DSCP for Emergency calls

[mcgookin]

We have a network of 3300's with only one pair connected to the PSTN. Others are connected via Mitel IP networking (G711).

Is it possible to assign a different DSCP to specific users on the remote PBX's for inter-PBX/ PSTN calls so that their calls are never dropped when comms fail over to a low bandwidth secondary link?

I'm wondering if I could could set a different DSCP on the specific emergency phones (manually or using a different DHCP scope) so that priority users are DSCP 46/ EF and other users (and the main PBX for Vmail, etc), DSCP 41 (AF, high priority, low drop).

What I'm unsure of is if the 3300 will rewrite the DSCP code on the RTP packets- I'm struggling to remember if for inter-Mitel/ tandem calls the RTP path is just between the end points or transits the PBX.

We used to use COR to give access to a separate TDM trunk group straight into muxes but with only having the calls between two IP addresses it's harder to differentiate the call to Cisco QoS land...

Any thoughts?

Thanks!

Chris

 

[mcgookin]

Sorry, to follow up post myself but thinking more even if this worked one way if it's a PSTN call then the receive RTP I presume would get the marking that's on the transit 3300- not that of the sending IP phone...

 

[Lundah]

You can assign the DSCP either via DHCP or hard-code it into the network settings of the phone, but you also have to have the data network set up to trust the DSCP from the device rather than overwriting it based on VLAN membership.