[aprssig] Periodic Disconnects from APRS-IS

AE5PL Lists HamLists at ametx.com
Thu Jan 18 06:04:59 CST 2007

Are you having an issue where you get disconnected from an APRS-IS
server periodically (sometimes as often as every minute)?  Are you
connecting to a full feed (port 23, 10151, 10152 on the core)?  Time to
update your server list and start connecting to a filtered port (14580 -
user defined, others may exist that are predefined, visit the web status
page of the server you are connecting to for more information on
available ports http://aprsserver:14501).

I just did a scan of the core server status pages and found over 10
clients with 5 to 15 seconds of packets backed up scheduled to go to the
client.  This is caused by the client not being able to handle the
packet flow from the server.  At 15 seconds of queued transmissions,
your client will be disconnected to prevent loops.  Most of the time,
this inability to handle the packet flow from the server is caused by
the client software not being able to keep up.

However, this could also be caused by a bottleneck enroute to or from
your client (remember that your client is generating an ack for every
packet if it has properly shut off the Nagel algorithm).  It may seem
like you have plenty of bandwidth, but the full feed _averages_ 25-30
packets per second which is significant for residential broadband and
very significant for dial-up.  It is also very significant for most
mapping clients to keep up with processing each station report.

If you are accessing a full feed from an APRS-IS server and having
problems staying connected, re-evaluate your need to connect to a full
feed.  Most people have found that connecting to a filtered feed makes
their PC and client much more responsive yet you still get full
messaging capabilities even if your client is an IGate.  If you have a
question about what kind of filters are available, check out

This is an informational post and in no way is meant to impugn anyone's
operation or configuration.


Pete Loveall AE5PL
pete at ae5pl.net

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