[FROG] OSPF Fast Convergence (RFC6976)?

Timo Schöler timo at kroenchenstadt.de
Wed Aug 15 05:18:10 EDT 2018


On 08/14/2018 02:34 PM, James Bensley wrote:
> On 14 August 2018 at 12:56, Timo Schöler <timo at kroenchenstadt.de> wrote:
>> Hi all,
>>
>> I came across
>>
>> ``Framework for Loop-Free Convergence – Using the Ordered Forwarding
>> Information Base (oFIB) Approach'' [0]
>>
>> which may be a phantastic remedy to a problem that occurs from time to
>> time in a network I maintain: Even restarting a single OSPF process (on
>> a group of about 20 routers in that area) causes trouble in
>> forwarding/routing of 60.000+ TCP streams that traverse that area.
>>
>> (EIGRP is said to be immune against that because of explicit termination
>> of the diffusing computations.)
>>
>> AFAICS it's not implemented yet in any free routing suite – are there
>> any plans of doing so (in FRR)?
>>
>> Best regards,
>>
>> Timo
>>
>> [0] – https://tools.ietf.org/html/rfc6976
> 
> Hi Timo,
> 
> Have you seen this darft?
> 
> https://tools.ietf.org/html/draft-ietf-rtgwg-backoff-algo-10

Hi James,

no, I hadn't seen it yet. Sounds like a more reasonable technique than
from the RFC I referenced.

@Donald: Maybe you want to modify it appropriately on
https://github.com/FRRouting/frr/wiki/Feature-Requests ?

> It discusses a simpler method to achieve similar results. RFC6979
> isn't implemented anywhere as far as I know, even by Cisco for example
> who co-wrote that RFC. I think in reality it wasn't the best approach.
> 
> If you use a heirarchical FIB then after detecting a failure the
> traffic loss from reconvergence alone can be as low as a few
> milliseconds.
>
> Cheers,
> James.
Best,

Timo



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