[c-nsp] Difference between ISIS NSR and ISIS NSF Cisco-Style

[Oliver Boehmer (oboehmer)]

>I would like to know the difference between actuall ISIS NSR and ISIS NSF
>cisco style.
> 
>Most documentation says they are same , however thereare some differences
>also and it's not real  NSR. Also i have seen in some packet sniffer in
>cisco style cisco router sends a dummy special CSNP packet to neighbour
>to get all the valid LSP's in database.
> 
>Will NSR also depends upon some refresh information from Neighbours ??

Which ISIS NSR implementation are you referring to?

I am asking as folks actually call "isis nsf cisco" "Non-Stop Routing".
There is a point as this NSF/GR implementation indeed does not require any
special help of the neighbours (the special CSNP packet triggering the
neighbours to send all their LSPs is just regular ISIS protocol
mechanism), unlike BGP GR or OSPF GR which requires protocol extensions.
So it is likely an academic discussion if "nsf cisco" is a creative GR or
an NSR implementation. From a design standpoint, "nsf cisco" does not
require any new function/config on the neighbors, so there is no
difference. That's at least how I look at it.

a "real" ISIS NSR implementation would require to sync the complete LSP
database between active and standby RP, not only the adjacency table which
is synced with "nsf cisco". But what would be the benefit to your
network/services/design over "nsf cisco"?

	oli