Direct Transfer Messages

Direct Transfer Messages

There are three different types of direct transfer message, two in the uplink and one in the downlink.

Initial Direct Transfer Message

This is the message used to transfer the first signalling initiation message from theNAS. This message tells the RNC about a request for a new connection, which in turn informs the CN that a new signalling connection is being set up. The information contained in this is the NAS message itself, the domain the signalling connection is to be established and something known as the intradomain NAS node selector, which contains information about the core network node the message is to be routed to. All this information is utilized by the RNC to cause a successful connection
to the requested domain.

Uplink Direct Transfer Message

After the transmission of the initial direct transfer message, any message sent by the NAS in the uplink for that domain will be sent in the uplink direct transfer message. This message just encapsulates the NAS message and contains the domain for which the message is meant.

Downlink Direct Transfer Message

The downlink direct transfer message contains the NAS message sent on the downlink. This message also contains the domain from which the message has originated so that the message can be routed to the correct domain in the NAS in the UE.