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[Didier Barvaux <question661412@xxxxxxxxxxxxxxxxxxxxx>]

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

    Status: Open => Answered

Didier Barvaux proposed the following answer:
Hello,

I analyzed the packet that you gave me. It is one UO-0 packet as defined
for the IP/UDP profile by the RFC3095 (see below the dissection).

The packet type UO-0 does not by itself transport enough information for
the Mobile to decompress the packet successfully. You have to initialize
the ROHC decompressor on the Mobile with IR packets. The packet type IR
contains enough information to initiate a compressed stream. Once the
Mobile ROHC decompressor succesfully decompressed at least one IR
packet, you can send one or more UO-0 packets such as the one you gave
to me.

If you did transmit one or more IR packets to the Mobile before the
given UO-0 packet, then provide them to me. Maybe the UO-0 packet is not
well-formed according to the information given in the IR packets.

* Are you able to get some information from the Mobile? Any debug traces/logs?
* What are the ROHC parameters for the Mobile? ROHCv1 or ROHCv2? large/small CID?

Ethernet II, Src: 00:00:00_00:00:00 (00:00:00:00:00:00), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: 00:00:00_00:00:00 (00:00:00:00:00:00)
    Type: Robust Header Compression(RoHC) (0x22f1)
RObust Header Compression (ROHC)
    UO-0: 7e09f4
        0... .... = UO-0 type octet: 0x00
        .111 1... = SN: 15
        .... .110 = CRC: 0x06
        UDP checksum: 0x09f4
    ROHC Context ID (CID): 0
    ROHC profile ID: ROHCv1 IP/UDP profile (RFC 3095) (0x0002)
    ROHC packet type: UO-0
    ROHC header length: 3
Data (1420 bytes)
0000  00 00 01 02 5a 38 cd 9a 00 0a 78 0c 00 00 00 00   ....Z8....x.....
0010  00 00 00 01 00 00 13 89 00 00 05 8c 00 00 00 00   ................
0020  c4 65 36 64 00 98 96 80 30 31 32 33 34 35 36 37   .e6d....01234567
0030  38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33   8901234567890123
.....

Regards,
Didier

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