Error detection is the process of ensuring that data sent between two network nodes arrives as intended. Error detection mechanisms include the following:

• Checksum
  
  The iSCSI protocol runs on top of TCP/IP, which provides a checksum mechanism to ensure data integrity. However, over unreliable and noisy links, TCP/IP checksum may not be sufficient to detect all error conditions.
  
  
• Digests
  
  The iSCSI protocol offers an additional safeguard called digests. Digests use 32-bit cyclic redundancy checksum (CRC). The iSCSI protocol provides error detection using the following:
  
  
  • Header digests, to ensure the validity of the header component of the protocol data unit (PDU).
    
    
  • Data digests, to validate the data segment of the PDU.
    
    
  These two options can be used separately or together. Microsoft iSCSI Software Target supports both header and data digest. For more information about the PDU, see Overview of Microsoft iSCSI Software Target.
  
  To use header or data digest, or both, enable the appropriate digest on the iSCSI initiator. iSCSI Software Target then automatically uses it for any iSCSI target to which that iSCSI initiator is assigned. This simplifies the configuration of the storage server.
  
  

  Note
  Enabling the use of digests will result in a slight increase in CPU utilization due to CRC computation.

Additional references