Layer 3 QoS Classification with DSCP

From the beginning, IP packets have always had a type of service (ToS) byte that can be used to mark packets. This byte is divided into a 3-bit IP Precedence value and a 4-bit ToS value. This offers a rather limited mechanism for QoS because only the 3 bits of IP Precedence are used to describe the per-hop QoS behavior. The DiffServ model keeps the existing IP ToS byte but uses it in a more scalable fashion. This byte also is referred to as the Differentiated Services (DS) field, with a...