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by nocarrier
3615 days ago
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The list of firewall-punchable level 4 protocols is frozen in time to just TCP and UDP, and it's sad at first glance, but it's not as bad as we think: * Most ISPs don't mangle UDP, and if you care enough about perf to be using UDP in the first place, you can afford to figure out who mangles UDP and fall back to TCP for those networks. It's a very small number of networks. * Any TCP/SCTP/etc inspired protocol you can think of can be implemented on top of UDP. Its header is only eight bytes long and it adds minimal overhead. UDP socket semantics are simple enough that you can treat them as a slightly smarter IP socket and build your protocol as if you were running directly on top of IPv6. * There's a huge advantage to being able to implement your protocol in userland since you get fine grained control over congestion and connection logic. There's a huge disadvantage too, since it's actually hard to implement that stuff yourself. But for the people who are large enough to build their own protocols (FB, Google, etc), it's worth it. * You can even encapsulate SCTP inside UDP to punch through middleware firewalls if you want to. I don't know of anyone doing that for real in the wild, but there's a RFC for it (RFC 6951). |
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The fine grained control over congestion and congestion logic is cool, sure. But more important in my mind is the fact that there's a cross-platform API available and you can rapidly make changes to how the protocol works without needing to require a specific kernel version or a specific operating system.
There's a whole lot of really cool frameworks for SDN to allow people to work at lower levels, but that's the problem - a standard API that everyone can expect to be widely available hasn't really emerged yet.