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New Member

LinkState convergence times

I am trying to decide based on calculations which routing protocol has better convergence time: OSPF or ISIS.

Assuming routers are in INIT state and going through all stages until FULL in OSPF or reaching the decision phase in ISIS.

When neutralizing all the non-routing process factors (network size, CPU, memory, link delay, etc’) I guess this would have to take into consideration the hello times, the updating process timers, SPF & PRC timers, size and structure of packets in LSDB an so on.

I would appreciate more in depth information on this issue, like: formulas, recent papers published on this issue, other aspect to take into consideration.

I know this is a wide issue, and out of the scope of this group but still, looking for leads.

Thanks in advance, Yaron

VIP Purple

Re: LinkState convergence times

Hello Yaron,

admittedly, my experience with ISIS is purely related to the (preparation for the) CCIE exam.

But maybe you find these documents useful:

Intermediate System-to-Intermediate System Protocol

Cisco NSF and Timer Manipulation for Fast Convergence

OSPF Design Guide



New Member

Re: LinkState convergence times

Hi GP,

Thanks for your response, but I am looking into more in depth information, rather than high level documents (though the NSF doc is very interesting).

I would appreciate the forum help on this.