Network Working Group                                        J. Welch 
   Internet Draft                                 IneoQuest Technologies 
   Intended Category:  Informational                            J. Clark 
                                                           Cisco Systems 
                                                            August, 2004 
    
    
                      A Proposed Media Delivery Index 
                          draft-welch-mdi-00.txt 
    
    
Status of this Memo 
    
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   disclosed, in accordance with RFC 3668. 
    
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   This memo provides information for the Internet community.  It does 
   not specify an Internet standard.  Distribution of this memo is 
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   The IETF takes no position regarding the validity or scope of any 
   Intellectual Property Rights or other rights that might be claimed to 
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   on the procedures with respect to rights in RFC documents can be 
   found in BCP 78 and BCP 79. 
 
 
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   By submitting this Internet-Draft, I accept the provisions of Section 
   3 of RFC 3667.  
    
    
Abstract 
    
   This memo defines a Media Delivery Index (MDI) measurement which can 
   be used as a diagnostic tool or a quality indicator for monitoring a 
   network intended to transport streaming media such as MPEG video or 
   other arrival time and packet loss sensitive information.  It 
   provides an indication of traffic jitter, a measure of deviation from 
   nominal flow rates, and data loss at-a-glance.  For instance, the MDI 
   may be used as a reference in characterizing and comparing networks 
   carrying constant bit rate streaming media. Included is a set of 
   managed objects for SNMP-based management of IP media streams for 
   which an MDI measurement is obtained. 
    
   The Media Delivery Index measurement and MIB defined in this memo is 
   intended for Information only. 
 
Conventions used in this document 
    
   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 RFC 2119 [n14]. 
    
Introduction 
    
   There has been considerable progress over the last several years in 
   the development of methods to provide for QOS over packet switched 
   networks to improve the delivery of streaming media and other time 
   and packet loss sensitive applications such as [i1], [i5], [i6], 
   [i7].  QOS is required for applications such as video transport to 
   assure the availability of network bandwidth by providing upper 
   limits on the number of flows admitted to a network as well as to 
   bound the packet jitter introduced by the network.  These bounds are 
   required to dimension a receiver`s buffer to properly display the 
   video in real time without buffer overflow or underflow. 
      
   Now that large scale implementations of such networks based on RSVP 
   and Diffserv are undergoing trials [i3] and being specified by major 
   service providers for the transport of streaming media such as MPEG 
   video [i4], there is a need to easily diagnose issues and monitor the 
   real time effectiveness of networks employing these QOS methods.  
   Furthermore, due to the significant installed base of legacy networks 
   without QOS methods, a delivery system`s transitional solution may be 
   comprised of both networks with and without these methods thus 
   increasing the difficulty in characterizing the dynamic behavior of  
 
 
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   these networks. 
    
   The purpose of this memo is to describe a set of measurements that 
   can be used to derive a Media Delivery Index (MDI) which indicates 
   the instantaneous and longer term behavior of networks carrying 
   streaming media such as MPEG data. 
    
   While this memo addresses monitoring MPEG Transport Stream (TS) 
   packets [i8] over UDP, the general approach is expected to be 
   applicable to other streaming media and protocols.  
    
Media Delivery Index Overview 
    
   The MDI provides a relative indicator of needed buffer depths at the 
   consumer node due to packet jitter and network latency as well as an 
   indication of lost packets.  By probing a streaming media network at 
   various nodes and under varying load conditions, it is possible to 
   quickly identify devices or locales which introduce significant 
   jitter or packet loss to the packet stream. By monitoring a network 
   continuously, deviations from nominal jitter or loss behavior can be 
   used to indicate an impending or ongoing fault condition such as 
   excessive load.  It is believed that the MDI provides the necessary 
   information to detect all network induced MPEG video display 
   impairments.  Other parameters may be required to troubleshoot and 
   correct the impairments. 
    
   The MDI is updated at the termination of selected time intervals 
   spanning multiple packets which contain the streaming media (such as 
   transport stream packets in the MPEG-2 case.)  The Maximums and 
   Minimums of the MDI component values are captured over a measurement 
   time.  The measurement time may range from just long enough to 
   capture an anticipated network anomaly during a troubleshooting 
   exercise to indefinitely long for a long term monitoring or  
   logging application. 
 
Media Delivery Index Components 
    
   - Delay Factor (DF):  The maximum difference, observed at the end of 
   each media stream packet, between the arrival of media data and the 
   drain of media data, assuming the drain rate is the nominal constant 
   traffic rate of media stream packet data.  If, at the sample time, 
   the number of bytes received equals the number transmitted, the 
   instantaneous flow rate balance will be zero, however the minimum DF 
   will be a line packet's worth of media data as that is the minimum 
   amount of data that must be buffered.  The DF is the maximum observed 
   value of the flow rate imbalance.  This buffered media data in bytes 
   is expressed in terms of how long it would take to drain (or fill) 
   this data at the nominal constant traffic rate in milliseconds to 
   obtain the DF.  The DF value MUST be updated and displayed at the end 
 
 
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   of a selected time interval.  The selected time interval is chosen to 
   be long enough to include a number of TS packets and will, therefore, 
   vary based on the nominal constant traffic rate.  The Delay Factor 
   indicates how long a data stream must be buffered (i.e. delayed) at 
   its nominal constant bit rate to prevent packet loss.  Thus, it is 
   also proportional to latency.  The DF`s max and min over the 
   measurement period MAY also be displayed to show the worst case 
   arrival time deviation, or jitter, relative to the nominal constant 
   traffic rate in a measurement period.  It provides a dynamic flow 
   rate balance indication with its max and min showing the worst 
   excursions from balance.  To arrive at a bounded DF, the long term 
   flow rate deviation (LFRD) must be 0, where LFRD is a running 
   deviation of flow rate from expected nominal constant traffic rate 
   over a measurement period.  A large positive or negative LFRD usually 
   indicates a media stream source failure or misconfiguration and would 
   cause the DF value to steadily increase from interval to interval. 
    
   The Delay Factor gives a hint of the size of the buffer required at 
   the next downstream node.  As a stream progresses, the variation of 
   the Delay Factor indicates packet bunching (jitter).  Greater DF 
   values also indicate more network latency to deliver a stream due to 
   the need to prefill a receive buffer before beginning the drain to 
   guarantee no underflow.   The DF is comprised of a fixed part based 
   on packet size and a variable part based on the various network  
   component switch elements` buffer utilization that comprise the 
   switched network infrastructure [i2].     
    
   - Media Loss Rate:  Lost or out of order Media packets counted over a 
   selected time interval, where Media packets are packets carrying 
   media information.  There may be 0 or more media packets in a single 
   layer 2 network packet such as Ethernet.  For example, it is common 
   to carry seven 188 Byte MPEG Transport Stream packets in a 1362 Byte 
   Ethernet frame.  In such a case, a single Ethernet frame loss would 
   result in 7 lost Media packets counted for the case where the 7 lost 
   Media packets did not include null packets.     
    
   Combining these quantities for presentation results in the MDI: 
    
                                  DF:MLR 
    
   Where: 
    
                          DF is the Delay Factor   
                        MLR is the Media Loss Rate 
    
   At a receiving node, knowing its nominal constant drain bit rate, the 
   DF`s max indicates the size of required buffer to accommodate packet 
   jitter.  Or, in terms of Leaky Bucket [i9] parameters, DF indicates 
   bucket size b expressed in time to transmit bucket traffic b, at the 
 
 
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   given nominal constant traffic rate, r.  In the case where a known, 
   well characterized receive node is separated from the data source by 
   unknown or less well characterized nodes such as intermediate switch 
   nodes, the MDI measured at intermediate data links provides a 
   relative indication of the behavior of upstream traffic flow.  DF 
   difference indications between one node and another in a data stream 
   for a given constant interval of calculation can indicate local areas 
   of traffic congestion or possibly misconfigured QOS flow 
   specification(s) leading to greater filling of measurement point 
   local device buffers, resultant flow rate deviations, and possible 
   data loss. 
    
   For a given MDI, if DF is high and/or the DF Max-Min captured over a  
   significant measurement period is high, jitter has been detected but 
   the longer term, average flow rate may be nominal.  This could be the 
   result of a transient flow upset due to a coincident traffic stream 
   unrelated to the flow of interest causing packet bunching.  A high DF 
   may cause downstream buffer overflow or underflow or unacceptable 
   latency even in the absence of lost data. 
    
   Due to transient network failures or DF excursions, packets may be 
   lost within the network.  The MLR component of the MDI shows this 
   condition.   
    
The Internet-Standard Management Framework 
    
   For a detailed overview of the documents that describe the current 
   Internet-Standard Management Framework, please refer to section 7 of 
   RFC 3410 [i10]. 
    
   Managed objects are accessed via a virtual information store, termed 
   the Management Information Base or MIB.  MIB objects are generally 
   accessed through the Simple Network Management Protocol (SNMP). 
   Objects in the MIB are defined using the mechanisms defined in the 
   Structure of Management Information (SMI).  This memo specifies a MIB 
   module that is compliant to the SMIv2, which is described in STD 58,   
   RFC 2578 [n11], STD 58, RFC 2579 [n12] and STD 58, RFC 2580 [n13]. 
    
MIB Overview 
    
   This MIB provides a set of objects required for the export of MDI 
   metrics of IP streaming media streams. 
    
MIB Definitions 
    
   -- 
   -- Media Stream Monitor MIB 
   --  
    
 
 
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   MEDIA-MONITOR-MIB DEFINITIONS ::= BEGIN 
    
   IMPORTS 
       MODULE-IDENTITY,  
       OBJECT-TYPE,  
       Integer32, 
       Unsigned32,  
       mib-2, 
       NOTIFICATION-TYPE, 
       OBJECT-IDENTITY, 
       IpAddress 
           FROM SNMPv2-SMI                  -- RFC2578 
       DisplayString 
           FROM SNMPv2-TC 
       MODULE-COMPLIANCE, OBJECT-GROUP, 
       NOTIFICATION-GROUP 
           FROM SNMPv2-CONF;                -- RFC2580 
    
   mediaMonitorMIB MODULE-IDENTITY 
       LAST-UPDATED "200404040000Z"         -- 04 April 2004 
    
       ORGANIZATION " xx " 
       CONTACT-INFO 
         "IneoQuest Technologies, Inc. 
              Postal: 170 Forbes Boulevard 
                      Mansfield, MA, 02048  
              Tel:    +1 508 618 0312 
              E-mail: jim.welch@ineoquest.com" 
    
       DESCRIPTION 
           "The media Monitor MIB (MEDIA-MONITOR-MIB) provides 
           Metrics for Monitoring IP streaming Media Flows." 
    
        --  Revision history 
    
        REVISION     "200404040000Z"         -- 04 April 2004 
        DESCRIPTION 
            "Initial version, published as RFC xxxx. (this RFC)" 
    
       ::= { xxxx } 
    
    -- Top level structure of the MIB 
    
     mediaMonitorObjects    OBJECT IDENTIFIER ::= { mediaMonitorMIB 1 } 
    
   ipMediaStreamMonitorTable OBJECT-TYPE 
       SYNTAX      SEQUENCE OF IpMediaStreamMonitorEntry 
       MAX-ACCESS  not-accessible 
       STATUS      current 
 
 
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       DESCRIPTION 
           "IP Stream Monitor Table. This table is indexed by the 
           Stream Handle. This Table only shows the currently ACTIVE 
           video Streams." 
       ::= { mediaMonitorObjects 1 } 
    
   ipMediaStreamMonitorEntry OBJECT-TYPE 
       SYNTAX IpMediaStreamMonitorEntry 
       MAX-ACCESS not-accessible 
       STATUS     current 
       DESCRIPTION 
            "IP Stream Monitor Table Entry." 
       INDEX  { ipMediaStreamMonitorHandle } 
       ::= { ipMediaStreamMonitorTable 1 } 
    
   IpMediaStreamMonitorEntry ::= SEQUENCE { 
       ipMediaStreamHandle 
           Unsigned32, 
       ipMediaStreamSourceIpAddress 
           IpAddress, 
       ipMediaStreamSourcePort 
           Unsigned32, 
       ipMediaStreamDestinationIpAddress 
           IpAddress, 
       ipMediaStreamDestinationPort 
           Unsigned32, 
       ipMediaStreamBitRate 
           Unsigned32, 
       ipMediaStreamInterval 
           Unsigned32, 
       ipMediaStreamStartTime 
           DisplayString, 
        ipMediaStreamMDIDelayFactor 
           Unsigned32, 
       ipMediaStreamMDILossRate 
           Unsigned32, 
       ipMediaStreamMDIDFThreshold 
           Unsigned32, 
       ipMediaStreamMDILRThreshold 
           Unsigned32, 
       ipMediaStreamMDIDFErrorIntervals 
           Unsigned32 
       ipMediaStreamMonitorMDIMLRErrorIntervals 
           Unsigned32 
           } 
               
   ipMediaStreamHandle OBJECT-TYPE 
       SYNTAX  Unsigned32 
       MAX-ACCESS read-only 
 
 
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       STATUS     current 
       DESCRIPTION 
            "Table is indexed by stream Handle. The table has one row 
            for each Media Stream detected from the Ip Interface.  The 
            Stream Handle shall be a unique value for the life of the 
            stream." 
       ::= { ipMediaStreamMonitorEntry 1 } 
    
   ipMediaStreamSourceIpAddress OBJECT-TYPE 
       SYNTAX     IpAddress  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "Source IpAddress for the Stream indexed by the Stream 
              Handle." 
       ::= { ipMediaStreamMonitorEntry 2 } 
    
   ipMediaStreamSourcePort OBJECT-TYPE 
       SYNTAX   Unsigned32  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "The Source port for the Stream indexed by the Stream 
              Handle." 
       ::= { ipMediaStreamMonitorEntry 3 } 
    
   ipMediaStreamDestinationIpAddress OBJECT-TYPE 
       SYNTAX     IpAddress  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "Destination IpAddress for the Stream indexed by the 
              Stream Handle." 
       ::= { ipMediaStreamMonitorEntry 4 } 
    
   ipMediaStreamDestinationPort OBJECT-TYPE 
       SYNTAX    Unsigned32 
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "The Destination port for the Stream indexed by the 
              Stream Handle." 
       ::= { ipMediaStreamMonitorEntry 5 } 
    
   ipMediaStreamBitRate OBJECT-TYPE 
       SYNTAX   Unsigned32  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
 
 
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              "The nominal Bit Rate of the Media Stream in bits/second."  
       ::= { ipMediaStreamMonitorEntry 6 } 
    
   ipMediaStreamInterval OBJECT-TYPE 
       SYNTAX   Unsigned32  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "The number indicates the minimum Interval in seconds for 
              a good MDI Measurement. The Interval is based on the 
              current Bit Rate of the Stream.  The minimum interval 
              should be chosen such that at least 10 IP packets occur 
              per interval.  This value defaults to 1 second and the 
              Interval is typically configured to 1 second unless the 
              above criteria is not met."  
       ::= { ipMediaStreamMonitorEntry 7 } 
       
   ipMediaStreamStartTime OBJECT-TYPE 
       SYNTAX     DisplayString  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "The Timestamp shows the Real time at which the stream was 
              detected.  The Timestamp format is YYYY/MM/DD/HH/MM/SS." 
       ::= { ipMediaStreamMonitorEntry 8 } 
    
   ipMediaStreamMDIDelayFactor OBJECT-TYPE 
       SYNTAX  Unsigned32 
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "This object displays the Media Delivery Index Delay 
              Factor parameter in units of milliseconds.  This parameter 
              indicates the burstiness of the stream." 
       ::= { ipMediaStreamMonitorEntry 9 } 
    
   ipMediaStreamMDILossRate OBJECT-TYPE 
       SYNTAX Unsigned32  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "This object displays the Media Delivery Index Media Loss 
              Rate in packets/sec. This parameter indicates rate of 
              lost media packets of the of the  stream." 
       ::= { ipMediaStreamMonitorEntry 10 } 
    
   ipMediaStreamMDIDFThreshold OBJECT-TYPE 
       SYNTAX  Unsigned32  
       MAX-ACCESS  read-write 
 
 
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       STATUS current 
       DESCRIPTION 
              "The Threshold for Media Delivery Index Delay Factor in 
              milliSeconds.  The default value is set to 0 indicating 
              that it is invalid until configured." 
       ::= { ipMediaStreamMonitorEntry 11 } 
    
   ipMediaStreamMDILRThreshold OBJECT-TYPE 
       SYNTAX  Unsigned32  
       MAX-ACCESS  read-write 
       STATUS current 
       DESCRIPTION 
              "The Threshold for Media Delivery Loss Rate 
              in Packets/second. The default value is set to 0xffffffff 
              indicating that it is invalid until configured." 
       ::= { ipMediaStreamMonitorEntry 12 } 
    
   ipMediaStreamMDIDFErrorIntervals OBJECT-TYPE 
       SYNTAX   Unsigned32  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "The number indicates the number of MDI DF Threshold 
              (ipMediaStreamMonitorMDIDFThreshold) Crossed Intervals 
              during the life of a stream. This shall be 0 and invalid 
              until the MDI DF Thresholds are configured." 
       ::= { ipMediaStreamMonitorEntry 13 } 
    
   ipMediaStreamMDIMLRErrorIntervals OBJECT-TYPE 
       SYNTAX   Unsigned32  
       MAX-ACCESS read-only 
       STATUS     current 
       DESCRIPTION 
              "The number indicates the number of MDI MLR Threshold 
              (ipMediaStreamMDILRThreshold)Crossed Intervals 
              during the life of a stream. This shall be 0 and invalid 
              until the MDI MLR Thresholds are configured." 
       ::= { ipMediaStreamMonitorEntry 14 } 
    
   END 
    
    
    
Summary 
    
   The MDI combines the Delay Factor which indicates potential for 
   impending data loss and Media Loss Rate as the indicator of lost 
   data.  By monitoring the DF and MLR and their min and max excursions 
   over a measurement period and at multiple strategic locations in a 
 
 
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   network, traffic congestion or device impairments may be detected and 
   isolated for a network carrying streaming media content.  The 
   included MIB provides a set of objects required for the export of MDI 
   metrics of IP streaming media streams. 
     
       
Security Considerations 
 
    
   The measurements identified in this document do not directly affect 
   the security of a network or user.  Actions taken in response to 
   these measurements which may affect the available bandwidth of the 
   network or availability of a service is out of scope for this 
   document.   
          
    
    
Normative References 
    
   n1. K. McCloghrie, D. Perkins, J. Schoenwaelder, J. Case, J. Rose, M. 
      and S. Waldbusser, 'Structure of Management Information Version 2 
      (SMIv2)', STD 58, RFC 2578, April 1999. 
   n2. K. McCloghrie, D. Perkins, J. Schoenwaelder, J. Case, J. Rose, M. 
      and S. Waldbusser, 'Textual Conventions for SMIv2', STD 58, RFC 
      2579, April 1999. 
   n3. K. McCloghrie, D. Perkins, J. Schoenwaelder, J. Case, J. Rose, M. 
      and S. Waldbusser, 'Conformance Statements for SMIv2', STD 58, RFC 
      2580, April 1999. 
   n4. S. Bradner, 'Key words for use in RFCs to Indicate Requirement 
      Levels', BCP 14, RFC 2119, March 1997. 
    
Informative References 
 
   i1. R. Braden et al., `Resource Reservation Protocol ` Version 1 
      Functional Specification`, RFC 2205, 1997. 
   i2. C. Partridge, `A Proposed Flow Specification`, RFC 1363, 1992. 
   i3. R. Fellman, `Hurdles to Overcome for Broadcast Quality Video 
      Delivery over IP` VidTranS 2002. 
   i4. CableLabs `PacketCable Dynamic Quality-of-Service Specification`, 
      PKT-SP-DQOS-I06-030415, 2003. 
   i5. S. Shenker, C. Partridge, R. Guerin, `Specification of Guaranteed 
      Quality of Service`, RFC 2212, 1997. 
   i6. J. Wroclawski, `Specification of the Controlled-Load Network 
      Element Service`, RFC 2211, 1997. 
   i7. R. Braden, D. Clark, S. Shenker, `Integrated Services in the 
      Internet Architecture: an Overview` RFC 1633, 1994. 
   i8. ISO/IEC 13818-1 (MPEG-2 Systems) 
   i9. V. Raisanen, `Implementing Service Quality in IP Networks`, John 
      Wiley & Sons Ltd., 2003. 
 
 
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   i10. J. Case, R. Mundy, D. Partain, B. Stewart, 'Introduction and 
      Applicability Statements for Internet Standard Management 
      Framework', RFC 3410, 2002. 
 
Acknowledgments 
    
   The authors gratefully acknowledge the contributions of Marc Todd and 
   Jesse Beeson of IneoQuest Technologies, Inc., Bill Trubey and John 
   Carlucci of Time Warner Cable, Nishith Sinha of Cox Communications, 
   Ken Chiquoine of SeaChange International, Phil Proulx of Bell Canada, 
   Dr Paul Stallard of TANDBERG Television, Gary Hughes of Broadbus 
   Technologies, Brad Medford of SBC Laboratories, John Roy of Adelphia 
   Communications, Cliff Mercer, PhD of Kasenna, Mathew Ho of Rogers 
   Cable, and Irl Duling of Optinel Systems for reviewing and evaluating 
   early drafts of this document and implementations for MDI. 
    
Authors' Address 
    
   James Welch 
   IneoQuest Technologies, Inc 
   170 Forbes Blvd 
   Mansfield, Massachusetts 02048 
   508 618 0312 
   Jim.Welch@ineoquest.com 
    
   James Clark 
   Cisco Systems, Inc 
   500 Northridge Road 
   Suite 800 
   Atlanta, Georgia 30350 
   678 352 2726 
   jiclark@cisco.com 
    
Copyright Notice 
    
   Copyright (C) The Internet Society 2004.  This document is subject to 
   the rights, licenses and restrictions contained in BCP 78, and except 
   as set forth therein, the authors retain all their rights. 
    
Disclaimer 
    
   This document and the information contained herein are provided on an 
   'AS IS' basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.' 
    
 
 
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Intellectual Property 
    
   The IETF takes no position regarding the validity or scope of any 
   Intellectual Property Rights or other rights that might be claimed to 
   pertain to the implementation or use of the technology described in 
   this document or the extent to which any license under such rights 
   might or might not be available; nor does it represent that it has 
   made any independent effort to identify any such rights.  Information 
   on the ISOC's procedures with respect to rights in ISOC Documents can 
   be found in BCP 78 and BCP 79. 
    
   Copies of IPR disclosures made to the IETF Secretariat and any 
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