ccna pdf espa?ol

ccna pdf espa?ol.3. JitterJitter is the variation in the delay of received packets. On the sender side, packets are sent in a continuous stream with uniform spacing between packets. Due to network congestion, incorrect queuing, or configuration errors, the delay between each packet may vary rather than remain constant. Latency and jitter need to be controlled and minimized to support real-time and interactive traffic.4. packet lossIf no QoS mechanism is implemented, packets are processed in the order in which they are received. When congestion occurs, network devices such as routers and switches may drop packets. This means that time-sensitive packets (such as real-time video and voice) will be dropped along with non-time-sensitive data (such as email and FTP applications). Packet loss is a very common cause of voice quality problems on IP networks. In a properly designed network, packet loss should be close to zero. Congestion can be prevented by increasing link capacity, increasing bandwidth, increasing buffer space, and dropping lower priority packets before congestion occurs.QoS will be a very important tool to solve the above problems. The basic idea of QoS is to classify packets and implement different services for different classes of packets according to their needs. QoS is relative to the network services, and while ensuring the quality of service for a certain class of services, it is also compromising the quality of service for other services. Because network resources are always limited, quality of service requirements will arise as long as there is a rush for network resources. It is important to emphasize that QoS does not increase the actual network bandwidth.Chapter 21 QoS .417 .21.1.3 QoS Models QoS includes three types of service models: best-effort service model, integrated service model and differential service model.1. Best-effort service modelThe best-effort service model is the simplest QoS service model, in which the network device treats all packets equally and forwards packets using the first-in-first-out (FIFO) rule to the maximum extent possible.The advantages of this model are described below.