How to route Phase II

[Paul Koning]

Thanks to help from Timothe Litt, I have Phase II support, including just enough "intercept" support to be useable, working in my Python router (svn://akdesign.dyndns.org/pydecnet/trunk/pydecnet).  Tested it with a KS-10 TOPS-20 setup.  I had it do NFT from a DECnet/E system two hops away.  Worked correctly including the handling of the text (ASCII) data.

It doesn't do all that is required for intercept nodes -- tracking NSP connections so it can disconnect them if the path goes away.  Also, Phase II NSP does not do packet timeout and retransmit, so if a packet is lost on the path to the destination, the connection is wedged.  I may end up doing a bit more than standard intercept operation and do timeout/retransmit on behalf of the end system.  That's cheating, of course, but why not?

Anyway, this may help those who have Phase II systems.  Comments and feedback and bug reports appreciated.

	paul