an 4 Gbps. It allows mul- tiple existing interface command sets such as IP, SCSI, IPI, HIPPI-FP, and audio/video. For example, SCSI is mapped onto a higher-layer protocol over the Fibre Channel stack. Fibre Channel topologies are sustained by switching fabric devices that closely resemble the switches found in more widely used packet networks. Most current SANs are built around Fibre Channel infrastructures as they allow the efficient SCSI- based transfer of data over large distances. This is something that SCSI cannot do, but Fibre Channel does this very well. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. STORAGE NETWORK PROCESSORS (SNPS) STORAGE NETWORK PROCESSORS (SNPs) 197 Incidentally, the University of New Hampshire Interoperability Lab (UNH IOL) offers services for the certification of interoperability of Fibre Channel products from different equipment and SNP vendors. Fibre Channel eliminates all scalability and bandwidth problems previously associated with the simple SCSI bus. It is important to note that current RAID storage devices ship with Fibre Channel loops directly integrated in their backplane for native support of Fibre Channel and for the modular capability of being hot swappable. Hot swappable means that one disk unit can be removed from the RAID array for service or replacement without affecting the availability of the overall RAID system. Before we discuss systems that allow interoperability between the Fibre Channel and the IP world, we must mention some of the main technical characteristics of the Fibre Channel: It provides transmission reliability by offering the option of delivery confirmation. Alternatively, an implementation can completely bypass the Fibre Channel protocol stack to increase performance. It fully supports widely known mechanisms of network self-discovery, including relevant protocols such as Addr