Re: Long Headers and Version Negotiation

[Martin Duke <[e-mail]>]

I agree. The only other alternative I can see is to make 0xff an invariant
for initial packets. I don't have a strong opinion one way or the other.

On Fri, Jan 5, 2018 at 2:46 PM, Nick Banks <[e-mail]> wrote:

> If you are sending 0-RTT packets then you have connected to this server
> before and should be able to remember the version you used. The only issue
> then, is if the server stops supporting a particular version and then you
> try to reconnect. Either way, a server might want to have some throttling
> logic for VN packets sent out; but I don’t think it would be the end of the
> world if it didn’t.
>
>
>
> - Nick Banks
>
>
>
> *From:* QUIC [mailto:[e-mail]] *On Behalf Of *Martin Duke
> *Sent:* Friday, January 5, 2018 2:39 PM
> *To:* IETF QUIC WG <[e-mail]>
> *Subject:* Long Headers and Version Negotiation
>
>
>
> The invariants draft
> <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf.org%2Fhtml%2Fdraft-thomson-quic-invariants-00&data=02%7C01%7Cnibanks%40microsoft.com%7Cd3a2449b9239497e80a608d5548d1eff%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636507887456170898&sdata=l1gMfIkx9QmJiJtkHRALPevafNru5A63IwiMsnUaj84%3D&reserved=0>
> only reserves the 0x80 and 0x40 codepoints in the first byte of the packet.
>
>
>
> The transport draft suggests that only initial packets should trigger
> version negotiation. However, the Initial Packet byte (0xff) is not
> invariant. So for version negotiation to work at all, servers must send VN
> packets for *any* long header type where the version is unsupported --
> otherwise, QUICv2 might select 0xe3 as the Initial Packet and v1 servers
> would ignore it.
>
>
>
> On the other hand, in 0RTT cases this might create a storm of VN packets
> if the version is wrong. I suppose clients are probably not sending 0RTT if
> they don't know the supported versions.
>
>
>
> Am I thinking about this correctly? If so, I'm happy to file an issue, and
> a PR if we agree that the correct solution is to reply with VN to all long
> headers with unsupported versions.
>
>
>
> - Martin Duke
>