All things related to multicast

[Marshall Eubanks <>]

Jon Dugan wrote:
> 
> On Thu, Jan 18, 2001 at 02:47:39PM +1100, Markus Buchhorn wrote:
> > At 21:25 17/01/01 -0600, Tony Rimovsky wrote:
> > >Does anyone have advice on a good rate limit value?  Some earlier mail 
> > >from
> > >Matt indicated that 50k SA's in 5 minutes had caused a problem.
> > [...]
> > >two sources, I generated 510 SA's in about 3 seconds (sending from NCSA
> > >(AS1224) and visible at ACCESS-DC (AS 5640).  All the SA's made it to
> > >ACCESS-DC and as far as I can tell, that rate generated no problem for
> > >abilene.  I am obviously leery of pushing this experiment too far.
> >
> > Is it really the *rate* of SA's that is a problem? Or the total number of
> > SA's? The issue seemed to be cpuhogging when the routers had 50k SA state
> > to deal with under the pressure of a normal background multicast flow.
> > Would it perhaps be better to limit the size of the total SA state? I
> > wonder what would happen if the 50k SA state has been slowly built up 
> > (over
> > days, rather than minutes).
> 
>   Unfortunately we have to work with what we're given.  JUNOS (and IOS 
> AFAIK)
>   doesn't support limiting the number of SAs (or other MSDP state) at the
>   present time.  However, we can rate limit packets with that source or
>   destinate port.
> 
>   I think this is good enough for now, because the SAs are triggered by
>   traffic that looks like a new multicast source but doesn't stay around 
> very
>   long (one packet I think... I suppose I should go read the source...).
> 

Jon;

I suspect it was just one packet per group - they vanish quickly.

Just for the record

Al noticed this with the NLANR beacon - we were all red outbound.
Al then saw the MSDP SA announcements in the  7204 logs.
The SA state would vanish very quickly - and our router was OK - but it
looked like some other routers out there melted down.

Marshall

> Jon
> --
> Jon Dugan             |  Senior Network Engineer, NCSA Network Development
> 
>   |  57C CAB, 605 E Springfield, Champaign, IL 61820
> 217/244-7715          |  http://www.ncsa.uiuc.edu/people/jdugan

-- 


                                   Regards
                                   Marshall Eubanks

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