FlowControl on 5400zl (or any other ProCurve)

[BOVC]

Hi,

I was wondering why flow control is disabled by default on the procurve switches?

What are the general recommendations and why?

Thanks in advance,
Rasmus

[Sergej Gurenko]

In Cisco switches in some situations (and releases) Flow Control conflicts with QoS. May be the same situation here?

[Matt Hobbs · Accepted solution]

I think flow control is disabled by default due to the design of the packet buffers in most new switches these days.

There is some great reading on google groups on the pros and cons of flow control (802.3x).

It's been mentioned that flow control can interfere with the flow control mechanisms built into TCP.

It can also cause more problems with congestion as if one switch has to start buffering, it will start sending pause frames to the next device, and so on.

Read any posts you can find by Rich Seifert, he seems to be an expert on the subject. I love this quote of his: "802.3x reminds me of my former marriage--at the time, they both seemed like
good ideas. However, in retrospect, neither made a lot of sense."

He has a highly recommended book which I think I'm going to have to order now.. 'The Switch Book: The Complete Guide to LAN Switching Technology'. Chapter 8 pays attention to flow control.

http://www.amazon.com/gp/product/0471345865/104-2640364-6444733?n=283155