Subject: Re: where is ifp->if_baudrate used?
To: David Young <>
From: Jason Thorpe <>
List: tech-net
Date: 03/19/2007 11:13:27
On Mar 18, 2007, at 3:41 AM, David Young wrote:

> I question whether any single rate suffices to describe many links.
> Consider that commonplace link technologies use multirate PHYs (56k
> modems, WLAN, powerline).  Also, a single ethernet/WLAN/powerline link
> may connect multiple stations.  The NIC may use a different rate to
> transmit to each station.  How can a single rate characterize such a  
> link?

The intent would be to update the value with the current rate being  
used by the link.

> Now, suppose we treat ifi_baudrate as a maximum PHY bit rate.  I feel
> dissatisfied comparing a 108 Mb/s WiFi link with a 100 Mb/s ethernet  
> link
> by their ifi_baudrate, if the former ifi_baudrate is set to 108 *  
> 10^6,
> and the latter to 100 * 10^6.  To make an "apples with apples"  
> comparison
> of the two links, I need more information than the ifi_baudrate.
> A slightly more practical measure of link speed tells how many
> ifi_mtu-sized link-layer payloads you can send using the top PHY  
> bitrate,
> figuring in all of the overheads; call this the "speed limit" on the  
> link.
> Dave
> -- 
> David Young             OJC Technologies
>      Urbana, IL * (217) 278-3933

-- thorpej