Re: [quicwg/base-drafts] Pull some H2 content into the introduction (#2683)

[MikkelFJ <[e-mail]>]

mikkelfj commented on this pull request.



> @@ -88,28 +88,100 @@ code and issues list for this draft can be found at
 
 HTTP semantics are used for a broad range of services on the Internet. These
 semantics have commonly been used with two different TCP mappings, HTTP/1.1 and
-HTTP/2.  HTTP/2 introduced a framing and multiplexing layer to improve latency
-without modifying the transport layer.  However, TCP's lack of visibility into
-parallel requests in both mappings limited the possible performance gains.
+HTTP/2.  HTTP/3 supports the same semantics over a new transport protocol, QUIC.
+
+## Prior versions of HTTP
+
+HTTP/1.1 was a TCP mapping which used whitespace-delimited text fields to convey

Past tense may not be appropriate as it is still in active use in a few places.

> @@ -88,28 +88,100 @@ code and issues list for this draft can be found at
 
 HTTP semantics are used for a broad range of services on the Internet. These
 semantics have commonly been used with two different TCP mappings, HTTP/1.1 and
-HTTP/2.  HTTP/2 introduced a framing and multiplexing layer to improve latency
-without modifying the transport layer.  However, TCP's lack of visibility into
-parallel requests in both mappings limited the possible performance gains.
+HTTP/2.  HTTP/3 supports the same semantics over a new transport protocol, QUIC.
+
+## Prior versions of HTTP
+
+HTTP/1.1 was a TCP mapping which used whitespace-delimited text fields to convey
+HTTP messages.  While these exchanges were human-readable, the whitespace led to
+parsing difficulties and workarounds to be tolerant of variant behavior.
+Because each connection could be used only for a single HTTP request and
+response at a time, multiple parallel TCP connections were used, reducing the

That is not true. Pipelining is a thing.

>  
 QUIC is described in {{QUIC-TRANSPORT}}.  For a full description of HTTP/2, see
-{{!RFC7540}}.
-
-
-## Notational Conventions
+{{!HTTP2=RFC7540}}.
+
+# HTTP/3 Protocol Overview
+
+HTTP/3 provides a transport for HTTP semantics using the QUIC transport protocol
+and an internal framing layer similar to HTTP/2.
+
+An HTTP/3 endpoint is discovered using HTTP Alternative Services.  Once a client

Can be

> +
+An HTTP/3 endpoint is discovered using HTTP Alternative Services.  Once a client
+knows that an HTTP/3 server exists at a certain endpoint, it opens a QUIC
+connection. QUIC provides protocol negotiation, stream-based multiplexing, and
+flow control.
+
+Within each stream, the basic unit of HTTP/3 communication is a frame
+({{frames}}).  Each frame type serves a different purpose.  For example, HEADERS
+and DATA frames form the frames form the basis of HTTP requests and responses
+({{request-response}}).  Other frame types like SETTINGS, PRIORITY, and GOAWAY
+are used to managed the overall connection.
+
+Multiplexing of requests is performed using the QUIC stream abstraction, with
+each request and response consuming a single QUIC stream.  Streams are largely
+independent of each other, so one stream that is blocked or suffers packet loss
+does not prevent progress on other streams.

But progress of other streams can when flow credits are exhausted.

> +  endpoint is discovered and a connection is established.
+- Stream Mapping and Usage ({{stream-mapping}}) describes the way QUIC streams
+  are used.
+- HTTP Framing Layer ({{http-framing-layer}}) describes the frames used on
+  most streams.
+- HTTP Request Lifecycle ({{http-request-lifecycle}}) describes how HTTP
+  semantics are expressed using frames.
+- Connection Closure ({{connection-closure}}) describes how connections are
+  terminated, either gracefully or abruptly.
+- Extensions to HTTP/3 ({{extensions}}) describes how new capabilities can be
+  added in future documents.
+- Error Handling ({{errors}}) describes how error conditions are handled and
+  expressed, either on a particular stream or for the connection as a whole.
+
+Readers familiar with HTTP/2 will find a more detailed comparison with that
+protocol in {{h2-considerations}}.

With that protocol? HTTP/1.1?

> +  and receive HTTP responses.
+
+connection:
+: A transport-layer connection between two endpoints, using QUIC as the
+  transport protocol.
+
+connection error:
+: An error that affects the entire HTTP/3 connection.
+
+endpoint:
+: Either the client or server of the connection.
+
+frame:
+: The smallest unit of communication within an HTTP/3 connection, consisting of
+  a header and a variable-length sequence of octets structured according to the
+  frame type.

It may be worth noting that frames can span mutiple packets unlike QUIC frames.

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