4. Examples of OSI Layer, their definition in order.

Tuesday, February 9, 2010

4. Examples of OSI Layer, their definition in order.

1Data Link Layer this layer deals with getting data across a specific medium and individual links by providing one or more data link connections between two network entities. End points are specifically identified, if required by the Network layer Sequencing. The frames are maintained in the correct sequence and there are facilities for Flow control and Quality of Service parameters such as Throughput, Service Availability and Transit Delay.
2.Session Layer the Session layer defines how data conversations are started, controlled and finished. The Session layer manages the transaction sequencing and in some cases authorization. The messages may be bidirectional and there may be many of them, the session layer manages these conversations and creates notifications if some messages fail. Indications show whether a packet is in the middle of a conversation flow or at the end. Only after a completed conversation will the data be passed up to layer.
3Physical Layer this layer deals with the physical aspects of the media being used to transmit the data. The electrical, mechanical, procedural and functional means This defines things like pin outs, electrical characteristics, modulation and encoding of data bits on carrier signals. It ensures bit synchronization and places the binary pattern that it receives into a receive buffer. Once it decodes the bit stream, the physical layer notifies the data link layer that a frame has been received and passes it up.
4.Network Layer this layer is responsible for the delivery of packets end to end and implements a logical addressing scheme to help accomplish this. This can be connectionless or connection-oriented and is independent of the topology or path that the data packets travel. Routing packets through a network is also defined at this layer plus a method to fragment large packets into smaller ones depending on MTUs for different media (Packet Switching). Once the data from layer 2 has been received, layer 3 examines the destination address and if it is the address of its own end station, it passes the data after the layer 3 header to layer 4.
5.Application Layer it is employed in software packages which implement client-server software. When an application on one computer starts communicating with another computer, then the Application layer is used. The header contains parameters that are agreed between applications. This header is often only sent at the beginning of an application operation.
6.Transport Layer this layer is resonsible for the ordering and reassembly of packets that may have been broken up to travel across certain media. Some protocols in this layer also perform error recovery. After error recovery and reordering the data part is passed up to layer 5.
7Presentation Layer this provides function call exchange between host operating systems and software layers. It defines the format of data being sent and any encryption that may be used, and makes it presentable to the Application layer.

Posted by michael at 11:41 PM

1.What is Network Topology?

Wednesday, February 10, 2010

1.What is Network Topology?

Network topology refers to the way that your computer network is arranged. The network can have a physical or a logical topology. The physical topology describes the layout of computers and where the workstations are positioned. The logical network topology describes how the information flows through the network.
Choosing your physical topology is important because if it is not chosen correctly, this could cause your network to not operate properly. There are several terms that describe the type of physical topology that a network can have. The most common topologies are bus, ring, star, and mesh. In communication networks, a topology is a usually schematic description of the arrangement of a network, including its nodes and connecting lines. There are two ways of defining network geometry: the physical topology and the logical (or signal) topology.

2.Examples of Network Topology, their Definition and post example picture.

1RING TOPOLOGY This topology is a simple design and consists of a single cable that forms the main data path in the shape of a ring. Each device is connected to a closed loop of cable. Signals travel in one direction from one node to all other nodes around the loop.

2.The Mesh topology is a variation of the bus, in which all devices are connected to one another in a daisy-chain fashion, as opposed to connecting in sequence to a single network cable. Each node is capable of transmitting, receiving, and routing data

3. STAR TOPOLOGY This is a form of LAN architecture is which nodes on a network are connected to a common central hub or switch, and this is done by the use of dedicated links

4.The Tree topology is essentially a hybrid of the bus and star layouts. The basic topology is similar to that of a bus, with nodes connected in sequence to a linear central cable. But tree networks may have "branches" that contain multiple workstations that are connected point-to-point in a star-like pattern. Signals from a transmitting node travel the length of the medium and are received by all other nodes

5. in the bus topology the server is at one end, and the client PCs (devices) are connected at different points or positions along the network. All signals pass through each of the devices. Each device has a unique identity and can recognize those signals intended for it. It is easy and simple to design and implement.

Tuesday, February 9, 2010

3. What is OSI Layer?

- Open System Interconnection, an ISO standard for worldwide communications that defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, proceeding to the bottom layer, over the channel to the next station and back up the hierarchy.

EXAMPLE OF NETWORK TOPOLOGY?

Topology in Network Design

Think of a topology as a network's virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle in a family room, but it would be highly unlikely to find a ring topology there.

Network topologies are categorized into the following basic types:

EXAMPLE OF NETWORK TOPOLOGY?

Think of a topology as a network's virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle in a family room, but it would be highly unlikely to find a ring topology there. Think of a topology as a network's virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle in a family room, but it would be highly unlikely to find a ring topology there.

Network topologies are categorized into the following basic type:BUS:RING:STAR:TREE:MESH.

WHAT IS NETWORKING TOPOLOGY?

Network topology is the physical interconnections of the elements (links, nodes, etc.) of a computer network.[1][2] A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology.