Draft: draft-ietf-quic-manageability

Commentary: excellent , thanks !
Paragraph (version A):
Multiple QUIC packets may be coalesced into a UDP datagram, with a
datagram carrying one or more long header packets followed by zero or
one short header packets.  When packets are coalesced, the Length
fields in the long headers are used to separate QUIC packets.  The
length header field is variable length and its position in the header
is also variable depending on the length of the source and
destionation connection ID.  See Section 4.6 of QUIC-TRANSPORT.
Paragraph (version B):
Multiple QUIC packets may be coalesced into a UDP datagram, with a
datagram carrying one or more long header packets followed by zero or
one short header packets.  When packets are coalesced, the Length
fields in the long headers are used to separate QUIC packets.  The
length header field is variable length and its position in the header
is also variable depending on the length of the source and
destination connection ID.  See Section 4.6 of QUIC-TRANSPORT.
Paragraph (version A):
To illustrate the information visible in the QUIC wire image during
the handshake, we first show the general communication pattern
visible in the UDP datagams containing the QUIC handshake, then
examine each of the datagrams in detail.
Paragraph (version B):
To illustrate the information visible in the QUIC wire image during
the handshake, we first show the general communication pattern
visible in the UDP datagrams containing the QUIC handshake, then
examine each of the datagrams in detail.
Paragraph (version A):
The Client Hello datagram exposes version number, source and
destination connection IDs, and information in the TLS Client Hello
message, including any TLS Server Name Indication (SNI) present, in
the clear.  The QUIC PADDING frame shown here may be present to
ensure the Client Hello datagram has a minumum size of 1200 octets,
to mitigate the possibility of handshake amplification.  Note that
the location of PADDING is implementation-dependent, and PADDING
frames may not appear in the Initial packet in a coalesced packet.
Paragraph (version B):
The Client Hello datagram exposes version number, source and
destination connection IDs, and information in the TLS Client Hello
message, including any TLS Server Name Indication (SNI) present, in
the clear.  The QUIC PADDING frame shown here may be present to
ensure the Client Hello datagram has a minimum size of 1200 octets,
to mitigate the possibility of handshake amplification.  Note that
the location of PADDING is implementation-dependent, and PADDING
frames may not appear in the Initial packet in a coalesced packet.
Paragraph (version A):
Similar to Initial Competion, Handshake Completion also exposes no
additional information; observing it serves only to determine that
the handshake has completed.
Paragraph (version B):
Similar to Initial Completion, Handshake Completion also exposes no
additional information; observing it serves only to determine that
the handshake has completed.
Paragraph (version A):
QUIC explicitly exposes which side of a connection is a client and
which side is a server during the handshake.  In addition, the
symmerty of a flow (whether primarily client-to-server, primarily
server-to-client, or roughly bidirectional, as input to basic traffic
classification techniques) can be inferred through the measurement of
data rate in each direction.  While QUIC traffic is protected and
ACKS may be padded, padding is not required.
Paragraph (version B):
QUIC explicitly exposes which side of a connection is a client and
which side is a server during the handshake.  In addition, the
symmetry of a flow (whether primarily client-to-server, primarily
server-to-client, or roughly bidirectional, as input to basic traffic
classification techniques) can be inferred through the measurement of
data rate in each direction.  While QUIC traffic is protected and
ACKs may be padded, padding is not required.
Paragraph (version A):
The spin bit provides an additional method to measure per-flow RTT
from observation points on the network path throughout the duration
of a connection.  Endpoint participation in spin bit signaling is
optional in QUIC.  That is, while its location is fixed in this
version of QUIC, an endpoint can unilaterally choose to not support
"spinning" the bit.  Use of the spin bit for RTT measurement by
devices on path is only possible when both endpoints enable it.  Some
endpoints may disable use of the the spin bit by default, others only
in specific deployment scenarios, e.g. for servers and clients where
the RTT would reveal the presence of a VPN or proxy.  In order to not
make these connections identifiable based on the usage of the spin
bit, it is recommended that all endpoints disable "spinning" randomly
for at least one eighth of connections, even if otherwise enabled by
default.  An endpoint not participating in spin bit signaling for a
given connection can use a fixed spin value for the duration of the
connection, or can set the bit randomly on each packet sent.
Paragraph (version B):
The spin bit provides an additional method to measure per-flow RTT
from observation points on the network path throughout the duration
of a connection.  Endpoint participation in spin bit signaling is
optional in QUIC.  That is, while its location is fixed in this
version of QUIC, an endpoint can unilaterally choose to not support
"spinning" the bit.  Use of the spin bit for RTT measurement by
devices on path is only possible when both endpoints enable it.  Some
endpoints may disable use of the spin bit by default, others only in
specific deployment scenarios, e.g. for servers and clients where the
RTT would reveal the presence of a VPN or proxy.  In order to not
make these connections identifiable based on the usage of the spin
bit, it is recommended that all endpoints disable "spinning" randomly
for at least one eighth of connections, even if otherwise enabled by
default.  An endpoint not participating in spin bit signaling for a
given connection can use a fixed spin value for the duration of the
connection, or can set the bit randomly on each packet sent.