The heart of Cisco TCP/IP Suite is a dependable, fully- functional TCP/IP stack. The TCP/IP stack's unique, layered architecture includes a kernel API (Application Program Interface) and a DPC (Deferred Procedure Call) layer optimized for Windows.
The Cisco TCP/IP kernel is implemented as a 32-bit VxD (Virtual Device Driver). A VxD is a multiplexing device driver that manages data exchanges between Windows applications and system services.
By running the kernel in a VxD, the kernel uses no DOS memory and conserves real-mode memory by running in protected-mode memory. The VxD also runs at Ring 0 priority level, which means that it does not stop when other applications interrupt control of the system. As a result, stack performance is not affected by other applications.
The kernel API is designed specifically for WinSock so that it minimizes communications between WinSock and the kernel. Because the stack fully supports the WinSock API, you can run any WinSock-compliant application over the TCP/IP stack without any changes.
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