tasklwIP - A Lightweight TCP/IP stack - Tasks: task #13780, lcp_echo_interval maximum value

 
 

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task #13780: lcp_echo_interval maximum value

Submitter:  Marco <marcoe>
Submitted:  Fri 16 Oct 2015 04:10:08 PM UTC
   
 
Category:  PPP Should Start On:  Fri 16 Oct 2015 12:00:00 AM UTC
Should be Finished on:  Sun 25 Oct 2015 12:00:00 AM UTC Priority:  5 - Normal
Status:  Cancelled Privacy:  Public
Assigned to:  None Percent Complete:  0%
Open/Closed:  Closed Planned Release:  None
Effort:  1.00

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Mon 26 Oct 2015 11:03:12 AM UTC, comment #9: 

Hello Marco,

> we have made some tests and I can confirm your thoughts.
> LCP reply/request mechanism doesn't generate GPRS traffic
> or, at least, if it does this is not counted as data usage.


Great!, let's keep it u8_t until someone find a real reason to
grow it, every byte saved is good.

Thank you for your patience, I know it's not easy to propose
a simple change like that and then having to explain into
details why :-)

Sylvain

Sylvain Rochet <gradator>
Group Member
Mon 26 Oct 2015 09:04:46 AM UTC, comment #8: 

Hello Sylvain,
we have made some tests and I can confirm your thoughts.
LCP reply/request mechanism doesn't generate GPRS traffic or, at least, if it does this is not counted as data usage.

Marco

Marco <marcoe>
Mon 19 Oct 2015 11:45:43 AM UTC, comment #7: 

Hi,


> if the LCP packets are only going back and forth over the serial link between
> our target and the GPRS modem, we need no more to reduce them because we were
> only trying to lower GPRS traffic.


Yeah, I was sure this is what you have in mind ;)


> I was wondering if at GPRS level there is some similar echo reply/request
> protocol to check the link


Indeed, that's a requirement for the handover handling in a GSM network,
those frames are of course not counted into your data usage.


> and if it is somewhat related to PPP/LCP...


Not that I am aware of. There is still an easy way to check if you
wish to be confident about that, check the TX activity of your GPRS
modem (they all have a GPIO you can configure to monitor TX burst),
and check its activity when LCP echo reply/request are being exchanged.


> P.S. Can you suggest me a good book on these topics? :)


Nope.


Sylvain

Sylvain Rochet <gradator>
Group Member
Mon 19 Oct 2015 10:24:41 AM UTC, comment #6: 

Hello Sylvain,
if the LCP packets are only going back and forth over the serial link between our target and the GPRS modem, we need no more to reduce them because we were only trying to lower GPRS traffic.
I was wondering if at GPRS level there is some similar echo reply/request protocol to check the link and if it is somewhat related to PPP/LCP...
P.S. Can you suggest me a good book on these topics? :)

Marco <marcoe>
Fri 16 Oct 2015 05:29:47 PM UTC, comment #5: 

Well, this is what I thought :-)

For cellular modems, the PPP link is only between your target running lwIP and your GPRS modems, LCP frames are not sent over the air, there is actually no PPP at all over the air. PPP is only used because it is a convenient way to frame IP packets over a serial link, that's why you don't need authentication (or a very weak one).

Do you really need to optimize the data exchanged between your target and your GPRS modem up to this point ? We are talking about a few tens of bytes every a couple of minutes. The modem is going to ping your target more often than you currently wish (unless it is configurable) and you have to answer to its LCP ping request on time.

In this context, do you still need to reduce the number of LCP ping requests ?

Sylvain

Sylvain Rochet <gradator>
Group Member
Fri 16 Oct 2015 05:18:28 PM UTC, comment #4: 

We use PPPoS with a 2G-GPRS modem.

Marco <marcoe>
Fri 16 Oct 2015 05:14:03 PM UTC, comment #3: 

Over which support type ? dialup ? GPRS/EDGE/UMTS/… ? L2TP ?

Sylvain Rochet <gradator>
Group Member
Fri 16 Oct 2015 04:55:25 PM UTC, comment #2: 

In our use case we setup a ppp connection and try to never end it. Every, let me say, 900 seconds we effectively use it for a short tcp connection.
We need to check that the connection is still alive but we need to reduce at minimum the communication trafic, so our idea was to set lcp_echo_interval to a value slightly greater than our communication interval and to enable the PPP_LCP_ADAPTIVE option. In this manner we expect to never waste bytes to check the link status. Is this correct?

Thank you
Marco

Marco <marcoe>
Fri 16 Oct 2015 04:33:51 PM UTC, comment #1: 

I am not strictly opposed to this, it only cost one byte after all for a 16 bit value, but still, why do you think you would need to set a value over 255 seconds ?

Sylvain

Sylvain Rochet <gradator>
Group Member
Fri 16 Oct 2015 04:10:08 PM UTC, original submission:  

Hello all, it is possible to define lcp_echo_interval field of the ppp_settings struct as a 16 o 32 bit value in order to set request intervals greater than 255 seconds?

Thank you

Marco <marcoe>

 

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    Date Changed by Updated Field Previous Value => Replaced by
    2015-10-26 gradator StatusNone Cancelled
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