[asterisk-bugs] [Asterisk 0018485]: [patch] IAX2 Retry Time Review

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=18485 
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Reported By:                netfuse
Assigned To:                
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Project:                    Asterisk
Issue ID:                   18485
Category:                   Channels/chan_iax2
Reproducibility:            have not tried
Severity:                   tweak
Priority:                   normal
Status:                     ready for review
Asterisk Version:           SVN 
JIRA:                       SWP-2754 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2010-12-16 09:41 CST
Last Modified:              2011-05-06 16:57 CDT
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Summary:                    [patch] IAX2 Retry Time Review
Description: 
Guys,

The IAX2 channel driver has a number of timeout settings for
communication. I have found that customers with network problems are not
particularly benefitted by these timeouts because they are so incredibly
high.

If you look at the maths, it will be at least 30 seconds with absolutely
no traffic before a DIAL on an IAX2 host fails. However, a SIP peer with
qualify=yes defaults to 2000ms. I recommend that the 2 seconds timeout
should be applied to dialling on IAX trunks also.

Patch attached for your consideration. I have tested this in production
use with good results.

Cheers
Leo
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 (0134618) dvossel (administrator) - 2011-05-06 16:57
 https://issues.asterisk.org/view.php?id=18485#c134618 
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The initial retry time is 2 times the last ping pong round trip time.  So
changing the default retry time shouldn't matter if qualifies are being
used... At least I think qualifies do the ping pong request, I can't
remember.

The RFC has this to say about retransmission timers.
7.2.1. Retransmission Timer


   The message retransmission procedures are described in Section 7.  On
   each call, there is a timer for how long to wait for an
   acknowledgment of a message.  This timer starts at twice the measured
   Round-Trip Time from the last PING/PONG command.  If a retransmission
   is needed, it is exponentially increased until it meets a boundary
   value.  The maximum retry time period boundary is 10 seconds.



So, it just needs to "exponentially" increase.  It should be safe to just
double it each retry, I believe that is what the SIP retransmission timer
does. 

Issue History 
Date Modified    Username       Field                    Change               
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2011-05-06 16:57 dvossel        Note Added: 0134618                          
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