DL10 documentation

Paul Koning paulkoning at comcast.net
Thu Jan 11 12:11:35 CST 2018

> On Jan 11, 2018, at 9:47 AM, Noel Chiappa via cctalk <cctalk at classiccmp.org> wrote:
> ...
> Like I said, we did 'borrow' some idea from IS-IS, in particular the sequence
> number thing - but that may have come direct from Radia's paper:
>  Radia Perlman, "Fault-Tolerant Broadcast of Routing Information", Computer
>    Networks, Dec. 1983

Yes, that documents work she did at DEC early on, while developing the original link state routing proposal that was intended to be Phase IV but was set aside as "too complicated".

> I don't recall where the concept of a designated router stuff came from, if
> IS-IS was any influence there or not.

Designated router was part of DECnet Phase IV, so early 1980s.  OSPF does it in a fundamentally different way: DECnet aimed to be deterministic, OSPF aims to be stable.  The consequence is that in DECnet a given topology always has the same designated router no matter the sequence in which things came together, while in OSPF the designated router depends the order in which things happened.  There are arguments for either approach; in routers it doesn't matter much.


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