Network Topology

Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer network.^[1][2] Network topologies may be physical or logical. Physical topology means 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.

Topology can be considered as a virtual shape or structure of a network. This shape does not 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.

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 has one or more links to one or more nodes in the network and the mapping of these links and nodes in a graph results in a geometric shape that may be used to describe the physical topology of the network. Likewise, the mapping of the data flow between the nodes in the network determines the logical topology of the network. The physical and logical topologies may or may not be identical in any particular network.

Physical topologies

The mapping of the nodes of a network and the physical connections between them – i.e., the layout of wiring, cables, the locations of nodes, and the interconnections between the nodes and the cabling or wiring system

Classification of physical topologies

 

Bus

In local area networks where bus topology is used, each machine is connected to a single cable. Each computer or server is connected to the single bus cable through some kind of connector. A terminator is required at each end of the bus cable to prevent the signal from bouncing back and forth on the bus cable. A signal from the source travels in both directions to all machines connected on the bus cable until it finds the MAC address or IP address on the network that is the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data. Alternatively, if the data does match the machine address, the data is accepted. Since the bus topology consists of only one wire, it is rather inexpensive to implement when compared to other topologies. However, the low cost of implementing the technology is offset by the high cost of managing the network. Additionally, since only one cable is utilized, it can be the single point of failure. If the network cable breaks, the entire network will be down.

Star

In local area networks with a star topology, each network host is connected to a central hub. In contrast to the bus topology, the star topology connects each node to the hub with a point-to-point connection. All traffic that traverses the network passes through the central hub. The hub acts as a signal booster or 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.

Ring

In local area networks where the ring topology is used, each computer is connected to the network in a closed loop or ring. Each machine or computer has a unique address that is used for identification purposes. The signal passes through each machine or computer connected to the ring in one direction. Ring topologies typically utilize a token passing scheme, used to control access to the network. By utilizing this scheme, only one machine can transmit on the network at a time. The machines or computers connected to the ring act as signal boosters or repeaters which strengthen the signals that traverse the network. The primary disadvantage of ring topology is the failure of one machine will cause the entire network to fail.

 

Mesh

The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by Reed's Law.

Fully connected mesh topology

The number of connections in a full mesh = n(n - 1) / 2

Tree

Also known as a hierarchical network.

The type of network topology in which a central 'root' node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central 'root' node, while each of the second level nodes that are connected to the top level central 'root' node will also have one or more other nodes that are one level lower in the hierarchy (i.e., the third level) connected to it, also with a point-to-point link, the top level central 'root' node being the only node that has no other node above it in the hierarchy (The hierarchy of the tree is symmetrical.) Each node in the network having a specific fixed number, of nodes connected to it at the next lower level in the hierarchy, the number, being referred to as the 'branching factor' of the hierarchical tree.This tree has individual peripheral nodes

Opera Mini Handler

            Rekan blogwalking mari kita berbagi ilmu. Karena sesuai moto Trick Gretz “Berbagi Itu Indah”. Jika kita memberikan ilmu kepada orang lain bukan berarti ilmu kita berkurang, akan tetapi ilmu yang kita miliki akan senantiasa bertambah.

            Mungkin teman-teman semua sudah ada yang mengenal atau sama sekali tidak kenal dengan O.P. atau Opmin?. Saya terangkan, O.P atau Opmin adalah singkatan dari aplikasi browser mobile di hanphone yang bernama Opera Mini. Pasti rekan-rekan semua sudah tidak asing lagi dengan nama Opera Mini, apalagi para pecandu dunia maya / Internet seperti saya ini. Terutama yang suka berinternet untuk jejaring social seperti Facebook, Twitter, YM, Plurk dan yang terbaru Koprol pasti diotaknya sudah tersimpan nama Opera Mini sebagai data. 

            Opera Mini adalah penjelajah web yang dirancang khusus untuk ponsel, PDA Phone dan Smartphone. Namun yang saya ingin sampaikan kepada teman-teman bukanlah Opera Mini versi ini. Melainkan Opera Mini versi untuk internet gratisan, istilah lain dalam Gretz atau KasKus adalah “Gretongan”. Opera Mini ini sering disebut Opera Mini mod atau ada juga Opera Mini Handler dan banyak lagi julukan lainnya. Perbedaannya dengan Opera Mini biasa adalah aplikasi ini dapat mengatur konfigurasi servernya (editable server). Saat menjalankan aplikasi ini dalam ponsel kita akan dijumpai halaman awal berupa menu konfigurasi server dan query yang dapat kita ubah. Settingan default akan tersimpan jika kita tidak melakukan perubahan apapun pada setting server.

            Dengan menggunakan aplikasi ini Insyaallah gratis, atau pun biaya internet menjadi lebih hemat. Contoh jika kita menggunakan Telkomsel, kita melakukan browsing apa saja menghabiskan ukuran kb-nya besar atau kecil hanya dikenai biaya Rp.5, yang tadinya Rp.5/kb, meskipun tidak gratis anggap saja sedekah. Tapi itu bisa di bilang untung karena bisa browsing sepuasnya. Begitu pula dengan operator yang lainnya. Tetapi pernah juga tidak dipungut biaya internet sepeserpun alias gratis. Namun tentunya pengguna harus melakukan pengeditan server dan query dengan tepat. Maklum saja  didunia ini tak ada yang sempurna, ciptaan manusia pasti ada kekurangannya. 

            Banyak pengguna telah merasakan nikmatnya berselancar gratis dengan aplikasi ini. Aplikasi dapat di download. Cari saja di Om Google, disana sudah ada seabreg Opmin dengan berbagai jenis. Atau bisa langsung ke alamat :

1.      www.aplikasi-hape.co.cc

2.      www.skylovers.xtgem.com

3.      www.greenafrei.xtgem.com

4.      Dll (tinggal search di Om Google)

Tambahan untuk ponsel tipe Java harus terlebih dahulu mendownload file prov. Yang ponsel symbian langsung download Gan…!

Selamat mencoba dan bereksperimen!

Dengan Latihan Awal Keberhasilan

-->

Semua manusia pasti memulai hidup dari bawah atau dari nol, tidak ada yang langsung memulai dari atas. Itulah siklus kehidupan, Allah menciptakan manusia tidak semena-mena langsung pintar tapi melalui step by step. Sebelum menuju tangga ke-8 pasti kita melawati dulu tangga ke-1, tangga ke-2 dan seterusnya. Manusia yang berhasil tidak dengan mudah mencapai keberhasilannya tersebut, tapi dia juga melakukan latihan… latihan… dan latihan…!!!

Ada pepatah yang mengatakan “lebih baik mandi keringat dalam latihan daripada mandi darah dalam pertempuran” pepatah tersebut sangatlah relevan. Gagal dalam latihan merupakan hal yang biasa karna itu bisa saja merupakan cara dari Allah untuk meninggikan kemampuan kita. Orang yang berhasil menjadikan kegagalannya tersebut sebagai batu loncatan untuk meraih keberhasilan. Semua itu diraih dengan latihan dan kerja kera.

Do you know????

Bahwa seorang atlet itu harus berlatih minimal 72 jam/minggu lho….!! Karna kalau seorang atlet tidak berlatih selama 72 jam/minggu, maka diperlukan 17 tahun untuk menjadi atlet yang berhasil (tobattt…tobatt)

Computer Network

A computer network, often simply referred to as a network, is a group of computers and devices interconnected by communications channels that facilitate communications among users and allows users to share resources. Networks may be classified according to a wide variety of characteristics.

Network classification

Connection method

Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber, Ethernet, Wireless LAN, HomePNA, Power line communication or G.hn.

Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges and/or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network.

Wired technologies

• Twisted pair wire is the most widely used medium for telecommunication. Twisted-pair wires are ordinary telephone wires which consist of two insulated copper wires twisted into pairs and are used for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed ranges from 2 million bits per second to 100 million bits per second.

• Coaxial cable is widely used for cable television systems, office buildings, and other worksites for local area networks. The cables consist of copper or aluminum wire wrapped with insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer. The layers of insulation help minimize interference and distortion. Transmission speed range from 200 million to more than 500 million bits per second.

• Optical fiber cable consists of one or more filaments of glass fiber wrapped in protective layers. It transmits light which can travel over extended distances. Fiber-optic cables are not affected by electromagnetic radiation. Transmission speed may reach trillions of bits per second. The transmission speed of fiber optics is hundreds of times faster than for coaxial cables and thousands of times faster than a twisted-pair wire

Wireless technologies

• Terrestrial Microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment look similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to line-of-sight. Path between relay stations spaced approx. 30 miles apart. Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks.

• Communications Satellites – The satellites use microwave radio as their telecommunications medium which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically 22,000 miles (for geosynchronous satellites) above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.

• Cellular and PCS Systems – Use several radio communications technologies. The systems are divided to different geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.

• Wireless LANs – Wireless local area network use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. An example of open-standards wireless radio-wave technology is IEEE

• Infrared communication , which can transmit signals between devices within small distances not more than 10 meters peer to peer or ( face to face ) without any body in the line of transmitting.