Implement congestion control

[dktapps]

Currently RakLib does not properly rate limit packet sending for sessions. This is a big problem because connections may have smaller bandwidth capability than RakLib sessions are trying to send. This causes the client to panic and flood the server with NAKs, causing the server to IP-ban the client for denial of service attack.

Generally this manifests in PM when sending resource packs or lots of chunks over bad connections resulting in an IP ban by the server.

[fabrififi]

How to fix it?

[dktapps]

Implement congestion control

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