Flow control question

Flow control has two disadvantages

1. Congestion Spreading

2. External Head of Line Blocking

Network administrator use TCP retransmission as it allows utilization of the full network bandwidth.

I think, it is better to disable this feature and use TCP retransmission.

In case you need to enable Flow control, it must be configure at machine NIC and switch port used by the machine.

so in my environment I should disable flow control on all the switches and devies? I think the nic default setting are either auto or disabled (so if's auto, do I still need to change it to disabled?)

and where is "TCP retransmission"? I don't see this in my switch setting...

thanks, >>Whenever there is gigE involved,set everything to auto period.
I have all the switches set to AUTO for the speed, but for Flow control, there is only 2 options, either ON or OFF. So I should disable it in my mix environment right?

If I set flow control to disable on switch port, and the connected workstation set to enable, what's going to happen? the switch take precedence?

And for the speed, if I set it to AUTO on switch, but the workstation set to full duplex 100, will the switch use fd100 or it will become half duplex?

ok, so you are suggesting me to set all switches and NIC on each workstaions to AUTO and disable Flow control on both switches and NIC on each workstations.

I think you missed some of my questiosns above, can you still tell me what's goign to happen in the situation?

>>
If I set flow control to disable on switch port, and the connected workstation set to enable, what's going to happen? the switch take precedence?

And for the speed, if I set it to AUTO on switch, but the workstation set to full duplex 100, will the switch use fd100 or it will become half duplex?

auto used with  manual duplex fd will cause packet loss(collisions)

This is a bad thing.


http://en.wikipedia.org/wiki/Duplex_mismatch

ok, so basically you are saying they always have to be identical otherwise there will be problem right? ex: auto and auto, full duplex and full duplex, so on...

and how about flow control? same apply?

thanks. I checked all my switches, the flow control is set to disabled. But I see some hp windows 7 workstations have default flow control set to enabled (see the screenshot)
So should I go aroudn all workstations and make sure they are all set to disabled? will there be any issue if I leave it like this?

If it's not enabled on the switches,shouldn't be an issue.

so the flow control is not the same manner as duplex setting you are saying? so as long as the switch has it diabled, it will ignore the setting on workstation correct?

pgm554, may I ask you one more question? if the device connected to port 3 is generating excessice CRC/alignment error, will that impact the whole network? or just the performance between the device and its destination? I believe if it's generating broadcast error, then for sure it will impact the whole network... not sure in this case..

If this is a switch.that port is it's own collision domain,so all that should be affected is the connection between the two devices.

http://en.wikipedia.org/wiki/Collision_domain

But a CRC on a switch is not a good thing and needs to be looked at.

It's usually a duplex mismatch,but it could be cables too.