Re: [DNA] Definition of "Link Up" and "Link Down" events?

[Erik Nordmark <erik.nordmark@sun.com>]

Bound, Jim wrote:

> I agree in theory.  In practice I may implement to bring the link-down, if
> it is not my only link-access, as far as IP stack is concerned.  Reason is
> node/device may have multiple link-access mediums and this one is not
> performing.  I think we all understand where I am going. My reason for
> stating the obvious is does this context affect what we do within DNA?

I think what we are doing is coming up with definitions of the concepts 
of link up/down that are useful for DNA, and does not prevent things 
like "link quality" to be taken into account, especially for hosts with 
multiple interfaces.

It is probably the case that a host with multiple interfaces will work 
best if it takes into account a number of factors (from packet loss 
rates and bandwidth, to monetary cost for using a NIC and application 
requirements) when choosing which NIC to use (and for what application 
traffic). I also suspect that such strategies doesn't require that DNA 
stop considering an interface. For instance, if the stack+applications 
decide to use the GPRS interface for VoIP traffic, it is probably still 
useful to have DNA monitor the 802.11 interface to detect when the host 
gets back in range of the AP.

But that clearly shouldn't prevent implementations that just use simpler 
strategies such as "haven't heard from the AP in 30 seconds" to just 
abandon the use of the 802.11 interface.

I don't see the definitions that Bernard updates as restricting the 
implementation in any way; could be as simple or as complicated as it 
wants when handling multiple NICs.
If you think they are restricting the implementations then we should 
clarify the definitions further.

    Erik