RE: Update to draft QUIC DPLPMTUD text i draft-ietf-tsvwg-datagram-plpmtud

"Lubashev, Igor" <ilubashe@akamai.com> Tue, 12 May 2020 14:00 UTC

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From: "Lubashev, Igor" <ilubashe@akamai.com>
To: Magnus Westerlund <magnus.westerlund=40ericsson.com@dmarc.ietf.org>, "quic@ietf.org" <quic@ietf.org>
CC: "draft-ietf-tsvwg-datagram-plpmtud.all@ietf.org" <draft-ietf-tsvwg-datagram-plpmtud.all@ietf.org>
Subject: RE: Update to draft QUIC DPLPMTUD text i draft-ietf-tsvwg-datagram-plpmtud
Thread-Topic: Update to draft QUIC DPLPMTUD text i draft-ietf-tsvwg-datagram-plpmtud
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Date: Tue, 12 May 2020 14:00:03 +0000
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Magnus,

Section "6.3.  DPLPMTUD for QUIC", quotes a very old version of the QUIC Transport draft.  The current text in QUIC transport says:

"
If a QUIC endpoint determines that the PMTU between any pair of local and remote IP addresses has fallen below the size needed to support the smallest allowed maximum packet size, it MUST immediately cease sending QUIC packets, except for PMTU probe packets, on the affected path. An endpoint MAY terminate the connection if an alternative path cannot be found.
"


  *   Igor

From: Magnus Westerlund <magnus.westerlund=40ericsson.com@dmarc.ietf.org>
Sent: Tuesday, May 12, 2020 4:50 AM
To: quic@ietf.org
Cc: draft-ietf-tsvwg-datagram-plpmtud.all@ietf.org
Subject: Update to draft QUIC DPLPMTUD text i draft-ietf-tsvwg-datagram-plpmtud

QUIC WG,

In response to the IESG evaluation of https://datatracker.ietf.org/doc/draft-ietf-tsvwg-datagram-plpmtud/ some changes was made to the QUIC chapter.

The current text is included below. And a Diff for the changes in this section -19 to -21 is here:

QUIC related section is 6.3:
https://www.ietf..org/rfcdiff?url1=draft-ietf-tsvwg-datagram-plpmtud-19&url2=draft-ietf-tsvwg-datagram-plpmtud-21<https://www.ietf.org/rfcdiff?url1=draft-ietf-tsvwg-datagram-plpmtud-19&url2=draft-ietf-tsvwg-datagram-plpmtud-21>

My plan is to approve this document on Friday after 12:00 (CEST) if not anyone yells.


6.3.  DPLPMTUD for QUIC

   QUIC [I-D.ietf-quic-transport] is a UDP-based transport that provides
   reception feedback.  The UDP payload includes the QUIC packet header,
   protected payload, and any authentication fields.  QUIC depends on a
   PMTU of at least 1280 bytes.

   Section 14 of [I-D.ietf-quic-transport] describes the path
   considerations when sending QUIC packets.  It recommends the use of
   PADDING frames to build the probe packet.  Pure probe-only packets
   are constructed with PADDING frames and PING frames to create a
   padding only packet that will elicit an acknowledgment.  Such padding
   only packets enable probing without affecting the transfer of other
   QUIC frames.

   The recommendation for QUIC endpoints implementing DPLPMTUD is that a
   MPS is maintained for each combination of local and remote IP
   addresses [I-D.ietf-quic-transport].  If a QUIC endpoint determines
   that the PMTU between any pair of local and remote IP addresses has
   fallen below the size required for an acceptable MPS, it immediately
   ceases to send QUIC packets on the affected path.  This could result
   in termination of the connection if an alternative path cannot be
   found [I-D.ietf-quic-transport].

6.3.1.  Initial Connectivity

   The base protocol is specified in [I-D.ietf-quic-transport].  This
   provides an acknowledged PL.  A sender can therefore enter the BASE
   state as soon as connectivity has been confirmed.

   QUIC provides an acknowledged PL, a sender can therefore enter the
   BASE state as soon as the connection handshake has been completed and
   the endpoint has an 1-RTT key established.

6.3.2.  Sending QUIC Probe Packets

   Probe packets consist of a QUIC Header and a payload containing a
   PING Frame and multiple PADDING Frames.  A PADDING Frame is
   represented by a single octet (0x00).  Several PADDING Frames are
   used together to control the length of the probe packet.  The PING
   Frame is used to trigger generation of an acknowledgement.

   The current specification of QUIC sets the following:

   *  BASE_PLPMTU: A QUIC sender pads initial packets to confirm the
      path can support packets of the required size, which sets the
      BASE_PLPMTU and MIN_PLPMTU.

   *  MIN_PLPMTU: A QUIC sender that determines the MIN_PLPMTU has
      fallen MUST immediately stop sending on the affected path.

6.3.3.  Validating the Path with QUIC

   QUIC provides an acknowledged PL, therefore a sender does not
   implement the CONFIRMATION_TIMER while in the SEARCH_COMPLETE state.

6.3.4.  Handling of PTB Messages by QUIC

   QUIC validates ICMP PTB messages.  In addition to UDP Port
  validation, QUIC can validate an ICMP message by using other PL
   information (e.g., validation of connection identifiers (CIDs) in the
   quoted packet of any received ICMP message).