gsm0808: Introduce Osmocom extensions to announce Osmux support

IE GSM0808_IE_OSMO_OSMUX_SUPPORT (T, 1 byte) is sent in AoIP appended to
BSSMAP RESET in order to announce the peer that its MGW supports handling
Osmux streams upon call set up.

IE GSM0808_IE_OSMO_OSMUX_CID (TV, T 1 byte & V 1 byte) is sent in AoIP
during call set up:
* MSC->BSC Assignment Request
* BSC->MSC Assignemnt Complete

The 1 byte value contains the local Osmux CID, aka the recvCID aka CID where the
peer sending the Assign Req/Compl will look for Osmux frames on that
call. Hence, the peer receiving this CID value must use it to send Osmux
frames for that call.

As a result, a given call leg BSC<->MSC can have one different Osmux CID
per direction. For example:
* MS => MGW_BSC ==CID 0==> MGW_MSC
* MS <= MGW_BSC <=CID 1=== MGW_MSC

This allows for setups with 256 call legs per BSC on scenarios where NAT
is not a problem, where MSC can have a pool of 256 CID per MGW_BSC (or
remote peer).

Related: OS#2551
Change-Id: I28f83e2e32b9533c99e65ccc1562900ac2aec74e

0 files changed, 0 insertions, 0 deletions