LIPA (Local IP Access) Function

Till now every thing is very clear for you how LIPA works and if you are new to this topic we would suggest you to visit or revisit Traffic Break-Out in LTE and SIPTO chapters.

In general LIPA and SIPTO both look same, but there are subtle differences that are as follow :
(1) In LIPA complete traffic bypasses the user plane of core network except HeNBs while in SIPTO only specific traffic bypasses core network. 
(2) LIPA can be achieved only when there is Breakout at enterprise IP network (means only with the help of L-GW co-located with HeNB)while SIPTO can be achieved by breakout from P-GW (i.e. Breakout at or above RAN)

LIPA is a mechanism that allows IP enabled UE to connect with HeNB to access IP enable services of residential/enterprise system without accessing user-plane of core network in which UE is roaming.

LIPA permissions are stored in HSS per APN basis. LIPA can be applied in both roaming and non-roaming and this permission is also stored in HSS. LIPA permission can be CSG specific, MME can release LIPA PDN connection if it founds UE is moving out of authorized CSG.

LIPA permissions for an APN are stored with following attributes:

Processing of permission
MME shall take decision of giving LIPA to an APN as,If VPLMN-LIPA-Allowed is set to LIPA_NOTALLOWED then LIPA shall not be given to roaming PLMN irrespective of value of LIPA-Permission. Now if VPLMN-LIPA-Allowed is set to LIPA_ALLOWED then need to check to check for LIPA-Permission value, if LIPA-Permission is set to
LIPA_PROHIBITED then LIPA is not given to considered APN, if
LIPA_ONLY then considered APN can only be accessed by LIPA mechanism, if LIPA_CONDITIONAL then APN can use any of the both LIPA mechanism and simple P-DN selection to make PDN connection.

Wildcard APNs can also use LIPA except those are specified in APN list. Entity VPLMN-Dynamic-Address-Allowed shall not be considered if entity VPLMN-LIPA-Allowed is present.

Your Comments /Suggestions and Questions are always welcome,  shall clarify with best of knowledge. So feel free to put Questions. 

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