Hi all,
I've recently deployed a gateway server to mediate communication between
clients and remote devices. The gateway works fine in a 'regular'
network, but now we're experiencing problems when the remote devices are
behind a GPRS network.
The gateway sends an application level (TCP) 'PING' message periodically
to the remote devices. For some reason the PING messages seem to queue
up in the GPRS connection, without the devices receiving them.
Meanwhile, sending an ICMP request to the same devices gives a much
smaller roundtrip time (~700ms) and no message losses. Also the messages
sent by the remote devices to the gateway always arrive properly.
I can't reproduce this problem with an ethernet connection so any help
with the GPRS network would be most welcome!
-Eero Nevalainen
Dawie Malan wrote:
You're quite right - there is something in the middle, and it does cause the
symptoms you are reporting.
A GPRS network has two essential elements:
*Serving GPRS Support Node (SGSN)-Sends data to and receives data from mobile
stations, and maintains information about the location of a mobile station (MS).
The SGSN communicates between the MS and the GGSN.
*Gateway GPRS Support Node (GGSN)-A wireless gateway that allows mobile cell
phone users to access the public data network (PDN) or specified private IP
networks.
The GGSN acts like a proxy and is the device that sends the ACKs to the phone
even though the session is already closed on the server side.
I hope this answers your question.
Regards,
Dawie Malan
-----Original Message-----
From: Michael Bauroth [mailto:[EMAIL PROTECTED]
Sent: 22 March 2007 04:40 PM
To: [email protected]
Subject: Session close problem
Hi,
I'm using currently the trunk version of Mina. I use it to communicate
with GPRS devices on the other side. In most cases this works very well!
But sometimes the things become strange. I've collected a bunch of
problems where I would need help / advices / ideas.
1. I call session.close() from inside my server. It seems, that the
session doesn't close as required.
2. I close the session. The GPRS device on the other side continues to
send data and seems to get ACKs too. It doesn't recognize, that the
other side of the connection (the server) has closed the session a while
before. It seems that there is something in the middle which responds
the ACKs even with not opened server session.
Knows anybody one of the two (most painful) problems and has an answer
for me?
Best Regards
Michael
