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DISCUSSION GauloisID 4 participants 5 messages Dec 11, 2008 PPP protocol drivers and compressors

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GauloisID

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#0 lore raw

Hi all,

I Would like to setup a permanent connection with a local rs232 GPRS modem. I Use kernel 2.6.24 and PPP 2.4.4.

My connection work fine (DNS, ICMP...), but sometimes my GPRS provider drop my connection due to timeout, moving....

Is there any way to tell ppp that sent packet (TCP/UDP) have retransmission timeout to indicate that the connection is dead ? In this case it would be easy to re-negociate the link.

Thanks for help.

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#1 lore raw

Selon GauloisID <[email protected]>:

Quoted 6 lines

Hi all,

I Would like to setup a permanent connection with a local rs232 GPRS modem. I Use kernel 2.6.24 and PPP 2.4.4.

Quoted 7 lines

My connection work fine (DNS, ICMP...), but sometimes my GPRS provider drop my connection due to timeout, moving....

Is there any way to tell ppp that sent packet (TCP/UDP) have retransmission timeout to indicate that the connection is dead ? In this case it would be easy to re-negociate the link.

That's achieved by lcp options you could activate when starting the connection (if the server support that, it usually should).
After lcp traffic has been interrupted a time defined by the combination of lcp options values, ppp session goes down and if persist option has been used, pppd restart the connection.

Gilles

author
#2 lore raw
In reply to GauloisID

Great! Thanks, that's exactly what i look for !

Quoted 37 lines · Gilles Espinasse

Selon GauloisID <[email protected]>:

Quoted 11 lines

Hi all,

I Would like to setup a permanent connection with a local rs232 GPRS modem.
I Use kernel 2.6.24 and PPP 2.4.4.

My connection work fine (DNS, ICMP...), but sometimes my GPRS provider drop
my connection due to timeout, moving....

Quoted 6 lines

Is there any way to tell ppp that sent packet (TCP/UDP) have retransmission
timeout to indicate that the connection is dead ? In this case it would be
easy to re-negociate the link.

That's achieved by lcp options you could activate when starting the connection
(if the server support that, it usually should).
After lcp traffic has been interrupted a time defined by the combination of lcp
options values, ppp session goes down and if persist option has been used, pppd
restart the connection.

Gilles
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#3 lore raw
In reply to GauloisID
Quoted 9 lines · GauloisID

I Would like to setup a permanent connection with a local rs232 GPRS modem. I Use kernel 2.6.24 and PPP 2.4.4.

My connection work fine (DNS, ICMP...), but sometimes my GPRS provider drop my connection due to timeout, moving....

Is there any way to tell ppp that sent packet (TCP/UDP) have retransmission timeout to indicate that the connection is dead ? In this case it would be easy to re-negociate the link.

If you actually want it to be up at all times, then the pppd "persist" option may be what you want. If you want it to trigger a new link when TCP or UDP sends a packet and the link is down, then you want "demand."

If you want the system to detect a "dead" link -- one where the low-level connection is still present, but the peer is no longer running PPP -- then you'll probably want to set up both the "lcp-echo-interval" and the "lcp-echo-failure" options.

For all of these options, see the man page.

However, beware: GPRS is weird in many ways. Having unexpected behavior (compared to "normal" PPP links) is just par for the course, so, though the above options should help, it's at least possible that you may encounter situations that pppd can't handle. I wouldn't be too surprised if you ended up writing some sort of little monitoring application that kills off and restarts pppd when there's trouble.

Signature · 1 line
James Carlson         42.703N 71.076W         <[email protected]>
#4 lore raw
In reply to GauloisID

In my experience with GPRS style modems, LCP echo continues to occur, because it is just the modem firmware responding. The LCP echo latency is very small, consistent with this. So LCP echo loss may not occur, and the PPP connection may remain up.

Signature · 2 lines
James Cameron
http://ftp.hp.com.au/sigs/jc/