Astrology

the papers are real tough material to live in

(Redirected from Network topologies)

Jump to: navigation, search

For other uses of "topology", see topology (disambiguation).

Diagram of different network topologies.

Diagram of different network topologies.

Network topology is the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially the physical (real) and logical (virtual) interconnections between nodes.[1] [2] [3]

Network topology is sometimes also refered to the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network.

A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical 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 determines the physical topology of the network. Likewise, the mapping of the flow of data between the nodes in the network determines the logical topology of the network. It is important to note that the physical and logical topologies might be identical in any particular network but they also may be different.

Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. LAN Network Topology is, therefore, technically a part of 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[2].

Contents

[hide]

* 1 Classification of network topologies

o 1.1 Physical topologies

+ 1.1.1 Classification of physical topologies

# 1.1.1.1 Point-to-point

# 1.1.1.2 Bus

# 1.1.1.3 Star

# 1.1.1.4 Ring

# 1.1.1.5 Mesh

# 1.1.1.6 Tree (also known as hierarchical):

+ 1.1.2 Hybrid network topologies

o 1.2 Signal topology

o 1.3 Logical topology

+ 1.3.1 Classification of logical topologies

* 2 Daisy chains

* 3 Centralization

* 4 Decentralization

* 5 Hybrids

* 6 See also

* 7 References

* 8 External links

[edit] Classification of network topologies

There are also three basic categories of network topologies:

* physical topologies

* signal topologies

* logical topologies

* new topology

The terms signal topology and logical topology are often used interchangeably even though there is a subtle difference between the two and the distinction is not often made between the two.

[edit] Physical topologies

The mapping of the nodes of a network and the physical connections between them вЂ" i.e., the layout of wiring, cables, the locations of nodes, and the interconnections between the nodes and the cabling or wiring system[1][3].

[edit] Classification of physical topologies

[edit] 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 the value of guaranteed, or nearly so, 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.

Permanent (dedicated)

Easiest to understand, of the variations of point-to-point topology, is a point-to-point communications channel that appears, to the user, to be permanently associated with the two endpoints. Children's "tin-can telephone" is one example, with a microphone to a single public address speaker is another. These are examples of physical dedicated channels.

Within many switched telecommunications systems, it is possible to establish a permanent circuit. One example might be a telephone in the lobby of a public building, which is programmed to ring only the number of a telephone dispatcher. "Nailing down" a switched connection saves the cost of running a physical circuit between the two points. The resources in such a connection can be released when no longer needed, as, for example, a television circuit from a parade route back to the studio.

Switched:

Using circuit-switching or packet-switching technologies, a point-to-pointcircuit can be set up dynamically, and dropped when no longer needed. This is the basic mode of conventional telephony.

[edit] Bus

Linear bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints (this is the 'bus', which is also commonly referred to as the backbone, or trunk) вЂ" all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network virtually simultaneously (disregarding propagation delays)[1][3].