Example1:
In the following call flow, the Modify Offers (in green) are suppressed if the Minimize Relaying Of Media Changes From Other Call Leg flag is enabled:
Ingress Peer |
| SBC |
| Egress Peer | |||
G711U | -> | SBC offers G711U as pass-through codec and G729A as a transcode option by reserving a DSP channel | -> | G711U,G729A | |||
G711U | <- | SBC releases the DSP channel resulting in a G711U pass-thru call | <- | G711U | |||
|
| Receive capabilities of SBC have changed as a codec G729A was removed and the DSP channel de-allocated. | -> | G711U | |||
|
|
| <- | G711U |
Example 2:
The messages (in green) can be suppressed if the Disable Media Lock Down field is enabled.
Ingress Peer |
| SBC |
| Egress Peer | ||||
G711U | -> | SBC offers G711U as pass-through codec and G729A as a transcode option by reserving a DSP channel | -> | G711U,G729A | ||||
G711U | <- | SBC releases the DSP channel resulting in a G711U pass-thru call | <- | G711U,G729A | ||||
| Receive capabilities of SBC have changed as a codec G729A was removed and the DSP channel de-allocated. | -> | G711U |
|
|
| ||
<- | G711U |
Ingress Peer |
| SBC |
| Egress Peer | ||
G711U | -> | SBC offers G711U as pass-through codec and G729A,G726 as transcode options by reserving a DSP channel | -> | G711U,G729A,G726 | ||
G711U | <- | Transcode G711-G729A call. Egress codec is locked down to G729A | <- | G729A,G726 |
| |
Receive capabilities of SBC have changed to G729A due to transcode. | -> | G729A |
|
| ||
| <- | G729A |
Example 3:
Scenario in which Disable Media Lockdown field can not suppress the media lock down messages (in green).
...
Ingress Peer |
| SBC |
| Egress Peer | ||
G711U | -> | SBC offers G711U as pass-through codec and G726,G729A as transcode options by reserving a DSP channel | -> | G711U,G726,G729A | ||
G711U | <- | Transcode G711-G726 call. Egress codec is locked down to G726 | <- | G729A,G726 | ||
|
| Receive capabilities of SBC have changed to G726 ( i.e. HRP is disabled). Since, the codec selected by SBC is different from Peer’s preferred codec (G729), though the flag DML is enabled SBC sends a Modify Offer to lockdown to G726. | -> | G726 | ||
|
| <- | G726 |
Example1:
The re-INVITEs (in green) are suppressed if the Minimize Relaying Of Media Changes From Other Call Leg flag is enabled.
Ingress Peer |
| SBC |
| Egress Peer | |||
G711U | -> | SBC offers G711U as pass-through codec and G729A as a transcode option by reserving a DSP channel | -> | G711U,G729A | |||
G711U | <- | SBC releases the DSP channel resulting in a G711U pass-thru call | <- | G711U |
| ||
Receive capabilities of SBC have changed as a codec G729A was removed; send Modify Offer to Peer to advertise the latest set of capabilities | -> | G711U |
|
|
| ||
<- | G711U |
Example2:
SBC suppresses a Modify Offer from the ingress peer. The offer changes the maxptime from 10 to 20ms. An increase in maxptime can be suppressed – a device that advertises a maxptime of 20ms can also receive 10ms packets.
Ingress Peer |
| SBC |
| Egress Peer | |
G711U 10ms | -> | -> | G711U 10ms | ||
G711U | <- | <- | G711U | ||
Re-INVITE (G711U 20ms) | -> | Suppress the re-INVITE if minimize media is enabled and respond to ingress peer; else forward the re-INVITE to egress | -> | G711U 20ms | |
G711U | <- |
| <- | G711U |
Conversely, irrespective of the state of the Minimize Relaying Of Media Changes From Other Call Leg flag All field cannot suppress a change of maxptime from 20ms to 10ms.
Ingress Peer |
| SBC |
| Egress Peer | |
G711U 20ms | -> |
| -> | G711U 20ms | |
G711U | <- | <- | G711U | ||
Re-INVITE (G711U 10ms) | -> | -> | G711U,10ms | ||
G711U | <- |
| <- | G711U |
Example3:
A change of data-path-mode from sendrecv to sendonly ( HOLD request) can also be suppressable. The rational is that SBC can always ignore the media received from the peer and continue to send it media.
Ingress Peer |
| SBC |
| Egress Peer |
G711U sendrecv | -> | <- | G711U sendrecv | |
G711U | <- | -> | G711U | |
Re-INVITE (G711U sendonly) | -> | Suppress the re-INVITE if minimize media is enabled and respond to ingress peer; else forward the re-INVITE to egress | <- | G711U sendonly |
G711U | <- | -> | G711U |
Conversely, SBC irrespective of the state of the Minimize Relaying Of Media Changes From Other Call Leg flag, cannot suppress a change of data-path-mode from sendonly to sendrecv.
Ingress Peer |
| SBC |
| Egress Peer |
G711U sendonly | -> | -> | G711U sendonly | |
G711U | <- | <- | G711U | |
Re-INVITE (G711U sendrecv) | -> | -> | G711U sendrecv | |
G711U | <- | <- | G711U |
Example1:
When Minimize Relaying Of Media Changes From Other Call Leg
flag is enabled, and when Relay Data Path Mode Change From Other Call Leg
is disabled:
Ingress Peer |
| SBC |
| Egress Peer | |||
G711U,G729A sendrecv | -> |
| -> | G711U,G729A sendrecv | |||
G711U | <- |
| <- | G711U | |||
Re-INVITE (G711U sendonly) | -> | Suppress the re-INVITE and respond to ingress peer. Discard media received from the egress peer |
|
| |||
G711U | <- |
|
|
|
Example2:
When the Minimize Relaying Of Media Changes From Other Call Leg
flag is enabled, and when Relay Data Path Mode Change From Other Call Leg
is enabled:
Ingress Peer |
| SBC |
| Egress Peer |
G711U,G729A sendrecv | -> | -> | G711U,G729A sendrecv | |
G711U | <- | <- | G711U | |
Re-INVITE (G711U sendonly) | -> | -> | G711U sendonly | |
G711U | <- | <- | G711U |