[SR-Users] [sr-dev] Confusion about various TCP expiry and lifetime parameters

Thu Aug 27 11:55:44 CEST 2015

Hello,

have you run kamailio with debug=3? There are lot more debug messages
and some will show what happens with the tcp connection.

It will be good to monitor opened connections via kamcmd (see kamcmd
help for the subcommands related to tcp).

Indeed, an ws connection is not opened by server side, but I was
referring to a tcp connection.

Let us know if you get any new details. If I get a chance, I will try to
test if the lifetime value is properly used for closing inactive
connections.

Cheers,
Daniel

On 27/08/15 05:12, M S wrote:
> Hi,
>
> We are using global tcp_connection_lifetime parameter. I haven't
> looked at tcpops module yet but will look at it to see if it helps.
>
> Almost all the testing is done remotely by QA team (they can view
> kamailio logs in syslog but nothing more then that). They simply take
> tcpdump and/or watch websockets frames in chrome debug console. When
> connection is closed, kamailio sends websocket close frame. The
> kamailio logs does not display any reason why connection is being closed.
>
> To check if connection is still active or not, we just publish sip
> presence (by changing logged-in user's status e.g. from available to
> busy and so on). Just to note kamailio can't open new connection as
> websocket client is behind NAT and using tls over websocket i.e. WSS.
> Also if there is any new connection opened by kamailio to web client
> then it would be logged and visible in JS console.
>
> Per our observation disconnection always initiated by kamailio, the
> disconnect WS frame is visible in JS console. We have been doing
> black-box testing so far, but we can try white-box testing to dig deeper.
>
> The problem mainly is that tcp_connection_lifetime never closes the
> connection when we expect it to do. If we set it to 610 seconds (sip
> register expiry is 600) it closes between 8-10 minutes i.e. BEFORE we
> are expecting it to close. If we set it to 70 seconds (keeping sip
> register expiry at 600), it does NOT closes even after 120 seconds.
>
> Additional problem is usrloc module parameter close_expired_tcp, only
> enabling it allows global tcp_connection_lifetime to close a tcp
> connection, otherwise connection never closes (we tested up to 30
> minutes).
>
> So far our prime suspect of this behavior is keepalive packets at tcp
> layer, however we don't have any check or control over it in chrome.
> But we expect if tcp keepalives are causing this then connection
> should be closed by chrome instead of kamailio (the WS close frame
> should be sent by chrome instead of kamailio).
>
> Anyways, i will do some low level debugging and see if i can find more
> info about it.
>
> Thank you.
>
>
>
> On Wed, Aug 26, 2015 at 9:28 AM, Daniel-Constantin Mierla
> <miconda at gmail.com <mailto:miconda at gmail.com>> wrote:
>
>     Hello,
>
>     On 25/08/15 20:21, M S wrote:
>>     Hi,
>>
>>     We have a bit of confusion regarding tcp_connecton_timeout core
>>     parameter.
>
>     are you talking about tcp_connect_timeout or tcp_connection_lifetime?
>
>     Are you using tcpops module?
>
>>     The documentation says,
>>
>>     --
>>     Lifetime in seconds for TCP sessions. TCP sessions which are
>>     inactive for longer than *tcp_connection_lifetime* will be closed
>>     by Kamailio.
>>     --
>>
>>     However we observe a strange behaviour.
>>
>>     1. The connection is NOT closed by Kamailio unless we
>>     additionally set "close_expired_tcp" parameter in usrloc module,
>
>     How do you monitor if the connection is still open or not? Have
>     you used kamcmd to list opened connection?
>
>>
>>     2. Secondly, if we set this parameter to a smaller value say 70
>>     seconds while sip register expiry is 600 seconds (and
>>     close_expired_tcp parameter enabled in usrloc module), the
>>     connection still remains active (tested after keeping it idle for
>>     120 seconds then sending a sip request on this connection, we
>>     expected the request to fail but it does not fails).
>
>     How did you sent the sip request on this connection? Can you
>     detail why you expected to fail? Depending on config options, the
>     server can also open a new connection.
>
>>
>>     3. if we set this parameter to greater then sip register value,
>>     e.g. 610 seconds and set close_expired_tcp parameter in usrloc,
>>     then we observe disconnect after about 8-10 minutes. Whereas we
>>     expect it to continue since user is re-registering every 600 seconds.
>
>     A disconnect can happen from various reason. Have you watched the
>     network packets to see what side closed the connection? You should
>     run kamailio with debug=3 to get more verbose log messages, that
>     should give more hints about what happens there.
>
>>
>>     Can you guys explain why this is happening? What keeps a tcp
>>     connection active or makes it inactive?
>>
>>     We are using websockets (which use TCP at lower layer) and we
>>     observe there is no websocket frame sent or received over the tcp
>>     connection, yet it remain active after tcp_connection_lifetime in
>>     case 2 above and becomes inactive in case 3.
>
>     Note that there is also a keepalive mechanism at tcp layer.
>
>     Your report is just listing some conclusions, we need more details
>     on how you tested (some questions asked above) to be able to
>     analyze properly here and be able to assist.
>
>     Cheers,
>     Daniel
>>
>>     We are using Kamailio v4.3.1 SVN Rev. 4717b5 on Debian Wheezy
>>     32bit OS.
>>
>>     Please suggest.
>>
>>     Thank you.
>>
>>
>>
>>
>>     _______________________________________________
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>
>     -- 
>     Daniel-Constantin Mierla
>     http://twitter.com/#!/miconda <http://twitter.com/#%21/miconda> - http://www.linkedin.com/in/miconda
>     Book: SIP Routing With Kamailio - http://www.asipto.com
>
>
>     _______________________________________________
>     SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing
>     list
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>
>

-- 
Daniel-Constantin Mierla
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Book: SIP Routing With Kamailio - http://www.asipto.com

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