[HECnet] Phase V Routing Specification

[Paul_Koning at Dell.com]

On Dec 18, 2012, at 5:07 PM, Rob Jarratt wrote:


http://bitsavers.trailing-edge.com/pdf/dec/decnet/EK-DNAPV-
GD_DECnet_Phase_V_General_Description_Sep87.pdf


Thanks for the link. I had a quick look. It does not go into the details of
the message formats, but it does say it interoperates with Phase IV, so I
just wonder if it was sufficient for me to accept Phase V messages as if
they were Phase IV and just ignore the version bytes. I might just give that
a quick go, which host is Phase V on HECnet now?

The way to interoperate with a version newer than what you implement is to speak the protocol as you know it.   That includes ignoring fields you're supposed to ignore, and messages for protocols (such as Ethertypes or 802.2 DSAPs) you don't implement.   If you do that, the rest is up to the newer version.

In the case of DECnet Phase V, that's essentially the OSI protocols -- such as OSI ES-IS and IS-IS.   Those run over 802.2 LLC type 1, DSAP address 0xFE.   So those packets are completely invisible to a Phase IV implementation.   What the DECnet Phase V node does is also listen to the Phase IV protocol (Ethertype 60-03); if it sees those, it records the sender as a Phase IV neighbor and sends whatever it has to say to such neighbors using Phase IV packets.

	paul