Re: [quicwg/base-drafts] Moving text on spinbit into transport (#2364)

[Martin Thomson <[e-mail]>]

martinthomson commented on this pull request.



> @@ -2818,6 +2825,44 @@ encoded as a single byte with the value 0x01.  An endpoint MAY treat the receipt
 of a frame type that uses a longer encoding than necessary as a connection error
 of type PROTOCOL_VIOLATION.
 
+## Latency Spin Bit {#spin-bit}
+
+The latency spin bit enables passive latency monitoring from observation points
+on the network path throughout the duration of a connection. The spin bit is
+only present in the short packet header, since it is possible to measure the
+initial RTT of a connection by observing the handshake. Therefore, the spin bit
+will appear after version negotiation and connection establishment are
+completed. On-path measurement and use of the Latency Spin Bit is further
+discussed in {{QUIC-MANAGEABILITY}}.
+
+The spin bit utilizes a single bit in the first byte of the short header. The

the word "utilizes" is banned from this document
```suggestion
The spin bit uses a single bit in the first byte of the short header. The
```

> +discussed in {{QUIC-MANAGEABILITY}}.
+
+The spin bit utilizes a single bit in the first byte of the short header. The
+location of the bit and procedures for how to set it by clients and servers are
+defined in {{short-header}}.
+
+Implementations MAY select to not implement the full spin bit functionality. In
+that case they are only REQUIRED to implement what is defined for the spin bit
+when it is disabled.
+
+Each endpoint unilaterally decides if the spin bit is enabled or disabled for a
+connection. Implementations SHOULD allow administrators of clients and servers
+to disable the spin bit either globally or on a per-connection basis. Even when
+the spin bit is not disabled by the administrator implementations SHOULD disable
+the spin bit on a randomly chosen fraction of connections. However, connections
+may be configured to explicitly enable spinning, for example in the case of

```suggestion
could be configured to explicitly enable spinning, for example in the case of
```

> +
+Each endpoint unilaterally decides if the spin bit is enabled or disabled for a
+connection. Implementations SHOULD allow administrators of clients and servers
+to disable the spin bit either globally or on a per-connection basis. Even when
+the spin bit is not disabled by the administrator implementations SHOULD disable
+the spin bit on a randomly chosen fraction of connections. However, connections
+may be configured to explicitly enable spinning, for example in the case of
+explicit customer support and debugging.
+The random selection process SHOULD be designed such that on average the spin
+bit is disabled for at least one eighth of network paths. The selection process
+should be externally unpredictable but consistent for any given combination of
+source and destination address and port. For instance, the implementation might
+have a static key which it uses to key a pseudorandom function over these values
+and use the output to determine whether to send the spin bit. The selection
+process performed at the beginning of the connection SHOULD be applied for all
+paths used by the connection.

Gah, this last sentence is bad.

> @@ -2818,6 +2825,44 @@ encoded as a single byte with the value 0x01.  An endpoint MAY treat the receipt
 of a frame type that uses a longer encoding than necessary as a connection error
 of type PROTOCOL_VIOLATION.
 
+## Latency Spin Bit {#spin-bit}

Please move this to a subsection under the Short Header description.

> @@ -3948,8 +3993,33 @@ Fixed Bit:
 
 Spin Bit (S):
 
-: The sixth bit (0x20) of byte 0 is the Latency Spin Bit, set as described in
-  {{!SPIN=I-D.ietf-quic-spin-exp}}.
+: The third most significant bit (0x20) of byte 0 is the Latency Spin Bit.
+
+: When the spin bit is disabled, endpoints MAY set the spin bit to any value,

Please don't have so many paragraphs nested like this.  A forward reference to a section that includes this text would be much better.

> @@ -3948,8 +3993,33 @@ Fixed Bit:
 
 Spin Bit (S):
 
-: The sixth bit (0x20) of byte 0 is the Latency Spin Bit, set as described in
-  {{!SPIN=I-D.ietf-quic-spin-exp}}.
+: The third most significant bit (0x20) of byte 0 is the Latency Spin Bit.
+
+: When the spin bit is disabled, endpoints MAY set the spin bit to any value,
+and MUST accept any incoming value. It is RECOMMENDED that they
+set the spin bit to a random value either chosen independently for each packet,
+or chosen independently for each path and kept constant for that path.
+
+: If the spin bit is enabled for the connection the endpoint maintains a spin

```suggestion
: If the spin bit is enabled for the connection, the endpoint maintains a spin
```

> @@ -3948,8 +3993,33 @@ Fixed Bit:
 
 Spin Bit (S):
 
-: The sixth bit (0x20) of byte 0 is the Latency Spin Bit, set as described in
-  {{!SPIN=I-D.ietf-quic-spin-exp}}.
+: The third most significant bit (0x20) of byte 0 is the Latency Spin Bit.
+
+: When the spin bit is disabled, endpoints MAY set the spin bit to any value,
+and MUST accept any incoming value. It is RECOMMENDED that they
+set the spin bit to a random value either chosen independently for each packet,
+or chosen independently for each path and kept constant for that path.
+
+: If the spin bit is enabled for the connection the endpoint maintains a spin
+value, 0 or 1, and sets the spin bit in the short header to the currently stored

```suggestion
value and sets the spin bit in the short header to the currently stored
```

> @@ -3997,6 +4067,7 @@ version.  See {{QUIC-INVARIANTS}} for details on how packets from different
 versions of QUIC are interpreted.
 
 
+

```suggestion
```

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