Network Topology

Refers to layout of a network and how different nodes in a network are connected to each other and how they communicate. Topology can be understood as the shape or structure of a network.
Network topologies may be physical or logical.In general physical topology relates to a core network whereas logical topology relates to basic network.

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.

This shape does not necessarily correspond to the actual physical design of the devices on the computer network. The computers on a home network can be arranged in a circle but it does not necessarily mean that it represents a ring topology.
Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. The study of network topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical.

The study of network topology recognizes eight basic topologies but we'll only show five of the most common:


Mesh Topology:
What is mesh topology anyway?
mesh is a network topology in which devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network.

•  Full mesh topology occurs when every node has a circuit connecting it to every other node in a network. Full mesh is very expensive to implement but yields the greatest amount of redundancy, so in the event that one of those nodes fails, network traffic can be directed to any of the other nodes. Full mesh is usually reserved for backbone networks.
• Partial mesh topology is less expensive to implement and yields less redundancy than full mesh topology. With partial mesh, some nodes are organized in a full mesh scheme but others are only connected to one or two in the network. Partial mesh topology is commonly found in peripheral networks connected to a full meshed backbone.

how data transmitted in this type : data transferred from each nodes to another is practicaly simple,but if there is problem occurs during the data transfer the data take another path to the destination nodes. ex: ( A want to send a message to F, but there is a technical problem between those two connecting cable, so the message take alternative path to D and then sent to F )

Star Topology:
In a star network devices are connected to a central computer, called a hub. Nodes communicate across the network by passing data through the hub.

Main advantage: one malfunction node doesn't affect the other.
Main disadvantage: if the central computer fails, the entire network become unuseable.

how data transmitted : In a star network, each node is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. A hub does not perform any type of filtering or routing of the data. It is simply a junction that joins all the different nodes together. ex: ( C is central node, A want to deliver message to D, that message must take path to C and then go to D, if C fail and so does the others, no data can go any where)


Bus Topology:

In networking a bus is the central cable -- the main wire -- that connects all devices on a local-area network (LAN). This is often used to describe the main network connections composing the Internet.  Bus networks are relatively inexpensive and easy to install for small networks.(ex:ethernet)

Main advantage:  It’s easy to connect a computer or device and typically it requires less cable than a star topology.

Main disadvantage: The entire network shuts down if there is a break in the main wire and it can be difficult to identify the problem if the network shuts down.

how data transmitted:  Information sent from a node travels along the backbone until it reaches its destination node. Each end of a bus network must be terminated with a resistor to keep the signal that is sent by a node across the network from bouncing back when it reaches the end of the cable.
ex: ( A want to sent some data to C, A's data didn't pass trough B to go to C, A's data go directly to C by following the main cable, if one of the nodes fail it doesn't affect the other nodes just the node itself, but let say this cable has been bitten by a rat, then all of the network become unusable because the main cable is the BACKBONE of the network )

Ring Topology:

All of the nodes are connected in a closed loop. Messages travel around the ring, with each node reading those messages addressed to it. One main advantage to a ring network is that it can span larger distances than other types of networks, such as bus networks, because each node regenerates messages as they pass through it.

how data transmitted : each node takes a turn sending and receiving information through the use of a token. The token, along with any data, is sent from the first node to the second node, which extracts the data addressed to it and adds any data it wishes to send. Then, the second node passes the token and data to the third node, and so on until it comes back around to the first node again. Only the node with the token is allowed to send data. All other nodes must wait for the token to come to them. ex( A want to deliver C some photos, the data itself must make route to B and then go to C, when the data is passing trough B, B make the duplicate for itself, but if the connection in B is somewhat fail the data will reroute to E then to D and make their way to C, in each nodes those data pass by, they make the duplicates for the records )

Tree Topology:

This is a "hybrid" topology that combines characteristics of linear bus and star topologies. In a tree network, groups of star-configured networks are connected to a linear bus backbone cable.

Main advantage: A Tree topology is a good choice for large computer networks as the tree topology "divides" the whole network into parts that are more easily manageable.

Main disadvantage: The entire network depends on a central hub and a failure of the central hub can cripple the whole network.



how data transferred : this type just like the combination of ring and bus but this type however definitely rely on the main cable. ex( just like the picture shown to you, there are 3 star linked in one main cable, let say the nodes with AA,1,2,3 and BB,1,2,3 and CC,1,2,3 with AA,BB,CC is the hub of those star network, A1 want to deliver message to C3, A1 message must take route to AA then following the main cable to go to CC then go to C3, if the hubs fail the data cannot transferred to another hubs in different star network, and if the main cable fail, the entire tree is crippled).

Hierarchy of tree topology :
A type of data structure in which each element is attached to one or more elements directly beneath it. The connections between elements are called branches. Trees are often called inverted trees because they are normally drawn with the root at the top.
The elements at the very bottom of an inverted tree (that is, those that have no elements below them) are called leaves( Items at the very bottom of a hierarchical tree structure. In hierarchical file systems, files are leaves because they can have nothing below them. Directories, on the other hand, are nodes). Inverted trees are the data structures used to represent hierarchical file structures. In this case, the leaves are files and the other elements above the leaves are directories.


Definiton of LAN, MAN, WAN :

1.LAN : A local area network supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other WAN.

2.MAN : A MAN usually interconnects a number of local area networks using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks and the Internet. MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities. A MAN might be owned and operated by a single organization, such as the government of those cities. MANs might also be owned and operated as public utilities.

3.WAN : Wide Area Network. WAN spans a large geographic area, such as a state, province or country. WANs often connect multiple smaller networks, such as local area networks (LANs) or metro area networks (MANs). The world's most popular WAN is the Internet. Some segments of the Internet, like VPN-based extranets, are also WANs in themselves.




Windows Server: 
A series of server operating systems developed by Microsoft Corporation. Windows servers are more powerful versions of their desktop operating system counterparts and are designed to more efficiently handle corporate networking, Internet/intranet hosting, databases, enterprise-scale messaging and similar functions.

Linux Server:
A Linux server is a high-powered variant of the Linux open source operating system that's designed to handle the more demanding needs of business applications such as network and system administration, database management and Web services.
Linux servers are frequently selected over other server operating systems for their stability, security and flexibility advantages. Leading Linux server operating systems include CentOS, Debian, Ubuntu Server, Slackware and Gentoo.