HP StorageWorks 4000/6000/8000 .HP StorageWorks SAN Design Reference Guide, Pa - Page 359

• Maximum size of the data payload • Support for unsolicited data • Time-out values During iSCSI login, the initiator and target also exchange nonnegotiable values such as names and aliases. During an iSCSI session, unique session IDs are created for the initiator and target: 1. An initiator creates a unique ID by combining its iSCSI name with an ISID. 2. During login, the initiator sends the ISID to the target. 3. The target creates a unique ID by combining its iSCSI name with a TSID. The target sends the TSID to the initiator. When login is complete, the iSCSI session enters the full-feature phase with normal iSCSI transactions. Security Because iSCSI must accommodate untrusted IP environments, the specification for the iSCSI protocol defines multiple security methods: • Encryption solutions that reside below the iSCSI protocol, such as IPsec, require no special nl negotiation between iSCSI end devices and are transparent to the upper layers. • The iSCSI protocol, which has several encryption solutions including: • Kerberos • Public/private key exchanges Security solutions can include an iSNS server that acts as a repository for public keys. Text fields mediate the negotiation for the type of security supported by the end devices. If the negotiation is successful, the devices format their communications to follow the negotiated security routine. Software and hardware iSCSI initiators An IP host can access an iSCSI environment using one of the following initiators: • Software iSCSI initiator-The iSCSI code runs on the host and allows an Ethernet NIC to handle iSCSI traffic. Software iSCSI offers low cost with a performance penalty and CPU overhead. Software iSCSI initiators are available from many vendors. • TOE NIC-Shifts processing of the communications protocol stack (TCP/IP) from the server processor to the NIC, lowering CPU overhead and use. • Hardware iSCSI initiator (iSCSI HBA)-A high-performance HBA integrates both TCP/IP and iSCSI functions. Although integration adds cost to the HBA, it also provides high-speed iSCSI transport and minimal CPU overhead. The HBA transfers SCSI commands and data encapsulated by iSCSI directly to the host. Bridging and routing iSCSI routers and bridges are gateway devices that connect storage protocols such as Fibre Channel or SCSI to IP networks. iSCSI routers and bridges enable block-level access across networks. Routing data requests from an IP network device to a Fibre Channel device involves these steps: 1. An iSCSI host makes a storage data request. SAN Design Reference Guide 359