[SIPForum-discussion] SIP transport over Air interface in IMS

[Balaji B]

Hi All,

As you are all know before that In IMS world, SIP is used for Signaling.
IMS defines the interface Gm in 3GPP 23.228. It describes Gm as the
reference point between UE and P-CSCF.

My doubt is how SIP Register method generated by UE is transferred to P-CSCF.
Is the UE directly contacts the P-CSCF over the air interface or SIP
is carried as payload over RRC and then thru RANAP and finaly reaches
the SGSN /GGSN from which the SIP paylod is transferred to p-CSCF.

My second doubt is that if compressed SIP is directly transferred over
air interface (Gm interface ?) , how the P-CSCF is able to receive it?

It would be really helpful for me if some one can clarify this .

Regards,
Madhu