ccna pdf ebook free download

ccna pdf ebook free download.Today's network traffic consists of 3 main categories: voice, video, and data. Voice traffic has predictable bandwidth requirements and known packet arrival times, video traffic is real-time and unpredictable, while data traffic is not real-time traffic and has unpredictable bandwidth requirements. Voice, video and data traffic have different types of demands on the network, and voice and video traffic will account for an increasing share of future network applications.1. VoiceVoice is very sensitive to latency and packet loss, so voice packets must receive a high priority. Voice traffic typically requires a delay of no more than 150 ms, jitter of no more than 30 ms, packet loss of no more than 1%, and a bandwidth of at least 30 kbpso2. VideoWithout QoS (QualityofService) and a significant amount of additional bandwidth, video quality is often degraded, as evidenced by pictures that look blurry, jagged, or in slow motion, and the audio portion of the video source may be out of sync with the video. Compared to voice traffic, video traffic tends to be unpredictable, inconsistent, and bursty. Video traffic typically requires a latency of no more than 400 ms, jitter of no more than 50 ms, packet loss of no more than 1%, and a bandwidth of at least 384 kbpso3. DataData traffic is divided into user data traffic, which can be bursty, and network control traffic, which is usually predictable. Although data traffic is relatively less sensitive to packet loss and latency than voice and video traffic, network administrators still need to consider the user experience.21.1.2 Characteristics of Network CongestionIf the size of network traffic is larger than the network's own carrying capacity, the network becomes congested, mainly in terms of lack of bandwidth, too much delay, jitter, and packet loss.1. Lack of bandwidth