Throughput

[newIntern]

Hello,

I have an internet of 400 Mbps to my ISP, but the router that receives the signal from the ISP despite having 1G ports, has a throughput of 250 Mbps. Does this mean that my internet connection will be limited to 250 Mbps?

Thank you.

[marce1000]

 - Depends on what your router model is , which you don't mention , some models require additional license for higher throughput.

 M.

[newIntern]

Hello, 

Thanks for your repply.

For instance, this one from cisco: C931-4P.

Thanks. 

[marce1000]

 - Scrutinize the datasheet(s) for your device  , look for items related to your question :

            https://www.cisco.com/c/en/us/products/collateral/routers/900-series-integrated-services-routers-isr/datasheet-c78-741615.html

 M.

[newIntern]

I had already read this document and seen all the equipment specifications. Therefore, I resorted to the most knowledgeable in the meteria (you) to understand these small aspects.

It is clear then that the actual speed is defined by the throughput, right?

[Jon Marshall]

Yes basically. 

Jon

[newIntern]

So the question is:

Why would they make a router with 1G ports but with a throughput that low ?

[Jon Marshall]

Because if the device can do more than 100Mbps then you have to use 1Gbps interface ie. there is no interface between 100Mbps and 1Gbps. 

Jon

[newIntern]

Ok.

Thanks.

[marce1000 · Accepted solution]

 - (Also) I found : https://www.ciscolive.com/c/dam/r/ciscolive/us/docs/2019/pdf/BRKARC-3001.pdf   , search for Cisco 900 Series Integrated Services Routers (with find in Browser) at right of circle you  see 'High Performance' (which I just nearly  wrote as 'Sigh Performance' (LOL)) , you will read ..Up to 250 Mbps VPN throughput

 M.

[Joseph W. Doherty]

"I have an internet of 400 Mbps to my ISP, but the router that receives the signal from the ISP despite having 1G ports, has a throughput of 250 Mbps. Does this mean that my internet connection will be limited to 250 Mbps?"

You're looking at three different issues, all of which can impact your effective throughput.

First, if you physical hand-off (i.e. interface "speed") is gig, frames are always (again always) transmitted and received at 1 Gbps, as that's the media specification.

Second, if your ISP restricts you to 400 Mbps, that means, over some time period, your ISP is "counting" your actual usage, and if, over that time period you start to exceed what would be the 40% of link capacity, the ISP will shape or police your excess usage.  I.e. effectively, you cannot use more than what a 400 Mbps link would provide, although, again, this is a counted usage over some time period.  Also, your ISP might impose different limits on "up" vs. "down".

Lastly, if your router has a licensed limit of 250 Mbps, it works much as just described for ISP bandwidth limits.  But routers have their own capacity limits, as to how many packets per second (PPS) they can process.  Almost always, smaller packets result in a lower bandwidth throughput capacity then larger packets.  (I.e. PPS is more [but not totally] dependent on fixed time per packet, rather than packet's size.)  Processing time per packet also is much impacted by what needs to be done beyond just routing the packet, i.e. QoS, NAT, encryption, etc.  (More things to do, usually results in a lower PPS, as it take more time to process each packet.)  If your router's throughput is not limited by license, effective throughput very much depends on your traffic mix and your router's configuration.

In other words, if your router is "rated" as 250 Mbps capable (again, not a license limit), the 250 Mbps might be the best possible case, but often cannot be achieved in the "real world".  Whatever, your router's performance limit is (which can change moment-by-moment, as traffic mix does), you'll be limited by that too.

Your overall, effective bandwidth capacity, will be the least value for all the above.