[Spread-users] changing TTL to use IP multicast in WAN

Stanisław Trytek tryteks at pit.edu.pl
Fri Jun 23 02:34:30 EDT 2006

As far as I am concerned publicly accesible version of spread uses  
modified Ring protocol in WAN
with one difference: instead of broadcast/multicast it uses point to point  
udp protocol.
It differs a lot from HOP described in article "A Low Latency, Loss  
Tolerant Architecture and Protocol for Wide Area Group Communcation "
There are no such wonderful mechanizms as in HOP.  Thus each daemon sends  
message to all daemons.
Simply, the problem is with scalability. Number of messages sent by each  
daemon is n*(m-1) where m is number of daemons.
Having totally 10 daemons and one (or more) daemon working on lower  
channel can be real problem.

Hopefully I am using spread in wide area network where it is possible to  
use IP-Multicast.
I have changed TTL option (and timeouts of course) and treat all deameons  
as they work in one segment (in configuration file they all are in one  
It seems to work fine. The problem I have is same race conditions, the  
token somehow overtakes messages and I causes retransmissions.
But hope it is the issue of proper configuration of routers.

Have someone experience with such aproach? Are there any disadventages or  

Stanisław Trytek

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