CompTIA Network+

Answer: A, B - ATM and MPLS have built in QoS in their protocols.

Key takeaway: ATM or Asynchronous Transfer Mode is an outlining specification for a method of data, voice and video encoding and transfer. The methods that ATM uses make it compatible with a wide range of network uses, from high speed data transfer to latency sensitive data transfer such as voice and video. Because of this, ATM has built in Quality of Service specifications to ensure data requirements are met.

MPLS is multiprotocol label switching. This mechanism is used to map data from one network device to another via path labels instead of IP addresses which are longer. During the MPLS operation, QoS information is inserted into the label to attempt to limit multi-layer engineering, thus saving time. VoIP is a real-time application that relies on being best effort, connectionless for speed, not necessarily reliability. VoIP does not initially have QoS built in to it; however QoS should be one of the main considerations when troubleshooting this technology. PDH is plesiochronous digital hierarchy is a data transportation technology for typically larger amounts of data and has been greatly replaced with SDH, or Synchronous Digital Hierarchy. IPv4, much like VoIP is a connectionless, best effort protocol that does not have QoS built in to it.