[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-ott-xrblock-rtcp-xt-discard-metrics) 00 01 02 03 04 05 06 07 08 09 RFC 7097

XR Block Working Group                                            J. Ott
Internet-Draft                                             V. Singh, Ed.
Intended status: Standards Track                        Aalto University
Expires: May 16, 2014                                          I. Curcio
                                                   Nokia Research Center
                                                       November 12, 2013


RTP Control Protocol (RTCP) Extended Report (XR) for Run Length Encoding
                       (RLE) of Discarded Packets
           draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-09

Abstract

   The RTP Control Protocol (RTCP) is used in conjunction with the Real-
   time Transport Protocol (RTP) in to provide a variety of short-term
   and long-term reception statistics.  The available reporting may
   include aggregate information across longer periods of time as well
   as individual packet reporting.  This document specifies a per-packet
   report metric capturing individual packets discarded from the de-
   jitter buffer after successful reception.

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 May 16, 2014.

Copyright Notice

   Copyright (c) 2013 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



Ott, et al.               Expires May 16, 2014                  [Page 1]

Internet-Draft            RTCP XR Discard RLE              November 2013


   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  XR Discard RLE Report Block . . . . . . . . . . . . . . . . .   4
   4.  Protocol Operation  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Reporting Node (Receiver) . . . . . . . . . . . . . . . .   6
     4.2.  Media Sender  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  SDP signaling . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  XR Report Block Registration  . . . . . . . . . . . . . .   7
     7.2.  SDP Parameter Registration  . . . . . . . . . . . . . . .   8
     7.3.  Contact information for IANA registrations  . . . . . . .   8
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Metrics represented using RFC6390 Template . . . . .   9
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  10
     B.1.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-00  . . . . . . . . . . . . . . . . . . . . . . .  10
     B.2.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-01  . . . . . . . . . . . . . . . . . . . . . . .  10
     B.3.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-02  . . . . . . . . . . . . . . . . . . . . . . .  10
     B.4.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-03  . . . . . . . . . . . . . . . . . . . . . . .  10
     B.5.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-04  . . . . . . . . . . . . . . . . . . . . . . .  11
     B.6.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-05  . . . . . . . . . . . . . . . . . . . . . . .  11
     B.7.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-06  . . . . . . . . . . . . . . . . . . . . . . .  11
     B.8.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-07  . . . . . . . . . . . . . . . . . . . . . . .  11
     B.9.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-08  . . . . . . . . . . . . . . . . . . . . . . .  11
     B.10. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-
           metrics-09  . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11




Ott, et al.               Expires May 16, 2014                  [Page 2]

Internet-Draft            RTCP XR Discard RLE              November 2013


1.  Introduction

   RTP [RFC3550] provides a transport for real-time media flows such as
   audio and video together with the RTP control protocol (RTCP) which
   provides periodic feedback about the media streams received in a
   specific duration.  In addition, RTCP can be used for timely feedback
   about individual events to report (e.g., packet loss) [RFC4585].
   Both long-term and short-term feedback enable a media sender to adapt
   its media transmission and/or encoding dynamically to the observed
   path characteristics.

   RFC3611 [RFC3611] defines RTCP Extended Reports as a detailed
   reporting framework to provide more than just the coarse Receiver
   Report (RR) statistics.  The detailed reporting may enable a media
   sender to react more appropriately to the observed networking
   conditions as these can be characterized better, although at the
   expense of extra overhead.

   Among many other report blocks, RFC3611 specifies the Loss Run Length
   Encoding (RLE) block which reports runs of packets received and lost
   with the granularity of individual packets.  This can help both error
   recovery and path loss characterization.  In addition to lost
   packets, RFC3611 defines the notion of "discarded" packets: packets
   that were received but dropped from the de-jitter buffer because they
   were either too early (for buffering) or too late (for playout).  The
   "discard rate" metric is part of the VoIP metrics report block even
   though it is not just applicable to audio: it is specified as the
   fraction of discarded packets since the beginning of the session.
   See section 4.7.1 of RFC3611 [RFC3611].  The discard metric is
   believed to be applicable to a large class of RTP applications which
   use a de-jitter buffer RFC5481 [RFC5481].

   Recently proposed extensions to the Extended Reports (XR) reporting
   suggest enhancing this discard metric:

   o  Reporting the number of discarded packets in a measurement
      interval, i.e., during either the last reporting interval or since
      the beginning of the session, as indicated by a flag in the
      suggested XR report [RFC7002].  If an endpoint needs to report
      packet discard due to other reasons than early- and late-arrival
      (for example, discard due to duplication, redundancy, etc.)  then
      it should consider using the Discarded Packets Report Block
      [RFC7002].

   o  Reporting gaps and bursts of discarded packets during a
      measurement interval, i.e., the last reporting interval or the
      duration of the session [RFC7003].




Ott, et al.               Expires May 16, 2014                  [Page 3]

Internet-Draft            RTCP XR Discard RLE              November 2013


   o  Reporting the sum of payload bytes discarded during a measurement
      interval, i.e., the last reporting interval or the duration of the
      session [I-D.ietf-xrblock-rtcp-xr-bytes-discarded-metric].

   However, none of these metrics allow a receiver to report precisely
   which packets were discarded.  While this information could in theory
   be derived from high-frequency reporting on the number of discarded
   packets [RFC7002] or from the gap/burst report [RFC7003], these two
   mechanisms do not appear feasible: The former would require an unduly
   high amount of reporting which still might not be sufficient due to
   the non-deterministic scheduling of RTCP packets.  The latter incur
   significant complexity and reporting overhead and might still not
   deliver the desired accuracy.

   This document defines a discard report block following the idea of
   the run-length encoding applied for lost and received packets in
   [RFC3611].

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119].

   The terminology defined in RTP [RFC3550] and in the extensions for XR
   reporting [RFC3611] applies.

3.  XR Discard RLE Report Block

   The XR Discard RLE report block uses the same format as specified for
   the loss and duplicate report blocks in [RFC3611].  Figure 1
   describes the packet format.  The fields "BT", "T", "block length",
   "SSRC of source", "begin_seq", and "end_seq" have the same semantics
   and representation as defined in [RFC3611], with the addition of the
   "E" flag to indicate the reason for discard.  The "chunks" encoding
   the run length have the same representation as in RFC3611, but encode
   discarded packets.  A definition of a discarded packet is given in
   [RFC7002].






    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



Ott, et al.               Expires May 16, 2014                  [Page 4]

Internet-Draft            RTCP XR Discard RLE              November 2013


   |     BT=DRLE   |rsvd |E|   T   |         block length          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        SSRC of source                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          begin_seq            |             end_seq           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          chunk 1              |             chunk 2           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                              ...                              :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          chunk n-1            |             chunk n           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 1: XR Discard RLE Report Block

   Block Type (BT, 8 bits): A Run-length encoded Discarded Packets
   Report Block is identified by the constant DRLE.

   [Note to RFC Editor: please replace DRLE with the IANA provided RTCP
   XR block type for this block.  Please remove this note prior to
   publication as an RFC.]

   rsvd (3 bits): This field is reserved for future definition.  In the
   absence of such definition, the bits in this field MUST be set to
   zero and MUST be ignored by the receiver.

   The 'E' bit is introduced to distinguish between packets discarded
   due to early arrival and those discarded due to late arrival.  The
   'E' bit is set to '1' if the chunks represent packets discarded due
   to too early arrival and is set to '0' otherwise.

   In case both early and late discarded packets shall be reported, two
   Discard RLE report blocks MUST be included; their sequence number
   range MAY overlap, but individual packets MUST only be reported as
   either early or late and not appear marked in both.  If packets
   appear in both report blocks, the conflicting packets are ignored.
   Packets reported in neither are considered to be properly received
   and not discarded.

   Discard RLE Report Blocks SHOULD be sent in conjunction with an RTCP
   RR as a compound RTCP packet.

4.  Protocol Operation

   This section describes the behavior of the reporting node (= media
   receiver) and the media sender.





Ott, et al.               Expires May 16, 2014                  [Page 5]

Internet-Draft            RTCP XR Discard RLE              November 2013


4.1.  Reporting Node (Receiver)

   Transmission of RTCP XR Discard RLE Reports is up to the discretion
   of the media receiver, as is the reporting granularity.  However, it
   is RECOMMENDED that the media receiver signals all discarded packets
   using the method defined in this document.  If all packets over a
   reporting period were discarded, the media receiver MAY use the
   Discard Report Block [RFC7002] instead.  In case of limited available
   reporting bandwidth, it is up to the receiver whether or not to
   include RTCP XR Discard RLE reports.

   The media receiver MAY send the Discard RLE Reports as part of the
   regularly scheduled RTCP packets as per RFC3550.  It MAY also include
   Discard RLE Reports in immediate or early feedback packets as per
   RFC4585.

4.2.  Media Sender

   The media sender MUST be prepared to operate without receiving any
   Discard RLE reports.  If Discard RLE reports are generated by the
   media receiver, the media sender cannot rely on all these reports
   being received, nor can the media sender rely on a regular generation
   pattern from the media receiver.

   However, if the media sender receives any RTCP reports but no Discard
   RLE report blocks and is aware that the media receiver supports
   Discard RLE report blocks, it MAY assume that no packets were
   discarded at the media receiver.

5.  SDP signaling

   A participant of a media session MAY use SDP to signal its support
   for the report block specified in this document or use them without
   any prior signaling (see section 5 of [RFC3611]).

   For signaling in SDP, the RTCP XR attribute as defined in [RFC3611]
   MUST be used.  The SDP [RFC4566] attribute 'xr-format' defined in
   RFC3611 is augmented as described in the following to indicate the
   the discard RLE metric.

      rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)]
                       CRLF   ; defined in [RFC3611]

      xr-format       =/ xr-discard-rle

      xr-discard-rle   = "discard-rle"





Ott, et al.               Expires May 16, 2014                  [Page 6]

Internet-Draft            RTCP XR Discard RLE              November 2013


   The parameter 'discard-rle' is used to indicate support for the
   Discard RLE Report Block defined in Section 3.

   When SDP is used in Offer/Answer context, the mechanism defined in
   [RFC3611] for unilateral "rtcp-xr" attribute parameters applies (see
   section 5.2 of [RFC3611]).

6.  Security Considerations

   The Discard RLE block provides per-packet statistics so the risk to
   confidentiality documented in Section 7, paragraph 3 of [RFC3611]
   applies.  In some situations, returning very detailed error
   information (e.g., over-range measurement or measurement unavailable)
   using this report block can provide an attacker with insight into the
   security processing.  Implementers should consider the guidance in
   [I-D.ietf-avt-srtp-not-mandatory] for using appropriate security
   mechanisms, i.e., where security is a concern, the implementation
   should apply encryption and authentication to the report block.  For
   example this can be achieved by using the AVPF profile together with
   the Secure RTP profile as defined in [RFC3711]; an appropriate
   combination of the two profiles (an "SAVPF") is specified in
   [RFC5124].  However, other mechanisms also exist (documented in
   [I-D.ietf-avtcore-rtp-security-options]) and might be more suitable.

   Additionally, The security considerations of [RFC3550], [RFC3611],
   and [RFC4585] apply.

7.  IANA Considerations

   New block types for RTCP XR are subject to IANA registration.  For
   general guidelines on IANA considerations for RTCP XR, refer to
   [RFC3611].

7.1.  XR Report Block Registration

   This document extends the IANA "RTP Control Protocol Extended Reports
   (RTCP XR) Block Type Registry" by a new value: DRLE (Discard RLE
   Report).

   [Note to RFC Editor: please replace DRLE with the IANA provided RTCP
   XR block type for this block here and in the diagrams above.  Please
   remove this note prior to publication as an RFC.]









Ott, et al.               Expires May 16, 2014                  [Page 7]

Internet-Draft            RTCP XR Discard RLE              November 2013


7.2.  SDP Parameter Registration

   This document registers a new parameters for the Session Description
   Protocol (SDP), "discard-rle" in the "RTP Control Protocol Extended
   Reports (RTCP XR) Session Description Protocol (SDP) Parameters
   Registry".

7.3.  Contact information for IANA registrations

   Joerg Ott (jo@comnet.tkk.fi)

   Aalto University Comnet, Otakaari 5A, 02150 Espoo, Finland.

8.  Acknowledgments

   The authors would like to thank Alan Clark, Roni Even, Sam Hartman,
   Colin Perkins, Dan Romascanu, Dan Wing, and Qin Wu for providing
   valuable feedback on earlier versions of this draft.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, July 2003.

   [RFC3611]  Friedman, T., Caceres, R., and A. Clark, "RTP Control
              Protocol Extended Reports (RTCP XR)", RFC 3611, November
              2003.

   [RFC4585]  Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
              "Extended RTP Profile for Real-time Transport Control
              Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July
              2006.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC7002]  Clark, A., Zorn, G., and Q. Wu, "RTP Control Protocol
              (RTCP) Extended Report (XR) Block for Discard Count Metric
              Reporting", RFC 7002, September 2013.

9.2.  Informative References




Ott, et al.               Expires May 16, 2014                  [Page 8]

Internet-Draft            RTCP XR Discard RLE              November 2013


   [RFC7003]  Clark, A., Huang, R., and Q. Wu, "RTP Control Protocol
              (RTCP) Extended Report (XR) Block for Burst/Gap Discard
              Metric Reporting", RFC 7003, September 2013.

   [RFC5481]  Morton, A. and B. Claise, "Packet Delay Variation
              Applicability Statement", RFC 5481, March 2009.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, March 2004.

   [RFC5124]  Ott, J. and E. Carrara, "Extended Secure RTP Profile for
              Real-time Transport Control Protocol (RTCP)-Based Feedback
              (RTP/SAVPF)", RFC 5124, February 2008.

   [I-D.ietf-avt-srtp-not-mandatory]
              Perkins, C. and M. Westerlund, "Securing the RTP Protocol
              Framework: Why RTP Does Not Mandate a Single Media
              Security Solution", draft-ietf-avt-srtp-not-mandatory-13
              (work in progress), May 2013.

   [I-D.ietf-avtcore-rtp-security-options]
              Westerlund, M. and C. Perkins, "Options for Securing RTP
              Sessions", draft-ietf-avtcore-rtp-security-options-04
              (work in progress), July 2013.

   [I-D.ietf-xrblock-rtcp-xr-bytes-discarded-metric]
              Singh, V., Ott, J., and I. Curcio, "RTP Control Protocol
              (RTCP) Extended Report (XR) for Bytes Discarded Metric",
              draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-00 (work
              in progress), October 2013.

Appendix A.  Metrics represented using RFC6390 Template

   RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC
   number, when assigned.

   a.  Run-length encoding of Discarded RTP Packets Metric

       *  Metric Name: Run-length encoding of Discarded RTP Packets
          Metric.

       *  Metric Description: Instances of RTP packets discarded over
          the period covered by this report.

       *  Method of Measurement or Calculation: See section 3, for the
          definition of Discard run-length encoding [RFCXXXX] and
          section 4.1 of RFC3611 for Run-length encoding.



Ott, et al.               Expires May 16, 2014                  [Page 9]

Internet-Draft            RTCP XR Discard RLE              November 2013


       *  Units of Measurement: Every RTP packet in the interval is
          reported as discarded or not.  See section 3 for the
          definition of [RFCXXXX].

       *  Measurement Point(s) with Potential Measurement Domain: The
          measurement of these metrics is made at the receiving end of
          the RTP stream.

       *  Measurement Timing: Each RTP packet between a beginning
          sequence number (begin_seq) and ending sequence number
          (end_seq) are reported as discarded or not.  See section 3 for
          the definition of Discard run-length encoding [RFCXXXX].

       *  Use and applications: See section 1, paragraph 1 of [RFCXXXX].

       *  Reporting model: See RFC3611.

Appendix B.  Change Log

   Note to the RFC-Editor: please remove this section prior to
   publication as an RFC.

B.1.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-00

   o  Changed the interval flag from 1 to 2 bits in the discarded bytes
      report.  Also added the measurement identification tag to the
      block.

   o  Added this section.

B.2.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-01

   o  Removed the measurement identification tag in the bytes discarded
      block.

B.3.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-02

   o  Removed the extra Tag bits from the Discarded bytes XR block.

   o  Clarified use of measurement identity block in Section 4 and 5.2

B.4.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-03

   o  Added explanation for block length in bytes discarded block.

   o  Added an acknowledgement section.





Ott, et al.               Expires May 16, 2014                 [Page 10]

Internet-Draft            RTCP XR Discard RLE              November 2013


B.5.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-04

   o  Added Block Type definition to each XRBlock.

   o  Made changes requested in WGLC.

B.6.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-05

   o  Made changes requested by SDP directorate.

B.7.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-06

   o  Editorial fixes based on review from Gen-art and IESG review.

B.8.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-07

   o  Editorial fixes based on review from IESG.

   o  Editorial fixes based on Security and PM directorate.

   o  Split bytes discarded from this draft to another.

   o  Updated Security Considerations Section.

   o  This draft now normatively cites the definition of discards in
      'packets discarded' draft.

B.9.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-08

   o  Editorial fixes: Updated references from drafts to RFCs.

   o  Updated RFC6390 template with RTP keyword.

B.10.  changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-09

   o  Removed (RLE) from RFC6390 template.

Authors' Addresses

   Joerg Ott
   Aalto University
   School of Electrical Engineering
   Otakaari 5 A
   Espoo, FIN  02150
   Finland

   Email: jo@comnet.tkk.fi




Ott, et al.               Expires May 16, 2014                 [Page 11]

Internet-Draft            RTCP XR Discard RLE              November 2013


   Varun Singh (editor)
   Aalto University
   School of Electrical Engineering
   Otakaari 5 A
   Espoo, FIN  02150
   Finland

   Email: varun@comnet.tkk.fi
   URI:   http://www.netlab.tkk.fi/~varun/


   Igor D.D. Curcio
   Nokia Research Center
   P.O. Box 1000 (Visiokatu 3)
   Tampere, FIN  33721
   Finland

   Email: igor.curcio@nokia.com
































Ott, et al.               Expires May 16, 2014                 [Page 12]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/