BASICS NETWORKING PROBLEMS

BASICS NETWORKING

What Is Network?

Networking Is The Sharing Of Information And Services. Networking Is Possible When Individuals Or Groups Have Information Or Abilities That They Wish To Share With Others. Computer Networking Provides The Communication Tools To Allow Computers To Share Information And Abilities.

.Network: Group Of Computers And Other Devices That Are Connected By Some Type Of Transmission Media

.A Signal Is An Electric Quantity Typically Composed Of Voltage And Current Traveling On A Conductor (Wire) To Convey Information, Data, Or Commands; Has Two Main Characteristics: Namely, Amplitude And Time Base .

.A Uniform Set Of Rules That Enable Two Devices To Connect And Transmit Data To One Another. Protocols Determine How Data Are Transmitted Between Computing Devices And Over Networks.

• LAN - Local Area Network: Confined To A Relatively Small Space, Such As A Building Or An Office

• 1. Maximum Distance < = 10 Kms

• 2. Normally One Type Of Transmission Media

• 3. Normally Within A Building Or Campus

• MAN - Metropolitan Area Network: Larger Than A LAN; Connects Clients And Servers From Multiple Buildings.

• Maximum Distance > 10 Kms < = 100 Kms

• Transmission Media May Be More Than One Type.

• Within A City.

• WAN - Wide Area Network: Connects Two Or More Geographically Distinct Lans Or Mans.

Inter City Or Inter Country

Simplex, Half-Duplex, And Duplex

.Simplex Transmission: Signals May Travel In Only One Direction

.Half-Duplex Transmission: Signals May Travel In Both Directions Over A Medium

§ Only One Direction At A Time.

Full-Duplex Or Duplex: Signals Free To Travel In Both Directions Over A Medium Simultaneously

§ Used On Data Networks

§ Channel: Distinct Communication Path Between Nodes

§ May Be Separated Logically Or Physically

Multiplexing: Transmission Form Allowing Multiple Signals To Travel Simultaneously Over One Medium

Channel Logically Separated Into Sub Channels

Multiplexer (Mux): Combines Multiple Signals

Sending End Of Channel

Demultiplexer (Demux): Separates Combined Signals And Regenerates Them In Original Form

Receiving End Of Channel .

Baseband: Digital Signals Sent Through Direct Current (DC) Pulses Applied To A Wire Requires Exclusive Use Of Wire’s Capacity Baseband Systems Can Transmit One Signal At A Time Ethernet

Broadband: Signals Modulated As Radiofrequency (RF) Analog Waves That Use Different Frequency Ranges

.Does Not Encode Information As Digital Pulses

.EIA And TIA

.Electronic Industries Alliance (EIA): Trade Organization Composed Of Representatives From .Electronics Manufacturing Firms Across US

.Sets Standards For Its Members

.Helps Write ANSI Standards

.Lobbies For Legislation Favorable To Growth Of Computer And Electronics Industries

.Telecommunications Industry Association (TIA): Focuses On Standards For Information Technology (IT), Wireless, Satellite, Fiber Optics, And Telephone Equipment

THE OSI MODEL

In 1983, The International Organization For Standardization (ISO) And What Is Now The Telecommunication Standardization Sector Of The International Telecommunication Union (ITU-T) Published A Document Called "The Basic Reference Model For Open Systems Interconnection."

Open Systems Interconnection (OSI) Model: Divides Network Communications Into Seven Layers. The OSI model has Seven layers. The principles that were applied to arrive at these seven layers are as follows: -

Physical, Data Link, Network, Transport, Session, Presentation, And Application

.Protocols Perform Services Unique To Layer

.Protocols Interact With Protocols In Layers Directly Above And Below

.Protocol: Set Of Instructions To Perform A Function Or Group Of Functions.

Application Layer -:

The application layer contains a variety of protocols that are commonly needed by users. One widely-used application protocol is HTTP (Hypertext Transfer Protocol), which is the basis for the World Wide Web. When a browser wants a Web page, it sends the name of the page it wants to the server using HTTP. The server then sends the page back. Other application protocols are used for file transfer, electronic mail, and network news.

.Services Facilitate Communication Between Software And Lower-Layer Network Services

.Helps Software Applications Negotiate Formatting, Procedural, Security, Synchronization, And Other Requirements With Network

.Hypertext Transfer Protocol (HTTP): Formats And Sends Requests From Client’s Browser To Server

.Also Formats And Sends Web Server’s Response Back To Client’s Browser

.Application Program Interface (API): Set Of Routines That Make Up Part Of A Software Application

Presentation Layer -:

Unlike lower layers, which are mostly concerned with moving bits around, the presentation layer is concerned with the syntax and semantics of the information transmitted. In order to make it possible for computers with different data representations to communicate, the data structures to be exchanged can be defined in an abstract way, along with a standard encoding to be used “on the wire.” The presentation layer manages these abstract data structures and allows higher-level data structures (e.g. banking records), to be defined and exchanged.

.Protocols Accept Application Layer Data And Format It

.So That One Type Of Application And Host Can Understand Data From Another Type Of Application And Host

. E.G., Translation And Conversion Between Graphics File Types

.Manages Data Encryption And Decryption.

Session Layer -:

The session layer allows users on different machines to establish sessions between them. Sessions offer various services, including dialog control (keeping track of whose turn it is to transmit), token management (preventing two parties from attempting the same critical operation at the same time), and synchronization (check pointing long transmissions to allow them to continue from where they were after a crash).

.Protocols Coordinate And Maintain Communications Between Two Network Nodes

.Establish And Maintain Communications Link For Duration Of Session

. Keep Communication Secure

.Synchronize Dialogue Between Two Nodes

.Determine If Communications Have Been Cut Off

.Determine Where To Restart Transmission

.Terminate Communications.

Transport Layer -:

The basic function of the transport layer is to accept data from above, split in up into smaller units if need be, pass these to the network layer, and ensure that the pieces all arrive correctly at the other end. Furthermore, all this must be done efficiently and in a way that isolates the upper layers from the inevitable changes in the hardware technology. The transport layer also determines what type of service to provide to the session layer, and, ultimately, to the users of the network. The most popular type of transport connection is an error-free point-to-point channel that delivers messages or bytes in the order in which they were sent. The transport layer is a true end-to-end layer, all the way from the source to the destination. In other words, a program on the source machine carries on a conversation with a similar program on the destination machine, using the message headers and control messages.

.Protocols Accept Data From Session Layer And Manage End-To-End Delivery Of Data

.Ensure Data Transferred Reliably, In Correct Sequence, And Without Errors

.Protocols Also Handle Flow Control

.Gauging Appropriate Rate Of Transmission Based On How Fast Recipient Can Accept Data

.Transmission Control Protocol (TCP): Takes Care Of Reliably Transmitting HTTP Requests From Client To Server And Vice Versa.

Network Layer -:

The network layer controls the operation of the subnet. A key design issue is determining how packets are routed from source to destination. Routes can be based on static tables that are “wired into” the network and rarely changed. They can also be determined at the start of each conversation, for example, a terminal session (e.g., a login to a remote machine). Finally, they can be highly dynamic, being determined anew for each packet, to reflect the current network load.

In broadcast networks, the routing problem is simple, so the network layer is often thin or even nonexistent.

.Primary Functions Of Protocols:

.Translate Network Addresses Into Physical Counterparts

. Decide How To Route Data From Sender To Receiver

.Each Node Has Two Types Of Addresses:

. Network Address: Follows Hierarchical Addressing Scheme

.Can Be Assigned Through OS Software

.Network Layer Addresses, Logical Addresses, Or Virtual Addresses

.Physical Address.

Data Link Layer -:

The main task of the data link layer is to transform a raw transmission facility into a line that appears free of undetected transmission errors to the network layer. It accomplishes this task by having the sender break up the input data into data frames (typically a few hundred or a few thousand bytes) and transmits the frames sequentially. If the service is reliable, the receiver confirms correct receipt of each frame by sending back an acknowledgment frame.

.Protocols Divide Received Data Into Distinct Frames

.Can Then Be Transmitted By Physical Layer

.Frame: Structured Package For Moving Data

.Raw Data

.“Payload”

.Sender’s And Receiver’s Network Addresses

.Error Checking And Control Information

Physical Layer -:

.Protocols Accept Frames From Data Link Layer And Generate Voltage To Transmit Signals

.When Receiving Data, Protocols Detect Voltage And Accept Signals

.Protocols Also Set Data Transmission Rate And Monitor Data Error Rates

.Cannot Perform Error Correction

.Nics Operate At Both Physical Layer And Data Link Layer

.Network Administrators Mostly Concerned With Bottom Four Layers Of OSI Model

Summary

.Standards Are Documented Agreements Containing Precise Criteria That Are Used As Guidelines To Ensure That Materials, Products, Processes, And Services Suit Their Purpose

.Iso’s Osi Model Divides Networking Architecture Into Seven Layers

.Each Osi Layer Has Its Own Set Of Functions And Interacts With The Layers Directly Above And Below It.

.Application Layer Protocols Enable Software To Negotiate Their Formatting, Procedural, Security, And Synchronization With The Network.

.Presentation Layer Protocols Serve As Translators Between The Application And The Network

.Session Layer Protocols Coordinate And Maintain Links Between Two Devices For The Duration Of Their Communication

.Transport Layer Protocols Oversee End-To-End Data Delivery

.Network Layer Protocols Manage Logical Addressing And Determine Routes Based On Addressing, Patterns Of Usage, And Availability

.Data Link Layer Protocols Organize Data They Receive From The Network Layer Into Frames That Contain Error Checking Routines And Can Then Be Transmitted By The Physical Layer

.Physical Layer Protocols Generate And Detect Voltage To Transmit And Receive Signals Carrying Data Over A Network Medium

.Data Frames Are Small Blocks Of Data With Control, Addressing, And Handling Information Attached To Them