[Kamailio-Users] add_path_received and OBP problems

[Klaus Darilion]

Florian Meister schrieb:
>> btw: many providers (and me) choose to apply NAT handling (fixing
>> contact) in all cases - to simplify the config and security.
> 
> I see. Does that have any negative impacts ? 

Depends ....

For SIP NAT traversal. Almost all SIP clients are symmetric 
(send/receive SIP on the same port) - thus by always use the "received" 
information instead of the provided "Contact" you should not have 
negative impacts. Exception: IIRC, I once saw Cisco SIP phones behind a 
Cisco PIX which were asymmetric (can't remember if it was SIP or RTP).

Also, applying NAT traversal in all cases, does not allows 3rd party 
registrations (which are usually not needed).

Regarding RTP NAT traversal. By activating the media relay for all calls 
you have:
  - you need more bandwith
  - you may need more RTP proxies (high call volume)
  - you might add more delay (this is probably a problem if the relay is 
in e.g. Europe and caller/callee are in US. If at least on of the 
parties is "near" the RTP proxy the additional delay should me negligible)
  + less customers will ask for help due to NAT problems (e.g. NAT 
detection does not work, stupid SIP clients ...)
  + some countries require lawful intercept, which must not be 
noticeable by the costumer. As the LI requires a media relay (to record 
audio) you do not have a choice and have to activate the media relay for 
all calls anyway.

regards
klaus

> 
> Regards, Florian
> 
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