ccna certification utah

ccna certification utah.When the switch detects a data frame at the input port, it examines the frame header of the frame and starts forwarding the frame data as soon as the destination MAC address of the frame is obtained. Its advantage is that the entire data frame does not need to be read before starting forwarding, the delay is very small and the switching process is very fast. Its disadvantage is that the contents of the data frame are not cached by the switch, so it is not possible to check whether the transmitted data frame is incorrect, and it does not provide error detection capability.Fragment.Free forwardingThis is an improved version of direct forwarding, which is an intermediate forwarding method between the previous two. Since most conflicts occur before 64 bytes in a normally operating network, the fragment-free method starts forwarding the data frame after reading the first 64 bytes of the frame. This method also does not provide data checksum, and its data processing speed is much faster than the store-and-forward method, although slower than the direct forward method.As can be seen from the three switching methods, the data forwarding latency and error rate of the switch depends on which switching method is used. The store-and-forward method has the highest latency, the unfragmented method the second lowest, and the direct forwarding method the smallest; however, the store-and-forward method has the lowest frame error rate, the unfragmented method the second lowest, and the direct forwarding method the largest. There is a trade-off in the switching method used. Many switches can now be designed to use pass-through forwarding under normal conditions and automatically switch to store-and-forward when the error rate of the data reaches a certain level.7.1.3 Conflict domains and broadcast domains1.Conflict DomainsOn a hub-based Ethernet segment, network devices compete for media, and a segment that shares the same bandwidth between devices is called a conflict domain because conflicts may occur when two or more devices in the segment try to communicate at the same time, and the method for resolving conflicts is Carrier Sense Multiple Access with Collision Detection, CSMA/CD). A switch can divide a network into segments to reduce the number of devices competing for bandwidth. Each port of a switch is a separate conflict domain.2. Broadcast DomainWhen a switch receives a broadcast frame, it forwards the frame to every port in the same VLAN as itself (except the port receiving the broadcast frame), so the switch cannot filter the broadcast frame, and the set of connected switches constitutes a broadcast domain. On the networkChapter 7 Switching Networks .91. too many broadcast frames can cause network congestion and result in reduced switch network performance and even broadcast storms. Routers can be used to split the conflict domain and the broadcast domain.