Hi;
As i know; If you are using GPRS or whatever; you gotta connect to the WAP GW. By using GGSN and SSGN nodes you reach to the WAP GW. For mobile communication you use WAP protocol only between a mobile and GW, rest is simple HTTP.
Only difference between CSD and GPRS is; with CSD you connect only one time slot but with GPRS you can connect different time slots and send/receive information in packet data form. Of course you are always connect to GGSN and SSGN nodes (APNs)you can easily send and receive packets.
On the other hand Packet switching means that GPRS radio resources are used only when users are actually sending or receiving data. Rather than dedicating a radio channel to a mobile data user for a fixed period of time..The available radio resource can be concurrently shared between several users.
And finally EPOC is a deprecated term. It refers to Symbian OS which is an operating system for mobiles. for more information visit
www.symbian.com [ April 08, 2002: Message edited by: Ercan ]