BW CALCULATION OF ROUTER/SWITCH PORT

[er.vansh17091]

Hello Everyone,

In order to calculate the Bandwidth of the interface I want understand the role of following:-

(1) Tx/Rx load ?

(2) Input/output rates?

(3) Interface speed 1Gb

(4) Can we test the committed ISP 1 GB link on router with ping and MTU size load with multiple sessions?

I want to know that how port utilization is calculated on Router if we have below Tx and Rx Load. Can I combine both Tx and Rx percentile while calculate utilization.

Note :- We have 2gbps P2P link. below example calculated with 2 Gbps link.

Example :- Tx=185/255=  72.54% of the total bandwidth.

                  Rx=66/255= 25.88% of the total Bandwidth.

If we combine both then it will be 97% of the total bandwidth. 

Then what's the role of interface speed 1GB?

  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
    ????

BW 100000 Kbit, DLY 1000 usec
???

Full-duplex, 1000Mb/s
What could be the impact if we change 100 Kb?
and what's the role here while calculating the BW?

 I have gone through below article 

https://study-ccna.com/show-interfaces-status-command/

BUT MY QUESTION IS HERE HOW ALL ABOVE ARE LINKED WITH EACH OTHER WHILE CALCULATING THE BANDWIDTH?????????????

[Leo Laohoo]

Full-duplex, 1000Mb/s
What could be the impact if we change 100 Kb?

Nothing.  You'll get a syntax error. 

Copper link speed can only be set to 10-, 100-, 1000 Mbps.  
Optical transceivers have their speed and duplex hard-coded.  

The confusion you're having is the "bandwidth".  Bandwidth is entirely different and it comes into play when dealing with different routing protocols.  

Without using Google, I think one of the metrics for OSPF is "bandwidth" statement in the interface configuration.   Don't get confused with the link speed and the bandwidth statement.  

[er.vansh17091]

Hi Thank you for quick response

Can you please help me out with bandwidth calculation?

For both terms ?

Like input and output rate ?

TX/ RX load?

Above these when comes in the picture?

How can we calculate the BW in  other scenarios?

[Giuseppe Larosa]

Hello @er.vansh17091 ,

the bandwidth parameter is an administrative value that can be also configured, if not configured manually it is determined by the speed of the physical interface.

The bandwidth parameter is used by routing protocols like OSPF and EIGRP and by modular QoS to create a reference for QoS features like shapers, policers and schedulers (queueing).

The tx load and rx load are still present in the output of show interface but they are not used by any feature of today networking.

To be noted both the tx load and the rx load are expressed in fractions of 255 so 255/255 is 100% of usage.

It is not correct to sum them as you did in your first post in this thread.it would be more appropriate to make an average.

In the past when DDR Dial on Demand Routing was used over ISDN there was a feature called BOD Bandwith on Demand that was able to add an additional B channel ( 64bkps) to a PPP multilink if the usage of the single B  channel was greater then a configured threshold based on the tx load or both tx and rx load.

With the execption of Germany that has and had  flat fees in all other countries every call over iSDN was paid on time usage. So DDR was used as a backup route when the primary link had failed.

As far as I remember this was the only feature that actually used the tx/rx load on interfaces.

To be noted EiGRP is not able to follow dynamically the load of an interface even if it was declared to be able to do it.

Simply if EIGRP would be able to follow dynamically the load of interfaces when enabling the corresponding metric components it would lead to instable networks.

So look at TX /RX load just as indicators of the load, to be honest I look directly at packet rate and bit rate over the interface tx and rx in troubleshooting.

Hope to help

Giuseppe