Editing Differentiated services (section)

==Background==
Modern data networks carry many different types of services, including voice, video, streaming music, web pages and email. Many of the proposed QoS mechanisms that allowed these services to co-exist were both complex and failed to scale to meet the demands of the [[public Internet]]. In December 1998, the [[IETF]] replaced the ''TOS'' and ''IP precedence'' fields in the [[IPv4 header]] with the ''DS field'', which was later split to refer to only the top 6 bits with the ''ECN field'' in the bottom two bits.{{Ref RFC|2474}}{{Ref RFC|3168}} In the [[IPv6 header]] the ''DS field'' is part of the ''Traffic Class'' field where it occupies the 6 most significant bits.{{Ref RFC|2474}}

In the DS field, a range of eight values (class selectors) is used for backward compatibility with the former IPv4 ''IP precedence'' field. Today, DiffServ has largely supplanted [[Type of service|TOS]] and other [[layer-3]] QoS mechanisms, such as [[integrated services]] (IntServ), as the primary architecture [[Router (computing)|router]]s use to provide QoS.