(QoS (qualityofserver) (used only in case of congestion) which problems will affect the data transmission of the network 1. Limited bandwidth 2. Delay 3. Jitter (buffering is to solve jitter) 4. Methods to solve the available bandwidth of packet loss: 1. Upgrade the bandwidth and increase the link bandwidth 2. Let the traffic with high priority pass first 3. Compress the frame of layer 2 4. Compress the header of IP packets)