[asterisk-dev] Native Bridging: terminology

[Klaus Darilion]

Am 18.03.2010 16:54, schrieb Kevin P. Fleming:
> Mark Michelson wrote:
>
>> The term "native bridge" is a bit overloaded in Asterisk. On the surface, it
>> simply means that the two legs of a call have the same channel->tech->bridge
>> function.
>
> Right. The channel driver can then choose how it wants to implement
> 'native bridging' and even offer multiple options.
>
>> I can't speak for DAHDI, but within SIP, native bridging has two subcategories.
>> One, typically referred to as "SIP native bridging" is used when reINVITEs are
>> enabled. The endpoints send their media directly to one another. The other
>> subcategory is called "Packet 2 Packet" or "P2P" bridging. If reINVITEs are not
>> enabled, but there are also no features that require the Asterisk core to be in
>> the voice path, then the bridging will be done at the RTP layer of Asterisk.
>
> For chan_dahdi, native bridging means the channels are bridged in DAHDI,
> and the audio never passes through Asterisk. For cases where the two
> channels involved live on the same DAHDI-driven card, and the card
> supports direct timeslot bridging (interchange), then the audio won't
> even pass across the system bus at all. If that can't be done, then the
> bridging will be done in the DAHDI core in the kernel.
>
> For chan_iax2, native bridging means a media-only transfer (similar to a
>   SIP reinvite that only changes the media destination addresses/ports)
> will be attempted to keep the media from going through Asterisk at all.
>
> For chan_sip, the native bridging is actually (mostly) handled by the
> RTP engine being used, and thus it would be possible to 'native bridge'
> between any two channel drivers that use the same RTP engine... but in
> practice, the non-SIP channel drivers that use RTP don't have any way to
> tell endpoints to redirect their media to a different address, so any
> native bridging involving those channel drivers is limited to
> Packet2Packet mode.

Just for the records: "Packet2Packet mode" means that the media is 
bridged in Asterisk's rtp module?

thanks
klaus