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.
Default behavior is to send Modify Offer; to suppress, the Minimize Relaying Of Media Changes From Other Call Leg flag should be enabled

->

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.
Default behavior is to send Modify Offer; the Minimize Relaying Of Media Changes From Other Call Leg flag cannot suppress this Modify Offer as a common codec in the original offer and answer (G729A) has been removed; To suppress this re-INVITE, enable DML

->

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.
Default behavior is to send Modify Offer to lockdown to G729A; the Minimize Relaying Of Media Changes From Other Call Leg flag cannot suppress this Modify Offer as a common codec in the original offer and answer (G726) has been removed; To suppress this re-INVITE, enable DML

->

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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