16 • Architecture
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S N O M
4 S N A T F
I L T E R
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Content-Length: 0
SIP/2.0 200 Ok
Via: SIP/2.0/UDP 217.115.141.99:5082;branch=z9hG4bK-e8d1feb8138c3d85
0637ced821ef40a3;ua=c9b140ab598290e5bb491e9c3aaca440
Via: SIP/2.0/UDP 203.145.183.113:12975;branch=z9hG4bK-
abx3au3mxb01;rport=17401
From: “denny” <sip:[email protected]>;tag=k9p6fmeg7h
To: “denny” <sip:[email protected]>;tag=epuy85kzm5
Call-ID: 3c26701d7cb9-pady07b5783t@203-145-183-113
CSeq: 14 REGISTER
Contact: <sip:217.115.141.99:5082;ua=c9b140ab598290e5bb491e9c3aaca44
0>;expires=3600;gruu=”sip:[email protected];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:[email protected]>;tag=k9p6fmeg7h
To: “denny” <sip:[email protected]>;tag=epuy85kzm5
Call-ID: 3c26701d7cb9-pady07b5783t@203-145-183-113
CSeq: 14 REGISTER
Contact: <sip:[email protected]:12975;line=lhynyb3y>;expires=360
0;gruu=”sip:[email protected];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 the NAT Filter usu-
ally 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. When the user
agent refreshes the bindings, the port is opened again automati-
2.
