ISDN Raw IE - decoding

[vsunh]

I am receiving the raw IE values in binary when i make incoming call over an ISDN PRI terminated on Dialogic Platform. The Hex coversion of the binary data is as follows :-

2200A104039090A31803

1E00A104038890A31803

How to decode the above values, usual HEx to Ascii convereters show "?????????", what does it mean???

 

[ISDNman]

Are you sure that Dialogic does not have some primitive protocol analyzer that will convert this for you?

The information you seek is somewhere in ITU-T Q.931 but it ain't going to be fun to manually translate it.

You really need a protocol analyzer to do this efficiently, but let me at least give a shot at decoding the message type.

The key is to understand that each pair of hex digits is a hex "octet" and represents an 8 bit binary word.

Octet 1 = Protocol Discriminator and should be 08 for call control signaling.

Octet 2 = always starts with 0000. The remaining digits indicate the length of the Information element.

Octet 3 First digit is 0 1 one and is used as a flag and should be ignored.

Octet 4 is the message type

Lets see the first 7th and 8th digits (fourth octet) of both of the IEs you give is 04 = 4 dec = 00000100

Q.931 defines this as "bearer capability". This is the type of call (voice, 3.1 kHz, or unrestricted digital information) and rate and related information.

The second Octet of the Bearer capability IE (e.g. digits 9 and 10) is the length of this IE and the third octet of the IE (11 and 12) are the transfer capability information.

So... digits 11 and 12 are 90 in the one message and 88 in the other case

90 hex = 144 decimal = 10010000

This is 3.1 kHz Audio (often used interchangeably with voice ). This is a call from a telephone. If you are a "modem" you probably would reject this call.

88 hex = 136 decimal = 10001000

This is is unrestricted digital information. This is a call from an ISDN digital device that is sending data. If you are a PBX you might reject this call (or limit access to DID numbers associate with ISDN data devices)

I am about 80% sure the above is right, but you need to get some sort of protocol analyzer. Took me over 30 minutes and I have some idea how it works and the correct standards to refer to.

I hope this helps

Good Luck.

 

[ISDNman]

PS, what are you developing? Where are you? Are you hiring?

 

[vsunh]

Many Thanks for the effort & information, It is a very valuable information for me, still i need to know the following in the ISDN raw data :-

2200A104039090A31803
1E00A104038890A31803

1. Does above code contains ANI/DNIS? if yes which octet to look at?

2.Is there any UUI or user defined IE information?

I am based in UAE.i am trying to test UUI or IE sending/receiving. One dialogic channel makes a call & i try to send UUI information to the receiving dialogic channel over iSDN.

 

[ISDNman]

I have been told ISDN PRI is not available in UAE. I have been told only E1 R2 signaling is available. I would appreciate any information you might have on how to get ISDN in UAE.

More later

 

[ISDNman]

Friend, I would suggest that you

1) Verify for 100% certain that UUI is supported on the PRI's you will be using for your application. To determine this you need to check with the Telco. Odds are good that if they support it at all that it would be optional.

2) Verify the ISDN protocol for certain. IS this Euro ISDN per ETS-300, or some other protocol. This is important because the different protocols have different use of the IE's so you should decode according to the correct standard.

3) Check with Dialogic to see if they have a built in protocol analyzer that can spit out a Layer 3 decode of some sort.

and/or

4) Get a protocol analyzer you can put on this line. This has the advantage of being completely independent from the Dialogic.

Manual decoding is far too time consuming to do much useful troubleshooting (you can see from my example how hard it was to decode just one octet).

To answer your question, if this is in fact the IE for "Bearer Capability" then it does not include calling party number or UUI information