[xcp] Embedding XCP signalling in IP header

[Tim Shepard]

> Of course we should. But we should also not ignore that IPv4 is here to stay, 
> and that the lack of compatibility with current IPv4/TCP stacks equals the 
> inability to interact with any of the existing systems / applications. If we 
> could gain that compatibility, XCP would certainly see a much faster path for 
> wide deployment and acceptance. That's what my proposal was all about...


I don't see how your proposal is better than putting the XCP header
between the IPv4 header and the TCP header.

In either case, there must be a mechanism that lets each end determine
if the other end can switch in to our new special XCP mode (an extra
header or your re-use of IPv4 fragmentation-related fields).  Once
you've determined that the other end can handle XCP packets, then it
hardly matters which method is used to carry the XCP information.

In what way is an XCP header between the IPv4 header and the TCP
header incompatible with todays stacks that your proposal is not?


			-Tim Shepard
			 shep at alum.mit.edu