Hi,

We had dilemma how to negotiate media capabilities when
interworking with ISUP.

We are very appreciated your time to response to us.

What we can think of that there are three choices:

1) using OPTIONS

ISUP            UAC                     UAS             ISUP
|------IAM---------->|-----INVITE------------------>|           |
|               |<--------100--------------------|              |
|               |                       |               |
|               |<--------OPTIONS ----------|           |
|               |                       |               |
|               |---------200 OK ------------->|---------IAM------>|
|               |                       |               |
|<-----ACM---------|<--------180 - -----------------|<-------ACM-------|
|               |                       |               |
|<----ANM----------|<--------200 OK -------------       |<-------ANM-------|

2) using reliable provisional response

ISUP            UAC                     UAS             ISUP
|------IAM---------->|-----INVITE------------------>|           |
|               |<--------100--------------------|              |
|               |                       |               |
|               |<--------183 -------------------|              |
|               |----------PRACK------------>|          |
|               |<-------200 OK --------------|---------IAM------>|
|               |                       |               |
|<-----ACM---------|<--------180 - -----------------|<-------ACM-------|
|               |                       |               |
|<----ANM----------|<--------200 OK -------------       |<-------ANM-------|

3) No 183 arrived.

ISUP            UAC                     UAS             ISUP
|------IAM---------->|-----INVITE------------------>|           |
|               |<--------100--------------------|              |
|               |                       |-------IAM--------->|
|               |<--------180 -------------------|<------ACM--------|
|               |----------PRACK------------>|          |
|               |<-------200 OK --------------|         |
|               |                       |               |
|<-----ACM (??)--|                      |               
|               |                       |               |
|<----ANM----------|<--------200 OK -------------       |<-------ANM-------|


Questions:
Are they all valid call flow? any pros and cons?        

Thanks very much,


Best Regards,

Helen Luo
[EMAIL PROTECTED]

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