Mlitka,
I have included the only official CISCO comment on your topic. But have also included some comments to help you.
The problem with using 50% average utilization is that depending on the traffic pattern you may be setting a standard that would flood your circuit. Example: You have a regular user base - 9am-5pm M-F but a 24 hour network. Are you capturing traffic 24 hours or during the prime busy hours? Do you include Saturday and Sunday? If you are - the majority of your traffic could be minimal. Are you including failover? Can you re-route traffic in case of circuit failure?
My network has a blend of circuits types with and without resiliency. For some I use a simple failover calculation. For others, we use 70% - 95th percentile utilization for prime busy hour/busy day traffic.
The following is an excerpt from the following URL:
https://www.cisco.com/c/en/us/products/collateral/routers/wan-automation-engine/white_paper_c11-728551.html?dtid=osscdc000283
"The simplest core capacity planning processes use passive measurements of core link utilization statistics and apply rules of thumb, such as upgrading links when they reach 50 percent average utilization, or some other general utilization target. The aim of such simple processes is to attempt to ensure that the core links are always significantly overprovisioned relative to the offered average load, on the assumption that this will ensure that they are also sufficiently overprovisioned relative to the peak load, that congestion will not occur, and hence that the SLA requirements will be met.
@mlitka wrote:
Can any one point me in to some documentation regarding best practices for determining when to upgrade bandwidth on a circuit?
I realize this can vary due to the applications in use, etc.
I would like to use our average circuit utilization graphs as a starting point to make this decision.
Is there a rule of thumb, say 50% average utilization, that should be used to determine when more
bandwidth is required?
