Intel IXP400 manual Buffer Management, What’s New, Overview

	Intel® IXP400 Software
Buffer Management	3

This chapter describes the data buffer system used in Intel® IXP400 Software v2.0, and includes definitions of the IXP400 software internal memory buffers, cache management strategies, and other related information.

3.1What’s New

There are no changes or enhancements to this component in software release 2.0.

3.2Overview

Buffer management is the general principle of how and where network data buffers are allocated and freed in the entire system. Network data buffers, whose formats are known to all involved components, need to flow between access-layer components.

As shown in Figure 3, the IXP400 software access-layer follows a simple buffer-management principle: All buffers used between access-layer component and clients above the access-layer component must be allocated and freed by the clients, that is, in this case, the operating system driver. The client passes a buffer to an access-layer component for various purposes (generally, Tx and Rx), and the access-layer component returns the buffer to the client when the requested job is completed. The access-layer component’s Operating System Abstraction Layer module provides the mapping of the OS buffer header fields to the IXP buffer format. Clients can also implement their own utilities to convert their buffers to the IXP_BUF format and vice-versa. Depending upon the service requested, the NPE modifies the IXP_BUF’s shared structure and hands the buffer back to the access-layer component. The Figure 3 shows different stages where the different fields in the IXP_BUF buffer gets updated at transmit and receive time.

Programmer’s Guide	IXP400 Software Version 2.0	April 2005
	Document Number: 252539, Revision: 007	35