Do you tag inbound RTP traffic for voip?

[zackburf]

Im sorry if this is dumb question but still learning all the voip ins and outs.  We are having some issues with the sound on our outbound calls being choppy.  The receiver has no issues hearing us though.  I pulled a wireshark capture and all the outbound streams are tagged correctly but the inbound streams are tagged at AF11.

My question is do I need to set up a map to tag that inbound traffic? I thought the sender was supposed to be tagging it on their end.

Thank you.

[wintermute000]

In a L3VPN or any kind of WAN that is QoS enabled and where you have control at both ends, yes that's correct. You tag outbound and the carrier honors the markings. You need to coordinate so the queues line up, no point you outputting with a 20% priority queue but the carrier is set to 10% for example.

Internet well anything goes, its best efforts, but think about it: how is tagging it inbound going to help anything? its already arrived late.

[icecream-guy]

There is a saying something like "Never trust a tag, Always re-tag" This is due to one never knowing the QoS policy for anothers tagging.  Always mark the tags to conform with _YOUR_ QoS policy, so you know how things are marked,  even if something is coming tagged AF11, and you are going to tag it at AF11, retag it, JIC so something unexpected comes through the door, You will be 100% compliance with your QoS Policy, Also tag at all the perimeters of your QoS Domain.
   

[wintermute000]

If the carrier is stripping/not honouring your markings then they're not performing QoS properly are they? So its moot.


Moreover, by the time the packet has arrived for you to tag incoming, how is the re-tagging going to affect the behaviour its already seen on the way in? It can't fix 'upstream' congestion or incorrect queuing because its already happened.

You can re-tag sure but its not standard practice, refer to any Cisco Validated Design or any exam question in the design syllabus :p

Re-tagging incurs a configuration sanity / maintenance overhead, CPU impact yes minimal but operations overhead all adds up IMO