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Re: [Question #661412]: Question Regarding interoperability testing

 

Question #661412 on rohc changed:
https://answers.launchpad.net/rohc/+question/661412

Didier Barvaux proposed the following answer:
Hi,

The LOG_ROHC_DECOMP_RCVD_PKT_PROFILE_UNKNOWN error seems to be raised
when the UE receives one ROHC packet that is not IR (UO-0 for example)
without having established the context with IR packets first. The debug
trace "RoHC Decompression failed due to rceived pkt profile is unknown
(Context ID: 0)" seems to confirm this hypothesis. The failure cause
0x00000013 described by EFFRCCM_ILLEGAL_CID seems to confirm the
hypothesis too.

So, the other LOG_ROHC_DECOMP_FAILED errors seem to be the root cause of
the problem. They are raised by IR packets. The associated failure cause
0x00080001 described by EFFRCCM_PROFILE_DOWN_GRADE is not obvious. I
might refer to the fact to downgrade a context from one profile to
another. See https://tools.ietf.org/html/rfc4815#section-7.2.2 for more
details.

While reading the RFCs, I might have found a problem with the D flag of
the IR packet. I considered that it should be 0, but reading again the
RFC makes me think differently. The D flag should probably be
implemented for the IP-only, IP/UDP, IP/ESP, IP/UDP-Lite and IP/UDP-
Lite/RTP profiles in the same way as it is for the IP/UDP/RTP profile.

Here is my attempt at implementing the D flag with my new understanding:
https://github.com/didier-barvaux/rohc/tree/dev_compat_with_UE_mobile

To get it from an existing Git clone:
$ git fetch
$ git checkout dev_compat_with_UE_mobile
$ make all

Then try again with the UE simulator.

Regards,
Didier

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