Week 6:

Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer^[ or biological network. Network topologies may be physical or logical.Physical topology 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.

There are basic categories two of network topologies;

Physical topology:

                Any given node in the LAN will have one or more links to one or more other nodes in the network and the mapping of these links and nodes onto a graph results in a geometrical shape that Logical topology :

                the mapping of the flow of data between the nodes in the network determines the logical topology of the network etermines the physical topology of the network.

The study of network topology recognizes eight basic topologies:^[

Point-to-point;

The simplest topology is a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as Metcalfe's Law.

Bus network topology ;

Topologi "linear bus" terdiri daripada suatu kabel utama dengan suatu penamat (terminator) dikedua-dua hujungnya. Semua nod (seperti komputer pelayan, stesyen kerja dan peranti lain) disambung kepada kabel linear ini. Contoh rangkaian yang menggunakan topologi Linear Bus ini ialah Ethernet dan LocalTalk.

Star network topology ;

In local area networks with a star topology, each network host is connected to a central hub with a point-to-point connection. The network does not necessarily have to resemble a star to be classified as a star network, but all of the nodes on the network must be connected to one central device. All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure.

Advantages

v  Easy to install, and wire.

v  Easy to add new workstations

v  No disruptions to the network when connecting or removing devices.

v  Any non-centralised failure will have very little effect on the network

v  Easy to detect faults and to remove parts.

v  Centralized control

v  Centralized network/hub monitoring

Disadvantages

v  Requires more cable length than a linear topology.

v  If the hub or concentrator fails, nodes attached are disabled.

More expensive than linear bus topologies because of the cost of the concentrators

Ring network topology;

A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.

Fully connected mesh topology;

Partially connected mesh topology;

The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link – this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network.

Tree network topology

Advantage

v  Point-to-point wiring for individual segments.

Disadvantages

Overall length of each segment is limited by the type of cabling used.

If the backbone line breaks, the entire segment goes down.

More difficult to configure and wire than other topologies.

Hybrid;

Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network topology. A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: star ring network and star bus network.

Daisy chain;

Except for star-based networks, the easiest way to add more computers into a network is by daisy-chaining, or connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.

week 5

what is networking ?

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. 

Two very common types of networks include;

·         local Area Network (LAN) 

           Wide Area Network (WAN)

You may also see references to a Metropolitan Area Networks (MAN), a Wireless LAN (WLAN), or a Wireless WAN (WWAN).

 Local Area Network

A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. Computers connected to a network are broadly categorized as servers or workstations.

Workstations are called such because they typically do have a human user which interacts with the network through them. Workstations were traditionally considered a desktop, consisting of a computer, keyboard, display, and mouse, or a laptop, with integrated keyboard, display, and touchpad. With the advent of the tablet computer, and the touch screen devices such as iPad and iPhone, our definition of workstation is quickly evolving to include those devices, because of their ability to interact with the network and utilize network services. 

Wide Area Network

Wide Area Networks (WANs) connect networks in larger geographic areas, such as Florida, the United States, or the world. Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of global network.

sing a WAN, schools in Florida can communicate with places like Tokyo in a matter of seconds, without paying enormous phone bills. Two users a half-world apart with workstations equipped with microphones and a webcams might teleconference in real time. A WAN is complicated. It uses multiplexers, bridges, and routers to connect local and metropolitan networks to global communications networks like the Internet. To users, however, a WAN will not appear to be much different than a LAN.

Metropolitan area network

A metropolitan  area network (MAN) is a computer network that usually spans a city or a large campus. A MAN usually inter connects a number of local area network (LAN) using a high-capacity backbone technology, such as fiber-optical links,and provides up-link services to wide area network(or WAN) and the internet.

Personal area network

 A personal area network (PAN) is a computer network used for communication  among computerized devices, including telephones  and personal digital assistans. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the internet(an uplink). 
A wireless personal area network (WPAN) is a PAN carried over wireless network technologies such as irDA, Bluetooth,Wireless USB, zigBee, or even Body carried over wired computer buses such as USB and FireWire.
A wireless personal area network (WPAN) is a personal area network - a network for interconnecting devices centered around an individual person's workspace - in which the connections are wireless. Wireless PAN is based on the standard IEEE 802.15. The three kinds of wireless technologies used for WPAN are Bluetooth,infrared data Association, and Wi-Fi.

Bluetooth

Bluetooth uses short-range radio waves over distances up to approximately 10 metres. For example, Bluetooth devices such as a keyboards, pointing devices, audio head sets, printers may connect to personal digital assistants (PDAs), cell phones,or computers wirelessly.

A Bluetooth PAN is also called a piconet(combination of the prefix "pico," meaning very small or one trillionth, and network), and is composed of up to 8 active devices in a master-slave relationship (a very large number of devices can be connected in "parked" mode). The first Bluetooth device in the piconet is the master, and all other devices are slaves that communicate with the master. A piconet typically has a range of 10 metres (33 ft), although ranges of up to 100 metres (330 ft) can be reached under ideal circumstances.