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streaming RTP through Asterisk not optimal

To: "asterisk_channel_lantiq@linux-mips.org" <asterisk_channel_lantiq@linux-mips.org>
Subject: streaming RTP through Asterisk not optimal
From: "Pukitis Martins (LQLA CPE ST VD)" <Martins.Pukitis@lantiq.com>
Date: Tue, 3 Jul 2012 09:44:51 +0000
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Thread-topic: streaming RTP through Asterisk not optimal

Dear Lantiq channel driver for Asterisk user.

 

Please, note that the current implementation of lantiq channel driver is not the most efficient.

In current channel driver implementation:

-              CPE devices send/receive RTP packets through channel driver read/write interface.

-              SVIP device (VoIp CentralOffice device) sends/receives RTP packets through userspace sockets.

In both cases packets go through userspace and are passed to / received from Asterisk.

For CPE the packet exchange over the file descriptors through user space is deprecated because it causes voice quality issues. The preferred solution is to use the KPI2UDP driver which transports RTP packets in kernel space directly between the TAPI and the Linux network stack. But this requires a patch to the Linux network stack.

SVIP device has its own ethernet interface and is capable of sending/receiving RTP stream directly (redirection to the remote peer by NAT kernel module in necessary to hide the internal IP/MAC address of SVIP device).

Passing packets through userspace adds aditional delay and jitter. There are definite problems in QOS tests using userspace.

For SVIP we did the easiest implementation first, because currently we don’t know how to use Asterisk only for call negotiation and not to send RTP stream through it.

 

Regards,

Martins Pukitis.

 

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