[Users] nathelper and flag 2

[Klaus Darilion]

Andreas Granig wrote:
> Klaus,
> 
> Another, not directly related question:
> 
> If you have a nated UAC, RTP-Proxies usually wait for packets arriving 
> on each call leg before bridging them together. Now if you have a 
> peering with another provider which has the same setup using i-enum and 
> peering policies, you are stuck because both RTP-Proxies wait for 
> packets to arrive from the peering-leg. How would you handle that? Is 
> there an option in the peering policies, which negotiates which 
> provider's RTP-proxy is going to be used?

The RTP proxy should wait for packets from both destinations. It should 
forward immediately to the socket announced in the SDP and fall back to 
the socket from which it received the packet. If the both RTP proxies 
have a public IP then the socket in the SDP can be reached directly.

I think rtpproxy will forward to the IP:port in the SDP and then fall 
back to the IP:port a packet is received from if this is different.

I do not know how mediaproxy handles this.

In a "strict" peering environment you do not want your rtp proxy to 
change the destination if someone sends you an RTP packet from any 
destiantion. Thus you will tell the rtp proxy to by symmetric on one 
side and to use the SDP on the other side. (like the "r" flag 
http://www.openser.org/docs/modules/1.1.x/nathelper#AEN275)

regards
klaus


> 
> Andreas
> 
> Klaus Darilion wrote:
>> Probably not solving your problem but this is my newest pragmatic 
>> aproach:
>>
>> A client should support symmetric SIP. Thus, I use force_rport for all
>> local clients. As usually also all SIP proxies are symmetric I also do
>> force_port for requests from external nodes.
>>
>> For REGISTER I do not trust the information in the Contact header at 
>> all -
>> I always use fix_nated_register. Further, I always use fix_nated_contact
>> for local SIP users - thus for SIP NAT traversal I do not need any tests.
>>
>> Regarding RTP NAT traversal - if you want to save bandwidth on your RTP
>> proxy - of course you still need a nat-test.
>>
>> regards
>> klaus
>>
>>
>> On Tue, February 13, 2007 17:36, Andreas Granig said:
>>> Hi,
>>>
>>> Today I found a UAC which is *not* located behind NAT (public IP
>>> 1.2.3.4) and sends this Via-Header, which seems perfectly valid
>>> according to RFC3261:
>>>
>>> SIP/2.0/UDP VINNASUP06C:5060;maddr=1.2.3.4;branch=z9hG4bK-2198d2
>>>
>>> I used to check for nated clients using nat_uac_test("3"), which detects
>>> NAT in this case, because the host-part doesn't match the
>>> received-address. So is the test-flag "2" useless, since the host-part
>>> can be "hostname / IPv4address / IPv6reference", or should this
>>> particular test be extended to also check for the maddr-parameter?
>>>
>>> In the meanwhile, I've changed my nat-test to "17" for only testing
>>> Contact and Via-Port instead of Contact and Via-Address, but it's still
>>> not optimal.
>>>
>>> Any opinions on this?
>>>
>>> Andreas
>>>
>>> This e-mail is confidential and may well also be legally privileged. If
>>> you have received it in error, you are on notice of its status. Please
>>> notify us immediately by reply e-mail and then delete this message from
>>> your system. Please do not copy it or use it for any purposes, or 
>>> disclose
>>> its contents to any other person: to do so could be a breach of
>>> confidence. Thank you for your cooperation.
>>>
>>> _______________________________________________
>>> Users mailing list
>>> Users at openser.org
>>> http://openser.org/cgi-bin/mailman/listinfo/users
>>>
>>
>>
> 
> 
> This e-mail is confidential and may well also be legally privileged. If 
> you have received it in error, you are on notice of its status. Please 
> notify us immediately by reply e-mail and then delete this message from 
> your system. Please do not copy it or use it for any purposes, or 
> disclose its contents to any other person: to do so could be a breach of 
> confidence. Thank you for your cooperation.


-- 
Klaus Darilion
nic.at