@startuml "TD_VoLTE_ECO_RMI_INI_03.png"
/'Editor: https://plantuml-editor.kkeisuke.com/ '/
/'Syntax: http://plantuml.com/fr/sequence-diagram '/
!include etsi-style.iuml  
!pragma teoz true
'
participant "UE A\nRoaming"
box "EPC A" #LightBlue
  participant PGw
end box
box "IMS A" #LightBlue
  participant "P-CSCF"

end box


'
rnote right  "UE A\nRoaming"         : S8
& rnote right "P-CSCF"      : Mw
& rnote right "PGw"         : Gm
'


"UE A\nRoaming"      -->   "PGw"   : INVITE\n(urn:service:sos*)
& "PGw"      ->   "P-CSCF"   : INVITE\n(urn:service:sos*)
rnote over "PGw", PCRF #FFAAAA: Installation of emergency Bearer - \nEmergency Session not possible
'"P-CSCF"    ->   "PCRF"     : AAR
'& "PCRF"    ->   "PGw"      : RAR
'rnote over "P-CSCF", PCRF #FFAAAA: Emergency Session not possible

"P-CSCF"    ->   "PGw"     : 380 (Alternative Service)
& "PGw"    -->   "UE A\nRoaming"     : 380 (Alternative Service)
"UE A\nRoaming" --> "PGw" : ACK
& "PGw" -> "P-CSCF" : ACK



@enduml