Conventional Internet routers and LAN switches lack the ability to provide quality of service guarantees. This made Internet equipment less expensive, faster and thus more popular than competing more complex technologies that provided QoS mechanisms, for example X.25. Internet traditionally therefore runs at default QoS level, or "best effort". There were four "Type of Service" bits and three "Precedence" bits provided in each IP packet, but they were ignored. These bits were later re-defined as DiffServ Code Points (DSCP) and are sometimes honored in peered links on the modern Internet.
With the advent of IP-TV and IP-telephony, QoS mechanisms are increasingly available to the end user.
A number of attempts for layer 2 technologies that add QoS tags to the data have gained popularity during the years, but then lost attention. Examples are Frame relay and ATM. Recently, MPLS (a technique between layer 2 and 3) have gained some attention. However, today Ethernet may offer QoS and is, by far, the most popular layer 2 technology.
In Ethernet, Virtual LANs (VLAN) may be used to separate different QoS levels. For example in fibre-to-the-home switches typically offer several Ethernet ports connected to different VLAN:s. One VLAN may be used for Internet access (low priority), one for IP-TV (higher priority) and one for IP telephony (highest priority). Different Internet providers may use the different VLANs.
With the advent of IP-TV and IP-telephony, QoS mechanisms are increasingly available to the end user.
A number of attempts for layer 2 technologies that add QoS tags to the data have gained popularity during the years, but then lost attention. Examples are Frame relay and ATM. Recently, MPLS (a technique between layer 2 and 3) have gained some attention. However, today Ethernet may offer QoS and is, by far, the most popular layer 2 technology.
In Ethernet, Virtual LANs (VLAN) may be used to separate different QoS levels. For example in fibre-to-the-home switches typically offer several Ethernet ports connected to different VLAN:s. One VLAN may be used for Internet access (low priority), one for IP-TV (higher priority) and one for IP telephony (highest priority). Different Internet providers may use the different VLANs.
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