ccna r&s arabic pdf

ccna r&s arabic pdf.4.2.2 SwitchesLike bridges, switches operate at the data link layer and have the three main functions of bridges: learning, forwarding, and loop avoidance. However, switches also have many features that bridges do not have; for example, they use application-specific integrated circuits (ASICs) to make switching decisions in hardware.ASICs are specialized processors designed to perform a number of specific tasks; because they do only a few things, ASICs are much more cost-efficient than general-purpose processors, such as PC processors. Like most networking vendors, Cisco makes extensive use of ASICs in its switching productsoCertification Objectives 4.034.3 Bridges and SwitchesThe primary function of bridges and switches is to resolve bandwidth (conflict) issues. Don't forget that in Ethernet, multiple devices may share media, so multiple devices may try to transmit data at the same time, resulting in a conflict that requires retransmission. The more devices that share media, the greater the likelihood of conflict.In the early days of networking technology, either hubs were used to connect devices together, or 10Base5 or 10Base2 cables were used (many devices sharing a single cable). If conflicts occurred consistently or in large numbers, bridges (and later switches) could be used to divide user devices into multiple network segments, which reduced the number of users per segment and, in turn, reduced conflicts. Routers can also be used to provide this functionality, but routers have the disadvantage of being much more expensive than bridges and switches. This section provides an overview of bridges and switches.Hubs are powerless to solve bandwidth (conflict) problems, while bridges and switches can. Bridges and switches divide large conflict domains into smaller conflict domains. in the sense that they increase the number of conflict domains (because each interface of a Layer 2 device is a separate conflict domain) and thus reduce the number of devices contained in each conflict domain. This process is known as micro-segmentation. Routers run at the network layer and are also able to resolve conflicts, but at a higher price than bridges and switches.Although bridges and switches both run at Layer 2, they differ in many ways. Switches have many advantages over bridges, including: . Support for full duplex mode, which allows devices to send and receive data simultaneously .. Support for different Ethernet speeds for different switch ports, such as lOBaseT, lOOBaseTX, and Gigabit Ethernet .. The connection from the switch port to the router, PC, or server is dedicated; . The ability to transmit multiple simultaneous sessions between switch ports; .