MM1, unknown byte in front of to/from party fields?

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Message

Robert Barretto
New member
Username: Barretto

Post Number: 27
Registered: 09-2019

Posted on Thursday, July 16, 2020 - 08:56 pm:

Hi all,

I'm looking at an MM1 group message origination message and I've found a byte which I don't know what means. I'm hoping someone in the forums might know what it is and/or what it's used for.

I see two TO parties:

To party 1: 12145555273/TYPE=PLMN
97 17 ea 31 32 31 34 35 35 35 35 32 37 33 2f 54 59 50 45 3d 50 4c 4d 4e 00

To party 2: 14695552301/TYPE=PLMN
97 17 ea 31 34 36 39 35 35 35 32 33 30 31 2f 54 59 50 45 3d 50 4c 4d 4e 00

so I can understand the ID 0x97 is the To Party, and 0x17 is the length. What I don't understand is the leading 0xEA. It displays as ê in my hex->string converter.

The same 0xEA is in the From party (ID: 0x80)

Here's another weird point... the above data is from an Group MMS origination on an Android phone. If I repeat the test but use an iPhone for the Group MMS origination, instead of 0xEA I see 0x83. I was expecting to see the same value, but now I'm not quite sure what to make of it.

The iPhone MM1 origination does not include a From header, just the two To parties.

To party 1: 12145555273/TYPE=PLMN
97 17 83 31 32 31 34 35 35 35 35 32 37 33 2f 54 59 50 45 3d 50 4c 4d 4e 00

To party 2: 14695552301/TYPE=PLMN
97 17 83 31 34 36 39 35 35 35 32 33 30 31 2f 54 59 50 45 3d 50 4c 4d 4e 00

This is the first time I've ever really looked closely at the bytes of an MM1, so I don't really know how to interpret what I'm seeing.

I was expecting that if anything came before the digits it would be 0x2B (which would be the + sign for international +<e.164> format, but I'm at a loss for the two different values.

I found the OMA MMS Encapsulation Protocol spec (OMA-TS-MMS_ENC-V1_3-20110913-A). Don't know if this is the right spec or not.

Which says (7.3.61 To Field):
To-value = Encoded-string-value (see chapter 8 for addressing model)

From chapter 8 I appears that the To parties are using format:

device-address = ( global-phone-number "/TYPE=PLMN" )
global-phone-number = ["+"] 1*( DIGIT / written-sep )
written-sep =("-"/".")

Anyhow, I'm just curious as to what that extra byte is/does and why it would be different between Android and iOS.

Thanks,
//Robert

The entire MM1 data stream is below, if that helps any...

8c 80 98 54 31 37 33 35 38 35 37 33 64 32 35 8d 92 85 04 5f 10 78 a3 89 19 80 17 ea 31 34 36 39 35 35 35 32 31 31 33 2f 54 59 50 45 3d 50 4c 4d 4e 97 17 ea 31 32 31 34 35 35 35 35 32 37 33 2f 54 59 50 45 3d 50 4c 4d 4e 97 17 ea 31 34 36 39 35 35 35 32 33 30 31 2f 54 59 50 45 3d 50 4c 4d 4e 8a 80 88 05 81 03 09 3a 80 8f 81 86 81 90 81 84 1b b3 8a 3c 73 6d 69 6c 3e 89 61 70 70 6c 69 63 61 74 69 6f 6e 2f 73 6d 69 6c 02 2f 81 48 1b 61 70 70 6c 69 63 61 74 69 6f 6e 2f 73 6d 69 6c 85 73 6d 69 6c 2e 78 6d 6c c0 22 3c 73 6d 69 6c 3e 8e 73 6d 69 6c 2e 78 6d 6c 3c 73 6d 69 6c 3e 3c 68 65 61 64 3e 3c 6c 61 79 6f 75 74 3e 3c 72 6f 6f 74 2d 6c 61 79 6f 75 74 2f 3e 3c 72 65 67 69 6f 6e 20 69 64 3d 22 54 65 78 74 22 20 74 6f 70 3d 22 30 22 20 6c 65 66 74 3d 22 30 22 20 68 65 69 67 68 74 3d 22 31 30 30 25 22 20 77 69 64 74 68 3d 22 31 30 30 25 22 2f 3e 3c 2f 6c 61 79 6f 75 74 3e 3c 2f 68 65 61 64 3e 3c 62 6f 64 79 3e 3c 70 61 72 20 64 75 72 3d 22 35 30 30 30 6d 73 22 3e 3c 74 65 78 74 20 73 72 63 3d 22 74 65 78 74 30 30 30 30 30 31 2e 74 78 74 22 20 72 65 67 69 6f 6e 3d 22 54 65 78 74 22 20 2f 3e 3c 2f 70 61 72 3e 3c 2f 62 6f 64 79 3e 3c 2f 73 6d 69 6c 3e 33 1a 13 83 85 74 65 78 74 30 30 30 30 30 31 2e 74 78 74 81 ea c0 22 3c 74 65 78 74 30 30 30 30 30 31 3e 8e 74 65 78 74 30 30 30 30 30 31 2e 74 78 74 47 72 6f 75 70 20 74 65 73 74 20 33 20 66 72 6f 6d 20 41 6e 64 72 6f 69 64 2e

Any insight provided would be much appreciated. Thanks!

Bryce Norwood - NowSMS Support
Board Administrator
Username: Bryce

Post Number: 8344
Registered: 10-2002

Posted on Thursday, July 16, 2020 - 10:03 pm:

Hi Robert,

It is the character set.

7.2.9. Encoded-string-value
Encoded-string-value = Text -string | Value-length Char-set Text -string

0x83 = 0x80 | 0x03 (us-ascii)
0xEA = 0x80 | 0x6A (UTF-8)

Cheers,

Bryce Norwood
Now SMS/MMS Support