NAS level Security in the LTE

Question

What is the main reason for introducing ciphering/integrity at NAS level (when the same is present at RRC level as in UMTS)?

Comments

See the thread suggested by Chandra but some additional thoughts -
1. May be the LTE is whole IP so additional security is required.
2. UE can be connected to multiple MME and so requires additional security.

Answer 1

Pls refer this http://tech.queryhome.com/6670/why-is-security-command-required-at-both-nas-and-rrc-levels