oza.4h07 at gmail.com Guest
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Posted: Fri Mar 04, 2016 4:13 am Post subject: [asterisk-users] Rasterisk freeze on 4G link [SOLVED] |
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Thank you all for pointing me in the right direction.
Now I learned I have to care about MTU.
Best regards
2016-03-03 21:27 GMT+01:00 Toufic Khreish (Gmail) <toufic.khreish@gmail.com (toufic.khreish@gmail.com)>:
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Hello,
You need to determine the correct MTU value by doing the following:
ping www.google.com -f -l 1400 and you go up or down
An example:
1440 Max packet size from Ping Test
+ 28 IP and ICMP headers
1468 is your optimum MTU Setting
Reference : http://www.tp-link.fr/FAQ-190.html
Once you determine the correct MTU you just set it on the VPN server, it will not break any connection the worst will be slow connection that is all.
From my experience the MTU value for 3G was 1400.
Best regards
Toufic
From: asterisk-users-bounces@lists.digium.com (asterisk-users-bounces@lists.digium.com) [mailto:asterisk-users-bounces@lists.digium.com (asterisk-users-bounces@lists.digium.com)] On Behalf Of Duncan
Sent: Thursday, March 03, 2016 9:02 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion <asterisk-users@lists.digium.com (asterisk-users@lists.digium.com)>
Subject: Re: [asterisk-users] Rasterisk freeze on 4G link
Quote: | With this new link, whenever I launch a vim, a nano or a rasterisk session, my terminal freezes (rasterisk) or remains empty (nano, vim).
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When a session is frozon, I can open a new one at the same so it excludes a basic connectivity loss.
| Usually incorrect MTU gives you this effect. Use ping with MTU size set to test and find what works. |
I think its value: it's 1272, which amazes me.
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You will probably also break it with any large text dump eg cat /var/log/syslog will also do it |
Yes "cat /var/log/syslog" also broke my console.
Why would my console break because of inadequate MTU and other PC on the same location, seem unaffected ?
Because, they most probably mostly use SMTP and HTTP ?
Is possible to simulate a given MTU on a LAN to reproduce such freezes ?
(the remote location is at the other side of the country and I would like to prepare things as much as possible).
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I think you need to go through a router or some device that can constrain the MTU. But live changing your server MTU should be straight forward as openvpn should try and reconnect, and you can change the server back. I haven't lost connectivity before with this
Also the session is probably timed out rather than gone, in 10-15 mins maybe less it will come back (or does for me)
Cheers Duncan
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