[c-nsp] Question about monitoring DSCP marking

[Nick Voth]

Hello folks,

Here's the situation. I have a number of customers who are using XO
Communications for T1 DIA access. These customers are also VoIP customers of
ours and their VoIP (SIP) traffic all aggregates through a session border
controller in our network. All inbound and outbound VoIP goes through these
session border controllers.

Their SIP traffic traverses the XO network and to a peering point with us.
We have set up QoS rules on the customer's CPE equipment, (Cisco 1800 series
routers), so that their outbound VoIP traffic is prioritized in to a
priority queue. That works fine.

XO has just released a product that will allow for priority queuing on the
network switch that is closest to the customer. It marks the traffic with
DSCP value of 46, (ef), and puts this designated traffic in a priority queue
pointing towards the end user. In theory, this should help prioritize the
VoIP traffic from both ends of the customer's T1.

Nice in concept, but here's the question. Without having direct packet
capture capabilities in a customer's network, is there any way in the Cisco
IOS to see if the incoming VoIP packets really do have the express
forwarding bit set?

On the outbound side from the customer that's easy, but I don't know how to
verify that XO is really doing what they say without actually seeing the
packets in something like Wireshark.

Thanks for any advice.

-Nick Voth