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Update MTU post

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Neil Alexander 2018-07-13 10:34:11 +01:00
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_posts/2018-07-13-about-mtu.md
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@ -24,13 +24,14 @@ operating system will have to fragment the packet down into smaller ones before
sending out onto the wire. sending out onto the wire.
With a smaller MTU, you will be forced to re-send the IP headers (and possibly With a smaller MTU, you will be forced to re-send the IP headers (and possibly
other headers) along with every single packet. Those are not only wasted bytes other headers) far more often with every single packet. Those are not only
on the wire, but every packet likely requires a new set of system calls to wasted bytes on the wire, but every packet likely requires a new set of system
handle. In the case of Yggdrasil, we rely on system calls not just for socket calls to handle. In the case of Yggdrasil, we rely on system calls not just for
operations but also for TUN/TAP. Each system call requires a context switch, socket operations but also for TUN/TAP. Each system call requires a context
which is a slow operation. On embedded platforms, this can be a real killer for switch, which is a slow operation. On embedded platforms, this can be a real
performance - in fact, on an EdgeRouter X, context switching for the TUN/TAP killer for performance - in fact, on an EdgeRouter X, context switching for the
adapter is a greater bottleneck than the cryptographic algorithms themselves! TUN/TAP adapter is a greater bottleneck than the cryptographic algorithms
themselves!
### Selecting TCP instead of UDP ### Selecting TCP instead of UDP