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Full Discussion: TCP Packet size
Special Forums IP Networking TCP Packet size Post 302523124 by olle on Wednesday 18th of May 2011 03:16:29 AM
Old 05-18-2011
mcnamara: No, there is unfortunately no way to get around using another chip.
And I should have mentioned that the MSS given from this device/chip is at 536 bytes. And this communication takes place at a local network. And there are no ICMP messages indicating that this MSS is set too high.

From a Windows application, which too communicates with this device, the packet size used is 536 bytes (well, only when needed of course). The chip is terrible slow anyway, but doing all this extra ACK'ing is making it much worse.

I'm passing buffers to send() which, some of them, are quite a lot bigger than 536 bytes and still the biggest TCP packet seen has a data length of 268 bytes. And as said the window size announced is always at 536 bytes from the chip. Still I fail to see how this makes any sense.

DGPickett: I can see that send() is swallowing chunks bigger than 268 bytes. I have tried playing around with TCP options like NODELAY, and changing socket buffer sizes. And have tried to change some of the settings found at /proc/sys/net related to TCP, but still nothing have changed this behavior.

Thank you for helping, and more tips are welcome Smilie
 

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PNPBIOS(4)						 BSD/i386 Kernel Interfaces Manual						PNPBIOS(4)

NAME
pnpbios -- support for embedded devices on the motherboard DESCRIPTION
The pnpbios driver enumerates embedded ISA devices on the motherboard whose BIOS supports ``Plug and Play BIOS Specification''. It assigns ISA bus resources (interrupt line, DMA channel, I/O ports, and memory region) to each device and activates it. If it cannot assign necessary resources to a device without causing conflict with other devices in the system, the device will not be acti- vated and will be unavailable to programs. CAVEATS
There is no explicit way to disable individual embedded devices. The pnpbios driver will find all devices reported by the ``Plug and Play (PnP)'' BIOS and try to activate them all. There is no way to explicitly assign particular resource to a device. The resource assignment is fully automatic and there is no provision for manual override. SEE ALSO
pnp(4) STANDARDS
Compaq, Phenix, and Intel, Plug and Play BIOS Specification Version 1.0A, May 5, 1994. Compaq, Phenix, and Intel, Plug and Play BIOS CLARIFICATION Paper for Plug and Play BIOS Specification Version 1.0A, October 6, 1994. HISTORY
The pnpbios driver first appeared in FreeBSD 4.0. AUTHORS
The pnpbios driver was written by Mike Smith. BSD
September 20, 2001 BSD
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