07-19-2006 06:05 AM - edited 03-13-2019 02:14 PM
I have a customer with central site and branch sites, all PSTN traffic goes out via the central site over WAN (MPLS). They are expereincing some quality issues, it appears that the traffic from remote site to HQ is marked fine and LLQ works, however the traffic back is not. How do I ensure that traffic from PSTN gets marked properly? Using MGCP GW.
CHris
07-19-2006 08:07 AM
you should be able to setup an outbound interface policy (via mqc) on the pstn gateway at the central site. remember to nest a child policy into a parent policy... so ALL traffic is shaped, and mgcp traffic
is let out first! (This assumes the bandwidth between the central site and the far site is 768000, customize for you needs)
!wan router at main
!
class-map match-all mgcp
match protocol mgcp
!
!
policy-map voip-prioritize
class mgcp
priority percent 30
class class-default
fair-queue
policy-map voip-prioritize-parent
class class-default
shape average 768000
service-policy voip-prioritize
!
int f0/0
desc facing pstn gateway internally
ip nbar protocol-discovery
!
int s0/0
desc interface towards remote site/Call Manager
ip nbar protocol-discovery
service-policy output voip-prioritize-parent
07-19-2006 08:15 AM
I have LLQ configured properly what I am referring to is to actually mark the RTP traffic accordingly, does CCM take care of it using it's default DSCP setting EF- for RTP, CS3 for SCCP?
Chris
07-19-2006 08:36 AM
Chris,
The RTP stream is between the remote ip phone and central PSTN gateway. So you need to trust the dscp that PSTN gateway marks RTP packets with on the switch port. Map the cos values to internal DSCP properly and on the egress port that your wan gateway is connected, you can enable wrr-queueing (or srr) with priority queue enabled on that port. LLQ should take care of the wan (which you have properly configured).
For marking mgcp control packets with right qos, (control) you need
mgcp ip qos dscp cs3 signalling. (not af31, since your callmanager is possibly 4.1)
I would create a service policy to mark all rtp packets on the Fast E interface of the PSTN switch.
class-map VoiceB
match ip rtp 16384 16383
policy-map MarkRTP
class VoiceB
set ip dscp ef
int fa0/0
service-policy output MarkRTP
On the ingress port on the switch, where the PSTN gateway is connected,
assuming commands are for a 3550:
mls qos
mls qos cos-map 0 8 16 24 34 46 48 56
int fa0/1
switchport mode dynamic desirable
switchport access vlan 20 (this is your voice vlan)
spanning-tree portfast
wrr-queue cos-map 4 5
wrr-queue cos-map 3 3 6 7
wrr-queue cos-map 1 0 1 2 4
priority-queue out
mls qos trust dscp --- trust dscp from the PSTN gateway
On the egress port that goes into the WAN gateway:
int fa0/24
switchport mode dynamic desirable
switchport access vlan 200 (this is your vlan for wan gateway)
spanning-tree portfast
wrr-queue cos-map 4 5
wrr-queue cos-map 3 3 6 7
wrr-queue cos-map 1 0 1 2 4
priority-queue out -- priority queues RTP traffic
mls qos trust dscp --- trust dscp from the packets coming in from WAN
Depending on your switches, WRR may change to SRR.
HTH
Sankar.
07-19-2006 12:45 PM
Chris,
Btw, you with Meridian IT Chicago?
07-19-2006 02:54 PM
I am, I've been with them for about 5 months now. Why do you ask?
Chris
07-19-2006 04:30 PM
Have a colleague who used to work there and moved to TX few months back..we were talking about Meridian IT over lunch and when I came back i noticed you were working for the same..
Let me know if the qos settings i posted above helps..
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