include::{commondir}/chapters/osmux/osmux.adoc[]

=== Osmux Support in {program-name}

==== {program-name} in a A/IP with IPA/SCCPlite network setup

In this kind of setup, Osmux is transparent to {program-name} and no specific
configuration is required here, since the CN-side of the BSC-attached MGW is
managed directly by the MSC.

So, in this case, only MSC and MGW (both for MSC-attached one and BSC-attached
one) need to be configured explicitly.

==== {program-name} in a 3GPP AoIP network setup

Osmux usage in {program-name} in managed through the VTY command `osmux
(on|off|only)`. Once enabled (`on` or `only`), {program-name} will start
appending the vendor specific _Osmux Support_ IE in _BSSMAP RESET_ and _BSSMAP
RESET-ACK_ message towards the MSC in order to announce it supports Osmux. This
way, the MSC can decide whether to use Osmux or not based on this information
when setting up a call (this time using _Osmux CID_ IE). It should be noted that
this option should not be enabled unless MSC managing {program-name} supports
handling this extension IE (like OsmoMSC), a 3rd-party MSC might otherwise
refuse the related _RESET_/_RESET-ACK_ messages.

{program-name} will behave differently during call set up based on the VTY
command presented above:

* `off`: If _BSSMAP Assign Request_ from MSC contains _Osmux CID_ IE, meaning
  MSC wants to use Osmux for this call, then {program-name} will reject the
  assignment and the call set up will fail.
* `on`: BSC will support and accept both Osmux and non-Osmux (RTP) upon call set
  up. If _BSSMAP Assign Request_ from MSC contains _Osmux CID_ IE,
  {program-name} will instruct its MGW to set up an Osmux connection on the
  CN-side of the MGCP endpoint, and will provide the MSC with its _recvCID_
  through the extension IE _Osmux CID_ appended to the _BSSMAP Assign Complete_
  message. On the other hand, if _BSSMAP Assign Request_ doesn't contain an
  _Osmux CID_ IE, {program-name} will instruct its MGW to set up a regular RTP
  connection on the CN-side of the MGCP endpoint.
* `only`: Same as per `on`, except that {program-name} will accept only Osmux
  calls on the CN-side, this is, if  _BSSMAP Assign Request_ from MSC doesn't
  contain an _Osmux CID_ IE, it will reject the assignment and the call set up
  will fail.