[Spread-users] is sprecv generating an incorrect report?

John Schultz jschultz at spreadconcepts.com
Thu Mar 13 16:16:39 EDT 2008

Spread does handle out of order packets.  spsend + sprecv only use the 
data link layer of Spread and their heuristic for handling/reporting 
out-of-order packets is not great.  spsend + sprecv essentially assume 
FIFO in-order delivery of packets.  Spread does not.

However, out-of-order packets can sometimes cause Spread to request 
retransmissions.  In particular, when a daemon gets the control token if 
it perceives it has holes (e.g. - due to packets being delivered 
out-of-order), then it will request retransmission on the token.  So, 
there is something of race going on -- will the missed packets show up 
before the token or not?  If they do, then Spread will not request 
retransmission, if they don't then it will request retransmission.

Debug version of Spread should be fine.

Daemons communicate across segments using point-to-point UDP.  Depending 
on the type of communication it may communicate directly with its target 
daemon or it may communicate with the segment leader (system-wide or 
segment broadcast) who will then pass it on to its segment.


John Schultz
Spread Concepts
Phn: 443 838 2200

On Thu, 13 Mar 2008, chanh hua wrote:

> John, does spread handle out of order packets or does it treat them as drops causing retrans?
> for testing, i'm using iperf (http://dast.nlanr.net/Projects/Iperf/)
> i'm running the debug build for spread, this shouldn't cause any issue, correct?
> how does daemons communicate across segments?  does it still use udp?
> thanks

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