>> 3) If you write an application using anything other than UDP or TCP, >> it won't work on most networks (with some minor exceptions for PPTP >> and IPSEC, which work sometimes). > > This hasn't been my experience unless you're behind some form of NAT. > Yes, it is well known that NAT breaks most protocols.
I've come across a non-zero number of "residential" providers, who, with or without NAT, explicitly discard protocols 50 and 51. The same argument is applied - if you want this, you must buy a "business" connection. Which is usually double-speak for "add an order of magnitude to the price, turn off *some* of the broken-ness". Regards, Tim.
