UDP Isn't Unreliable, It's a Conertible

Re:UDP Isn't Unreliable, It's a Conertible by jeroenhd on Thursday October 30, 2025 @03:25PM (#45764196)

UDP has a checksum for a reason, bitflips happen and packets get mandled or lost, even if you control both sides of the link.

Your chances are better but you can't assume packet loss or data errors can't happen just because the fiber is right in front of you.

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Re:UDP Isn't Unreliable, It's a Conertible by jandrese on Thursday October 30, 2025 @03:46PM (#45764454)

The UDP checksum is optional and weak. It's mostly a waste of time.

It's far more likely if you get a bit flip that the layer 1 hardware will just drop the packet because it has a much better checksum that detected the error first. Even if you know every part of the hardware and software stack you have to plan for an occasional packet drop.

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Re:UDP Isn't Unreliable, It's a Conertible by jeroenhd on Friday October 31, 2025 @04:59AM (#45769820)

My point wasn't that you should rely on the weak checksum, but rather that the possibility for failure is already baked in even for such a small set of fields, because errors of any kind can happen at any point even in the simplest setups.

The statement

    With adjustments to ring buffers, IRQ/core affinity, and receive buffer size, you can receive a saturated 40GbE stream with no packet loss.

_Probably_ works out _most_ of the time in physical setups (especially in server environments with strict ECC memory), but it's not something you can write a protocol around if you need all of that data to _actually_ arrive.

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