Can anyone guess what protocol these packets belong to?

Question

We see these packets being injected in an FTP-DTP channel during a downlink file transfer on Telstra's NEXTG mobile network. We are not sure if these are network level packets, a problem with our 3G modem (HC25 based) or something like our firewall injecting in the stream.

Using a tool we noticed that the PPP framing fails with protocol length errors, so they are mostly likely mobile network packets.

I am hoping someone here can identify the signature of the packets so that I can chase this up with the appropriate vendor.

There is definitely a format to these packets: -

Packet1: 00 00 00 24 c4 b8 7b 1a 00 90 7f 43 0f a1 08 00 45 00 01 10 f4 4e 00 00 40 06 2f 13 cb 7a 9d e9 7b d0 71 52 7a ed 04 06 8c 61 5d a9 01 f7 0c eb 50 10 ff ff 58 b9 00 00

Packet2: 00 00 00 24 c4 b8 7b 1a 00 90 7f 43 0f a1 08 00 45 00 00 ff 6b 50 00 00 40 06 b8 22 cb 7a 9d e9 7b d0 71 52 7a ed 04 06 8c 61 7b 82 01 f7 0c eb 50 10 ff ff a3 79 00 00

Packet3: 00 00 00 24 c4 b8 7b 1a 00 90 7f 43 0f a1 08 00 45 00 02 20 5b 50 00 00 40 06 c7 01 cb 7a 9d e9 7b d0 71 52 7a ed 04 06 8c 61 7c 59 01 f7 0c eb 50 10 ff ff e2 5d 00 00

Packet4: 00 00 00 24 c4 b8 7b 1a 00 90 7f 43 0f a1 08 00 45 00 01 38 d8 52 00 00 40 06 4a e7 cb 7a 9d e9 7b d0 71 52 7a ed 04 06 8c 62 42 f9 01 f7 0c eb 50 10 ff ff 20 91 00 00

Packet5: 00 00 00 24 c4 b8 7b 1a 00 90 7f 43 0f a1 08 00 45 00 00 d0 4d 58 00 00 40 06 d6 49 cb 7a 9d e9 7b d0 71 52 7a ee 04 08 4b fb 0b 8f 03 5d 51 1a 50 10 ff ff e9 88 00 00

Answer 1

I converted your packet trace snippet into a format understood by text2pcap so I could convert them into the pcap format for viewing in Wireshark (a very handy packet capture and analysis tool):

Looks like some sort of IPv4 multicast traffic at a very rough guess. Here's what I got from the first packet (rest came up as malformed):

No.     Time        Source                Destination           Protocol Info
      1 0.000000    7b:1a:00:90:7f:43     00:00:00_24:c4:b8     0x0fa1   Ethernet II

Frame 1 (31 bytes on wire, 31 bytes captured)
    Arrival Time: Dec  1, 2009 00:33:05.000000000
    [Time delta from previous captured frame: 0.000000000 seconds]
    [Time delta from previous displayed frame: 0.000000000 seconds]
    [Time since reference or first frame: 0.000000000 seconds]
    Frame Number: 1
    Frame Length: 31 bytes
    Capture Length: 31 bytes
    [Frame is marked: False]
    [Protocols in frame: eth:data]
Ethernet II, Src: 7b:1a:00:90:7f:43 (7b:1a:00:90:7f:43), Dst: 00:00:00_24:c4:b8 (00:00:00:24:c4:b8)
    Destination: 00:00:00_24:c4:b8 (00:00:00:24:c4:b8)
        Address: 00:00:00_24:c4:b8 (00:00:00:24:c4:b8)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
    Source: 7b:1a:00:90:7f:43 (7b:1a:00:90:7f:43)
        Address: 7b:1a:00:90:7f:43 (7b:1a:00:90:7f:43)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
        .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
    Type: Unknown (0x0fa1)
Data (17 bytes)

0000  08 00 45 00 01 10 f4 4e 00 00 40 06 2f 13 cb 7a   ..E....N..@./..z
0010  9d                                                .
    Data: 080045000110F44E000040062F13CB7A9D