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Showing posts from 2006

Ethernet Hub - Physical Layer Device

Hub is a network device connects multiple devices and makes single network segment. Hub works in Physical layer of OSI Reference Model. Since it is a layer one device, it does not have the feature to read the signals it transmit. All the devices connected to the hub feel they are connected to the same physical wire. So we can say hub has single collision domain. In other words a hub simply repeat the signal it receives. Let us check the working of hubs.


How Hubs work
When a computer connected to a hub sends packets, hub broadcast the packets to all the ports except the one it came from. Here we can see the difference between Switch and hub. Hub does not read the packets and it broadcast to all ports but Switch is intelligent device and read the packet and just unicast it. So Switch is more efficient compared to hub. Another problem with hub is the higher chances of packet collisions. We know hub has single collision domain and the chances of collision is very high.


Now a days very ra…

Internet Control Message Protocol (ICMP)

One of the important part we need to do while troubleshooting a network is to check the connectivity of two devices. We have many utilities to check the connectivity and availability of destination device. All these utilities are based on ICMP, defined in RFC 792. Internet Control Message Protocol (ICMP) is used to send error and control information between devices which support TCP/IP. Utilities like ping, tracert, pathping etc works using ICMP. This tutorial explains the functions of Internet Control Message Protocol and the list of error messages generated by ICMP.

Important Functions of ICMP Send echo requests from a TCP/IP device to another

Responds to Echo request

Helps to find routing path issues

ICMP echo message verify the availability of destination
List of Messages Generated by ICMP Address Request

Address reply

Destination unreachable

To learn more about the Destination unreachable message generated by Internet Control Message Protocol, visit the links below.

Destination Net Unreac…

DMZ In Network Security (Demilitarized Zone)

Now most of the modern Small Office Home Office routers offer DMZ host feature. For those who don't know about the use of DMZ, this tutorial may give an overall idea about it. If you place a device in your network in DMZ, that device won't have much access to other devices connected to the network. Device placed in DMZ is more exposed to external threats as it is logically placed outside the network with limited security. Also all ports of DMZ host are open and exposed to external network. DMZ host has its on merits and demerits.


What is The Use of DMZ in a Network
If you are a hardcore online gamer, you know the hurdles created by the router firewall and NAT. In most cases simple port forwarding allows you to continue online gaming but rarely some users face issues. Ultimate solution for the firewall issues in online gaming is to place your gaming computer in DMZ. However, after this step, your gaming computer is no longer protected by router firewall. Also your computer face …

Network Address Translation( NAT)

Network Address Translation (NAT) allows you to convert one IP address in to another address. Address Translation process changes the IP address information in a packet to different address. NAT feature is introduced to solve two major issues faced in networking: face the shortage of IP addresses and hide the network scheme. Now the major function of Address Translation is to convert the private IP addresses in a network in to a public IP address. This tutorial explains the major functions, different types and working of NAT.

Different Types of Address Translation
Address Translation is of different types depends on the way and the number of IP addresses they translate.
Static NAT

In Static Network Address Translation, one IP address in a packet is translated to different IP address manually. It is one to one mapping.

Dynamic NAT

In Dynamic Network Address Translation, address translation device picks an IP address dynamically to convert from a list of allowed IP addresses. Dynamic NAT…

Dynamic Host Configuration Protocol (DHCP) CCNA Exam Tutorial

The Dynamic Host Configuration Protocol (DHCP) allows devices to dynamically get IP address information. It is very important in networks especially for big networks because it assigns IP addresses to each devices in the network automatically. Think about a network having thousands of devices. It is very difficult to assign static IP addresses to each devices without having errors. Here Dynamic Host Configuration Protocol helps us. This protocol assigns IP address to each device without any errors and is very easy to manage. It contains two parts, server and client.


Working of Dynamic Host Configuration Protocol
We can simply use the term DORA to explain the working of DHCP. It is a four stage process and each stage is explained below.

D-- DHCP Discovery

When a client connected to a network, it sends broadcast to discover the DHCP server. This broadcast is termed as DHCPDISCOVER.

O--- DHCP Offer

At this stage, server responds to the client DISCOVERY message and sends a DHCPOFFER unicas…

Fundamentals of Ethernet

Ethernet is LAN media type that uses CSMA/CD to send information and functions at Data Link Layer of OSI Reference Model. Ethernet media type having different physical topologies but having single logical topology: bus topology. With various physical topologies we can design an this network with different shapes but the communication happens in Bus topology only. It has two versions right now. One of them is DIX version and the second is IEEE version. This tutorial explains various topologies and versions of Ethernet.


Physical Topologies Supported Bus topology

Star Topology

Point to Point
Two Versions Of Ethernet DIX Version

DIX  Ethernet or Ethernet 2 is widely using now. This version does not split Data Link layer in to two. Ethernet 2 has frame value more than 1500. This standard is designed by the combined work of three companies. Those companies are DEC, Intel and Xerox. This standard is named as DIX by taking the first letter from the names of these three companies.

IEEE Version

T…

What is WiFi & Different IEEE 802.11 Wireless Standards

Wi-Fi is the term used to denote Wireless Local Area Networks which are using IEEE802.11 wireless standards. Now the term WiFi is representing all Wireless Local Area Networks. Wireless technologies used in WiFi are IEEE 802.11a, b, g, n and ac. In this tutorial let us check what is WiFi and the major 802.11 standards. You can also see a list of WiFi devices which supports them. At the end of the tutorial, you can see a backward compatibility checker chart. Using this chart you can take decisions related to extending your WLAN networks. With the help of the chart you can avoid situations of buying a device which is not compatible with existing devices (standards which are not backward compatible).

IEEE 802.11 Wireless Standards Available In Industry
IEEE802.11a

IEEE802.11b

IEEE802.11g

IEEE802.11n

IEEE802.11ac
Compatibility Between Different 802.11 Wireless Standards

Not all 802.11 technologies are backward compatible because of the different frequencies supported by different standards. S…

IP Addressing Guide (IPv4 & IPv6 Addressing)

IP address is the third layer address in TCP/IP Protocol Stack, given to each devices connected to a network. In Internet layer of TCP/IP Protocol Stack, each device in a network is assigned with unique address known as IP address. There are two versions of TCP/IP: IPv4 and IPv6. Right now we are using IPv4 version to assign logical address to devices in a network. In this tutorial you will learn the differences between IPv4 addressing and IPv6 addressing with different classes of IPv4 addresses.


Differences Between IPv4 and IPv6
Length

IPv4 is 32 bit address broken in to four octets which are separated by a period. IPversion6 is 128 bit long address having the capability to give more addresses than IPversion4 offers. Examples of IPversion4 and IPversion6 addresses are given below.

IPversion4 addressing : 10.0.0.1 or in binary form 00001010 00000000 00000000 00000001
IPv6 addressing : E3D7:0000:0000:0000:51F4:9BC8:C0A8:6420

Representation

IPv6 is 128 bit binary number represented …

Bluetooth Technology

Bluetooth is a short distance wireless technology defined as IEEE 802.15.1 to create Personal Area Networks. Right now Bluetooth is widely used in mobile phones to send and receive data. According to Bluetooth technology there is a master and slave devices. A master device can connect to maximum seven slaves at a time. Frequency of Bluetooth is similar to IEEE 802.11 g/b. It is in the range 2.4 to 2.485 GHz. Major advantages of Bluetooth over Wi-Fi is its low cost and low power. However, Wi-Fi has wider range and faster data transfer rate.


Major Uses of Bluetooth Technology
There are variety of applications run with the help of Bluetooth technology. Some of the uses are:
Make easy connection between mobile phones to send and receive files

Bluetooth technology enables wireless mouse and keyboard

Create a Local connection between PCs

Helps to create short range wireless network

Different Versions of Bluetooth Bluetooth V1.1 and V1.2

Bluetooth Version 2.0 +EDR

Bluetooth V2.1 + EDR

Bluetooth v3.…

Basic Wireless Networks Tutorial

Wireless network uses wireless signal to communicate between devices connected in the network. Here we use signals like radio waves, microwaves or infrared to send and receive data between two devices. Just like normal network types, they too classified in to Wireless LAN, MAN, WAN etc. They are mentioned as WLAN, WMAN and W-WAN respectively. This article gives you a brief introduction of each type of WiFi networks. We order them below according to the  size of area they cover.



Types of Wireless Networks WPAN

Wireless Personal Area Network (WPAN) uses to transfer data between two devices which are in short distance. Examples are Bluetooth and infrared. Some of the applications like WiFi keyboard, WiFi mouse etc. To learn more about it visit the link below.
An Explanation of Bluetooth Technology

Wireless LAN

WLAN uses IEEE802.11 standards to communicate between devices. It is also called WI-Fi and operates in different frequencies like 2.4GHz and 5GHz. To learn more about WLAN, click on t…

What is Router & Major Functions

Router is a layer three (Network Layer in OSI Reference Model) device used to connect different networks. For example if you want to connect two networks one is FDDI and other is Ethernet, we need router. It also connects networks with different network address. To move information between devices having different network numbers, we need layer 3 device. Routers can switch packets on the same interface using VLANs.


Router and Routing Tables
Router makes routing decisions based on the routing table it has. Routing table consists of path information to send packets to neighboring routers. Routing table with routing protocols helps router to find shortest path to send packets to destination.

Examples of Routing Protocols
Interior Gateway Routing Protocol (IGRP)

Routing Information Protocol (RIP)

Address Resolution Protocol (ARP)

Internet Control Message Protocol (ICMP)

Dynamic Host Configuration Protocol (DHCP)

Functions of Router

We cannot finish an article about routers without mentioning t…

Wide Area Networks (WAN) Tutorial

Wide Area Networks(WAN) covers a large area extends from countries to continents. It is used to connect LANs together. It is like when we need to connect two LANs at different locations separated by a long distance, we need WAN to connect them. There are different WAN services used to connect different LANs situated at different locations. Cable and DSL are two most popular WAN connections. Other than these two, there is a list of WAN services available.


List of Popular WAN Services Digital Subscriber Line (DSL)

Cable

Dedicated circuits

ATM

Analog Dialup

Frame Relay

ISDN

X.25

SMDS (Switched Multi-megabit Data Services)
Popular Connection Types Used in WAN Services
There are four different connection types used in Wide Area Networks service. They are:
Circuit switched:

Circuit switched services provide a temporary connection using a phone circuit. Analog dialup and ISDN are examples of circuit switched WAN connection types.

Cell Switched:

Cell switched service use dedicated connections but it can…

Metropolitan Area Network (MAN)

Metropolitan Area Networks in short MAN usually covers the area of a metropolitan city and is a hybrid between LAN and WAN. This type of networks covers a few kilometers. Cable TV network is an example of Metropolitan Area Network. But there is a difference. MAN is a computer network but cable TV connection provides TV broadcast. In a Metropolitan Area Network, two buildings in a city is connected and start data transfer. That means this connect two devices which are located far away but limited to a metropolitan location. It has the size of a metropolitan city. One of the differences between WAN and MAN is the connection speed. WAN offers low to medium connection speed but Metropolitan Area Network offers high speed connection.

Technologies Used in MAN
ATM (Asynchronous Transfer Mode)

FDDI

SMDS

Ethernet based MAN

MAN Standards for Data Communication

Distributed Queue Dual Bus (DQDB) is the Metropolitan Area Network standard for data communication. It is specified in the IEEE 802.6 standa…

Basics of Computer Networking

A network consists of all devices connecting each other in order to communicate between them across a small or large distances. Major components in it are computers, connecting cables, router, switch etc. It is important to create a network to improve the efficiency of users by allowing them to send and receive information easily. They are classified in to LAN, MAN and WAN according to the area it covers. Let us check each type of networks here.



Network Types

LAN

To read more about LAN, click the link below.
Local Area Network

MAN

For the details about Metropolitan Area Network,click the link below....
Metropolitan Area Networks

WAN

To learn more about it, click the link below.
Wide Area Network

Wireless Networks

To learn more about it, visit the link below.
Wireless Networks

Major Components in a Computer Network
All the hardware and software parts included in a network are network components. It includes computers, storage devices, hubs and switches, router, Ethernet cable etc. Let us check e…

Local Area Network (LAN) -CCNA Study Material

Local Area Network(LAN) is used to connect networking devices in a small area like an office or campus building. The media type used to connect devices in a Local Area Network(LAN) are Ethernet, FDDI, Token Ring etc. LAN helps to communicate between devices in a smaller area and improve the efficiency of working of an office. Let us consider common topologies used in Local Area Network because it is in CCNA Exam Syllabus. It is classified in to physical and logical topology. In Physical Topology, you can see how devices in a LAN are connected but in Logical Topology we can see how these devices are communicating.

LAN Physical Topologies
Point to Point

Here two devices are connected without any any interference from other devices. In this LAN topology these two devices are connected and communicated. Wireless Bridge is a good example of Wireless Point to Point Topology.
How to Configure Linksys WAP54G in to Wireless Bridge Mode

Bus T

You can say it is an extension of Point to Point topo…