On which basis MME selects the S-GW?

Question

When UE sends an attach request then on which bases MME selects S-GW for that UE?
does this information is passing from HSS with the subscriber profile information?

Comments

On behalf of Subhu Singh
From Hss, it gets Apn and then it does dns query for PGW which serves this Apn. After PGW is selected, then dns query is done to select SGW which serves this PGW.

Answer 1

I think, ECGI comes within the "Initial UE message" plays major role while selecting SGW for an UE. MME objective is to minimize the chance of SGW relocation based on current location of UE within E-UTRAN. While TAI receives in "Initial UE Mesage" help MME while assigning TAI list to UE and helps to MME while paging procedure when UE is in idle mode.

Looking for others to respond.

Answer 2

MME selects S-GW is selected based on TAI in S1AP message.