abit Ethernet ports are standard GMII interfaced, whereas the System Packet Interface, 3 (SPI-3) interface is 2.5 Gbps (OC-48) and aimed at switch/router applications. The iSNAP software architecture is equally versatile, as shown in Figure 11.8. It is modular and layered SO that it provides the necessary flexibility that enables the future upgrading of equipment or modification to accommodate new requirements in protocols and functionality. Driver and firmware combinations enable services such as iSCSI and Link Layer. Link Layer's interface provides standard acceleration such as checksum offload or interrupt coalescing for TCP/IP stacks that may preexist in some systems. The firmware offers extensive management features. These are important factors for mission-critical data storage applications. In addition, several services can be run simultaneously over the same port, such as iSCSI and NAS acceleration. The flexible approach enables a user to start out with just iSCSI and a native TCP/IP CIFS.NFS iSCSI Core services Diagnostics CIFS/NFS iSCSI Link Layer Firmware Foundation Layer Event/Queue Encapsulation Classification Timer Memory Manager Engine Engine FIGURE 11.8 The software architecture of the iSNAP processor. (Source: Silverback Systems) 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) 214 NETWORK PROCESSORS stack running over the Link Layer. Depending on the necessary functionality, the user can add other services such as TOE. We do not intend to give a full-fledged description of each product. Interested readers can obtain this information directly from the companies. We introduced a couple of existing SNP solutions to show the direction of the storage industry and depict an important application area for high-performance net- work-processing technology. Without the appropriate SNPs, this evolution 