This is conversational type of traffic (with similar requirements in both directions, from calling party A to called party B, and vice versa) and has constant bitrate when sending or receiving. Also, voice requires relatively small IP packets (e.g. 50-200 bytes). Video traffic. This generally has high variable bitrate, which is dependent upon the codec efficiency of the moving pictures (e.g. Moving Picture Experts Group 2 Internet QoS (MPEG-2), MPEG-4 various codec types). Video is typically unidirectional traffic (in downstream, i.e. downlink, direction regarding the end-user), SO it can use the largest possible IP packets since it can eliminate IP packet delay variations with delayed playback on the receiving side. Since local access to the Internet in homes, offices, or public places is unified to Ethernet or WiFi (except in mobile networks), the maximum IP packet size for video traffic is limited by the MTU (message transfer unit) of Ethernet (and similarly WiFi), which is 1500 bytes. Data traffic. This is typically the non-real-time (NRT) traffic on the Internet, the most prominent examples being the WWW and email. This type of traffic is typically TCP-based (regarding transport protocol, which goes over IP, thus giving TCP/IP). 2.3.1 Audio Traffic Characterization Audio traffic usually refers to voice. The conversational voice (i.e. telephony) is most sensitive to delay and jitter. Regarding telephony, the recommended delay in PSTN is below 150 ms, while above 400 ms is not acceptable because the people talking will start interrupting each other [23]. However, in IP environments the delay is always higher than in PSTN/ISDN due to packetization (creation of IP packets with payload many times bigger than the IP header due to efficiency reasons, that is, lower redundancy), buffering in network nodes (every router first buffers the packets and then sends them over a given network interface on the next hop, which is different than PSTN where bits and bytes are being transferred from one end to the other end with