What is ITU-T E-Model

Most of the existent games consist of multiple players, connected over a network, collaborating and competing in a virtual world. In this world, each player typically controls a single virtual entity. Communication between players can be achieved by sharing entity state information, such as positioning using synchronisation messages. These messages are periodically transmitted across the connecting network, and update the remote state of the virtual entity, which is the state replicated on other players’ computers. If the games are using the Internet as a connecting network, latency, jitter, and packet loss, can have a significant impact upon the service experienced by application user (end-user). More specifically, latency or delay can by introduced by various types of delays, such as propagation, serialisation, and queuing delays. Jitter is the variation in latency experienced by consecutive packets. Not all of the packets in a given flow will take the same path through the network. The time taken to traverse different routes is likely to vary due to factors such as their different physical distance, the number of hops, or physical link properties. On lower bandwidth links, which have a greater serialization delay, variation in packet lengths can introduce jitter. The size distribution and arrival patterns of other traffic flows on shared links may influence the queuing delay experienced by packets in one particular flow and is, in itself, a source of jitter. There are a number of different points on the network where packets may be lost. At the physical layer, all links experience some rate of data corruption, known as the bit error rate (BER). This may be caused by a high signal-to-noise ratio (SNR) during digital to analog conversion processes, which causes erroneous encoding or decoding of data, or it may be caused by faulty hardware. Forward error correction (FEC) is sometimes used at the link layer to recover from one- or two-bit errors. A cyclic redundancy check (CRC) may be applied to detect whether or not errors are included in the frame. Occasionally, transient congestion, with the subsequent queuing of packets, is so severe that it causes the routing queue buffer to overflow. When this occurs, newly arriving packets will be dropped until there is sufficient space in the buffer to place new packets. On other occasions, dynamic routing changes or route flapping may result in a temporarily incomplete network path, which causes losses.