Certification to the professional network
Topology architectures
Bus network: is a communication architecture where hardware is connected via a bus shared by all users. Bus networks allow for the simple connection of multiple devices but pose problems when two machines want to transmit data simultaneously over the bus. Systems using a bus topology normally have an arbiter that manages access to the bus.
This bus topology was very widespread because its installation cost is low. It is very easy to connect
several workstations in the same room or to connect two or three computers at home. Today, this topology is no longer suitable for large networks. Ring network: All machines are connected to each other in a closed loop. Data flows in a single direction, from one entity to the next. The computers communicate in turn. It resembles a bus, but it is closed in on itself: the last node is connected to the first. Often, in a ring topology, the computers are not connected in a loop but are connected to a cross-connect. (called MAU, Multi-Station Access Unit)
which will manage communication between the computers connected to it by allocating speaking time to each of them. It uses the "token ring" access method. Data travels from station to station along the ring, each time regenerating the signal. The token determines which station can transmit and is then transferred in turn to the next station. When the station that sent the data retrieves it, it removes it from the network and passes the token to the next station, and so on. The ring topology is called an "active topology" because the electrical signal is intercepted and regenerated by each machine. Mesh network: is a network topology that describes networks (wired or not) in which all hosts are connected peer-to-peer without a central hierarchy, thus forming a net-like structure. Therefore, each node must receive, send, and relay data. This avoids having hotspots, which, in the event of a failure, isolate part of the network. If a host is down, its neighbors will take another route. Mesh networks use multiple transfer paths between the different nodes. This method guarantees data transfer in the event of a node failure.
The Internet is based on a mesh topology (on the WAN, it guarantees stability in the event of a node failure). Tree (or hierarchical) network: A tree topology can be thought of as a collection of star networks arranged in a hierarchy. This network is divided into levels. The top, high-level node is connected to several lower-level nodes in the hierarchy. These nodes may themselves be connected to several lower-level nodes. As in a conventional star network, individual nodes can still be isolated from the network by a single point failure along a transmission path to the node. If a link connecting a branch fails, that branch is isolated; if a connection to a node fails, an entire section of the network becomes isolated from the rest.
Recall that to communicate between layers and between hosts on a network, OSI uses the principle of encapsulation. A packet is the basic unit of information transferred over a network, consisting of, at a minimum, a header with the addresses of the sending and receiving hosts and a body.
with the data to be transferred. As the packet traverses the TCP/IP protocol stack, the protocols at each layer add or remove fields from the base header. When a protocol on the sending host adds data to the packet header, the process is called data encapsulation. Additionally, each layer has a different term for the modified packet, as shown in Data decapsulation is simply the reverse of encapsulation. It occurs when an incoming transmission (to be received by the destination computer) is decompressed as it moves up the protocol stack. The information contained in the header is used to determine the network to which the data should be delivered.