[Spread-users] Many packet retransmited in WAN

Stanisław Trytek tryteks at pit.edu.pl
Tue Jun 13 01:42:07 EDT 2006

Further to my earlier (not commented) questions I am specifying the  
problem more precisely (exactly, I am going to present results of two  

The issue:
Two demons are connected in WAN using channel (made up of two routers)  
with clockrate 19200kb/s.
The problem is that for example sending 2 packets per second (!) causes  
retransmissions number to increase enormously (there is no other traffic).

user A (name: stan1)  ->  node0070  <->  router A  <->  router B  <->   
lap0001  ->  user B

Test network as follows:

Spread_Segment {

Spread_Segment {

See attached logs for daemon A(master) and B.
User A sends 10  FIFO messages (1000 bytes) in one burst. Daemon A sends  
them all to daemon B of course. Interesting thing is
that the daemon B receives and delivers the first message and ask the  
daemon A to retransmit next 9 packets. Next, having again token, daemon B  
delivers the second message and asks about 8, and so on ... . It gives  
totally 54 retransmitted packets per 10 delivered in 10 token rounds.  
Delivering to user 10 messages lasts 5 seconds, but delivering  
retransmitted packets to daemon B lasts next 60 seconds and they all are  
being deleted due to they have already been delivered to user.

That test shows that spread is completely useless in WAN with analogues  
channels and/or channels with smaller capacity.

User A is sending 2 messages per second. At the beginning User B is  
receiving messages with delay that increases very fast. It is caused by
large number of retransmissions. Increasing number of retransmissions  
causes that router drops incomming packets what leads to more  
retransmissions. After some time the system is completely blocked and  
unable to deliver messages. Spread traffic is taking all of router  

To sum up sending 2 messages per second in 360 second (720 messages)  
causes about 50 000 retransmitions ( read from spmonitor ) !!!

My questions:

Why daemon B delivers only one message per token round? Is it desired  
Is it possible to force spread to deliver more than one message per token  

I would be grateful to people who use spread in WAN for any comments and  

Stanislaw Trytek
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