[Spread-users] What is the difference between u-, s- and b-retrans?

John Lane Schultz jschultz at spreadconcepts.com
Wed Jun 13 12:44:31 EDT 2007

Jonathan, Yair, please correct me if any of the following is not accurate.

Retransmission requests are put onto the token by daemons that notice message 
holes.  When a retransmitting daemon fulfills the request, it removes the 
requests for that message from the token before passing the token.

u-retrans stands for unicast retransmission.  They occur when a retransmitting 
daemon sees only a single daemon requesting retransmission of the message on the 

s-retrans stands for segment (LAN) retransmission.  They occur when a 
retransmitting daemon sees multiple daemons within its segment requesting 
retransmission for the same message on the token.

b-retrans stands for broadcast (system wide) retransmission.  They occur 
whenever the two above cases do not hold for a message.

The fact that you are seeing s-retrans go up probably implies that you have some 
kind of network fault with that sender.  It could be that the sender's NIC is 
faulty.  It could be that the switch or router isn't doing a good job of 
multi/broadcast within that segment.

Good luck!

Doug Palmer wrote:
> This is a follow up to
> http://commedia.cnds.jhu.edu/pipermail/spread-users/2007-May/003340.html
> We've been seeing certain combinations of sender-receiver pairs where
> s-retransmissions start going up. However, we don't have enough
> knowledge to be able to interpret what we're seeing. Is there any
> information on what the various sorts of retransmissions mean?
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> Spread-users mailing list
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John Schultz
Spread Concepts LLC
Phn: 443 838 2200
Fax: 301 560 8875

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