fix: Address packet overflow issues in the UTP adapter (1.1.0) #1415
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It doesn't mean anything now. Anything sent on fragmented pipelines will be broken up at 1400 bytes boundaries, and everything sent on a non-fragmented pipeline is limited to a maximum size of 1400 bytes (including overhead from the underlying protocols). Allowing to set that limit can only lead to confusion among users.
This is not the cleanest of solution, but until we figure out something better in UTP, this can at least unblock Boss Room. The core issue being fixed here is that we'd allow sending payloads up to the MTU in size on a non-fragmented pipeline. But that's incorrect since UTP must add its own overhead to the payload. If sending a payload close to the MTU in size, the overhead would bring the total packet size over the limit of the MTU. Since UTP lacks a good way of figuring out what's the actual maximum payload size that can be sent, for now we patch over the issue by sending everything on a fragmented pipeline. The exception is the unreliable messages. The fragmentation pipeline doesn't cleanly handle having multiple fragmented payloads in flight (and possibly arriving out of order). The reliable pipeline stage fixes that, but for unreliable traffic it's better not to fragment it.
Which is 2000 bytes. We won't need to hardcode that default value when the new NetworkSettings API lands. So having a magical number floating like that in the code is a temporary thing.
Cosmin-B
approved these changes
Nov 16, 2021
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This is a backport of PR #1403.
Changelog
com.unity.netcode.adapter.utp
Testing and Documentation