QOS and TCP over UDP.

I know this is a touchy subject, but I am working on a remote presence robotic project and am currently investigating different methods of handling packet priority scheduling.

Just like SL, I need both fast response messages for movement controls and slower reliable data transfers. I am also using the science museums Internet connection for this project and I must limit my peak bandwidth.

Option A.
Implement a complete TCP over UDP by modifying a copy of the Linux TCP/IP stack so that the "raw write" is redirected into the real TCP/IP system as a UDP packet with an extra header. (I am ok with the GPL license)

Pros:
1. I can pre-resend duplicate UDP packets as needed to increase chances of delivery.
2. I can shorten the time-out delay.
3. I can control end to end bandwidth.
4. OS independent.
5. Does not require QOS support.
6. I can use the Skype technique to get threw firewalls on both sides.

Cons:
1. Non standard since the industry is moving towards IP V6
2. Time to write.

Option B.
QOS, TCP/IP V6, and uPNP

Pros:
1. Standard

Cons:
2. Not supported in all locations or enabled on all computers.

Please let's just discuss the topic from a abstract ideal point of view and not get into the current SL implementation.

PS:
This is relevant to SL since LL is moving towards transporting all textures over TCP instead of its custom protocol and yet I have not heard anything about how they are going to handle QOS (Quality of service)

Since the SL client is getting data from other sources it is probably better for LL to move to a standard QOS system, but I have not heard anything about what we will need to support QOS.

SL will get a lot more laggy in terms of movement responses if they complete the conversion to TCP without dealing with this issue.