[j-nsp] Link aggregation and RSVP

[Phil Bedard]

On May 6, 2010, at 10:42 AM, Richard A Steenbergen wrote:
> 
> 
> One big problem with link agg is that Juniper has no way to adjust the
> RSVP bandwidth of a bundle based on the actual capacity, so for example
> if you have a 60G bundle and you lose a 10G member (or two) RSVP will
> continue trying to pump 60G into the bundle, with the expected Very Bad
> Things (tm) as a result. Of course, if you do lose a member during
> non-peak times the link-agg mechanisms do a much faster job of detecting
> and recovering from the issue than RSVP does, and you end up avoiding a 
> network-wide event with a lot of preemption and resignaling.    


It always adjusts the link agg RSVP interface bandwidth based on up member links unless you have it set statically.  You do run into a problem however if you do not have aggressive session preemption turned on since the RSVP interface will actually go into negative bandwidth but the lowest reservable bw value OSPF can advertise is 0.  So the sessions on the agg stay on the agg.  Aggressive preemption boots everything off in order of hold priority.  

Phil