Moving past TCP in the data center, part 1

Posted Nov 2, 2022 21:19 UTC (Wed) by joib (subscriber, #8541)
In reply to: Moving past TCP in the data center, part 1 by jenro
Parent article: Moving past TCP in the data center, part 1

> Is it just me, who thinks some of these ideas sound rather strange?

It's just you.

> Is it really true, that all or at least most traffic in a DC is some kind of RPC or request/reply system? Is it really true, that small packages are the ones that the whole DC needs to be optimized for? I highly doubt this.

No, the argument is that 'lots of small messages' is an important usecase that TCP struggles with, due to inherent features in the TCP design. Large transfers are certainly not unimportant, but OTOH, if you can fill your pipe with lots of small messages, then the special case of a few very large messages is kind of trivial.

> if I want to give up my reliable TCP connections for Homa.

So with TCP you get 'reliable stream', and with UDP you get 'unreliable datagram'. The argument here is that for a lot of applications, the correct primitive is neither of these, but rather a 'reliable datagram' kind of service. Which is what this Homa proposal is apparently providing. Incidentally, Amazon's SRD is another design that has converged to a roughly similar conclusion.

Moving past TCP in the data center, part 1

Posted Nov 2, 2022 23:39 UTC (Wed) by willy (subscriber, #9762) [Link]

It sounds like it's reliable out-of-order datagrams which is different from SOCK_SEQPACKET (reliable in-order datagrams)

Moving past TCP in the data center, part 1

Posted Nov 2, 2022 23:43 UTC (Wed) by rcampos (subscriber, #59737) [Link]

TIPC is another protocol that offers reliable datagram. It's merged in Linux since the 2.6 era at least.

It is a very interesting protocol for local networks, but don't know benchmarks about it.