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Re: [lwip-users] Hardware Assisted Checksum

From: Timmy Brolin
Subject: Re: [lwip-users] Hardware Assisted Checksum
Date: Wed, 23 Nov 2005 20:20:37 +0100
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax)

I guess Ethernet MACs integrated into PC chipsets may have this feature, especially the gigabit interfaces. But I have never seen this in a Ethernet MAC intended for embedded systems. Have you?
The only exception would be MACs implemented in FPGAs..

/Timmy Brolin

It is common these days to have TCP/UDP/IP checksum assistance in ethernet interface chips. This is a very appropriate place for the checksum, since everything is ready for checksumming by the time it gets to the chip.

The amount of preparation necessary in order to use this varies from chip to chip. For that reason, driver level work is required. I believe that FreeBSD and Linux driver interfaces have been modified to accommodate the availability of checksumming services. It may be an appropriate future consideration for lwIP.

If lwIP allowed checksumming services to be performed at the driver level or beneath, then systems having special hardware - either in the ethernet chip or some other FPGA - could be used.

Jim Gibbons
Gibbons and Associates, Inc.
        TEL: (408) 984-1441
900 Lafayette, Suite 704, Santa Clara, CA
        FAX: (408) 247-6395

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