Storage Basics: Deciphering SESAs (Strange, Esoteric Storage Acronyms) Page 2


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Often confused with FCIP is the closely named iFCP. The Internet Fibre Channel Protocol (iFCP), however, is an entirely different technology. iFCP allows an organization to extend Fibre Channel storage networks over the Internet using TCP/IP. As with FCIP, TCP is responsible for managing congestion control as well as error detection and recovery services.

The differences between the two technologies are straightforward. FCIP is used to extend an existing Fibre Channel fabric with an IP-based tunnel, allowing networking over distances. This means that the FCIP tunnel is IP-based, but everything else remains Fibre Channel.

iFCP, on the other hand, represents a potential migration strategy from current Fibre Channel SANs to future IP SANs. iFCP gateways can either complement existing Fibre Channel fabrics or replace them altogether. iFCP allows an organization to create an IP SAN fabric that minimizes the Fibre Channel fabric component and maximizes use of the company's TCP/IP infrastructure.

Storage over IP (SoIP)

Another technology that harnesses IP-based storage is known as Storage over IP (SoIP). SoIP refers to the merging of Fibre Channel technologies with IP-based technology. As mentioned when discussing iFCP and FCIP, merging Fibre Channel technology and IP allows high availability and high performance storage solutions over great distances. SoIP uses standard IP-based protocols, including Open Shortest Path First (OSPF), Simple Mail Transfer Protocol (SMTP), and Routing Information Protocol (RIP).

As you can imagine, using familiar IP-based protocols makes SoIP highly compatible with existing Ethernet infrastructures. For those wondering about how SoIP differs from technologies such as iSCSI, the difference is in the IP transport protocol used. iSCSI uses the TCP protocol for transport, while SoIP uses the User Datagram Protocol (UDP).

TCP is a protocol that provides connection-oriented (guaranteed) delivery of packets across the network. Unlike TCP, UDP offers a best delivery mechanism for packets. As such, it offers lower overhead and therefore more efficient transport. UDP is a connectionless protocol and does not guarantee the delivery of data packets. UDP is used when reliable delivery is not necessary (i.e. when another protocol or service is already responsible for handling this).

Because of the use of UDP, SoIP data transport is faster, yet more unreliable, than iSCSI. The goal of SoIP, like other IP storage options, is to use an existing IP infrastructure to reduce additional hardware costs and retraining.

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