Registering With Ua Support - Snom 4S NAT Filter Admin Manual

0>;expires=3600;gruu="sip:denny@snomag.de;gruu=hobiv52b"
Date: Wed, 26 May 2004 16:03:33 GMT
Server: snom proxy (Unix) 2.42.6
Content-Length: 0
SIP/2.0 200 Ok
Via: SIP/2.0/UDP 203.145.183.113:12975;branch=z9hG4bK-
abx3au3mxb01;rport=17401
From: "denny" <sip:denny@snomag.de>;tag=k9p6fmeg7h
To: "denny" <sip:denny@snomag.de>;tag=epuy85kzm5
Call-ID: 3c26701d7cb9-pady07b5783t@203-145-183-113
CSeq: 14 REGISTER
Contact: <sip:denny@203.145.183.113:12975;line=lhynyb3y>;expires=360
0;gruu="sip:denny@snomag.de;gruu=hobiv52b"
Server: snom proxy (Unix) 2.42.6
Date: Wed, 26 May 2004 16:03:33 GMT
Content-Length: 0

2.3.2 Registering with UA Support

Leaving the refreshing of the UDP binding to NAT Filter usually
will keep the connection alive. However, it is better if the user agent
refreshes the binding:
• When the user is taken off the network the NAT Filter does not gen-
erate unnecessary refreshes. The same happens when for example
the DSL router is turned off.
• When refresh packets cannot be delivered because of congestion
or other network problems, the NAT router will close the ports and
there is no way to open them again from the outside. If the user
agent refreshes the bindings, the port is opened automatically
again.
• User agents may send from time to STUN packets and process the
answer to check if the IP address has changed. In this case, the user
agent may refresh the SIP binding.
A user agent that supports this way of refreshing the bindings
includes a "P-NAT-Refresh" header in the REGISTER message:
REGISTER sip:snom.com SIP/2.0
Via: SIP/2.0/UDP 192.168.1.10:5060;branch=z9hG4bK-fozdn9kbolfw
From: "Karl Klammer" <sip:kk@snom.com>;tag=9e9mynnnwa
To: " Karl Klammer" <sip:kk@snom.com>
Call-ID: 10f2c240790b-cj4sy7drgp6q@192-168-1-10
CSeq: 2 REGISTER
14 • Architecture
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