The dec and ieee spanning tree protocols are functionally the same,
but incompatible.
I don't have the packet formats from the dec spanning tree algorithm.
I assumed there are no devices talking the dec variant around any more.
The dec variant predated the ieee standard. The dec variant used
Ethernet envelopes rather than 802.2 envelope. Given that IEEE definitely
wouldn't standardize on something that didn't use 802.2 envelopes, dec
didn't make any attempt to get them to keep any of the rest of the packet
formats, since it would have to be incompatible with the deployed dec
bridges no matter what.
As I remember it, the timers in the dec dialect were in units of seconds,
and in ieee, in units of 256ths of seconds. And ieee added a "port priority"
field.
Just for curiosity (I seem to have jumped into the middle of a thread here),
why does anyone care about the original dec spanning tree? I didn't bother
writing it down for the book since I assumed (in 1992!) that it would
quickly become irrelevant, and the differences are not intellectually
interesting...just if you have to interwork. So are people trying to
interwork with 10 year old bridges?
Radia
