Regarding STP

[ManojKumar37257]

Hi Team,

Can STP cause latency in the network ?  If yes , what can be the cause ?

[Seb Rupik]

Hi there,

The STP protocol is lightweight, so the traffic itself would not saturate a link.

When a topology reconverges and cycles through the STP states (depending on the STP version) it can cause connectivity issues. 

The only way for it to increase latency would be for it to reconverge in an inefficient state, caused by incorrect placement of a root bridge or incorrect costs applied to links causing slower links to be placed in a forwarding state.

cheers,

Seb.

[Sergiu.Daniluk]

Hi @ManojKumar37257 

Most of the times, latency is translated in:

+ big buffering times -> this usually means congestion

+ large processing times (firewall inspection, de-/encapsulations etc)

+ software forwarding vs hardware forwarding -> data plane traffic being handled by CPU instead of ASICs

+ time of the packet on the medium (e.g. optic fiber vs satellite)

If there is an instability/reconvergence issues in STP, you will see packet drops and communication being interrupted, due to interfaces going into blocking. There might be let's say TCNs being forwarded throughout the L2 domain, caused by a flapping non-edge port, and this would generate L2 traffic being flooded (plus other issues if you are having an ACI fabric).

Short summary, I do not think latency will be one of the symptoms you will be seeing when STP causes some problems. 

Or let's put it this way: if you experience issues with STP, you will have other problems to worry about other then latency.

Stay safe,

Sergiu