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Re: [qemu-s390x] [PATCH v2 0/4] pc-bios/s390-ccw: Allow network booting

From: Viktor VM Mihajlovski
Subject: Re: [qemu-s390x] [PATCH v2 0/4] pc-bios/s390-ccw: Allow network booting via pxelinux.cfg
Date: Wed, 13 Jun 2018 12:56:08 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0

On 12.06.2018 08:17, Thomas Huth wrote:
> On 11.06.2018 14:03, Viktor VM Mihajlovski wrote:
> If you have the time to look at the traffic, could you please also check
> the TFTP block size option that is negotiated at the beginning of the
> TFTP transfer? If this other client is negotiating a transfer block size
> that is bigger than the one from the s390-ccw firmware, this could
> explain the differences in the downloading time, too.
> libnet from SLOF currently uses a block size of 1428. This is the size
> where all TFTP data should still fit nicely into one ethernet packet -
> and this is also the size which is still supported by all TFTP servers
> that support the blksize option. But theoretically it's also possible to
> use a bigger block sizes if both, the server and the client support
> fragmented UDP packets. Unfortunately, as far as I can see, SLOF's
> libnet does not support fragmented UDP packets, so we can't increase the
> block size here anymore so easily.
You will be pleased to hear that the SLOF TFTP client outperforms the
busybox version (which uses 544-byte packets) by 30%. There's some
randomness introduced by the differences in DHCP response times which is
clearly not the client's fault. All is good...
  Viktor Mihajlovski

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