Re: Poor performance of SOCK_RAW/PF_PACKET on MacOSX.. (libpcap is better.. sorta..)
Re: Poor performance of SOCK_RAW/PF_PACKET on MacOSX.. (libpcap is better.. sorta..)
- Subject: Re: Poor performance of SOCK_RAW/PF_PACKET on MacOSX.. (libpcap is better.. sorta..)
- From: Jens Alfke <email@hidden>
- Date: Thu, 13 Feb 2014 07:14:43 -0800
On Feb 13, 2014, at 6:02 AM, Robert Monaghan < email@hidden> wrote: I am working on a software package that reads custom network frames from a hardware device.
This device works over 10GBaseT and can saturate the network pretty easily. As the data is image data, all of the data is needed.
Dropped packets during a transfer, means that the entire image has to be re-downloaded.
[Somewhat off-topic; I don't have the low-level POSIX/BSD chops to answer your specific questions]
The above requirements seem contradictory to me, as Ethernet is explicitly a lossy medium. Any packet-level network protocol has to work with the assumption that packets can and will get dropped. There can be collisions on the wire; the switch/router is free to drop packets if it can't keep up, as is your local network interface, etc.
These days packet losses across one hop on an Ethernet LAN are pretty low. But they're nonzero, and if gigabits-per-second of data are being sent then I'd imagine you'd find dropped packets pretty regularly.
This may not be your fault if you're not the developer of the hardware device, but it seems like someone screwed up in designing its network protocol.
—Jens |
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