serving gateway in UMTS

It is the gateway which terminates the interface towards E-UTRAN.for each UE associated with the EPS at given point of time there is a single serving GW.

It is responsible for handovers also data transfer in terms   of all packets across user plane. To its duties belongs taking care about mobility interface to other networks such as 2G/3G.

Functions:

1.     local Mobility Anchor point for inter-eNodeB handover;

2.    sending of one or more "end marker" to the source eNodeB, source SGSN or source RNC immediately after switching the path during inter-eNodeB and inter-RAT handover, especially to assist the reordering function in eNodeB.

3.    Mobility anchoring for inter-3GPP mobility (terminating S4 and relaying the traffic between 2G/3G system and PDN GW);

4.    Lawful Interception;

5.    Packet routing and forwarding;