(S2D) iSCSI in OSI & TCP/IP

📘 First, What Is iSCSI?

• iSCSI is a block-level storage protocol that allows clients (initiators) to send SCSI commands over IP networks to storage devices (targets).
• It uses TCP (usually port 3260) for reliable transport.
• It lets servers access remote storage as if it were a local disk — ideal for SANs (Storage Area Networks) over Ethernet.

🖼️ Visual Diagram: iSCSI in OSI & TCP/IP

Here’s a simplified diagram to help visualize where iSCSI fits:

OSI Model            | TCP/IP Model        | iSCSI Function
---------------------|---------------------|-----------------------------
7. Application       | 4. Application      | iSCSI protocol (initiator/target software)
6. Presentation      |                     | (not used by iSCSI)
5. Session           |                     | iSCSI login/session management
4. Transport         | 3. Transport        | TCP (connection, error handling)
3. Network           | 2. Internet         | IP (routing, addressing)
2. Data Link         | 1. Network Access   | Ethernet (frames, MAC addresses)
1. Physical          |                     | Cables, switches, NICs