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We need a replacement for TCP in the datacenter [pdf]

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Re: We need a replacement for TCP in the datacenter [pdf]

#22

Post by DonHopkins »

I'd tell you a UDP joke, but you probably wouldn't get it.

So here's a TCP joke:

Hello, would you like to hear a TCP joke?

Yes, I'd like to hear a TCP joke.

OK, I'll tell you a TCP joke.

OK, I'll hear a TCP joke.

Are you ready to hear a TCP joke?

Yes, I am ready to hear a TCP joke.

OK, I'm about to send the TCP joke. It will last 10 seconds, it has two characters, it does not have a setting, it ends with a punchline.

OK, I'm ready to hear the TCP joke that will last 10 seconds, has two characters, does not have a setting and will end with a punchline.

I'm sorry, your connection has timed out... ...Hello, would you like to hear a TCP joke?

Re: We need a replacement for TCP in the datacenter [pdf]

#23

Post by PixelOfDeath »

vore wrote: post #8
manv1 wrote: post #7

It's interesting that everyone (including the author) talks about UDP as a lossy protocol, but it doesn't seem that UDP drops actually occur on a routine basis anywhere. The UDP-based DDOS attacks seem to prove that; if UDP really was being dropped, those DDOS attacks wouldn't be so problematic. That said, it's an interesting read. TCP is inefficient, but that inefficiency has been patched/masked by hardware solution…

I think re UDP the point regarding it being unreliable is that you have to design your applications to take the unreliability into account, because it does happen even if it may be infrequent: assuming that it is reliable when you can get unreliable behavior will result in correctness issues.

I see UDP more like a low level interface allowing you to build your own on top. Where you decide what packages need to be revived 100% and which one can be dropped. Basically the foundation of your very own TCP with hookers and blackjack.

Re: We need a replacement for TCP in the datacenter [pdf]

#25

Post by pstuart »

DonHopkins wrote: post #22

I'd tell you a UDP joke, but you probably wouldn't get it. So here's a TCP joke: Hello, would you like to hear a TCP joke? Yes, I'd like to hear a TCP joke. OK, I'll tell you a TCP joke. OK, I'll hear a TCP joke. Are you ready to hear a TCP joke? Yes, I am ready to hear a TCP joke. OK, I'm about to send the TCP joke. It will last 10 seconds, it has two characters, it does not have a setting, it ends with a punchline.…

Ack.

Re: We need a replacement for TCP in the datacenter [pdf]

#26

Post by jeffbee »

There's a little misleading point on page 2, or just a mistake. It says "Driving a 100 Gbps network at 80% utilization in both directions consumes 10–20 cores just in the networking stack" and it cites Google's Snap paper from 2019. But the Snap paper quite clearly says nothing like that. It says that Snap can drive a 100gbps NIC to 80gpbs with just 1.05 cores (Table 1) and that the whole-machine CPU load at 80gpbs in an RPC benchmark is 4 CPUs per side (Figure 6(b)).

Aside from that I completely agree that TCP is trash.

Re: We need a replacement for TCP in the datacenter [pdf]

#27

Post by DonHopkins »

pstuart wrote: post #25
DonHopkins wrote: post #22

I'd tell you a UDP joke, but you probably wouldn't get it. So here's a TCP joke: Hello, would you like to hear a TCP joke? Yes, I'd like to hear a TCP joke. OK, I'll tell you a TCP joke. OK, I'll hear a TCP joke. Are you ready to hear a TCP joke? Yes, I am ready to hear a TCP joke. OK, I'm about to send the TCP joke. It will last 10 seconds, it has two characters, it does not have a setting, it ends with a punchline.…

Ack.

Fin!

Re: We need a replacement for TCP in the datacenter [pdf]

#29

Post by jeffbee »

manv1 wrote: post #7

It's interesting that everyone (including the author) talks about UDP as a lossy protocol, but it doesn't seem that UDP drops actually occur on a routine basis anywhere. The UDP-based DDOS attacks seem to prove that; if UDP really was being dropped, those DDOS attacks wouldn't be so problematic. That said, it's an interesting read. TCP is inefficient, but that inefficiency has been patched/masked by hardware solution…

Frame drops are endemic to cloud datacenters. High levels, all the time.
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