[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
segment).
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
threats?
Stanisław Trytek
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