The correct answer is iSCSI.

iSCSI delivers block level storage by encapsulating SCSI commands in TCP and it runs over standard IP networks so it is widely adopted for enterprise virtual servers and SANs. It supports initiator and target roles and integrates with hypervisors so virtual machines can boot from and store data on remote block devices while using existing Ethernet infrastructure. Implementations commonly use TCP port 3260 and can use CHAP for optional authentication.

Fibre Channel is incorrect because it is a block level transport that normally runs over dedicated Fibre Channel networks rather than over IP. That makes it a SAN technology but not the protocol that delivers block storage over IP networks.

CHAP is incorrect because it is an authentication protocol used by iSCSI and other services. It does not carry storage traffic and it is not a block storage transport.

SMB is incorrect because it is a file level network file sharing protocol and it does not provide block level storage over IP.

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