Re: [quicwg/base-drafts] renamed max_packet_size to max_udp_size (#3473)

Kazuho Oku <notifications@github.com> Thu, 20 February 2020 23:49 UTC

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Subject: Re: [quicwg/base-drafts] renamed max_packet_size to max_udp_size (#3473)
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kazuho commented on this pull request.



>  
-: The maximum packet size parameter is an integer value that limits the size of
-  packets that the endpoint is willing to receive.  This indicates that packets
-  larger than this limit will be dropped.  The default for this parameter is the
-  maximum permitted UDP payload of 65527.  Values below 1200 are invalid.  This
-  limit only applies to protected packets ({{packet-protected}}).
+: The maximum udp size parameter is an integer value that limits the size of
+  UDP payloads that the endpoint is willing to receive.  This indicates that
+  packets larger than this limit are likely not to be processed by the receiver.

I think we need to talk about both UDP payload size and QUIC packet size, because they are different things.

I would assume that we'd all agree that an endpoint is allowed to process UDP datagrams that are larger than the advertised maximum. The endpoint cannot consider that as a protocol violation, because UDP datagrams are not authenticated.

Contrary to that, certain QUIC packets are "protected," and an endpoint _can_ report a protocol violation if it receives a protected QUIC packet that can be decrypted, but is larger than the advertised maximum. If such check needs to be done (or should not be done) is under debate in #3447.

The new text says that "packets larger than this limit are likely not to be processed."

I'd interpret this as "a receiver MAY process packets larger than this limit", and therefore would consider that this PR at the moment is trying to also close #3447, by implying that "a receiver MUST NOT close the connection when it receives a QUIC packet that is greater than the advertised limit."

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