Network Working Group                                           J. Hedin
Internet-Draft                                                 G. Mirsky
Updates: 5357 (if approved)                              S.  Baillargeon
Intended status: Standards Track                         S.  Baillargeon
Expires: November 21, 2015                                Ericsson
Expires: May 20, 7, 2016                                    November 4, 2015

 Differentiated Service Code Point and Explicit Congestion Notification
       Monitoring in Two-Way Active Measurement Protocol (TWAMP)
                   draft-ietf-ippm-type-p-monitor-02
                   draft-ietf-ippm-type-p-monitor-03

Abstract

   This document describes an OPTIONAL optional extension for Two-Way Active
   Measurement Protocol (TWAMP) allowing the monitoring of the
   Differentiated Service Code Point and Explicit Congestion
   Notification fields with the TWAMP-Test protocol.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 22, 2015. May 7, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions used in this document . . . . . . . . . . . .   3
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   3
   2.  TWAMP Extensions  . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Setting Up Connection to Monitor DSCP and ECN . . . . . .   3
     2.2.  TWAMP-Test Extension  . . . . . . . . . . . . . . . . . .   4
       2.2.1.  Session-Reflector Packet Format for DSCP and ECN
               Monitoring  . . . . . . . . . . . . . . . . . . . . .   4
       2.2.2.  DSCP and ECN Monitoring with RFC 6038 extensions  . .   7
       2.2.3.  Consideration for TWAMP Light mode  . . . . . . . . .   8
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8   9
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8   9
   6.  Normative  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9  10

1.  Introduction

   The One-Way Active Measurement Protocol (OWAMP) [RFC4656] defines the
   Type-P
   descriptor Descriptor field and negotiation of its value in OWAMP-Control
   protocol.  The Two-Way Active Measurement Protocol (TWAMP) [RFC5357]
   states that only a Differentiated Service Services Code Point (DSCP) values
   [RFC2474], [RFC3168], [RFC3260] value can be defined by Type-P descriptor
   Descriptor and the negotiated value must be used by both
   Session-Sender Session-
   Sender and Session-Reflector.  The TWAMP specification also states
   that the same DSCP value (found in the Session-Sender packet) MUST be
   used in the test packet reflected by the Session-Reflector.  However
   the TWAMP-Test protocol does not specify any methods to determine or
   report when the DSCP value has changed or is different than expected
   in the forward or reverse direction.  Re-marking the DSCP (changing
   its original value) in IP networks is possible and often accomplished
   by a Diffserv Differentiated Services policy configured on a single node along
   the IP path.  In many cases, a change of the DSCP value indicates an
   unintentional or erroneous behavior.  At best, the Session-Sender can
   detect a change of the DSCP reverse direction assuming such change is
   actually detectable.

   This document describes an OPTIONAL feature for TWAMP.  It is called
   the DSCP and ECN monitoring feature.  This feature Monitoring.  It allows the Session-Sender to know
   the actual DSCP value received at the Session-
   Reflector. Session-Reflector.  Furthermore
   this OPTIONAL feature tracks the Explicit Congestion Notification (ECN)
   [RFC2474], [RFC3168], [RFC3260] value received at the Session-
   Reflector.  This is helpful to determine if ECN is actually operating
   or if an ECN-capable node has detected congestion in the forward
   direction.

1.1.  Conventions used in this document

1.1.1.  Terminology

   DSCP: Differentiated Service Codepoint Services Code Point

   ECN: Explicit Congestion Notification

   IPPM: IP Performance Measurement

   TWAMP: Two-Way Active Measurement Protocol

   OWAMP: One-Way Active Measurement Protocol

1.1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

2.  TWAMP Extensions

   TWAMP connection establishment follows the procedure defined in
   Section 3.1 of [RFC4656] and Section 3.1 of [RFC5357] where the Modes
   field is used to identify and select specific communication
   capabilities.  At the same time the Modes field been recognized and
   used as an extension mechanism [RFC6038].  The new feature requires a
   new flag to identify the ability of a Session-Reflector to return
   value of received DSCP and ECN values back to a Session-Sender, and
   to support the new Session-Reflector packet format in the TWAMP-Test
   protocol.  See the Section 3 for details on the assigned bit
   position.

2.1.  Setting Up Connection to Monitor DSCP and ECN

   The Server sets the DSCP and ECN Monitoring flag in the Modes field
   of the Server Greeting message to indicate its capabilities and
   willingness to monitor them.  If the Control-Client agrees to monitor
   DSCP and ECN on some or all test sessions invoked with this control
   connection, it MUST set the DSCP and ECN Monitoring flag in the Modes
   field in the Setup Response message.

2.2.  TWAMP-Test Extension

   Monitoring of DSCP and ECN requires support by the Session-Reflector
   and changes the format of its test packet format both in
   unauthenticated, all the original
   (unauthenticated, authenticated and encrypted encrypted) modes.  Monitoring of
   DSCP and ECN does not alter the Session-Sender test packet format but
   certain considerations must be taken when and if this mode is
   accepted in combination with Symmetrical Size mode [RFC6038].

2.2.1.  Session-Reflector Packet Format for DSCP and ECN Monitoring

   When the Session-Reflector supports DSCP and ECN Monitoring it MUST
   construct
   constructs the Sender DSCP and ECN (S-DSCP-ECN) field field, presented in
   Figure 1, for each test packet it sends to Session-Sender according
   to the following procedure:

   o  the first six (least-significant) bits of the Differentiated Service
      field MUST be copied from received Session-Sender test packet into
      Sender DSCP (S-DSCP) field;

   o  the following two bits of the ECN field MUST be copied from received
      Session-Sender test packet into Sender ECN (S-ECN) field.

      0   1   2   3   4   5   6   7     8
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    +---+---+---+---+---+---+---+---+
    |         S-DSCP        | S-ECN |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    +---+---+---+---+---+---+---+---+

                Figure 1: Sender DSCP and ECN field format

   Formats of the test packet transmitted by the Session-Reflector in
   unauthenticated, authenticated and encrypted modes been defined in
   Section 4.2.1 [RFC5357].  For the Session-Reflector that supports
   DSCP and ECN Monitoring these formats are displayed in Figure 2 and
   Figure 3.

   For unauthenticated mode:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Sequence Number                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Timestamp                          |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Error Estimate        |             MBZ               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Receive Timestamp                       |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Sender Sequence Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Sender Timestamp                        |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Sender Error Estimate    |             MBZ               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Sender TTL  |  S-DSCP-ECN   |             MBZ               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                             |
    +                                                             +
    |                                                             |
    .                                                             .
    .
    ~                        Packet Padding                       .                       ~
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 2: Session-Reflector test packet format with DSCP and ECN
                    monitoring
                    Monitoring in unauthenticated mode

   The DSCP and ECN values (part of the Type-P Descriptor [RFC4656]) can
   be provisioned through TWAMP-Control or by other means (CLI or
   Central Controller).  The DSCP and ECN values are often copied into
   reflected test packets with current TWAMP implementations without
   TWAMP-Control protocol.  With DSCP and ECN Monitoring Extension, the
   Session-Reflector handles DSCP as following:

   o  the Session-Reflector MUST extract the DSCP and ECN values from
      the received packet and MUST populate with them S-DSCP-ECN field
      of the corresponding reflected packet;

   o  the Session-Reflector MUST transmit each reflected test packet
      with DSCP set to the provisioned value;

   o  if the provisioned DSCP value is not known (e.g.  TWAMP Light),
      the choice of the DSCP is implementation specific.  For instance,
      Session-Reflector MAY copy the DSCP value from the received test
      packet and set it as DSCP in a reflected packet.  Alternatively
      Session-Reflector MAY set DSCP value to CS0 (zero) [RFC2474];

   o  if the provisioned ECN value is not known, ECN SHOULD be set to
      Not-ECT codepoint value [RFC3168].  Otherwise, the provisioned ECN
      value for the session SHALL be used.

   A Session-Reflector in the DSCP and ECN Monitoring mode does not
   analyze, nor acts on ECN value of the received TWAMP test packet and
   therefore ignores congestion indications from the network.  It is
   expected that sending rates are low enough, as TWAMP deployment
   experience had demonstrated since TWAMP base RFC 5357 publication in
   2008, that ignoring these congestion indications will not
   significantly contribute to network congestion.

   For authenticated and encrypted modes:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Sequence Number                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                             |
    |                     MBZ (12 octets)                         |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Timestamp                             |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Error Estimate        |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    |                        MBZ (6 octets)                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Receive Timestamp                      |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       MBZ (8 octets)                        |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Sender Sequence Number                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                             |
    |                      MBZ (12 octets)                        |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Sender Timestamp                       |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Sender Error Estimate    |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    |                       MBZ (6 octets)                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Sender TTL  |  S-DSCP-ECN   |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    |                                                             |
    +                                                             +
    |                       MBZ (14 octets)                       |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                             |
    |                      HMAC (16 octets)                       |
    |                                                             |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                             |
    .                                                             .
    .
    ~                   Packet Padding                            .                            ~
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 3: Session-Reflector test packet format with DSCP and ECN
              monitoring
              Monitoring in authenticated or encrypted modes

   The DSCP value is often copied into reflected test packets with
   current TWAMP implementations (with or without TWAMP-Control
   protocol).  With DSCP and ECN Monitoring Extension, the Session-
   Reflector handles DSCP as following:

   o  the Session-Reflector MUST extracts the S-DSCP-ECN value from the
      DSCP and ECN values of received packets;

   o  the Session-Reflector MUST transmit each reflected test packet
      with DSCP set to the negotiated/provisioned value;

   o  if the negotiated/provisioned DSCP value is not known (e.g.  TWAMP
      Light), the choice of the DSCP is implementation specific.  For
      instance, Session-Reflector MAY copy the DSCP value from the
      received test packet and set it as DSCP in a reflected packet.

2.2.2.  DSCP and ECN Monitoring with RFC 6038 extensions

   [RFC6038] defined two extensions to TWAMP.  First, to ensure that
   Session-Sender and Session-Reflector exchange TWAMP-Test packets of
   equal size.  Second, to specify number of octets to be reflected by
   Session-Reflector.  If DSCP and ECN monitoring Monitoring and Symmetrical Size
   and/or Reflects Octets modes are being negotiated between Server and
   Control-Client in Unauthenticated mode, then, because Sender DSCP and
   Sender ECN increase size of unauthenticated Session-Reflector packet
   by 4 octets, the Padding Length value SHOULD be >= 28 octets to allow
   for the truncation process that TWAMP recommends in Section 4.2. 1 4.2.1 of
   [RFC5357].

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Sequence Number                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Timestamp                          |
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Error Estimate        |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    |                                                             |
    |                       MBZ (28 octets)                       |
    |                                                             |
    +                             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                             |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    |                                                             |
    .                                                             .
    .                        Packet Padding                       .
    |                                                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 4: Session-Sender test packet format with DSCP and ECN
      monitoring
      Monitoring and Symmetrical Test Packet in unauthenticated mode

2.2.3.  Consideration for TWAMP Light mode

   Appendix I of [RFC5357] does not explicitly state how the value of
   the Type-P descriptor Descriptor is synchronized between Session-Sender and
   Session-Reflector and whether different values are considered as
   error condition and SHOULD be reported.  We assume that by some means
   the Session-Sender and the Session-Reflector of the given TWAMP-Test
   session been informed to use the same DSCP value.  Same means, i.e.
   configuration, could be used to inform Session-Reflector to support
   DSCP and ECN monitoring Monitoring mode by copying data from received TWAMP test
   packets.  Then Session-Sender may be informed to use Sender DSCP and
   ECN field in reflected TWAMP test packet.

3.  IANA Considerations

   The TWAMP-Modes registry defined in [RFC5618].

   IANA is requested to reserve a new DSCP and ECN Monitoring Capability
   as follows:

   +-----+------------------------+---------------------+--------------+
   | Bit | Description            | Semantics           | Reference    |
   |     |                        | Definition          |              |
   +-----+------------------------+---------------------+--------------+
   | TBA | DSCP and ECN           | Section 2           | This         |
   |     | Monitoring Capability  |                     | document     |
   +-----+------------------------+---------------------+--------------+

           Table 1: New Type-P Descriptor Monitoring Capability

4.  Security Considerations

   Monitoring of DSCP and ECN does not appear to introduce any
   additional security threat to hosts that communicate with TWAMP as
   defined in [RFC5357], and existing extensions [RFC6038].  Sections
   such as 3.2, 4., 4.1.2, 4.2, and 4.2.1 of [RFC5357] discuss
   unauthenticated, authenticated, and encrypted modes in varying
   degrees of detail.  The security considerations that apply to any
   active measurement of live networks are relevant here as well.  See
   the Security Considerations sections in [RFC4656] and [RFC5357].

5.  Acknowledgements

   Authors greatly appreciate thorough review and thoughtful comments by
   Bill Cerveny, Christofer Flinta and Samita Chakrabarti.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997. 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <http://www.rfc-editor.org/info/rfc2474>.

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, DOI 10.17487/RFC3168, September 2001,
              <http://www.rfc-editor.org/info/rfc3168>.

   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006. 2006,
              <http://www.rfc-editor.org/info/rfc4656>.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, DOI 10.17487/RFC5357, October 2008. 2008,
              <http://www.rfc-editor.org/info/rfc5357>.

   [RFC5618]  Morton, A. and K. Hedayat, "Mixed Security Mode for the
              Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
              DOI 10.17487/RFC5618, August 2009. 2009,
              <http://www.rfc-editor.org/info/rfc5618>.

   [RFC6038]  Morton, A. and L. Ciavattone, "Two-Way Active Measurement
              Protocol (TWAMP) Reflect Octets and Symmetrical Size
              Features", RFC 6038, DOI 10.17487/RFC6038, October 2010. 2010,
              <http://www.rfc-editor.org/info/rfc6038>.

6.2.  Informative References

   [RFC3260]  Grossman, D., "New Terminology and Clarifications for
              Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002,
              <http://www.rfc-editor.org/info/rfc3260>.

Authors' Addresses

   Jonas Hedin
   Ericsson

   Email: jonas.hedin@ericsson.com

   Greg Mirsky
   Ericsson

   Email: gregory.mirsky@ericsson.com

   Steve  Baillargeon
   Ericsson

   Email: steve.baillargeon@ericsson.com