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iSCSI Protocol

Fast emerging as an industry standard, the Small Computer Systems Interface over IP (iSCSI) enables universal access to shared storage devices over IP networks. To learn more about iSCSI, IP storage networking, and the Cisco iSCSi implementation for storage networking read:

Defining iSCSI
Defining FCIP
IP Storage Networking Benefits
iSCSI Standardization
Cisco Implementation

Defining iSCSI
The iSCSI protocol enables universal access to storage over standard, Ethernet-based TCP/IP networks. iSCSI is a SCSI transport protocol for mapping block-oriented storage over TCP/IP networks.

Making direct access to storage over IP possible, the iSCSI protocol allows IP-connected hosts to access iSCSI or Fibre Channel-connected storage.



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iSCSI is fully compatible with existing Ethernet and IP WAN infrastructures. Using iSCSI, users can access storage across campus and wide area networks allowing data center storage to scale across the enterprise.

Relying on existing IP network infrastructures, local and wide area routers and switches transparently extend storage access across the WAN for applications such as remote disk copy and tape backup and restore. In the WAN environment, TCP/IP ensures data reliability, manages network congestion, and controls WAN retransmissions.

Defining FCIP
Another important technology for linking Fibre Channel storage area networks (SAN) is Fibre Channel over IP (FCIP). FCIP and iSCSI are complementary solutions for enabling company wide access to storage. FCIP transparently interconnects Fibre Channel (FC) SAN islands over IP networks, while iSCSI allows IP-connected hosts to access iSCSI or FC-connected storage.

iSCSI and FCIP are typically used for different purposes. With iSCSI, SCSI commands and data frames are encapsulated in IP to support I/O disk access over an IP network. With FCIP, Fibre Channel frames are encapsulated in IP so that both SCSI and non-SCSI frames can be transported over an IP network.

The combination of FCIP and iSCSI allows enterprises to:

Interconnect SAN islands
Provide applications including remote backup and replication, in addition to performing Fibre Channel I/O communication

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IP Storage Networking Benefits
Relying on industry standards, network managers benefit from cost effective, centralized management by implementing storage access using high speed IP connections and Gigabit Ethernet.

IP storage networking advantages include:

Delivery of universal access to storage from the data center, campus, metropolitan area network (MAN), and WAN
Reliance on a single access technology for block and file-based storage
Availability of intelligent IP network services for management, security, and quality of service (QoS)
Simplified network design, administration, and support by relying on existing IP network expertise
Economies of scale by using existing, standards-based IP infrastructures, products, and services

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iSCSI Standardization
Proposed by Cisco and IBM, iSCSI is an Internet Engineering Task Force (IETF) draft standard. The IETF work groups develop Internet standard specifications for iSCSI and FCIP. For more information on standardization and definition drafts, visit the IP Storage Work Group.

As co-founder and co-chair of the Storage Networking Industry Association (SNIA) IP Storage Forum, Cisco is working with SNIA members to sponsor work groups and develop Fibre Channel recommendations to submit to standards organizations. For more information, visit SNIA.

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Cisco iSCSI Implementation
As the industry's first iSCSI networking product, the Cisco SN 5420 Storage Router offers iSCSI connectivity for storage networks. The Cisco SN 5420 provides secure IP access to stored data from any IP-connected server, enabling universal access to storage.

The Cisco SN 5420 fits seamlessly into existing Fibre Channel storage and TCP/IP data networks enabling users to consolidate stored data. By implementing iSCSI on servers and deploying the Cisco SN 5420, users effectively share disks over an existing network or over a dedicated Gigabit Ethernet infrastructure for high performance applications.



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The Cisco SN 5420 can support a variety of network configurations. For IP access to shared storage, attach the Cisco SN 5420 to a Cisco Catalyst& 6000 Switch to connect intranets, the Internet, and iSCSI-enabled servers with iSCSI network interface cards (NICs). To facilitate IP access to a centralized storage pool, a Gigabit Ethernet link can connect a router or switch to the Internet or an organization's intranet.

To learn more about iSCSI, read:

iSCSI Protocol Concepts and Implementation
iSCSI Requirements and Design Considerations
Cisco's Cree Makes Case for iSCSI Internet World

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