Migration to MPLS
Strictly speaking, MPLS doesn't provide a great deal of assistance in managing VoIP. Rather, MPLS helps the service provider in designing the network core by provisioning label-switched paths (LSPs) and traffic-engineered tunnels. The latter can explicitly reserve the combination of paths and QoS ahead of the arrival of any traffic. In addition, the QoS model known as Differentiated Services (DiffServ) allows for the marking of individual IP packets. This marking is written into the IP packet header and is then used downstream to supply a specific QoS ("per-hop behavior"). An important aspect of DiffServ is that the initial packet marking should occur as close to the source as possible, to facilitate the network in applying the required QoS treatment for the marked packet. One might say that MPLS will help in SLA definition by allowing service providers to carve up their networks into specific QoS regions.