Why change TTL:
You want to use ICS and your ISP is sending you packets with TTL=1
What can you do:
Clients can output packets with TTL= 129, this way your ISP want notice that packets hop through a desktop PC with enabled ICS. So on the client machines set:
HKEY_LOCAL_MACHINESystemCurrentControlSetServicesTcpipParameters
DefaulTTL = 129
I don’t see any point in enabling IPEnableRouter. I don’t fully understand what it does but if it will do routing we don’t need it. ICS takes care of everything.
Next thing we need is a way to change the incoming packets of the Desktop PC that shares connection. This is needed as when “routing” the packet to a client, it’ll decrease TTL and drop the packet if the “bad” ISP has sent a value of 1.
This can be made with a little changes to the PassThru example of the Framework. I think the link that SerpentFly provided is also a good example of packet modification in the tunnel.