Merge branch 'master' into pr4473

.lint.py

@@ -7,7 +7,7 @@
 parser = argparse.ArgumentParser(description="Lint markdown drafts.")
 parser.add_argument("files", metavar="file", nargs="+", help="Files to lint")
 parser.add_argument("-l", dest="maxLineLength", default=80)
-parser.add_argument("-f", dest="maxFigureLineLength", default=65)
+parser.add_argument("-f", dest="maxFigureLineLength", default=66)
 
 args = parser.parse_args()
 

draft-ietf-quic-invariants.md

@@ -58,8 +58,7 @@ informative:
 --- abstract
 
 This document defines the properties of the QUIC transport protocol that are
-expected to remain unchanged over time as new versions of the protocol are
-developed.
+common to all versions of the protocol.
 
 
 --- note_Note_to_Readers
@@ -102,9 +101,9 @@ minimal amount of information that is made available to entities other than
 endpoints.  Unless specifically prohibited in this document, any aspect of the
 protocol can change between different versions.
 
-{{bad-assumptions}} is a non-exhaustive list of some incorrect assumptions that
-might be made based on knowledge of QUIC version 1; these do not apply to every
-version of QUIC.
+{{bad-assumptions}} contains a non-exhaustive list of some incorrect assumptions
+that might be made based on knowledge of QUIC version 1; these do not apply to
+every version of QUIC.
 
 
 # Conventions and Definitions
@@ -119,8 +118,8 @@ This document uses terms and notational conventions from {{QUIC-TRANSPORT}}.
 
 # Notational Conventions
 
-Packet diagrams in this document use a format defined in {{QUIC-TRANSPORT}} to
-illustrate the order and size of fields.
+The format of packets is described using the notation defined in this section.
+This notation is the same as that used in {{QUIC-TRANSPORT}}.
 
 Complex fields are named and then followed by a list of fields surrounded by a
 pair of matching braces. Each field in this list is separated by commas.
@@ -137,12 +136,12 @@ x (A..B):
   a minimum of zero bits and B can be omitted to indicate no set upper limit;
   values in this format always end on an byte boundary
 
-x (?) = C:
-: Indicates that x has a fixed value of C
+x (L) = C:
+: Indicates that x, with a length described by L, has a fixed value of C
 
-x (E) ...:
+x (L) ...:
 : Indicates that x is repeated zero or more times (and that each instance is
-  length E)
+  length L)
 
 This document uses network byte order (that is, big endian) values.  Fields
 are placed starting from the high-order bits of each byte.
@@ -316,8 +315,8 @@ packet it receives in the Destination Connection ID field.  The value for Source
 Connection ID MUST be copied from the Destination Connection ID of the received
 packet, which is initially randomly selected by a client.  Echoing both
 connection IDs gives clients some assurance that the server received the packet
-and that the Version Negotiation packet was not generated by an off-path
-attacker.
+and that the Version Negotiation packet was not generated by an attacker that is
+unable to observe packets.
 
 An endpoint that receives a Version Negotiation packet might change the version
 that it decides to use for subsequent packets.  The conditions under which an
@@ -343,9 +342,9 @@ reliably extracting information from a flow based on version-specific traits
 requires that middleboxes retain state for every connection ID they see.
 
 The Version Negotiation packet described in this document is not
-integrity-protected; it only has modest protection against insertion by off-path
-attackers.  An endpoint MUST authenticate the semantic content of a Version Negotiation
-packet if it attempts a different QUIC version as a result.
+integrity-protected; it only has modest protection against insertion by
+attackers.  An endpoint MUST authenticate the semantic content of a Version
+Negotiation packet if it attempts a different QUIC version as a result.
 
 
 # IANA Considerations
@@ -361,10 +360,10 @@ There are several traits of QUIC version 1 {{QUIC-TRANSPORT}} that are not
 protected from observation, but are nonetheless considered to be changeable when
 a new version is deployed.
 
-This section lists a sampling of incorrect assumptions that might be made based
-on knowledge of QUIC version 1.  Some of these statements are not even true for
-QUIC version 1.  This is not an exhaustive list; it is intended to be
-illustrative only.
+This section lists a sampling of incorrect assumptions that might be made about
+QUIC based on knowledge of QUIC version 1.  Some of these statements are not
+even true for QUIC version 1.  This is not an exhaustive list; it is intended to
+be illustrative only.
 
 **Any and all of the following statements can be false for a given QUIC
 version:**

draft-ietf-quic-recovery.md

@@ -209,9 +209,10 @@ multiple round trips.
 
 ## No Reneging
 
-QUIC ACKs contain information that is similar to TCP SACK, but QUIC does not
-allow any acknowledged packet to be reneged, greatly simplifying implementations
-on both sides and reducing memory pressure on the sender.
+QUIC ACK frames contain information similar to that in TCP Selective
+Acknowledgements (SACKs, {{?RFC2018}}). However, QUIC does not allow a packet
+acknowledgement to be reneged, greatly simplifying implementations on both sides
+and reducing memory pressure on the sender.
 
 ## More ACK Ranges
 
@@ -228,27 +229,25 @@ more accurate round-trip time estimate; see Section 13.2 of {{QUIC-TRANSPORT}}.
 ## Probe Timeout Replaces RTO and TLP
 
 QUIC uses a probe timeout (PTO; see {{pto}}), with a timer based on TCP's RTO
-computation.  QUIC's PTO includes the peer's maximum expected acknowledgment
-delay instead of using a fixed minimum timeout. QUIC does not collapse the
-congestion window until persistent congestion ({{persistent-congestion}}) is
-declared, unlike TCP, which collapses the congestion window upon expiry of an
-RTO.  Instead of collapsing the congestion window and declaring everything
-in-flight lost, QUIC allows probe packets to temporarily exceed the congestion
-window whenever the timer expires.
-
-In doing this, QUIC avoids unnecessary congestion window reductions, obviating
-the need for correcting mechanisms such as F-RTO ({{?RFC5682}}). Since QUIC does
-not collapse the congestion window on a PTO expiration, a QUIC sender is not
+computation; see {{?RFC6297}}.  QUIC's PTO includes the peer's maximum expected
+acknowledgment delay instead of using a fixed minimum timeout.
+
+Similar to the RACK-TLP loss detection algorithm for TCP
+({{?RACK=I-D.ietf-tcpm-rack}}), QUIC does not collapse the congestion window
+when the PTO expires, since a single packet loss at the tail does not indicate
+persistent congestion.  Instead, QUIC collapses the congestion window when
+persistent congestion is declared; see {{persistent-congestion}}. In doing this,
+QUIC avoids unnecessary congestion window reductions, obviating the need for
+correcting mechanisms such as F-RTO ({{?RFC5682}}). Since QUIC does not
+collapse the congestion window on a PTO expiration, a QUIC sender is not
 limited from sending more in-flight packets after a PTO expiration if it still
 has available congestion window. This occurs when a sender is
 application-limited and the PTO timer expires. This is more aggressive than
 TCP's RTO mechanism when application-limited, but identical when not
 application-limited.
 
-A single packet loss at the tail does not indicate persistent congestion, so
-QUIC specifies a time-based definition to ensure one or more packets are sent
-prior to a dramatic decrease in congestion window; see
-{{persistent-congestion}}.
+QUIC allows probe packets to temporarily exceed the congestion window whenever
+the timer expires.
 
 ## The Minimum Congestion Window is Two Packets
 
@@ -467,7 +466,7 @@ path, whereas loss detection also relies upon key availability.
 
 Acknowledgment-based loss detection implements the spirit of TCP's Fast
 Retransmit ({{?RFC5681}}), Early Retransmit ({{?RFC5827}}), FACK ({{FACK}}),
-SACK loss recovery ({{?RFC6675}}), and RACK ({{?RACK=I-D.ietf-tcpm-rack}}). This
+SACK loss recovery ({{?RFC6675}}), and RACK-TLP ({{?RACK}}). This
 section provides an overview of how these algorithms are implemented in QUIC.
 
 A packet is declared lost if it meets all the following conditions:
@@ -535,7 +534,7 @@ multiplier, is 9/8. The RECOMMENDED value of the timer granularity
 
 Note:
 
-: TCP's RACK ({{?RACK=I-D.ietf-tcpm-rack}}) specifies a slightly larger
+: TCP's RACK ({{?RACK}}) specifies a slightly larger
 threshold, equivalent to 5/4, for a similar purpose. Experience with QUIC shows
 that 9/8 works well.
 
@@ -830,7 +829,7 @@ an initial value.  Endpoints SHOULD use an initial congestion window of 10 times
 the maximum datagram size (max_datagram_size), limited to the larger of 14720
 bytes or twice the maximum datagram size. This follows the analysis and
 recommendations in {{?RFC6928}}, increasing the byte limit to account for the
-smaller 8 byte overhead of UDP compared to the 20 byte overhead for TCP.
+smaller 8-byte overhead of UDP compared to the 20-byte overhead for TCP.
 
 If the maximum datagram size changes during the connection, the initial
 congestion window SHOULD be recalculated with the new size.  If the maximum