CUCM 8.x VPN for IP Phones (Phone VPN) and ASA Priority Queueing

[calmichael]

For those that are piloting or have deployed CUCM 8.x (or higher) VPN for IP Phones (Phone VPN) feature, how did you set your priority queueing on the edge ASA?

Is looking for traffic marked with DSCP EF still the standard?

!

priority-queue outside
!

class-map priority_voicemedia
match dscp ef
!
policy-map voice_policy
class priority_voicemedia
  priority
!
service-policy voice_policy interface outside

!

Or even TCP/443 traffic due to Phone VPN?

!

priority-queue <outside interface name>
!

class-map priority_voicemedia
match port tcp eq 443

!
policy-map voice_policy
class priority_voicemedia
  priority
!
service-policy voice_policy interface outside

!

I ask as using EF traffic does not seem to be getting hits nor does using TCP:443.

post# show service-policy priority

Interface outside:
  Service-policy: voice_policy
    Class-map: priority_voicemedia
      Priority:
        Interface outside: aggregate drop 0, aggregate transmit 0
post#

What is the correct method?

Matching via RTP does work but it seems less exact.

!

priority-queue <outside interface name>
!

class-map priority_voicemedia
match rtp 16384 16383

!
policy-map voice_policy
class priority_voicemedia
  priority
!
service-policy voice_policy interface outside

!

post# show service-policy priority

Interface outside:
  Service-policy: voice_policy
    Class-map: priority_voicemedia
      Priority:
        Interface outside: aggregate drop 0, aggregate transmit 690
post#

Cheers

[paolo bevilacqua]

To be honest with you, I fail to see the point of configuring priority (or any other type) of queueing on an ASA.

The reason is that these are Ethernet interfaces like 100Mb/s or 1Gb/s, that never experience congestion, consequently priority queuing will never be triggered.

If you need QoS, you will have to configure it where congestion occours, not on the ASA.

[pheidema]

The reason you would want to setup priority queuing is because any packets in the Low-Latency Queue (LLQ) are serviced ahead of any packets in the Best-Effort Queue (BEQ).  This helps reduce delay of Real-time Transport Protocol (RTP) packets out of the interface.  This happens regardless of whether or not the interface is congested.   LLQ priority queuing was a new feature in ASA 7.x code.