PJSIP Channel - Direct Media "issues" when receiving 2 IPs on A Leg

Asterisk Asterisk SIP
1

Dear Community,

I’ve been working with Direct Media the last couple of days, and i noticed a behavior that “breaks” my VoIP infrastructure,

imagen
imagen1900×708 54.7 KB

Currently, A Leg propagates 2 IPs for RTP Media,
And asterisk, with direct media enabled on A and B side, doesn’t actually send any of the A Leg IP addresses to the B Leg SDP information.

Meaning that Direct media isn’t working, and Asterisk is using RTP resources
I’ve read a bit of SDP RFC and it seems that there is no restriction in having multiple IP addresses between

SDP
o= IP A
c= IP B, IP C, IP D

If someone could give any advice it will be greatly appreciated
Warm Regards

2

hello Diego,
my request is off topic. please team me, which command or software do you use to get this type of graphical trace?

3

sngrep

4

There is no way that that is compliant with RFC 4566. Multiple addresses are normally only used for multicast, and have to be either a group address or on multiple lines, in a media section.

Multiple addresses or “c=” lines MAY be specified on a per-media
basis only if they provide multicast addresses for different layers
in a hierarchical or layered encoding scheme. They MUST NOT be
specified for a session-level “c=” field

Asterisk only supports direct media for audio streams. It may well only do so for a single stream.

The only way you could have 2 IPs on the A leg, is if there is more than one media stream, in which case there will be an m= line between the c= lines.

Aterisk only uses direct media, if, amongst other things, it is not recording, not spying, and no feature codes are enabled.

5

thank you

6

Dear David,

Thanks for your reply, maybe i didn’t check RFC 4566,
Based on the shared screenshot, the Only IP that should be allowed for Direct Media is the one mentioned in the
o=
parameter of the SDP session right?

Warm Regards

7

The o= lines is not used for routing. Only the c= lines.

Maybe that is the nature of your original misunderstanding; there is only one media address in your original packet capture, that ending in 238.197. The one ending in 104.58 is the address of the entity originating the SDP, not a media address.

There are lots of reasons why Asterisk will refuse to use direct media, including: call recording, and the need to see RFC 2833/4733, or inband, DTMF digits, for feature code activation.

8

Dear David,

Thanks for your reply,
I’m trying to understand why my Asterisk is not sending the A Leg RTP IP addresses to my B Leg SDP packets,
The shared screenshot has a single IP in the c= parameters
Do you know how can i debug this?

Warm Regards

9
10

Dear David,

Such basic “issue”…
ALeg Native Codec was different from BLeg side,
Debug information is really verbose

Thanks a lot!
Warm Regards

11

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