11.9. Release of a session
11.9.1. User-initiated session release
Of course, Tobias and Theresa will at one point stop their conversation. Let us say that Theresa meets one of her friends at Stephansdom in Vienna and has to say goodbye to her brother (Figure 11.11). She will be the one who drops the call by pressing the red button on her mobile phone.
Consequently, her UE will generate a BYE request, which is sent to Tobias's UE in the same way as any other subsequent request. In parallel to this, her UE will also drop the media PDP context that was established for the session:
Figure 11.11. Theresa releases the session.
BYE sip:[5555:1:2:3:4]:1357 SIP/2.0 Route: <sip:pcscf2.home2.hu:1511;lr> Route: <sip:scscf2.home2.hu;lr> Route: <sip:scscf1.home1.fr;lr> Route: <sip:pcscf1.visited1.fi;lr> To: "Your Brother" <sip:tobi@brother.com>;tag=veli From: "My beloved Sister" <sip:Theresa@sister.com>;tag=schwester
We can see from this BYE request that the information in the To and From headers has been swapped, as this request is now sent from Theresa's end.
Tobias's UE will drop its PDP context immediately after it receives the BYE request. It will also respond to the request with a 200 (OK) response, which will be sent back toward Theresa. The four CSCFs and all ASs on the route will clear all dialog states and information related to the session.
11.9.2. P-CSCF performing network-initiated ...
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