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

From: [email-masked]
Date: Tue, 4 May 2010 14:30:15 +0800

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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---

From: Christer Holmberg <[email-masked]>
Date: Tue, 4 May 2010 13:46:56 +0200

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: [email-masked] [mailto:[email-masked]] On Behalf Of [email-masked]
Sent: 4. toukokuuta 2010 9:30
To: [email-masked]
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

---

From: [email-masked]
Date: Tue, 4 May 2010 20:15:28 +0800

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

Christer Holmberg <[email-masked]> 
2010-05-04 19:46

收件人
"[email-masked]'" <[email-masked]>, "[email-masked]" 
<[email-masked]>
抄送
Paul Kyzivat <[email-masked]>
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: [email-masked] [mailto:[email-masked]] On Behalf 
Of [email-masked]
Sent: 4. toukokuuta 2010 9:30
To: [email-masked]
Cc: Paul Kyzivat
Subject: [Sipping] About changing sending address during session:

IETF level: 

Thanks, 

Gao 

===================================
Zip    : 210012
Tel    : 87211
Tel2   :(+86)-025-52877211
e_mail : [email-masked]
===================================
--------------------------------------------------------
ZTE Information Security Notice: The information contained in this mail is 
solely property of the sender's organization. This mail communication is 
confidential. Recipients named above are obligated to maintain secrecy and 
are not permitted to disclose the contents of this communication to 
others.
This email and any files transmitted with it are confidential and intended 
solely for the use of the individual or entity to whom they are addressed. 
If you have received this email in error please notify the originator of 
the message. Any views expressed in this message are those of the 
individual sender.
This message has been scanned for viruses and Spam by ZTE Anti-Spam 
system.