fiberman - Thanks for asking your question on the forum!
You will need to set a traffic-shape rate to your WAN interface on the NetVanta so that when QoS makes its calculations as to its available bandwidth, it uses the traffic-shape rate as opposed to the negotiated speed between the Gig-e handoff and itself.
To set up a QoS map for this, you will need to create a map that matches your voice traffic, and then set the priority to be the 88Kbps you want to reserve for voice calls. The 'priority' keyword will allow that bandwidth to be used by other applications if it is not in use by the voice packets. You can use this guide to read more details regarding QoS: Configuring QoS in AOS You can find examples starting on page 41.
Regarding your question about rate-limiting affecting the download speed, it is possible. I would think you may run into this with TCP transmissions as TCP window scaling comes into play. However, with UDP transmisssions, I would expect the download speed would be as advertised.
Let us know if you have any further questions.
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