IMS Stopped Looking Like a PBX Once I Split P-CSCF, I-CSCF and S-CSCF
The three CSCF roles made IMS easier to understand when I treated them as separate signalling responsibilities instead of one oversized SIP server.
IMS
SQN Sync in IMS AKA Was the Authentication Detail I Kept Missing
IMS AKA stopped looking like a simple password check once I traced the sequence number and resynchronization path.
Kamailio Diameter Integration Exposed the Limits of Reusing SIP Assumptions
Kamailio felt familiar on the SIP side, but Diameter peer state and application routing forced me to treat the second protocol on its own terms.
QCI 5 for IMS Signalling and QCI 1 for Voice Made QoS Concrete
VoLTE QoS became easier to understand when I separated the persistent IMS signalling bearer from the dedicated low-latency bearer created for voice media.
Tracing an IMS REGISTER Showed Me Where SIP Meets Diameter
An IMS registration capture connected familiar SIP REGISTER messages with the less visible Diameter exchanges used to select and authorize serving functions.
Walking a VoLTE Call End to End Connected the EPC, IMS and RTP Pieces
Following one VoLTE call from LTE attachment through IMS registration, SIP session setup, bearer creation and RTP finally connected the year's separate labs.