1.What is CHAP？
Challenge-Handshake Authentication Protocol
iSCSI initiators and targets prove their identity to each other using the CHAP protocol, which includes a mechanism to prevent cleartext passwords from appearing on the wire.
2. iSCSI support two tpye chap authentication：
Initiator authentication和Target authentication
2.1 Initiator authentication：
When initiator(SUT) connect to target, initator should provide user name and password to target. The user name which initiator provdie is "incoming" account.
Initiator authentication can authentication independently, it call " Uni-directional Authentication"，One way authentication
2.2 target authentication：
When initiator connect to target, target should provide user name and password to initiator. Tis is "outcoming" account
target authentication have to authentication on both initiator and target , it call " Bi-directional Authentication"，Mutual authentication
iSCSI CHAP password length requirement must have 12~16 words