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QoS for VoIP for Site to Site IPsec VPN with Pix 515 7.0

I have 2 sites setup with IPsec vpn between then. They are at 7.0 on the pix. How do I go about setting up the QoS for Voice between the 2 sites. Would I also have to set up QoS on the screening router??


Re: QoS for VoIP for Site to Site IPsec VPN with Pix 515 7.0

Hi ,

Pls do let us know is your Voice application working fine with Ipsec bcos a real time application getting encrypted and getting decrypted will have performance issues and doing QOS is not going to help you out.

Pls share the same.


vanesh k

Re: QoS for VoIP for Site to Site IPsec VPN with Pix 515 7.0


QoS is - among other things - used to sort out overload conditions. So every device will need QoS configuration if an interface can potentially be overloaded.

VoIP over IPSec can work given that the voice requirements/recommendations are met: less than 150 ms one-way delay, less than 30 ms jitter, less than 1% packet drop (ITU G.114 standard).

IPSec standard mandates, that the DSCP values from the original IP header are copied to the new IPSec header. Thus an intermediate router can implement QOS based on DSCP values, IF the markings are set properly before encryption. VoIP phones usually do this for voip traffic.

On the intermediate routers LLQ with properly set priority bandwidth to support all your voip calls would be advisable.

Regards, Martin

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