about the feedback

Asked by regulararmy on 2013-10-12

Dear Didier,
           As for the rohc 1.5.1 or 1.6.0, I wonder if there are some errors in the feedback processing. when the mode changes from O-Mode to U-Mode, according to the RFC3095( section 5.6.6), there are three we should build a NACK feedback with the mode field U_MODE to the compressor firstly, However, I can't find the related codes.
           can you tell me why, thank you.

Regards,
chenxisheng

Question information

Language:
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Status:
Solved
For:
rohc Edit question
Assignee:
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Solved by:
Didier Barvaux
Solved:
2013-10-16
Last query:
2013-10-16
Last reply:
2013-10-15
regulararmy (regulararmy) said : #1

Dear Didier,
           As for the rohc 1.5.1 or 1.6.0, I wonder if there are some errors in the feedback processing. when the mode changes from O-Mode to U-Mode, according to the RFC3095( section 5.6.6), we should build a NACK feedback with the mode field being U_MODE to the compressor firstly, However, I can't find the related codes.
           can you tell me why, thank you.

Regards,
chenxisheng

Hello,

The ROHC library does not support that feature yet. I added it to the TODO list on the wiki:
http://rohc-lib.org/wiki/doku.php?id=library-todo&#rohc_features

Regards,
Didier

regulararmy (regulararmy) said : #3

          As to the triggering condition of modes transitons, RFC3095 documnet does not state it clearly. I wonder if a packet successful decompression makes the decompressor decide to change current mode to the next higher mode(i.e. U->O/O->R), and a failed decompression makes the transitons from current mode to the lower modeļ¼ˆi.e. R->O/O->U). If not, can you tell me where and when ,and which conditions trigger the modes' transiton,do you know it, thank you very much.

Regards,
chenxisheng

Hello,

Currently, the ROHC library doesn't support R-mode. It doesn't support transition from O-mode to U-mode too. So, the only supported transition is U-mode to O-mode. It happens after a successful decompression if you associated a compressor to the decompressor.

Regards,
Didier

regulararmy (regulararmy) said : #5

and which conditions trigger the mode transiton from O->U? It happens after a failedl decompression if you associated a compressor to the decompressor.

Hello,

As I said, the transition from O-mode to U-mode is not implemented in the ROHC library.

If I would implement it, I would probably make it happen on an external event: the application using the ROHC library would tell the library that it didn't want O-mode anymore and prefer the U-mode. It would let the application decide when to perform the transition. It could be because the application lost the connectivity on the feedback channel for example.

Regards,
Didier

regulararmy (regulararmy) said : #7

Thanks Didier Barvaux, that solved my question.