Re: [quicwg/base-drafts] Initial size of dynamic table (#1530)

[Mike Bishop <[e-mail]>]

Ah, I see.  So the receiver has declared a maximum of 4KB, but if the encoder doesn't specify a size before sending instructions, what is the table size at that point?

My initial inclination matched yours, to say that it's the receiver's declared maximum, so that the encoder only needs to speak to reduce it. But there's a corner case: In 0-RTT, we assume the previous max; server can't accept 0-RTT if it's going to go *lower*, but can still increase its value when it sends the SETTINGS frame.  That means either the server has to detect whether particular instructions were sent before or after the handshake completed and change the implicit table size, or there's a nasty corner case when the client thinks it has overflowed the table but the server thinks it hasn't.

HPACK requires the size change instruction to be the first instruction of the first block following the change; I'd honestly never thought about whether that requires a size change to be the first instruction of the first header block sent on a connection.  Does it?

I think it has to be zero, and require the encoder to declare the size it intends to use.

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