Issue link: https://www.e-digitaleditions.com/i/1255991
In cases where the network switch or switches are not loaded and are properly managed, the majority of the latency budget will be consumed by the AVoIP network devices. 14 I ICT TODAY The size of the FEC matrix can vary based on field installations and lab experiments. If burst errors are expected in the network, it is advised to have more col- umns. When possible, that column should be at least the size of the burst. Row FEC packets are good for protecting against random packet loss patterns. It is important to note that activating and using FEC will result in generating additional data packets that are not part of the audio or video data stream. The FEC packets are additional traffic that will consume bit rate, and this needs to be considered when planning and allo- cating bit rate for video and audio (Table 1). Quality of Service – Differentiates Services Not all data types and packets are equal. There are data packets that need immediate forwarding and routing, and TABLE 1: Bit rate chart for FEC, audio and video. there are other types of data packets that can observe a bit of delay before getting processed. A quality of ser- vice (QoS) policy must be implemented by the organiza- tion that runs the IP network. The term "quality of service" can be thought of simi- larly to how an airline passenger is classified: first class, business class, or economy class. Through a process called packet marking, a value is assigned to the packet to deter- mine how that packet should be treated as it travels over the network. When a passenger boards a plane, flight attendants are not concerned with how a passenger was classified. However, by looking at the boarding pass, the attendant can then provide the passenger with that assigned level of service. The AVoIP traffic is delay-sensitive. As such, the traffic must be prioritized when arriving to a network switch. In the networking world, standardized protocols are used to implement policies. One of the protocols that is used to configure the network elements to clas- sify traffic is differentiated service (DiffServ). In a nut- shell, each data type will be assigned a differentiated service code point (DSCP) for classification. The DSCP value is assigned to each packet at the encoder, and it is mapped against five main precedence values: best effort, low, normal, high and highest. For networks that run AVoIP services in conjunction with other types of data, it is highly advised to prioritize AVoIP-related protocols (i.e., multicast and IGMP) over non-delay critical data. For highly congested network Configured Bit Rate FEC disabled FEC enabled, 4x4 FEC enabled, 10x10 FEC enabled, 20x20 FEC enabled, 4x4 FEC enabled, 10x10 FEC enabled, 20x20 900 Mb/s 900 Mb/s 900 Mb/s 900 Mb/s 450 Mb/s 450 Mb/s 450 Mb/s 900 Mb/s 600 Mb/s 750 Mb/s 818 Mb/s 300 Mb/s 375 Mb/s 409 Mb/s 0 Mb/s 300 Mb/s 150 Mb/s 82 Mb/s 150 Mb/s 75 Mb/s 41 Mb/s Used for Video Used for FEC