Network topology is the physical interconnections of the elements (links, nodes, etc.) of a computer 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 has one or more links to one or more other nodes in the network and the mapping of these links and nodes in a graph results in a geometrical shape that may be used to describe the physical topology of the network. Likewise, the mapping of the data flows 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.
Bus network topology
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.
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.
Star network topologyIn 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 transverses 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 network topology
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.
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 byReed's Law.
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 byReed's Law.
Tree network topologyAlso 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
Open System Interconnection
is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection (OSI) initiative. In its most basic form, it divides network architecture into seven layers which, from top to bottom, are the Application, Presentation, Session, Transport, Network, Data-Link, and Physical Layers. It is therefore often referred to as the OSI Seven Layer Model.
A layer is a collection of conceptually similar functions that provide services to the layer above it and receives service from the layer below it. On each layer an instance provides services to the instances at the layer above and requests service from the layer below. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of the path. Conceptually two instances at one layer are connected by a horizontal protocol connection on that layer.
Layer 1: Physical Layer
The Physical Layer defines the electrical and physical specifications for devices. In particular, it defines the relationship between a device and a physical medium. This includes the layout of pins, voltages, cablespecifications, hubs, repeaters, network adapters, host bus adapters(HBAs used in storage area networks) and more.
The Physical Layer defines the electrical and physical specifications for devices. In particular, it defines the relationship between a device and a physical medium. This includes the layout of pins, voltages, cablespecifications, hubs, repeaters, network adapters, host bus adapters(HBAs used in storage area networks) and more.
Layer 2: Data Link Layer
The Data Link Layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical Layer.
The Data Link Layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical Layer.
Layer 3: Network Layer
The Network Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks, while maintaining the quality of service requested by the Transport Layer.
The Network Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks, while maintaining the quality of service requested by the Transport Layer.
Layer 4: Transport Layer
The Transport Layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The Transport Layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. Some protocols are state and connection oriented. This means that the Transport Layer can keep track of the segments and retransmit those that fail.
The Transport Layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The Transport Layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. Some protocols are state and connection oriented. This means that the Transport Layer can keep track of the segments and retransmit those that fail.
Layer 5: Session Layer
The Session Layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures.
The Session Layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures.
Layer 6: Presentation Layer
The Presentation Layer establishes a context between Application Layer entities, in which the higher-layer entities can use different syntax and semantics, as long as the presentation service understands both and the mapping between them. The presentation service data units are then encapsulated into Session Protocol data units, and moved down the stack.
The Presentation Layer establishes a context between Application Layer entities, in which the higher-layer entities can use different syntax and semantics, as long as the presentation service understands both and the mapping between them. The presentation service data units are then encapsulated into Session Protocol data units, and moved down the stack.
Layer 7: Application Layer
The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component.
The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component.
computer network
is a group of computers that are interconnected by electronic circuits or wireless transmissions of various designs and technologies for the purpose of exchanging data or communicating information between them or their users. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of types and categories and also presents the basic components of a network.
Example of networkng
Gateway: device sitting at a network node for interfacing with another network that uses different protocols. Works on OSI layers 4 to 7.
Router: a specialized network device that determines the next network point to which to forward a data packet toward its destination. Unlike a gateway, it cannot interface different protocols. Works on OSI layer 3.
Bridge: a device that connects multiple network segments along the data link layer. Works on OSI layer 2.
Switch: a device that allocates traffic from one network segment to certain lines (intended destination(s)) which connect the segment to another network segment. So unlike a hub a switch splits the network traffic and sends it to different destinations rather than to all systems on the network. Works on OSI layer 2.
Hub: connects multiple Ethernet segments together making them act as a single segment. When using a hub, every attached device shares the same broadcast domain and the same collision domain. Therefore, only one computer connected to the hub is able to transmit at a time. Depending on the network topology, the hub provides a basic level 1 OSI model connection among the network objects (workstations, servers, etc). It provides bandwidth which is shared among all the objects, compared to switches, which provide a dedicated connection between individual nodes. Works on OSI layer 1.
Repeater: device to amplify or regenerate digital signals received while setting them from one part of a network into another.
Multilayer Switch: a switch which, in addition to switching on OSI layer 2, provides functionality at higher protocol layers.
Protocol Converter: a hardware device that converts between two different types of transmissions, such as asynchronous and synchronous transmissions.
Bridge Router(Brouter): Combine router and bridge functionality and are therefore working on OSI layers 2 and 3.
Digital media receiver: Connects a computer network to a home theatre
Hardware or software components that typically sit on the connection point of different networks, e.g. between an internal network and an external network:
Proxy: computer network service which allows clients to make indirect network connections to other network services
Firewall: a piece of hardware or software put on the network to prevent some communications forbidden by the network policy
video cables
like S-Video cables, are dedicated to one task; the task of transmitting video between home theater components. These video cables look similar to composite cables in that component video cables are also split into three separate lines with RCA connectors at the ends of each.
audio cables
used to connect those components.
network adapter
These adapters connect
to a standard USB port
available on
the back of most
newer computers. In general,
USB network adapters
are not much larger
in size than PC Card adapters.
Two LED lights on
the adapter indicate
its power and network link status.
USB cable
USB to mini-USB cable
to connect between
the PC to the PSP.
Video Extension cable is used to extend the length of a VGA monitor cable. Most CRT monitors have built-in VGA cables which cannot be disconnected, so this is the best way to relocate such displays as you need them.
Power Connector This cable is used for powering serial drives. Serial drives, unlike standard drives, do not use the four pin molex connector that comes off of your power supply. This cable converts the power supply's four pin molex connector to a 15 pin male serial connector, used for powering up the serial device.
PC Joystick Extension Cable can be used with a PC's DB15 joystick port. Male to Male configurations will connect a joystick port with the appropriate switch box while a Female to Male will extend the existing cable.
Crossover cable is used for networking and data transfer. For use from a DSL/cable modem directly to the PC and for a direct link from PC to PC. All our CAT-5E cables are 100% tested for performance and continuity in accordance with industry standards. We offer a wide selection of colors.
IDE cables it is a standard type of connection for storage devices in a PC. Generally, it refers to the types of cables and ports used to connect some hard drives to each other and to the  SATA cable This cable is superior in data transfer in that it is significantly faster, however SATA cables can only be used to connect a single device.  |
