Lets first understand what is Integrity protection in context of LTE -
In LTE two kind of security present, NAS security and AS security. NAS security is in between UE and MME where as AS security i.e. RRC level security in between UE and eNB.
There are two ways to do this, i.e. Integrity and Ciphering.
For C-Plane (i.e. DCCH data): Integrity protection applied. We can disable Ip by applying IEA0
For U-plane: Integrity protection and ciphering. We can disable it by applying EEA0.
In general term Integrity protection means, Receiver can verify that received message is the same as that Sender/Transmitter sends. It can be done by;
- “0000″ EIA0 Null Integrity Protection algorithm
- “0001″ 128-EIA1 SNOW 3G
- “0010″ 128-EIA2 AES
Now coming to your question why it is not applied on DRB
Say integrity protection is provided for data sent on DRBs, But question that pops up is what if integrity fails? Since layers in E-UTRAN and UE that provided integrity protection does not understand the data content of DRBs, what action should they take of integrity check failure? On the other hand E-UTRAN knows what to do when integrity protection of SRBs fails, as information on SRBs is initiated by it. I think because of this reason Integrity protection is not provided for DRBs.