DIFFERENT NETWORK TOPOLOGIES

TOPOLOGY – defines the structure of the network. There are two parts to the topology definition: the physical topology which is the actual layout of the wire (media) and the logical topology which defines how the media is accessed by the hosts. It refers also to how computers are being connected with each other.

The types of topologies:

1. BUS topology – uses a single backbone segment (length of cable) that all the hosts connect to directly. The idea is that is just like riding a bus. It has only one driver and many passengers who are riding.

2. RING topology – connects one host to the next and the last host to the first. This creates a physical ring of cable.

3. STAR topology – connects all cables to a central point of concentration. This point is usually a hub or switch. It has a focal point where all the resources are there.

4. EXTENDED STAR topology – uses the star topology to be created. It links individual stars together by linking the hubs/ switches. This will extend the length of the network

5. HIERARCHICAL topology - is created similar to an extended star but instead of linking the hubs/ switches together, the system is linked to a computer that controls the traffic on the topology

6. MESH topology – is used when there can be absolutely no break in communications. So as you can see in the graphic, each host has its connections to all other hosts. This also reflects the design of the internet which has multiple paths to any one location.

HOSTS – devices that connect directly to a network segment. These hosts include computers, both clients and servers, printers, scanners and many other devices. These devices provide the users with connection to the network, with which the users share, create and obtain information.

Network Interface Card (NIC) – is a printed circuit board that fits into the expansion slot of a bus on a computer’s motherboard or peripheral device. It is considered to be found in Layer 2 devices because each individual NIC throughout the world carries a unique code, called the Media Access Control (MAC) address.

You can build computer networks with many different media types. Each media has advantages and disadvantages. What is an advantage for one media (category 5 cost) might be a disadvantage for another (fiber optic cost). Some of the advantages and disadvantages are:

• Cost
  
• Ease of installation
  
• Cable length

REPEATER - is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances. It is used when the type of cable (CAT5 UTP) is long. CAT5 UTP has a maximum length of 100 meters (approximately 333 feet). The purpose of a repeater is regenerate and retimes network signals at the bit level to allow them to travel a longer distance on the media.

HUB - is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and thus making them act as a single network segment. 

There are different classifications of hubs in networking:

1. The first classification is active or passive. Most modern hubs are active; they take energy from a power supply to regenerate network signals. Some hubs are passive devices because they merely split signal for multiple users, like using a “Y” cord on a CD player to use more than one set of headphones.

2. Another classification of hubs is intelligent or dumb. Intelligent hubs have console ports, which mean they can be programmed to manage traffic in the network. Dumb hubs simply take an incoming networking signal and repeat it to every port without the ability to do any management.

BRIDGE – refers to a device which has just two parts. It filters the frames and how this is actually accomplished.

SWITCH – is to concentrate connectivity, while making data transmission more efficient. A device that is able to combine the connectivity of a hub with the traffic regulation of a bridge on each port.

ROUTER – the first device that you will work with that us at the OSI’s network layer, or other known as Layer 3. The purpose of a router is to examine incoming packets, choose the best path for them in a network and then switch them to the proper outgoing port