Editing Quality of service (section)

==History==
{{unreferenced section|date=April 2018}}
A number of attempts for [[layer 2]] technologies that add QoS tags to the data have gained popularity in the past. Examples are [[Frame Relay]], [[Asynchronous Transfer Mode]] (ATM) and [[Multiprotocol Label Switching]] (MPLS) (a technique between layer 2 and 3). Despite these network technologies remaining in use today, this kind of network lost attention after the advent of [[Ethernet]] networks. Today Ethernet is, by far, the most popular layer 2 technology. Conventional [[Internet router]]s and [[network switch]]es operate on a best-effort basis. This equipment is less expensive, less complex and faster and thus more popular than earlier more complex technologies that provide QoS mechanisms.

Ethernet optionally uses [[802.1p]] to signal the priority of a frame.

There were four ''[[type of service]]'' bits and three ''precedence'' bits originally provided in each [[IPv4 Header|IP packet header]], but they were not generally respected.  These bits were later re-defined as [[Differentiated services code point]]s (DSCP).

With the advent of [[IPTV]] and [[IP telephony]], QoS mechanisms are increasingly available to the end user.