Rtp Relay - Snom 4S NAT Filter Admin Manual

Max-Forwards: 70
Contact: <sip:kk@192.168.1.10:5060;line=5zy4hsui>;q=0.7
User-Agent: snom200-2.05h
P-NAT-Refresh: 15
Supported: gruu
Expires: 86400
Content-Length: 0
The NAT Filter will answer this request with a P-NAT-Header:
SIP/2.0 200 Ok
Via: SIP/2.0/UDP 192.168.1.10:5060;branch=z9hG4bK-iu90avx18fc6;rport
=34142;received=217.231.163.127
From: "Karl Klammer" <sip:cs@snom.com>;tag=9e9mynnnwa
To: "Karl Klammer" <sip:cs@snom.com>;tag=996wctfnen
Call-ID: 2605c340c91d-cj4sy7drgp6q@192-168-1-10
CSeq: 2 REGISTER
Contact: <sip:kk@192.168.1.10:5060;line=5zy4hsui>;expires=3600;gruu=
"sip:kk@snom.com;gruu=5npko91p"
Server: snom proxy (Unix) 2.42.7
Date: Sun, 06 Jun 2004 11:50:22 GMT
P-NAT-Refresh: 15
Content-Length: 0

2.3.3 RTP Relay

When initiating a call, user agents usually include a Session
Description Protocol (SDP) attachment that describes where they expect
media. If the user agent operates on a public Internet address, there is
no need to interfere in this process. In this case the filter will just forward
the request.
Operators should encourage customers to use equipment that
operates on a public Internet address or properly allocates a globally
routable Internet address. Because media relay is an expensive operation,
it reduces the overall load on the network and at the same time increases
the quality of the service.
However, when a user agent is behind NAT, it might not be able
to receive media directly. In some cases this is because the user agent is
simply not programmed to allocate an address properly or because it is
behind symmetrical NAT, which makes it impossible to properly allocate
this address. In this case, the help of the media filter will make sure that
media will always be delivered properly.
[ 4 S N A T F
S N O M
]
I L T E R
snom technology AG • 15