[Freeswitch-users] FS-HA RTP state

Michael Jerris mike at jerris.com
Mon Aug 18 23:40:37 MSD 2014

In the case of a failover, we initiate a re-invite, so its technically a new rtp stream.  We do not do in stream state update, so this works fairly well with applications that don't require state updates (such as bridged calls), not nearly as well when talking to an application like in the middle of an ivr or while recording a voicemail.  In the case of an application, it would re-enter that application from the start, unless that application has the capability of storing state (most do not, but the infrastructure to do so is in place).


On Aug 18, 2014, at 1:41 PM, Alex Balashov <abalashov at evaristesys.com> wrote:

> Hi,
> Sorry for the newbie question. Regarding this:
>    https://wiki.freeswitch.org/wiki/Freeswitch_HA
> How does FreeSWITCH pick up and resume RTP stream state in this 
> scenario, vis-a-vis the RTP sequence numbers? Or does it not?
> I don't really know how RTP works through the FreeSWITCH core. Based on 
> the fact that this type of failover works, I am guessing that Freeswitch 
> has several modes of RTP relay in a channel bridge:
> (1) Where the RTP is regenerated/reoriginated with logically independent 
> SSRC and sequence numbers, which would presumably be used in situations 
> where invasive DSP work, transcoding and/or other heavy media 
> involvement is required of the FreeSWITCH core. I assume this involves 
> marshalling the audio payload onto some sort of generic internal audio 
> frame bus, too.
> (2) "Light" mode, analogous to Asterisk's "Packet2Packet" bridging, 
> where the RTP is relayed more or less as-is between the endpoints, 
> without this type of mediation. This would presumably pass through the 
> endpoints' respective RTP stream properties.
> Is it reasonable to assume that the call recovery functionality relies 
> on #2, which would imply that the calls cannot be transcoded, use 
> in-band DTMF signalling, etc?
> Thanks!
> -- Alex
> -- 
> Alex Balashov - Principal
> Evariste Systems LLC
> Tel: +1-678-954-0670
> Web: http://www.evaristesys.com/, http://www.alexbalashov.com/
> Please be kind to the English language:
> http://www.entrepreneur.com/article/232906

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