Being in SP field I sometimes hear folks say "we do not need QoS, just let's make sure we have enough bandwidth". This has always been bothering me, because currently we have a network without any QoS in the core and there are no problems with services (Internet, IPTV, VPN).
The core links (bundled 10Gs) are utilized in 50%-70% at peak time.
Correct me if I'm wrong, but I think that we are just lucky enough to carry traffic that is not that bursty to fill up the links.
My understanding is that because of bursty nature of IP traffic QoS should be implemented on core links regardless of their utilization, or in the worst case, when the utilization reaches 50%.
Thanks for your comments. Actually my primary concern are microbursts. I understand the result of a microburst as a packet drop which occur when there is no noticeable congestion on an interface. I also understand that microbursts happen in every packet network.
I was curious if there is any "magic" link utilization percentage below which microbursts are harmless? (and we should be safe without QoS). I think I saw 50% as a best practice in some QoS book, but I don't remember the details.