Call Flow Examples
Call Flow Examples for 'Disable Media Lockdown' Flag
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).
The codecs configured at Egress route PSP are G711U, G726, G729A with HRP disabled.
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 |
Call Flow Examples for 'Minimize relaying of Media Changes From Other Call Leg All' Flag
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 |
Call Flow Examples for 'Relay Data Path Mode Change From Other Call Leg' Flag
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 |
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