how the computer detect connection speed end-to-end

[mohammed hashim]

hi,

when you have to computers want to communicate over the network like:

HostA-----------R1----------R2-------10Mb---------R3--------------R4-------------HostB

so the bottleneck of this connection is 10Mbps,

how these Hosts can detect the bottleneck before they start sending traffic !?

[Philip D'Ath]

Before sending any traffic - they can't.

[mohammed hashim]

how then they realize it after sending !?

[Philip D'Ath]

They could generate synthetic traffic to measure it.

They could just send traffic normally, and if they exceed the link capacity wait for packets to be dropped, and back off, like normal TCP.

If the routers supported it, they could also use explicit congestion notification.
https://en.wikipedia.org/wiki/Explicit_Congestion_Notification

If they needed guaranteed bandwidth and the network was configured for it they could also try using RSVP.
http://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcfrsvp.html

[mohammed hashim]

thanks a lot,

I will check these links