RE: MOPO and the 'ping' probes

> On Tue, 2005-03-08 at 10:06, Timothy Liu wrote:
> > There is an approach base on same idea, I am not sure if 
> this has been 
> > brought up before. Why not send DPD with the same sequence number
> > (simultaneously?) to all the paths that the peer wants to 
> test? From 
> > the other side it can treat is as retransmission and resend the DPD 
> > response through the different paths. The retransmission 
> policy on the 
> > requester side is only to retry along the primary path.
> 
> yes, but you also need to handle the case when the sender 
> didn't have enough window for even one request because all 
> window slots were occupied by messages which hadn't gone 
> through because the preferred path was broken..

Agreed.

> 
> One solution would be to use a real request instead of a DPD 
> ping when you actually have something real to send.

That depends on what you define as being 'something real'.  Is a normal DPD
something real?

For example, I notice that some TCP sessions are starting to time out
because the peer isn't ack'ing my packets.  Therefore, I elect to send a DPD
message to check for liveliness.  I would think this would qualify as a
'real' message, but wanted to double-check that we are on the same page.

> 
> I'd think simultaneous probes would be considered unfriendly 
> to the network; non-simulataneous (delay of a large fraction 
> of the RTT or so between each probe) might be nearly as good 
> at finding a path without generating nearly as much redundant 
> traffic...
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