Asterisk ToS (DSCP) And Public Internet

I have a very general question which I am hoping someone can shed some light on. I am really wondering if what I am seeing is normal, or if there is misconfigured hardware somewhere.

I have 2 asterisk servers connected over public internet connections. Multiple carriers in the route between the two. I have both servers configured with


I have done some tcpdump captures and am seeing both asterisk servers sending the IP packets with the approriate DSCP tag. I am also seeing the receiving end with either the QoS headers removed OR modified to a different value.

Is this normal when traversing the public internet? I haven’t done a lot of tcpdumps like this, so I don’t have much to compare to.


Yes this is normal.

Your ISP will not honor any IP DSCP or TOS modifications you make.

the only way to do QoS is on Outbound traffic at your own CPE. This will at least prioritise your outbound Voip as you do not have much control over your inbound and inbound bandwidth is normally higher.

You may find some ISP’s will honor your QoS settings at the other end but they are normally a pay for service.