Computer Network - Testing and Troubleshooting Networks

Loop back test is used to test if the ports are functioning properly.Cross over cables temporarily connect devices when router, switch or hub is not present.Faults in cables like twisted wire pairs, coaxial cables can be located using time-domain reflectometer.Network monitor provides information related to network traffic.Protocol analyzers perform the function of interpreting the contents of the packets that are intercepted.Ping, tracert, netstat, ipconfig, and  winipcfg are some commands that can be used to troubleshoot various network problems.Netstat is used to check the ports that are active on your system.

Computer Network - Network Security and Protocols

There are two types of threats: Internal and External threats.Internal threats are malicious practices done by the local networks users that do not allow efficient sharing of the network resources.External threats are threats in which a hacker at a remote location uses technical methods to gain illegal access to your network.Network security is a mechanism that protects the network resources from being attacked by the outside world.Security attacks can be passive or active.Cryptography is a science that deals with securing information and involves securing of messages, authentication, and digital signatures.Symmetric cryptographic systems use the same keys to encrypt and decrypt the message.Asymmetric cryptographic systems use two keys one for encryption and the other for decryption for securely transmitting the data.

Computer Network - Client Server System and Remote Connectivity

A network connected to the Internet but isolated from the Internet is called as a private network.Centralized processing is performed in one computer or in a cluster of computers in a single location.When more than one computer or processor is used to execute an application it is called as a distributed processing.The combination of centralized processing model and distributed processing model is called the client-server model.Radio Frequency (RF) is the wireless communication technology which uses electromagnetic waves used in radio communication to transmit and receive data.The part of the electromagnetic spectrum corresponding to radio frequencies is called as the radio frequency spectrum.Electromagnetic waves with wavelengths longer than those of infrared light, but shorter than those radio waves are called microwaves.

Computer Network - WAN Technologies

WAN covers a large geographical area and consists of two or more local area networks (LANs).Circuit switching, message switching and packet switching are types of switching technologies used by WAN.Leased lines are the permanent point-to-point links used for data communication.Circuit switching networks establish a direct physical connection between a sender and a receiver before communication occurs.In message switching, each switch stores the whole message and forwards it to the next switch.Packet switching network transmits messages in the form of packets.The telephone system that uses copper wires to carry analog voice data is called Public Switched Telephone Network (PSTN).Multiplexing is the technique that allows the simultaneous transmission of multiple signals across a single data link.

Computer Network - TCP/IP Services and Applications

SMTP protocol specifies how mail should be delivered from one host to another host.HTTP is a set of rules that is used for exchanging files on the World Wide Web.FTP protocol is used to exchange files from one host to another over the network.NNTP protocol is used for transfer Usenet news from one machine to another machine.SNMP is a framework that is used to manage devices that are connected to Internet using the TCP/IP protocol suite.POP3 is a protocol used to retrieve email from a remote server to a local machine over a TCP/IP connection.IMAP enables the users to work with the mail on the server and does not download the mail.

Computer Network - Working On INTERNET

Router is an Inter networking device used to link two different networks.NAT is a method in which it translates system’s IP address to a public IP address before they pass through larger network or Internet.Proxy server  allows network users to make an indirect network connection to different network services.Internet Explorer (IE) is the most widely used web browser.MS Outlook is a part of Microsoft Office and acts as a personal information manager.
MS Outlook offers e-mail service and comes under the category of e-mail client.Microsoft Outlook Express is an e-mail and news client.IP address can be allocated to a PC on boot process by a method called DHCP.DHCP offers dynamic leased configuration of host IP addresses and allots other configuration parameters to suitable network clients.

Computer Network - Network Servers

In Client-Server model, server controls the network.In P2P network, all the PCs act as both clients and servers.A Mail server is an application that receives e-mail from local net users, remote users and delivers these e-mails to the intended users.Name resolution is the process of mapping computer names to their associated IP addresses and this service is provided by DNS.Domain Name System (DNS) maps Fully Qualified Domain Name (FQDN) to corresponding IP address.DHCP provides temporary IP address with a particular amount of lease time.Windows Internet Name Service maps Network Basic Input/Output System (NetBIOS) computer names to corresponding IP addresses.A network operating system (NOS) deals concurrent requests from clients and provides the security necessary in a multi-user environment.

Computer Network - Wireless Networking

Peer-to-peer and ad-hoc access point wireless LAN are types of wireless networks.802.11 is a standard which was developed by Institute of Electrical and Electronic Engineers (IEEE) for defining all aspects of Radio Frequency Wireless networking.Bluetooth is a radio standard and communication protocol with low power consumption and short range of transmission and reception.The Bluetooth devices go through four different stages before starting a communication: device discovery, name discovery, association and service discovery
The various services that are supported by Bluetooth are known as profiles and there are 13 Bluetooth services.Hardware access points and Software access points are the two types of access points.Wireless bridge is used to connect two or more wireless or wired networks.

Computer Network - Installing The Network

Structured cabling system is a set of cabling which interconnects different equipments in an organization in a structured manner.Cable connectors are used to connect the cables.Cabling tolls are helpful to make connection between the cable and the connector.Colour Code helps to identify the types of wires.Cat5 cables are punched into Information outlet (IO) as per the color coding.Jack Panel is used to connect horizontal cabling to network.Straight through cables have the pin out connections similar at both the ends.Cross over cable change the pin out connections at one end.Installing the rack explains how to place networking equipments and accumulate different small equipment on the tray of the rack.Wire manager can organize the disorganized cables and makes it easy to access.

Computer Network - Internetworking Devices

Repeater is basically a re generator as it regenerates the signal.Repeater and Hub are layer 1 devices as they operate at the Physical layer of the OSI model.A multi-port repeater is known as Hub.Hubs are of three types, active hub, passive hub and intelligent hub.Active hub regenerates the signal before passing and Passive hub does not regenerate signal.
Types of bridges are Transparent bridge, Translational bridge and Source-route bridge.Switch uses cut through, store and forward or fragment free method for switching.A router is an intelligent device which functions at the Network layer.Router is capable of connecting many network segments even though the segments are far.Routers are of two types, Static router and Dynamic router.

Computer Network - IP Addressing

An IP address defines unique address of a device over a network.An IP address is a 32 Byte address and is divided into various classes namely Class A, Class B, Class C, Class D and Class E.In Classless addressing, network address field can extend further to Host Id field.Subnetting allows one to create multiple logical networks within a single Class A, B, or C address based network.A subnet mask is a 32-bit IP address, when bit-wise ANDed with given IP address provides with the address required to identify a subnet.CIDR makes use of VLSM to allocate IP addresses to sub nets depending upon the need of the organization.
Routing devices on the Internet discard any IP data gram or packet using private IP addresses.

Computer Network - Network Protocols

Network protocols are the set of predefined rules, used by the devices connected to network to communicate with each other.Different network protocols include NetBIOS/NetBEUI, TCP/IP and IPX/SPX.NetBIOS protocol is used for communication within a LAN and operates at the session layer of the OSI model.NetBIOS provides three types of services namely Name service, Session service and Datagram service.Name service allows an application to register its NetBIOS name in the network.Two computers can establish a session for data transfer using the Session service which is a connection-oriented service
In the connectionless Data gram service, data is transferred in the form of small packets called data grams.

Computer Network - Communication Using Network

The main components of data communication are sender, receiver, medium and message.The data to be sent is converted into signals and then transmitted over the network.Signaling techniques are of two types – broadband and base band.Base band signals transmit data at a single frequency.Broadband technique can transmit data using more than one frequency.Network Interface Cards are devices that are used to get connected to different computers on a network.Some examples of NIC are Ethernet Card and Token Ring Card.

Computer Network - Other Network Architecture

The network arrangement and data communication is given by logical topology.Token ring and token bus are the two logical topologies.A token passing mechanism is used in both token ring and token bus.100Base-FX, 100 Base SX and 100BaseBX and FDDI are types of fiber LAN.Single-attached station (SAS) and Dual-attached station (DAS) are the different types of FDDI stations.SAS is connected to the FDDI network through a single connector called S-port.Asynchronous Transfer Mode (ATM) network protocol converts data into a stream of fixed size cell before transmission.Apple Computers has designed a protocol suite known as Apple Talk.The network components of Apple Talk are sockets, nodes, network and zones.

Computer Network - Ethernet Advanced

The Standard Ethernet implementations are 10Base-T and 10Base-F.10Base-T is also known as twisted pair Ethernet and uses UTP cables.10Base-T uses star topology and hub is used as networking device.10Base-FL is a version of 10Base-F that uses fiber optic link instead of twisted pair cable.IEEE 802.3 implements 5-4-3 rule to limit the size of an Ethernet collision domain.High speed Ethernet was developed to increase the connectivity speed between computers in a network.The various high speed Ethernet standards are Fast Ethernet, Gigabit Ethernet and 10Gigabit Ethernet.100Base-T is also referred as Fast Ethernet that supports data transfer rate up to 100Mbps.

Computer Network - Local Area Network (LAN)

Ethernet is a local-area network (LAN) structural design developed by DEC, Intel and Xerox Corporation. Ethernet is a very common and widely used method of networking computers in a LAN environment.All nodes on an Ethernet network are either Data Terminal Equipment (DTE) or Data Communications Equipment (DCE).Protocols are set of rules that the nodes on a network use to communicate with each other.Carrier Sense Multiple Access/Collision Detection (CSMA/CD) is a network control protocol which uses a carrier sensing system.Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) is a set of rules used to avoid collisions.A repeater is a device that is used on a link to regenerate the signal to extend the physical length of a network.Bridges are usually used to divide a busy network into separate segments and to connect multiple LANs.

Computer Network-Transmission Media

In the Networking hardware involves mainly all peripheral devices, interface cards and other components like cables and wires which are used to establish network connection.The cables have certain characteristics like as segment length, bandwidth,attenuation, interference susceptibility, cost and number of segments.There are different types of medium are available for transmitting data over the network such as fiber optic medium, copper medium and wireless medium.In all the the copper medium includes coaxial cables and twisted pair cables.The Twisted pair cable consists of a pair of cables which is twisted around each other.Other two pair cable are STP and UTP.The Word Crosstalk is a important phenomenon in which signals of one wire interfere the signals transmitted over the other wire.

Computer Network-Topologies

A Network we say it is an interconnection of many communicating entities which are connected for the purpose of data communication.The topology which describes the way in which networking devices are connected with each other.The physical topologies, in all the wires are interconnected, while logical topology it is how the network behaves and inter operates.

Various types of topologies like Star, Node, Bus, Ring, Mesh, Tree and Hybrid.The single node topology, which is just a single device called dumb terminal is connected to the server.While Bus topology connects each device to a single cable and at either end of the cable terminator which is used to remove unsent data from the cable.

Computer Network-Introduction

The Computer network which is enables the user to share data and network resources. The Network allows remote users to communicate with each other.Computer networks are divided into LAN, CAN, MAN and WAN that depending on the coverage area.LAN is a small network and it is easy to create Client/Server configuration also called as two-tier architecture, it consist of two nodes, client and server.The OSI model consists of seven layers and it provides standards for computer communication. The Physical layer is responsible for actual transmission of bits over the medium.