█TOPOLOGY█
A ring network is a network topology in which each node connects to exactly two other nodes, forming a circular pathway for signals.
Because a ring topology provides only one pathway between any two nodes, ring networks may be disrupted by the failure of a single link. A node failure or cable break might isolate every node attached to the ring.
█STAR TOPOLOGY█
Star networks are one of the most common computer network topologies. a star network consists of one central switch, hub or computer which acts as a conduit to transmit messages. The star topology reduces the chance of network failure by connecting all of the systems to a central node.
Advantages
• Good performance.
• Scalable, Easy to set up and to expand.
• Any non-centralised failure will have very little effect on the network, whereas on a ring network it would all fail with one fault.
• Easy to detect faults
• Data Packets are sent quickly as they do not have to travel through any unnecessary nodes.
• It is used for centralised control.
█BUS TOPOLOGY█
A bus network topology is a network architecture in which a set of clients are connected via a shared communications line, called a bus.
Bus networks are the simplest way to connect multiple clients, but often have problems when two clients want to transmit at the same time on the same bus.
Advantages and disadvantages of a bus network
Advantages
• Easy to implement and extend
• Requires less cable length than a star topology
• Well suited for temporary or small networks not requiring high speeds(quick setup)
• Cheaper than other topologies
Disadvantages
• Limited cable length and number of stations.
• If there is a problem with the cable, the entire network goes down.
• Maintenance costs may be higher in the long run.
• Performance degrades as additional computers are added or on heavy traffic.
• Proper termination is required.(loop must be in closed path).
• If many computers are attached, the amount of data flowing causes the network to slow down.
• Significant Capacitive Load (each bus transaction must be able to stretch to most distant link).
• It works best with limited number of nodes.
█TREE TOPOLOGY█
A Tree Network consists of star-configured nodes connected to switches/concentrators, each connected to a linear bus backbone. Each hub/concentrator rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected.
MESH TOPOLOGY
Mesh networking is a way to route data, voice and instructions between nodes. It allows for continuous connections and reconfiguration around broken or blocked paths by “hopping” from node to node until the destination is reached. A mesh network whose nodes are all connected to each other is a fully connected network.
Mesh networks are self-healing: the network can still operate even when a node breaks down or a connection goes bad. As a result, a very reliable network is formed. This concept is applicable to wireless networks, wired networks, and software interaction.
OSI MODEL
The application layer is the seventh level of the seven-layer OSI model. It interfaces directly to and performs common application services for the application processes; it also issues requests to the presentation layer.
The common application layer services provide semantic conversion between associated application processes. Note: Examples of common application services of general interest include the virtual file, virtual terminal, and job transfer and manipulation protocols.
The application layer of the four layer and five layer TCP/IP models corresponds to the application layer
The presentation layer is the sixth level of the seven layer OSI model. It responds to service requests from the application layer and issues service requests to the session layer.
The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems. The presentation layer is the first one where people start to care about what they are sending at a more advanced level than just a bunch of ones and zeros.
The session layer is level five of the seven level OSI model. It responds to service requests from the presentation layer and issues service requests to the transport layer.
The Session layer provides the mechanism for managing the dialogue between end-user application processes. It provides for either full duplex or half-duplex operation and establishes check pointing, adjournment, termination, and restart procedures.
The Session layer is typically completely unused, but it does have a few places where it is useful. The idea is to allow information on different streams, perhaps originating from different sources, to be properly combined. In particular, it deals with synchronization issues, and ensuring nobody ever sees inconsistent versions of data, and similar things.
the transport layer is the second highest layer in the four and five layer TCP/IP reference models, where it responds to service requests from the application layer and issues service requests to the Internet layer. It is also the name of layer four of the seven layer OSI model, where it responds to service requests from the session layer and issues service requests to the network layer. The transport layer is typically handled by processes in the host computer operational system, and not by routers and switches. The transport layer usually turns the unreliable and very basic service provided by the Network layer into a more powerful one.
The network layer is the third layer out of seven in OSI model In essence, the network layer is responsible for end to end (source to destination) packet delivery, whereas the data link layer is responsible for node to node (hop to hop) packet delivery. 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, and error control functions.
The data link layer is layer two of the seven-layer OSI model This is the layer which transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network segment. The data link is all about getting information from one place to a selection of other places. The data link provides data transfer across the physical link. That transfer might or might not be reliable; many data link protocols do not have acknowledgments of successful frame reception and acceptance, and some data link protocols might not even have any form of check sum to check for transmission errors.
The physical layer is level one in the seven-level OSI model of computer networking as well as in the five-layer TCP/IP reference model. It performs services requested by the data link layer.
The physical layer is the most basic network layer, providing only the means of transmitting raw bits rather than packets over a physical data link connecting network nodes.
The Physical Layer defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes. The bit stream may be grouped into code words or symbols. and converted to a physical signal that is transmitted over a hardware transmission medium.
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