Clarification with respect to "To" and "From" headers

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Hi Forum,


I have a simple scenario as mentioned below -


EP1-------------------->SBC-------------------->EP2


As we all know that an SBC is a B2BUA device and its main function is
Topology Hiding that is achieved through header manipulation.

Now, for EP1, SBC acts as a UAS and for EP2 it acts as a UAC.

I have configured two endpoints EP1 with IP1 and EP2 with IP2 that access
the SBC through AP1 and AP2 respectively (Pls read AP as Access Point).  An
Access Point is nothing but an IP through which EP1 and EP2 communicate.

Say, EP1 sends INVITE to SBC containing as follows -


INVITE sip:5555@AP1 SIP/2.0
Via: SIP/2.0/UDP IP1;branch=z9hG4bK776asdhds
Max-Forwards: 70
To: <sip:5555@AP1>
From: <sip:1111@IP1>;tag=1928301774
Call-ID: a84b4c76e66710@IP1
CSeq: 1 INVITE
Contact: <sip:1111@IP1>
Content-Type: application/sdp

(SDP not shown)


Upon receiving INVITE, SBC forms a request and forwards to the EP2 as
follows -

INVITE sip:5555@IP2 SIP/2.0
Via: SIP/2.0/UDP AP2;branch=z9hG4bKhoiasdb
Max-Forwards: 69
To: <sip:5555@AP2>
From: <sip:1111@AP2>;tag=98765479
Call-ID: ufs8doi8afjnfd67asdfhu
CSeq: 1 INVITE
Contact: <sip:1111@AP2>
Content-Type: application/sdp

(SDP not shown)



Although the call was successful after responses from EP2, I would kindly
like to know from your side how correct is "To" and "From" header values
with respect to leg2 as highlighted ??  Though there is no impact due of
this behavior.

If it is correct, no issues !
If it is incorrect what should be the correct behavior ?



Thanks & Regards,

Abhishek Kumar Gupta

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<font style=3D"font-family: verdana,sans-serif;" size=3D"2">Hi Forum,<br><b=
r><br>I have a simple scenario as mentioned below -<br><br><br>EP1---------=
-----------&gt;SBC--------------------&gt;EP2<br><br><br>As we all know tha=
t an SBC is a B2BUA device and its main function is Topology Hiding that is=
 achieved through header manipulation.<br>
<br>Now, for EP1, SBC acts as a UAS and for EP2 it acts as a UAC.<br><br>I =
have configured two endpoints EP1 with IP1 and EP2 with IP2 that access the=
 SBC through AP1 and AP2 respectively (Pls read AP as Access Point).=A0 An =
Access Point is nothing but an IP through which EP1 and EP2 communicate.<br=
>
<br>Say, EP1 sends INVITE to SBC containing as follows -</font><br><br><br>=
<font size=3D"4"><span style=3D"font-family: courier new,monospace;">INVITE=
 sip:5555@AP1 SIP/2.0</span><br style=3D"font-family: courier new,monospace=
;">
<span style=3D"font-family: courier new,monospace;">Via: SIP/2.0/UDP IP1;br=
anch=3Dz9hG4bK776asdhds</span><br style=3D"font-family: courier new,monospa=
ce;"><span style=3D"font-family: courier new,monospace;">Max-Forwards: 70</=
span><br style=3D"font-family: courier new,monospace;">
<span style=3D"font-family: courier new,monospace;">To: &lt;sip:5555@AP1&gt=
;</span><br style=3D"font-family: courier new,monospace;"><span style=3D"fo=
nt-family: courier new,monospace;">From: &lt;sip:1111@IP1&gt;;tag=3D1928301=
774</span><br style=3D"font-family: courier new,monospace;">
<span style=3D"font-family: courier new,monospace;">Call-ID: a84b4c76e66710=
@IP1</span><br style=3D"font-family: courier new,monospace;"><span style=3D=
"font-family: courier new,monospace;">CSeq: 1 INVITE</span><br style=3D"fon=
t-family: courier new,monospace;">
<span style=3D"font-family: courier new,monospace;">Contact: &lt;sip:1111@I=
P1&gt;</span><br style=3D"font-family: courier new,monospace;"><span style=
=3D"font-family: courier new,monospace;">Content-Type: application/sdp</spa=
n><br style=3D"font-family: courier new,monospace;">
<br style=3D"font-family: courier new,monospace;"><span style=3D"font-famil=
y: courier new,monospace;">(SDP not shown)</span></font><br><br><br><font s=
ize=3D"2"><span style=3D"font-family: verdana,sans-serif;">Upon receiving I=
NVITE, SBC forms a request and forwards to the EP2 as follows -</span></fon=
t><br>
<br><font style=3D"font-family: courier new,monospace;" size=3D"4">INVITE s=
ip:5555@IP2 SIP/2.0<br>Via: SIP/2.0/UDP AP2;branch=3Dz9hG4bKhoiasdb<br>Max-=
Forwards: 69<br>To: <span style=3D"background-color: rgb(255, 204, 204);">&=
lt;sip:5555@AP2&gt;</span><br>
From: <span style=3D"background-color: rgb(255, 204, 204);">&lt;sip:1111@AP=
2&gt;</span>;tag=3D98765479<br>Call-ID: ufs8doi8afjnfd67asdfhu<br>CSeq: 1 I=
NVITE<br>Contact: &lt;sip:1111@AP2&gt;<br>Content-Type: application/sdp<br>
<br>(SDP not shown)</font><br><br><br><br><font size=3D"2"><span style=3D"f=
ont-family: verdana,sans-serif;">Although the call was successful after res=
ponses from EP2, I would kindly like to know from your side how correct is =
&quot;To&quot; and &quot;From&quot; header values with respect to leg2 as h=
ighlighted ??=A0 Though there is no impact due of this behavior. </span></f=
ont><br>
<br>If it is correct, no issues ! <br>If it is incorrect what should be the=
 correct behavior ? <br><br><br><br>Thanks &amp; Regards,<br><br>Abhishek K=
umar Gupta<br>

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