As I understand it, there is no internet protocol that provides true broadcast like in say a card game or a partially synchronous network assumption. How close can internet protocols come though?

We've many parties playing some card game. Alice has a "hairdresser" card she wishes to play, so she broadcasts "hairdresser". Eve really does not want Alice to be the hairdresser right now.

We're playing over the internet though, so Alice's broadcast actually tells everyone in sequence, so Alice might tell Eve first. In this case, Eve will massively DDoS Alice, say 30 million botnet nodes. Eve might not necessarily have any bots in the same data center as Alice though.

We could solve this problem with a reliable broadcast protocol, in which erasure coding prevents Eve from learning before enough others, but that brings other complications, so my question is: How can Alice ensure that many of her outgoing "hairdresser" messages survive Eve's DDoD?

Alice has previously established TLS connections with all other players, either TCP or UDP. As I understand it, UDP survives DDoS somewhat better because lost TCP ACKs could block Alice's outgoing messages, not sure if QUIC suffers this too, yes? Eve cannot DDoS all the other player because then the game makes no progress.

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    Alice can't make sure her outgoing message survives. This is like asking "How can I make sure my process get CPU cycles?" when your CPU is constantly running at 100%.
    – Jeroen
    Commented Dec 14, 2020 at 21:48

1 Answer 1


Any protocol that guarantees reliable delivery would suffer under a massive incoming DDoS. UDP per se won't, but QUIC, like TCP, would.

Some of this negative impact — under certain circumstances — could be handled with selective acknowledgment or different congestion control mechanisms, but in general, you'll need to drop acknowledgment completely.

In real gaming tournaments over the Internet a lot of effort is invested to make sure that the IP addresses of the competing teams don't leak to each other. A centralized server or a network of proxies are used to ensure that.

A fun story: there once was a bug in Skype that leaked the IP addresses of the Skype users. As a result, Skype was banned from most of the major gaming tournaments, and firing off a Skype window while in the game was enough to get you immediately disqualified from the competition.

  • Is there anything more reliable about the origin and port on a TCP packets than on UDP packets? If so, then maybe QUIC fares even less well than both TCP and UDP under DDoS? Or maybe it'll turn out mostly like TCP for DDoS? Commented Dec 15, 2020 at 10:54
  • "about the origin and port on a TCP packets than on UDP packets". Please rephrase, I don't understand the question.
    – ximaera
    Commented Dec 15, 2020 at 11:35

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