15-06-2012, 02:55 PM
INTRODUCTION TO NETWORKING
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Network
A network is a collection of individual computers, connected by some physical media and networking devices
Computer networking is sometimes considered a sub-discipline of electrical engineering,telecommunication , computer science, information technology since it relies heavily upon the theoretical and practical application of these scientific and engineering disciplines.
TOPOLOGY
Network topology is the layout pattern of interconnections of the various elements of computer or biological. Network topologies may be physical or logical refers to the physical design of a network including the devices, location and cable installation. Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.
Topology can be understood as the shape or structure of a network. This shape does not necessarily correspond to the actual physical design of the devices on the computer network.
Bus Topology
A bus topology is a linear LAN architecture in which transmissions from network stations propagate the length of the medium and are received by all other stations
Of the three most widely used LAN implementations, Ethernet/IEEE 802.3 networks, implement a bus topology, which is illustrated in Figure
A star topology is a LAN architecture in which the endpoints on a network are connected to a common central hub, or switch, by dedicated links
while
A Ring Topology A ring topology is a LAN architecture that consists of a series of devices connected to one another by unidirectional transmission links to form a single closed loop.
Both Token Ring/IEEE 802.5 and FDDI networks implement a ring topology. Figure depicts a logical ring topology
Fig showing the concept of star and Ring Topology
NETWORKING MEDIA
Networking media are like the medium by which different systems are connected to each other or it is that physical medium .
It has its own types ..
Twisted pair cables
Fiber Optical Cables
Coaxial Cables
Unshielded Twisted-Pair
Consists of one or more insulated wire pairs encased in a plastic sheath.
Does not contain additional shielding
To manage network cabling, it is necessary to be familiar with standards used on modern networks, particularly Category 3 (CAT3) and Category 5 (CAT5)
Fiber Optical Cables:-Contains one or several glass fibers at its core surrounding the fibers is a layer of glass called cladding eg telephone lines.
Coaxial Cables are the cables used where emi is least. Like in dish .
Cabling Connections
Cabling Connections are done with three source
1.Straight Cables:-
■ A hub to a router, PC, or file server
■ A switch to a router, PC, or file serve
2.Crossover Cables
■ A hub to another hub
■ A switch to another switch
■ A hub to a switch
3.Rollover Cables :-These are used For Configuring Devices.
Networking Model
OSI REFRENCE MODEL
The Open Systems Interconnection (OSI) model is a reference tool for understanding data communications between any two networked systems. It divides the communications processes into seven layers. Each layer both performs specific functions to support the layers above it and offers services to the layers below it. The three lowest layers focus on passing traffic through the network to an end system. The top four layers come into play in the end system to complete the process.
1.Physical 5.Session
2.Data Link 6.Presentation
3.Network 7.Application
4.Transport
LAYER 1:-Physical Layer:- The physical layer of the OSI model defines connector and interface specifications, as well as the medium (cable) requirements.
Components of the physical layer include:
Cabling system components
Hub, repeater, and patch panel specifications
Wireless system components
LAYER 2:- Data Link Layer Allows a device to access the network to send and receive messages
Offers a physical address so a device’s data can be sent on the network.
Common networking components that function at layer 2 include:
• Network interface cards
• Ethernet and Token Ring switches
• Bridges
LAYER 3:- NETWORK LAYER
The network layer of the OSI model, provides an end-to-end logical addressing system so that a packet of data can be routed across several layer 2 networks.
LAYER – 4 TRANSPORT LAYER
The transport layer of the OSI model, offers end-to-end communication between end devices through a network. Depending on the application, the transport layer either offers reliable, connection-oriented or connectionless, best-effort communications.
Some of the functions offered by the transport layer include:
• Application identification
• Client-side entity identification
• Confirmation that the entire message arrived intact
LAYER- 5 SESSION LAYER
• Virtual connection between application entities
• Synchronization of data flow
• Creation of dialog units
LAYER – 6 PRESENTATION LAYER
The presentation layer, is responsible for how an application formats the data to be sent out onto the network. The presentation layer basically allows an application to read (or understand) the message.
Examples of presentation layer functionality include:
• Encryption and decryption of a message for security
• Compression and expansion of a message so that it travels efficiently
• Graphics formatting
• Content translation
LAYER 7 APPLICATION LAYER
The application layer, provides an interface for the end user operating a device connected to a network.
• Support for file transfers
• Electronic mail
• Browsing the World Wide Web
COMMUNICTION
Communication simply means which work as a mediator through devices.
It can be done through 2 parts.
1.physical address
2.IP Address
Physical address:- It is a permanent address of a computer system or any device. This is different for every system.
2. IP addresses:- IPv4 addresses are 32 bits in length. However, to make the addresses readable, they are broken into four bytes (called octets), with a period (decimal) between each byte. Let’s look at a simple example: 11111111111111111111111111111111, which is 32 1’s. This is broken up into four octets, like this: 11111111.11111111.11111111.1111111.
Classes of Addresses
Network numbers is divided into five classes: Class A, B, C, D, and E. Each of these classes has a predefined network and host boundary:
■ With a Class A address, the first byte is a network number (8 bits) and the last 3 bytes are for host numbers (24 bits)
■ With a Class B address, the first two bytes are a network number (16 bits) and the last 2 bytes are for host numbers (16 bits)
■ With a Class C address, the first three bytes are a network number (24 bits) and the last 1 byte is for host numbers (8 bits)
■ Class D addresses are used for multicasting and Class E addresses are reserved
■ Class A addresses range from 1-126: 0 is reserved and represents all IP addresses; 127 is a reserved address and are used for testing, like a loop back on an interface: 00000001-01111111.
■ Class B addresses range from 128-191: 10000000-10111111.
■ Class C addresses range from 192-223: 11000000-11011111.
■ Class D addresses range from 224-239: 11100000-11101111.
■ Class E addresses range from 240-254: 255 is a reserved address and are used for broadcasting purposes.
NETWORKING DEVICES
HUB
Hub is a central device installed in a network.
The data is sent to every point and it is forwarded to the point where the hub finds the address of the destined computer. The switch is an advanced and more redefined form of networking Hubs.
SWITCH
The working of a networking Hub is not much different from a Switch. The advancement in Switches is that they have switching table in them which makes a network more secure and faster. The difference is between the technology and technique through which data is sent.
ROUTER
A Router is responsible for connecting two physical and logically different networks. Routers are connected in a series in a WAN or a LAN and they are called Hop in the series. The working of Router is very simple a Router in a LAN or a WAN finds the IP address of the next hop (next router) and the data is sent toward and so on.
REPEATERS
A REPEATER is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium
INTRODUCTION TO CISCO IOS
When we talk about Cisco router, it will run a power-on self-test (POST). If it passes, itwill then look for and load the Cisco IOS from flash memory—if an IOS file is present. The IOS then proceeds to load and looks for a valid configuration—the startupconfig— that’s stored by default in nonvolatile RAM, or NVRAM.The following messages appear when you first boot or reload a router:
It has different Ports like:
Auxilary port
Console port
Serial pors
Ann ethernet ports
Logging into the Router
After the interface status messages appear and you press Enter, the Router> prompt will appear. This is called user exec mode (user mode) and is mostly used to view statistics, but it’s also a stepping-stone to logging into privileged mode. You can only view and change the configuration of a Cisco router in privileged exec mode (privileged mode), which you get into with the enable command. Here’s how you would do that:
Router>
Router>enable
Router#
To configure from a CLI, you can make global changes to the router by typing configure terminal (or config t for short), which puts you in global configuration mode and changes what’s known as the running-config. A global command (a command run from global config) is one that is set once and affects the entire router.
Router#config
Router Interfaces
Different routers use different methods to choose the interfaces used on them.
Router(config)#int serial ?
<0-9> Serial interface number
interface type slot/port, as seen here:
Router(config)#int fastethernet ?
<0-1> FastEthernet interface number
Router(config)#int fastethernet 0
Configuring an IP Address and Host name
To configure IP addresses on an interface use the ip address command from interface configuration mode:
Router(config)#int e0
Router(config-if)#ip address 172.16.10.2 255.255.255.0
Router(config-if)#no shut
Router(config)#hostname Todd
Todd(config)#