A media termination point (MTP) is an entity that accepts two full-duplex media streams. It bridges the streams together and allows them to be set up and torn down independently. The streaming data received from the input stream on one connection is passed to the output stream on the other connection, and vice versa.
An MTP can be used to transcode G.711 a-law audio packets to G.711 mu-law packets and vice versa, or it can be used to bridge two connections that utilize different packetization periods (different sample sizes).
MTPs extend supplementary services, such as call hold, call transfer, call park, and conferencing, that are otherwise not available when a call is routed to an H.323 endpoint. Some H.323 gateways may require that calls use an MTP to enable supplementary call services, but normally, Cisco IOS gateways do not.
MTP Types
Software MTP provided by the Cisco IP Voice Media Streaming App service on Cisco Unified Communications Manager:
- This MTP type can convert G.711 mu-law to G.711 a-law and vice versa.
- This MTP type can packetize conversion for a given codec; for example, when one call leg uses 20-ms sample size and the other call leg uses 30-ms sample size.
Software MTP configured on Cisco IOS routers:
- This MTP type does not require any DSP resources on the Cisco router. Enable Cisco IOS Software MTPs by using the maximum session software n command.
- As many as 500 software-based sessions can be configured.
- The codec and packetization of both call legs must be identical.
- This MTP type typically is used for Resource Reservation Protocol (RSVP) agent configurations or Cisco Unified Border Element media flow-through configurations.
- Cisco Unified Communications Manager does not differentiate between software and hardware-based Cisco IOS MTP configurations. Every Cisco IOS Software MTP is considered as hardware MTP in Cisco Unified Communications Manager.
- Software MTPs are supported on the router only if the dsp services dspfarm command is not enabled on the voice card.
- Hardware and software keywords in configuration only require for MTP
Hardware MTP configured on Cisco IOS routers:
- DSP resources are required. Configure this MTP type by using the maximum session hardware <n> command. The maximum number of sessions is derived from the number of installed DSP resources on the Cisco IOS router.
- Use of the same audio codec but different packetization on both call legs is possible.
Network Solutions 