Why lawful interception is done by PGW and SGW, anyone entity is enough right?

Question

As per LTE core network architecture, MME shares S11 interface with SGW and SGW has S5/S8 interface with PGW.
I went through Create Session Response message sent by SGW to MME and found PGW-C and PGW-U tunnel ids.
I want to know what MME does with these PGW-C and PGW-U tunnel Ids ?

Answer 1

Lawful interception makes sense on nodes which come into data path. SGW and PGW both nodes come into data path that's the reason lawful interception is imposed into these two nodes. For an user two things are mainly applicable, one is user mobility and another data. Mobility for an user can be monitored through MME and data through SGW/PGW under the lawful interception policy.

Comments

Even ENB also comes into picture in case of data path then why ENB is not doing lawful interception?

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Number of eNodeBs will be more in a network compare to number of total SGW. So now you can think, lawful interception putting at eNodeB would be expensive that's the reason PGW and SGW are good options to implement Lawful interception. Since SGW serves roaming users also that's why lawful interception is implemented on SGW. All the traffic either from home users or roaming users can be monitored from SGW.