Re: [quicwg/base-drafts] Client that does not PAD does not negotiate? (#4021)

Mike Bishop <> Fri, 21 August 2020 13:58 UTC

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Date: Fri, 21 Aug 2020 06:58:51 -0700
From: Mike Bishop <>
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Subject: Re: [quicwg/base-drafts] Client that does not PAD does not negotiate? (#4021)
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So let's say a hypothetical client supports versions with the following minimum packet sizes to open a connection:
- A: 1250 bytes
- B: 1200 bytes
- C: 1720 bytes

The client is trying to open a connection with version B, so they MUST send at least 1200 bytes.  However, if the server only supports A and C, this won't provoke a Version Negotiation packet and the connection attempt will time out.  That's not incorrect, because the server doesn't support the attempted version.

The client SHOULD send at least 1720 bytes, because that guarantees the packet is large enough to trigger a Version Negotiation packet in the event there's any overlap in their supported version sets.  It's only a SHOULD, not a MUST, because there might be legitimate reasons a client would opt not to send a 1720-byte packet, such as expecting a 1500-byte MTU on the network.

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