Subject: Re: where is ifp->if_baudrate used?
To: Jason Thorpe <>
From: Greg Troxel <>
List: tech-net
Date: 03/19/2007 14:35:43

Jason Thorpe <> writes:

> 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.

The problem is that because of per-recipient rate adapation, there is
in general no such rate.  David's point really is that there are
interfaces for which the "baud rate" (which I will interpret at bit
rate) abstraction is inadequate.

really more to dyoung now:

Given that, until the entire networking stack has some richer
abstraction (and doing this isn't clearly a good idea), it makes sense
for some value to be reported, using the "if I know the reader of this
value will be interpreting it like a single speed as if for an
Ethernet, what should I tell them" test.  So perhaps some long term
average of the rates used, derated by inter-packet gaps.  In IBSS or
AP mode, this is pretty tough.  In STA mode, one could simply use the
value used to send packets to the AP.

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