Howto:Know if the ISDN line is point to point or point to multipoint

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Applies To

This information applies to

  • IP 6000
  • IP 3000
  • IP 800
  • IP 400
  • IP 305
  • IP 302
  • IP 202

all Builds


More Information

Assuming that a call is comming from the ISDN to the innovaphone Gateway , then you can find out if it´s an Point to Point (Ptp) or Point to Multipoint (PtMp) connection.

example trace:

PtP, Incomming call

22:1844:747:2 - ISAC.2 -> LAPD.2 : PH-RECV-RESULT
     data(46),ISAC
     02 01 30 ae  08 01 01 05  04 03 80 90  a3 18 01 89   ..0.............
     6c 0c 21 83  33 30 39 32  32 35 38 35  34 32 70 0a   l.!.3092258542p.
     c1 38 39 30  34 34 39 38  37 33 7d 02  91 81         .890449873}...  
     

exapmple trace:

PtMp, Incomming Call

15:0526:685:6 - IPAC-TE.0 -> LAPD.0 : PH-RECV-RESULT
     data(45),IPAC-TE
     02 ff 03 08  01 01 05 a1  04 03 80 90  a3 18 01 89   ................
     6c 0c 21 83  33 30 38 39  30 34 34 39  38 30 70 09   l.!.3089044980p.
     c1 39 32 32  35 38 35 34  32 7d 02 91  81            .92258542}...


The procedure:

Activate the Traceflag Diagnostics/Tracing/Interfaces/TELx or BRIx or PPP

so that Layer-2 informations get traced -

empty trace

1) Make an incomming call

2)Look for the Isdn Setup Message - this is the format:

   - 4 Byte:        Layer-2 Information
   - Der Wert '08': Protocol Discriminator=Q.931 Protocol for Layer-3 Call Control.
   - Der Wert '01': Length of Call Reference Value
   - 1 Byte:        Call Reference Value
   - 1 Byte '05':   Message Type=SETUP

3) According to 2) you know that it is an ISDN SETUP Message.

Now you can look for the 4 byte of the Layer 2 Information, there look at the second Byte where the Tei is quoted.

Important, the TEI takes only the upper 7 Bits, the lower 8 Bits are set to '1'

  - 02 01: Here is the TEI Tei=0 
  - 02 ff: Here is the TEI=127

4) Now you have to differ

  - At Tei=0 there will be only one fixed Terminal addressed .So it is an ISDN point-to-point connection.   
  - At Tei=127 there will be all Terminal Endpoints addressed.So it is an ISDN point-to-multipoint connection.