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It's time to replace TCP in the datacenter (2023)

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Re: It's time to replace TCP in the datacenter (2023)

#42

Post by stiray »

detaro wrote: post #36
stiray wrote: post #20

How long did we need to support ipv6? Is it supported yet and more widely in use than the ipv4, like in mobile networks where everything is stashed behind NAT and ipv4 kept? Another protocol, something completely new? Good luck with that, i would rather bet on global warming to put us out of our misery (/s)... https://imgs.xkcd.com/comics/standards.png

Mobile networks especially are widely IPv6, with IPv4 being translated/tunneled where still needed. (End-user connections in general skew IPv6 in many places - it's observable how traffic patterns shift with people being at work vs at home. Corporate networks without IPv6 leading to more IPv4 traffic during the day, in the evening IPv6 from consumer connections takes over)

Android: Settings -> About (just checked mine, 10...*), check your IP. We have 3 providers in our country, all 3 are using ipv4 "lan" for phone connectivity, behind NAT and I am observing this situation around most of EU (Germany, Austria, Portugal, Italy, Spain, France, various providers).

Re: It's time to replace TCP in the datacenter (2023)

#43

Post by GoblinSlayer »

> For many years, RDMA NICs could cache the state for only a few hundred connections; if the number of active connections exceeded the cache size, information had to be shuffled between host memory and the NIC, with a considerable loss in performance.

A massively parallel task? Sounds like something doable with GPGPU.

Re: It's time to replace TCP in the datacenter (2023)

#44

Post by iforgotpassword »

dveeden2 wrote: post #38

Wasn't something like HOMA already tried with SCTP?

And QUIC. And that thing tesla presented recently, with custom silicon even.

And as usual, hardware gets faster, better and cheaper over the next years and suddenly the problem isn't a problem anymore - if it even ever was for the vast majority of applications. We only recently got a new fleet of compute nodes with 100gbit NICs. The previous one only had 10, plus omnipath. We're going ethernet only this time.

I remember when saturating 10gbit/s was a challenge. This time around, reaching line speed with tcp, the server didn't even break a sweat. No jumbo frames, no fiddling with tunables. And that actually was while testing with 4 years old xeon boxes, not even the final hw.

Again, I can see how there are use cases that benefit from even lower latency, but thats a niche compared to all DC business, and I'd assume you might just want rdma in that case, instead of optimizing on top of ethernet or IP.

Re: It's time to replace TCP in the datacenter (2023)

#45

Post by silisili »

iforgotpassword wrote: post #44
dveeden2 wrote: post #38

Wasn't something like HOMA already tried with SCTP?

And QUIC. And that thing tesla presented recently, with custom silicon even. And as usual, hardware gets faster, better and cheaper over the next years and suddenly the problem isn't a problem anymore - if it even ever was for the vast majority of applications. We only recently got a new fleet of compute nodes with 100gbit NICs. The previous one only had 10, plus omnipath. We're going ethernet only this time. I remem…

This is a solid answer, as someone on the ground. TCP is not the bogeyman people point it out to be. It's the poison apple where some folks are looking for low hanging fruit.

Re: It's time to replace TCP in the datacenter (2023)

#46

Post by wejick »

UltraSane wrote: post #12

I wonder why Fibre Channel isn't used as a replacement for TCP in the datacenter. It is a very robust L3 protocol. It was designed to connect block storage devices to servers while making the OS think they are directly connected. OSs do NOT tolerate dropped data when reading and writing to block devices and so Fibre Channel has a extremely robust Token Bucket algorithm. The algo prevents congestion by allowing receiv…

I'm imagining having a shared memory mounted as block storages then do the RPC thru this block. Some synchronization and polling/notifications work will need to be done.

Re: It's time to replace TCP in the datacenter (2023)

#49

Post by pif »

> Although Homa is not API-compatible with TCP,

IPv6 anyone? People must start to understand that "Because this is the way it is" is a valid, actually extremely valid, answer to any question like "Why don't we just switch technology A with technology B?"

Despite all the shortcomings of the old technology, and the advantages of the new one, inertia _is_ a factor, and you must accept that most users will simply even refuse to acknowledge the problem you want to describe.

For you your solution to get any traction, it must deliver value right now, in the current ecosystem. Otherwise, it's doomed to fail by being ignored over and over.

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