process into seven logical layers, each of which has unique functionality and to which are assigned specific services and protocols.

In this model, information is passed from one layer to the next, starting at the Application layer on the transmitting host, proceeding down the hierarchy to the Physical layer, then passing over the communications channel to the destination host, where the information proceeds back up the hierarchy, ending at the Application layer. The figure depicts the steps in this process.

The Application layer, Layer seven, is the top layer of both the OSI and TCP/IP models. It is the layer that provides the interface between the applications we use to communicate and the underlying network over which our messages are transmitted. Application layer protocols are used to exchange data between programs running on the source and destination hosts.

The Application Layer

The Application layer provides the interface to the network.

The application layer prepares human communication to be transmitted over the data network.

The Presentation LayerThe Presentation layer has three primary functions:

Coding and conversion of Application layer data to ensure that data from the source device can be interpreted by the appropriate application on the destination device.

Compression of the data in a manner that can be decompressed by the destination device.

Encryption of the data for transmission and the decryption of data upon receipt by the destination.

The Session Layer As the name of the Session layer implies, functions at this layer create and maintain

dialogs between source and destination applications.

The Session layer handles the exchange of information to initiate dialogs, keep them active, and to restart sessions that are disrupted or idle for a long period of time.

The Transport Layer: The transport layer prepares the application data for transport over

the network and process the network data for use by application.

The Role of Transport Layer

The Transport layer provides for the segmentation of data and the control necessary to reassemble these pieces into the various communication streams. Its primary responsibilities to accomplish this are:

Tracking the individual communication between applications on the source and destination hosts

Segmenting data and managing each piece

Reassembling the segments into streams of application data

Identifying the different applications

Network Layer Protocols and Internet Protocol (IP) The basic role of the Network Layer in data networks

The Network layer encapsulation allows its contents to be passed to the destination within a network or on another network with minimum overhead.

To accomplish this end-to-end transport, Layer 3 uses four basic processes:• Addressing• Encapsulation• Routing• Decapsulation

The Data Link Layer

The data link layer provides a means for exchanging data over a common local media.

Data Link Layer – Accessing the Media why Data Link layer protocols are required to control media

access?

The Data Link Layer

The Data Link layer provides a means for exchanging data over a common local media.

The Data Link layer performs two basic services:

Allows the upper layers to access the media using techniques such as framing

Controls how data is placed onto the media and is received from the media using techniques such as media access control and error detection

Data Link Layer – Accessing the Media Describe the role the Data Link layer plays in linking the software and

hardware layers

The Data Link layer exists as a connecting layer between the software processes of the layers above it and the Physical layer below it. As such, it prepares the Network layer packets for transmission across some form of media, be it copper, fiber, or the atmosphere.

Data Link Sublayers

To support a wide variety of network functions, the Data Link layer is often divided into two sublayers: an upper sublayer and an lower sublayer.

The upper sublayer defines the software processes that provide services to the Network layer protocols.

The lower sublayer defines the media access processes performed by the hardware.

The two common LAN sublayers are:

Logical Link Control

Logical Link Control (LLC) places information in the frame that identifies which Network layer protocol is being used for the frame. This information allows multiple Layer 3 protocols, such as IP and IPX, to utilize the same network interface and media.

Media Access Control

Media Access Control (MAC) provides Data Link layer addressing and delimiting of data according to the physical signaling requirements of the medium and the type of Data Link layer protocol in use.

Physical Layer Protocols & ServicesPurpose of the Physical Layer

The role of the OSI physical layer is to encode the binary digits that represent data link layer frames into signals and to transmit and receive these signals across the physical media—copper wires, optical fiber, and wireless—that connect network devices.

Purpose of Physical Layer

To prepare a data-link frame for the journey across the medium, the physical layer encodes the logical frame with patterns of data that will make it recognizable to the device that will pick it up on the other end of the medium. The device can be a router that will forward the frame or the destination device.

The delivery of frames across the local media requires the following physical layer elements:

■ The physical media and associated connectors

■ A representation of bits on the media

■ Encoding of data and control information

■ Transmitter and receiver circuitry on the network devices

After the signals traverse the medium, they are decoded to their original bit representations of data and given to the data link layer as a complete frame.