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Autonomic Negotiation in Pre-OS Environments for Ethernet

IP.com Disclosure Number: IPCOM000022448D
Original Publication Date: 2004-Mar-15
Included in the Prior Art Database: 2004-Mar-15
Document File: 1 page(s) / 7K

Publishing Venue

IBM

Abstract

A method to handle an ethernet protocol mismatch in the pre-OS, pre-Device Driver load timeframe. At power-on and in the preboot environment, most Ethernet silicon today, by default, supports only auto-negotiation until a device driver changes those registers. Thus, it is easy to see how a duplex mismatch can occur when a user is performing a RIS or other image push using PXE. This article describes a method to allow the system BIOS and Ethernet hardware to automatically detect the duplex mismatch, based on Ethernet packet errors, and change duplex setting in the Ethernet hardware registers. This autonomic correcting of the mismatch allows the client to continue using Ethernet in the pre-OS environment without performance impacts.

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Autonomic Negotiation in Pre-OS Environments for Ethernet

Main Idea

Even though most Ethernet devices support auto-negotiation, network connectivity problems can still occur if one device is set for auto-negotiation and the other is at a forced speed/duplex. Both devices will link at the correct speed, but a duplex mismatch may occur. The concept of a duplex mismatch is well documented in industry, as referenced in this Cisco article: http://www.cisco.com/warp/public/473/46.html#auto_neg_valid. This article describes several duplex mismatch scenarios. For example, when Device #1 is set at Auto negotiation and Device #2 is set at 100Mbps/Full Duplex, the resulting connection is 100Mbps/Half Duplex. Since Device Number #2 is expecting full duplex, a duplex mismatch occurs, generating errors/collisions on the line, and extremely poor performance.

This article provides a method to handle a mismatch in the pre-OS, pre-Device Driver load timeframe. At power-on and in the preboot environment, most Ethernet silicon today, by default, supports only auto-negotiation until a device driver changes those registers. Thus, it is easy to see how a duplex mismatch can occur when a user is performing a RIS or other image push using PXE.

The article allows the system BIOS and Ethernet hardware to automatically detect the duplex mismatch, based on Ethernet packet errors, and change duplex setting in the Ethernet hardware registers. This autonomic correcting of the mismatch allows the client to continue using Ethernet in the pre-OS environment without performance impacts.

Based on the duplex discove...