21-09-2012, 05:27 PM
Networking
Networking.ppt (Size: 1.67 MB / Downloads: 24)
What is a network?
A network is simply a group of two or more Personal Computers linked together. The most common types of networks are Local-Area Networks (LANs), and Wide-Area Networks (WANs).
In a LAN, computers are connected together within a "local" area (for example, an office or home).
In a WAN, computers are further apart and are connected via telephone/communication lines, radio waves or other means of connection.
Networks are usually classified as:
Topology:It specifies the geometric arrangement of the network. Common topologies are a bus, ring and star.
Protocol:It specifies a common set of rules and signals the computers on the network use to communicate. Most networks use Ethernet, but some networks may use IBM's Token Ring protocol. We recommend Ethernet for both home and office networking. For more information, please select the Ethernet link on the left.
Architecture:It refers to one of the two major types of network architecture: Peer-to-peer or client/server. In a Peer-to-Peer networking configuration, there is no server, and computers simply connect with each other in a workgroup to share files, printers and Internet access. In a client/server network there is usually an NT Domain Controller, to which all of the computers log on. This server can provide various services, including centrally routed Internet Access, mail (including e-mail), file sharing and printer access, as well as ensuring security across the network. This is most commonly found in corporate configurations, where network security is essential.
Subnetting
The practice of dividing a network into subnetworks is called subnetting.
All computers that belong to a subnet are addressed with a common, identical, most-significant bit-group in their IP address. This results in the logical division of an IP address into two fields, a network or routing prefix and the rest field. By subnetting the network we can partition it to as many smaller networks as we need and this also helps reduce traffic and hides the complexity of the network.
A subnet mask is used to break the network into network id field and host id field.
By default, all type of Classes (A, B and C) have a subnet mask, called the Default Subnet mask .
Data Link Layer
The Datalink layer is subdivided into two other sublayers, the Media Access Control (MAC) and the Logical Link Control (LLC). Media Access Control (MAC) This defines how packets are placed on the media (cable). Physical addressing is defined here. Logical addressing is basically the address which is given by software e.g IP address.When you get an IP address, this is considered a "logical address" which is provided to you after your TCP/IP stack is loaded.Physical addressing is an address which is given not by the software, but the hardware. Every network card has a "MAC" address which is burnt into the card's eprom (a special memory chip) and this special address is used to uniquely identify a computer's network card from all the others on the network.Logical Link Control (LLC) This sublayer is responsible for identifying Network layer protocols and then encapsulating them when they are about to be transmitted onto the network or decapsulate them when it receives a packet from the network and pass it onto the layer above it, which is the Network layer. An LLC header tells the Datalink layer what to do with a packet once a frame is received. For example, a host (computer) will receive a frame and then look in the LLC header to understand that the packet is destined for the IP protocol at the Network layer. The LLCcan also provide flow control and sequencing of control bits.