[Users] Call-ID discrepancy

[Daniel-Constantin Mierla]

Hello,

On 05/24/06 13:53, Sam Lee wrote:
> Hi All,
>  
> I notice during the NGREP session , there is this field called Call-ID 
> . It is something like this format :-
> 9ce97fd3-1a800040 at 172.16.1.123 <mailto:9ce97fd3-1a800040 at 172.16.1.123>.
>  
> According to the RFC , it is said that this field is generated by the 
> UA who started the request. I was just wondering, how did they get the 
> IP Address at the back ? Which IP Address did they reference it from ?
The Call-ID should be unique, so many devices uses the local IP address 
to try to avoid as much as possible the duplicity of the call-id with 
other phones. Hoeever, this does not apply with devices running in 
private networks.
>  
> From the RFC, it also says that the all request/response in the dialog 
> should use the same Call-ID. When they say this, does it mean the 
> entire field with the ip address (eg. 9ce97fd3-1a800040 at 172.16.1.123 
> <mailto:9ce97fd3-1a800040 at 172.16.1.123> ) or just the front part of it 
> (eg. 9ce97fd3-1a800040 ) ?
The whole string including the IP address is the call-id.
>  
> I notice that during a dialog session from a UA to the server going to 
> the PSTN gateway, it was refering to this Call-ID until the point when 
> the request was forwarded to the PSTN gateway. When the PSTN gateway 
> replies, it replied with a same Call-ID with a different IP address at 
> the back (9ce97fd3-1a800040 at 123.234.123.234 
> <mailto:9ce97fd3-1a800040 at 123.234.123.234> )
That is very wrong. Maybe there is an ALG in the path which replaces the 
private address with public ones, but that should not apply to the 
call-id. The caller should reject the reply.

Cheers,
Daniel

>  
> 172.16.1.123 - Private address of the UA
> 123.234.123.234 - Public address of the UA
>  
> Strange ? Give your comment. Somehow i feel that this implementation 
> is wrong.
>  
> Regards,
> Sam
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