PPP Recovery

PPP Recovery

[GauloisID]

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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Re: PPP Recovery

[Gilles Espinasse]

Selon GauloisID <David.Babin@dmic.fr>:

>
> 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.
>
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

Re: PPP Recovery

[GauloisID]

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


Gilles Espinasse wrote:
> 
> Selon GauloisID <David.Babin@dmic.fr>:
> 
>>
>> 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.
>>
> 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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> 
> 

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Re: PPP Recovery

[James Carlson]

GauloisID writes:
> 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.

-- 
James Carlson         42.703N 71.076W         <carlsonj@workingcode.com>

Re: PPP Recovery

[James Cameron]

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.

-- 
James Cameron
http://ftp.hp.com.au/sigs/jc/