The TE requirements for stratified data services are quite distinct from voice over packet due to different statistical behaviors and different performance requirements. When compared to data and video, voice over packet flows are a relatively constant stream of small packets, even when silence-activity detection is enabled. Unlike data flows, voice over packet and video flows do not resend lost packets, so delay and loss are not coupled. Conversely, data flows are much more loss-intolerant than voice over packet and video, due to TCP's retransmission mechanism. Currently traffic loss on the Internet is estimated at 0.1 percent to 5 percent.
Bursty traffic arrives in clumps, rather than as a smooth, even flow.
Over the past 10 years, studies have concluded that the traffic ISPs and IXCs carry is excessivelybursty. Burstiness causes most of the packet loss over the Internet. Second-order statistics include familiar measures such as traffic packet rate variance and are the method for quantifying packet streamburstiness. The average packet rate does not characterize the burstiness of arrivals. Emerging measurement standards for the Internet are beginning to deal with burst characterization on multiple time scales, although additional work is needed.