The Sy interface - between PCRF and OCS

Now I have more work to do then I had and it's all focused on GGSN node part and additional equipment not covered by 3GPP specs.Few months ago, in comments some of you asked me to look deeper into the Sy interface. Have to admit that hadn't have much time lately and.. let's be honest, some kind of a mood to research, put together and publish new articles.

Back to the point where we should start.
     

The Sy interface overview

The Sy reference point is defined between the PCRF and the OCS. Big picture of the relationships between functional entities are shown in Fig 1. below.

Fig. 1. Sy overview

As you may (even should) notice on Fig 1. above are simoultaneously SPR and UDR. Those entities work separetly, that means if there is SPR with Sp interface, there is no UDR with Ud interface in the network. Those were put one one figure to save space. Cojunction or means there is the one OR the other. When UDC architecture is used, the SPR with Sp interface, whenever mentioned in this document, is replaced by UDR and Ud.