Re: [Sipping] About changing sending address during session:

[gao.yang2@xxxxxxxxxx]

Hi Christer,

As you can see, I have the same point.

But did you notice that I put the defintion
of media flow and IP flow from 3GPP. It would be a interworking problem
while IMS interworking with UE/Softphone from other IP networks.

Thanks,

Gao

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Christer Holmberg <christer.holmberg@xxxxxxxxxxxx>

2010-05-04 19:46

收件人	"'gao.yang2@xxxxxxxxxx'" <gao.yang2@xxxxxxxxxx>, "sipping@xxxxxxxx" <sipping@xxxxxxxx>
抄送	Paul Kyzivat <pkyzivat@xxxxxxxxx>
主题	RE: [Sipping] About changing sending address during session:

Hi,
 
From pure SIP/SDP perspective,
I think it's allowed to change source port. Of course, if you use the source
attribute to explicitly indicate your source port, you will have to update
that also.
 
Whether it will work is another
question... In many NAT/SBC cases it won't even work unless the media is
symmetrical.
 
Regards,
 
Christer

---

From: sipping-bounces@xxxxxxxx [mailto:sipping-bounces@xxxxxxxx]
On Behalf Of gao.yang2@xxxxxxxxxx
Sent: 4. toukokuuta 2010 9:30
To: sipping@xxxxxxxx
Cc: Paul Kyzivat
Subject: [Sipping] About changing sending address during session:


As we know, if one side's UA want change it's receiving address, it needs
a new O/A procedure. Not considering symmetrical RTP, can UA change it's
sending address during session? 

IETF level: 
By current RFC3264, it seems that there's no normative text to forbid such
behavior. 

3GPP(definition of media flow): 
IP Flow: Unidirectional flow of IP packets with the following properties:
-        same source IP address and port number;
-        same destination IP address and port number;
-        same transport protocol (port numbers are
only applicable if used by the transport protocol).
Media Flow: One or more IP flows carrying a single media instance, e.g.,
an audio stream or a video stream. In the context of this specification
the term Media Flow is used instead of IP Flow regardless of whether the
actual IP packet corresponds to media plane information (e.g. audio RTP
flow) or control signalling (e.g. RTCP or SIP Signalling).

[Inference] By 3GPP's definition, 3GPP's usage seems UE can not change
it's sending address(the media flow should has same source IP address and
port number). 

And informative: I heard lots of NAT/SBC equipment developers/providers
said that the media might be blocked by their equipment if UE changing
sending address during session.     

Today, someone asked me the problem again. But I am not sure about the
answer, so I'd like to hear people's points here. 

Thanks, 

Gao 

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