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Versions: (draft-claise-ipfix-export-per-sctp-stream) 00 01 02 03 04 05 06 07 08 RFC 6526

     IPFIX Working Group                                    B. Claise
     Internet-Draft                                         P. Aitken
     Intended Status: Standards Track                      A. Johnson
     Expires: May 19, 2010                        Cisco Systems, Inc.
                                                             G. Muenz
                                                          TU Muenchen
                                                    November 19, 2009
     
                       IPFIX Export per SCTP Stream
                draft-ietf-ipfix-export-per-sctp-stream-06
     
     
     Abstract
     
        This document specifies an extension to the specifications
        in RFC5101, IP Flow Information Export (IPFIX), when using
        the Partial Reliability extension of SCTP (PR-SCTP, Partial
        Reliability Stream Control Transmission Protocol).
        When implemented at both the Exporting and Collecting Processes,
        this method offers several advantages such as the ability to
        calculate Data Record losses for PR-SCTP, immediate export of
        Template Withdrawal Messages, immediate reuse of Template IDs
        within an SCTP stream, reduced likelihood of Data Record loss,
        and reduced demands on the Collecting Process.  When implemented
        in only the Collecting or Exporting Process then normal IPFIX
        behavior will be seen without these additional benefits.
     
     Status of this Memo
     
        This Internet-Draft is submitted to IETF in full conformance
        with the provisions of BCP 78 and BCP 79.
     
        Internet-Drafts are working documents of the Internet
        Engineering Task Force (IETF), its areas, and its working
        groups.  Note that other groups may also distribute working
        documents as Internet-Drafts.
     
        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."
     
        The list of current Internet-Drafts can be accessed at
        http://www.ietf.org/ietf/1id-abstracts.txt
     
        The list of Internet-Draft Shadow Directories can be accessed at
        http://www.ietf.org/shadow.html
     
        This Internet-Draft will expire on May, 2010.
     
     
     Copyright Notice
     

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        Copyright (c) 2009 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 in effect on the date of
        publication of this document (http://trustee.ietf.org/license-
        info).  Please review these documents carefully, as they
        describe your rights and restrictions with respect to this
        document.
     
     
     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 [RFC2119].
     
     
     Table of Contents
     
     
        1. Terminology.................................................3
           1.1. IPFIX Documents Overview...............................3
           1.2. PSAMP Documents Overview...............................4
        2. Introduction................................................4
           2.1. Relationship with IPFIX and PSAMP......................5
           2.2. Applicability..........................................6
           2.3. Limitations............................................6
        3. IPFIX Protocol Specifications Limitations and
        Improvements...................................................7
           3.1. Data Record Loss per Template..........................7
              3.1.1. IPFIX Protocol Specifications Limitation..........7
              3.1.2. IPFIX Export per SCTP Stream Advantage............8
           3.2. Transmission Order within an SCTP stream...............8
              3.2.1. IPFIX Protocol Specifications Limitation..........8
              3.2.2. IPFIX Export per SCTP Stream Advantages...........8
           3.3. No Transmission Order across SCTP Streams..............9
              3.3.1. IPFIX Protocol Specifications Limitation..........9
              3.3.2. IPFIX Export per SCTP Stream Advantages..........10
        4. Specifications.............................................10
           4.1. New Information Element...............................10
           4.2. Template Management...................................11
           4.3. SCTP..................................................12
           4.4. Template Withdrawal Message...........................13
           4.5. The Collecting Process's Side.........................14
        5. Performance Impact.........................................16
     
     
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        6. Examples...................................................16
        7. IANA Considerations........................................20
        8. Security Considerations....................................20
        9. References.................................................21
           9.1. Normative References..................................21
           9.2. Informative References................................21
        10. Acknowledgements..........................................22
        11. Author's Addresses........................................23
     
     
     
     1. Terminology
     
        IPFIX-specific terminology used in this document is defined
        in section 2 of [RFC5101].  As in [RFC5101], these IPFIX-
        specific terms have the first letter of a word capitalized
        when used in this document.
     
        Note that, in this document, "(Options) Template" is used to
        refer to Templates and Options Templates.  Unless otherwise
        specified, "Template" alone refers to Templates exclusive of
        Options Templates.
     
        Template Reuse Delay
     
           The time the Exporting Process needs to wait after sending
           the last Data Set described by a given Template before
           sending a Template Withdrawal Message for the Template.
           [RFC5101] specifies a default value of 5 seconds.
     
     
     1.1. IPFIX Documents Overview
     
        The IPFIX Protocol [RFC5101] provides network administrators
        with access to IP Flow information.
     
        The architecture for the export of measured IP Flow
        information out of an IPFIX Exporting Process to a Collecting
        Process is defined in the IPFIX Architecture [RFC5470], per
        the requirements defined in [RFC3917].
     
        The IPFIX Architecture [RFC5470] specifies how IPFIX Data
        Records and Templates are carried via a congestion-aware
        transport protocol from IPFIX Exporting Processes to IPFIX
        Collecting Processes.
     
     
     
     
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        IPFIX has a formal description of IPFIX Information Elements,
        their names, types and additional semantic information, as
        specified in the IPFIX Information Model [RFC5102].
     
        Finally the IPFIX Applicability Statement [RFC5472] describes
        what type of applications can use the IPFIX protocol and how
        they can use the information provided.  It furthermore shows
        how the IPFIX framework relates to other architectures and
        frameworks.
     
     1.2. PSAMP Documents Overview
     
        The document "A Framework for Packet Selection and Reporting"
        [RFC5474], describes the Packet Sampling (PSAMP) framework
        for network elements to select subsets of packets by
        statistical and other methods, and to export a stream of
        reports on the selected packets to a collector.
     
        The set of packet selection techniques (sampling, filtering,
        and hashing) supported by PSAMP are described in "Sampling
        and Filtering Techniques for IP Packet Selection" [RFC5475].
     
        The PSAMP protocol [RFC5476] specifies the export of packet
        information from a PSAMP Exporting Process to a PSAMP
        Collecting Process.  Like IPFIX, PSAMP has a formal
        description of its Information Elements, their names, types
        and additional semantic information.  The PSAMP information
        model is defined in [RFC5477].
     
        Finally [PSAMP-MIB] describes the PSAMP Management
        Information Base.
     
     
     2. Introduction
     
        The IPFIX protocol [RFC5101] has the goal of exporting IP
        Flow information.  This protocol is designed to export
        information about IP traffic Flows and related measurement
        data, where a Flow is defined by a set of key attributes
        (e.g., source and destination IP address, source and
        destination port, etc.).  However, thanks to its Template
        mechanism, the IPFIX protocol can export any type of
        information, as long as the relevant Information Element is
        specified in the IPFIX Information Model [RFC5102],
        registered with IANA, or specified as an enterprise-specific
        Information Element.
     
     
     
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        The IPFIX protocol [RFC5101] specifies that IP traffic
        measurements for Flows are exported using a TLV (type,
        length, value) format.  The information is exported using a
        Template Record which is sent once to export the {type,
        length} pairs that define the data format for the Information
        Elements in a Flow.  The Data Records specify values for each
        Flow.
     
        The IPFIX protocol [RFC5101] is flexible: it foresees the usage
        of multiple SCTP streams per association; it allows the
        transmission of Data Sets, Template Sets, and/or Options
        Template Sets on any SCTP stream; it offers full and partially
        reliable export of Data Sets; it proposes ordered or out-of-
        order delivery of Data Sets.  However, due to bandwidth
        restrictions and packet losses in the network as well as
        resource constraints on the Exporter and Collector (e.g.,
        limited buffer sizes), it is not always possible to export all
        Data Sets in a reliable way.
     
        This document specifies a method for exporting a Template Record
        and its associated Data Sets in a single SCTP stream, limiting
        each Template ID to a single SCTP stream if possible, and
        imposing in-order transmission.
     
        This method offers several advantages over IPFIX export as
        specified in [RFC5101] such as the ability to calculate Data
        Record losses for PR-SCTP, immediate export of Template
        Withdrawal Messages, immediate reuse of Template IDs within an
        SCTP stream, reduced likelihood of Data Record loss, and reduced
        demands on the Collecting Process.
     
     
     2.1. Relationship with IPFIX and PSAMP
     
        The specification in this document applies to the IPFIX
        protocol specifications [RFC5101].  However, it only applies
        to the SCTP transport protocol [RFC4960] option of the IPFIX
        protocol specifications, specifically in the case of the
        partial reliability extension [RFC3758].  All specifications
        from [RFC5101] apply unless specified otherwise in this
        document.
     
        As the Packet Sampling (PSAMP) protocol specifications
        [RFC5476] are based on the IPFIX protocol specifications, the
        specifications in this document are also valid for the PSAMP
        protocol.
     
     
     
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     2.2. Applicability
     
        The specifications contained in this document are applicable to
        cases where application requirements include knowing how many
        data records of a certain type (i.e., from a certain Template)
        were lost.  A typical example is a router exporting billing
        records.  Furthermore, they apply in cases where the Exporter
        can not afford to export all the Flow Records reliably, due to
        the limited resources to buffer the huge amount of Flow Records.
        Such situations may occur if Data Sets are generated at a higher
        rate at the Exporter than can be transferred to the Collector
        because of bandwidth limitations in the network or slow
        reception at the Collector.
     
        To be more precise, the specification applicability is the case
        where multiple Templates are simultaneously active within a
        single SCTP Transport Session and the calculation of the Data
        Record loss for a particular Template is required.  Indeed, with
        the current IPFIX specifications [RFC5101], if an IPFIX Message
        is lost (UDP or SCTP partially reliable), it is not possible to
        determine to which Template the lost Data Records belong to.
     
        Exporting Processes following this specification will
        interoperate with existing Collecting Processes that comply with
        [RFC5101]; no changes are required at the Collecting Process to
        receive data from an Exporting Process compliant with this
        method.  However, Collecting Processes may implement additional
        support for per-stream export specified in this document in
        order to realize all the benefits of the approach specified
        herein.
     
     
     2.3. Limitations
     
        When multiple Templates are required, this method requires
        multiple SCTP streams in the association between the Exporting
        and Collecting Process, ideally one per Template.  To properly
        handle the transmission of additional Templates during the
        Transport Session, additional SCTP streams are sometimes
        required.  These SCTP streams can only be added within the
        existing SCTP association if the specifications in [SCTP-RESET]
        are supported.
     
     
     
     
     
     
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     3. IPFIX Protocol Specifications Limitations and Improvements
     
        For three specific topics ("Data Record Loss per Template",
        "Transmission Order within an SCTP stream", "No Transmission
        Order across SCTP Streams"), this section explains the IPFIX
        protocol specifications limitations on the one hand, and the
        advantages of the method specified in this document on the other
        hand.
     
     
     3.1. Data Record Loss per Template
     
     3.1.1. IPFIX Protocol Specifications Limitation
     
        Section 6.3.2 of the "Requirements for IP Flow Information
        Export" [RFC3917] discusses the data transfer reliability
        issues: "Loss of flow records during the data transfer from
        the Exporting Process to the Collecting Process must be
        indicated at the Collecting Process."
     
        However, in some cases, it may be important to know how many
        Data Records of a certain type were lost (e.g., in the case
        of billing), and IPFIX does not conventionally provide this
        information.
     
        A Collector can detect out-of-sequence, dropped, or duplicate
        IPFIX Messages by tracking the Sequence Number [RFC5101].
        Note that the Sequence Number field in the IPFIX Message
        header increases with the number of IPFIX Data Records within
        the SCTP stream, so loss will be detected per stream.
     
        The IPFIX protocol specification [RFC5101] specifies that Data
        Records defined by any Template may be sent on any SCTP stream.
        As such, if there is more than one Template defined within the
        whole SCTP association, then there is no way of knowing which
        Template any lost Data Record is associated with.  This is true,
        no matter what convention the Exporting Process uses to send
        Data Records on different SCTP streams, as the protocol makes no
        guarantees.
     
        Note that a workaround allowed by the IPFIX specifications
        [RFC5101] is to use only one Template Record per SCTP Transport
        Session, at the cost of multiplying the number of SCTP Transport
        Sessions when multiple Template Records are required.
     
     
     
     
     
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     3.1.2. IPFIX Export per SCTP Stream Advantage
     
        Using the specification in this document, it is guaranteed that
        any lost Data Records will be associated only with the Templates
        that are defined on that SCTP  stream. By defining only one
        Template per SCTP stream, it is ensured that any loss is
        associated with that single Template.  So, by exporting each
        Template and the corresponding Data Records within a different
        SCTP stream, the loss pertaining to each specific Template can
        be deduced from the Sequence Number field in the IPFIX Message
        headers.
     
     
     3.2. Transmission Order within an SCTP stream
     
     3.2.1. IPFIX Protocol Specifications Limitation
     
        A Collecting Process must have received the Template Record
        associated with the Data Records to be able to decode the
        information in the Data Records.  [RFC5101] specifies:
     
           "The Exporting Process SHOULD transmit the Template Set
           and Options Template Set in advance of any Data Sets that
           use that (Options) Template ID, to help ensure that the
           Collector has the Template Record before receiving the
           first Data Record."
     
        The fact that the Collecting Process cannot decode the Data
        Records without the corresponding Template Record may result in
        Data Records being discarded by the Collector, as specified in
        [RFC5101]:
     
           "The Collecting Process normally receives Template Records
           from the Exporting Process before receiving Data Records.
           The Data Records are then decoded and stored by the
           Collector.  If the Template Records have not been received
           at the time Data Records are received, the Collecting
           Process MAY store the Data Records for a short period of
           time and decode them after the Template Records are
           received."
     
     
     3.2.2. IPFIX Export per SCTP Stream Advantages
     
        By exporting each Template Record and the corresponding Data
        Records within a single SCTP stream and imposing in-order
        transmission, the Template Record will always arrive before
     
     
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        the associated Data Records.  Therefore, there is no risk
        that the Collecting Process discards Data Records while
        waiting for the Template Record to arrive.
     
        Furthermore, when reusing a Template ID within an SCTP
        stream, the Template Withdrawal Message will be guaranteed to
        arrive before the new definition of the Template and
        therefore the Template Record may be sent directly after the
        Template Withdrawal Message.  In other words, the Template
        Reuse Delay restriction (by default, 5 seconds, as specified
        in [RFC5101] is removed for Template ID reuse within the same
        SCTP stream.
     
        Another advantage of the new specifications in this document
        is a reduced load on the Collecting Process.  Indeed, the
        Collecting Process doesn't have to store the Data Records
        while waiting for the Template Record, as the transmission
        order is always guaranteed.  This way, extra reliability of
        the Data Records is achieved without extra burden on the
        Collecting Process.
     
     
     3.3. No Transmission Order across SCTP Streams
     
     3.3.1. IPFIX Protocol Specifications Limitation
     
        The fact that the protocol specifications [RFC5101] are
        flexible in terms of SCTP stream(s) on which the Template
        Set, Options Template Set, and corresponding Data Sets are
        exported, implies that the (Options) Template Record might be
        exported on a different SCTP stream than the corresponding
        Data Records.  This might cause Data Record loss in the
        Collecting Process as ordered transmission across SCTP
        streams is not guaranteed.
     
        For example, a Template Record may be blocked pending
        reliable transmission on one SCTP stream while the
        corresponding Data Records may be transmitted immediately in
        another SCTP stream.  Also, due to different SCTP stream
        congestion, it is possible that even if the Template Record
        and corresponding Data Records are sent reliably, Data
        Records sent on a different SCTP stream than the Template
        Record might still arrive before the Template Record.
     
     
     
     
     
     
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     3.3.2. IPFIX Export per SCTP Stream Advantages
     
        By exporting each Template Record and all corresponding Data
        Records within a single SCTP stream, and imposing in-order
        transmission, the issue of ordered transmission across
        multiple SCTP streams is avoided.
     
        By exporting all corresponding Data Records within the same
        ordered SCTP stream as the Template Record, each SCTP stream is
        independent and self-contained and the interaction between SCTP
        streams is limited to that of Options Template and associated
        Data Records sent in different streams.  This has several
        advantageous consequences, including the order preservation that
        does not result in the blocking of unrelated data and load
        reduction on the Collecting Process (as the Template Records are
        guaranteed to be delivered before the associated Data Records,
        there is no need for the buffering of Data Sets which correspond
        with Templates that are missing).
     
     
     4. Specifications
     
        This section specifies Exporting Process and Collecting Process
        behavior different from that in [RFC5101] in order to realize
        the benefits of per-stream export. Note that Exporting Processes
        following these specifications will interoperate with [RFC5101]-
        compliant Collecting Processes, but that Collecting Processes
        will have to follow additional non-interoperable specifications
        to realize the full benefits of the technique.  These new
        specifications, which add to those in [RFC5101], are described
        with the key words described in [RFC2119].
     
     
     4.1. New Information Element
     
        dataRecordsReliability
     
           Description:
                The reliability of the export of Data Records, within
                this SCTP stream, for the element(s) in the Options
                Template scope, usually a templateID. A value of 'true'
                means that the Exporting Process MUST send any Data
                Records associated with the element(s) reliably within
                this SCTP stream.  A value of 'false' means that the
                Exporting Process MAY send any Data Records associated
                with the element(s) unreliably within this SCTP stream.
     
     
     
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           Abstract Data Type: boolean
           Data Type Semantics: identifier
           ElementId: XXX
           Status: current
     
        IANA NOTE: IANA should replace XXX with the assigned value
     
     
     4.2. Template Management
     
        To take advantage of per-stream export, Exporting Processes
        should follow the specification in this section in addition to
        Section 8, Template Management, of [RFC5101].
     
        As specified in [RFC5101], Template Sets and Options Template
        Sets MUST be sent reliably.
     
        Any Data Sets associated with a Template Record MUST be sent on
        the same SCTP stream on which the Template Record was sent.
     
        The Data Record Reliability Options Template is used to
        explicitly inform the Collecting Process which Templates will be
        used in each SCTP stream and whether each set of associated Data
        Records will be sent reliably or unreliably.  Before sending any
        Data Records on an SCTP stream, the Exporting Process MUST
        notify the Collecting Process of its intention to send those
        Data Records reliably or unreliably within that SCTP stream.  It
        does this by sending a Data Record defined by the Data Record
        Reliability Options Template for the Template associated with
        Data Records to be sent.  The one exception to this rule is that
        the Data Records associated with the Data Record Reliability
        Options Template don't require an explicit notification as these
        MUST always be sent reliably.
     
        The Data Record Reliability Options Template MUST contain the
        following Information Elements:
     
         Scope:     Template ID
         Non-scope: dataRecordsReliability
     
        A value of 'true' for the dataRecordsReliability Element means
        that the Exporting Process MUST send any Data Records associated
        with the Template ID reliably within this SCTP stream.  A value
        of 'false' for the dataRecordsReliability Element means that the
        Exporting Process MAY send any Data Records associated with the
        Template ID unreliably within this SCTP stream.
     
     
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        If the Exporter wants to change the export reliability value
        (from reliable to unreliable, or vice-versa) for Data Records on
        an SCTP stream, the Template MUST be withdrawn, and a new
        Template MUST be used.
     
        The Data Record Reliability Options Template MAY contain other
        non-scope Information Elements associated with the (Options)
        Template.
     
        When an Options Template, including the Data Record Reliability
        Options Template, and associated Data Records are sent in the
        same SCTP stream, the first associated Data Record can follow
        the Options Template immediately.  When the Options Template and
        associated Data Records are sent in different SCTP streams, the
        Exporting Process SHOULD transmit the Options Template in
        advance of any Data Sets that use it, to help ensure that the
        Collector has received the Options Template Record before
        receiving the first associated Data Record.
     
        It is RECOMMENDED that the Exporter only sends a single Template
        and corresponding Data Sets within a single SCTP stream in order
        to enable calculation of the potential Data Record loss for this
        Template.  The Exporter MAY group related (Options) Templates
        and their associated Data Records within a single SCTP stream so
        that loss statistics are calculated for the group of Templates
        that are being sent unreliably within the SCTP stream.  This is
        suitable in cases where there are only slight variations among
        the Templates in a group (e.g., the omission of unavailable
        fields for export efficiency) and may be necessary if the SCTP
        association does not support enough SCTP streams to export each
        Template in its own SCTP stream.
     
        If an SCTP stream contains a mixture of Data Records defined by
        Template Records and Options Template Records, the Data Records
        defined by the Options Template Records SHOULD be sent reliably
        so that the Collector does not consider any loss to be
        associated with the options Data Records.
     
     
     4.3. SCTP
     
        To take advantage of per-stream export, Exporting Processes
        should manage SCTP streams according to the specification in
        this section, in addition to Section 10.2.4.3, Stream, of
        [RFC5101].
     
     
     
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        PR-SCTP [RFC3758] MUST be implemented by all compliant
        implementations.
     
        All IPFIX Messages MUST be sent in order within an SCTP stream.
     
        As specified in [RFC5101], depending on the requirements of the
        application, the Exporting Process may send Data Sets with full
        or partial reliability.
     
        If the Exporting Process is required to export a new Template
        Record but there are no more free SCTP streams available, it
        SHOULD attempt to increase the number of outbound SCTP streams
        it is able to send to, per [SCTP-RESET].  Alternatively, the
        Exporting Process MAY add the Template Set and Data Records to
        an existing SCTP stream at the cost of diluting the granularity
        of Data Records loss.  An alternative, which is not practical in
        operational networks, is to restart the SCTP association with an
        increased number of SCTP streams.
     
     
     4.4. Template Withdrawal Message
     
        To take advantage of per-stream export, Exporting Processes
        should send Template Withdrawal Messages according to the
        specification in this section, in addition to Section 8,
        Template Management, of [RFC5101].
     
        As specified in [RFC5101], Templates which are not used anymore
        SHOULD be deleted.  Before reusing a Template ID, the Template
        MUST be deleted.  In order to delete an allocated Template, the
        Template is withdrawn through the use of a Template Withdrawal
        Message.
     
        The Template Withdrawal Message MUST be sent on the same SCTP
        stream as the associated Template Record.
     
        As the Template Withdrawal Message MUST be sent reliably, using
        SCTP-ordered delivery per [RFC5101], and as all IPFIX Messages
        are sent in order within an SCTP stream (per the specifications
        in this document), the IPFIX Message containing the Template
        Withdrawal Message will not arrive at the Collecting Process
        before any associated and previously sent Data Record.  As a
        consequence, no Data Records will be lost due to delayed arrival
        at the Collector.
     
        The Template ID from a withdrawn Template MAY be reused on the
        same SCTP stream immediately after the Template Withdrawal
     
     
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        Message is sent.  This case is equivalent to the use of a
        Template Reuse Delay value of 0.
     
        After reusing the Template ID, the Exporting Process MUST send a
        Data Record associated with the Data Record Reliability Options
        Template to specify the reliability level of the Data Records
        associated with the new Template.
     
        If the Template ID is to be reused on a different SCTP stream,
        the new Template Record MUST NOT be sent before the Template
        Reuse Delay.
     
        A Template Withdrawal Message to withdraw all Templates for the
        Observation Domain ID specified in the IPFIX Message header MUST
        NOT be used.
     
        Multiple Template IDs MAY be withdrawn with a single Template
        Withdrawal Message under the condition that all the Template IDs
        in the Template Withdrawal Message are used on the same SCTP
        stream as the Template Withdrawal Message.
     
     
     4.5. The Collecting Process's Side
     
        Collecting Processes must operate slightly contrary to [RFC5101]
        in order to realize the full benefits of per-stream export.
        However, the specification in this section contains a mechanism
        which allows per-stream-capable Collecting Processes to
        selectively enable per-stream export, in order to ensure
        interoperability of per-stream-capable Collecting Processes with
        Exporting Processes which do not implement per-stream export.
     
        As specified in [RFC5101], the Collecting Process SHOULD listen
        for a new association request from the Exporting Process.  The
        Exporting Process will request a number of SCTP streams to use
        for export.
     
        A Collecting Process SHOULD support the procedure for the
        addition of an SCTP stream [SCTP-RESET].
     
        Upon starting a new SCTP association, or restarting an SCTP
        association as per [SCTP-RESET], the Collecting Process SHOULD
        'enable' the per-SCTP-stream extension for that association.  As
        soon as the Exporting Process is seen to not follow the
        specifications of the extension then it MUST be 'disabled'.
        This means the Collecting Process MUST disable the per-SCTP-
        stream extension for the specific Exporter if:
     
     
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        1. A Data Record is received before the appropriate Data Record
        associated with the Data Records Reliability Options Template
        has been received on the same SCTP stream (see section 4.1).
     
        2. A Data Record associated with a Data Record Reliability
        Options Template is received on an SCTP stream for a (non-
        Options) Template that was defined on a different SCTP stream.
     
        3. Loss of Data Records is detected within a stream where there
        has not been received a Data Record associated with the Data
        Record Reliability Options Template indicating unreliable
        transmission for any template.
     
        4. A message is received with the SCTP U(nordered) flag set to
        1, (i.e., the message was sent unordered) even if it is
        processed in order.
     
        Note that it is not an error to receive a Data Record reliably
        if that Data Record is associated with a Template whose Data
        Records are expected to be sent unreliably.
     
        In the case where the Exporting Process does not support the
        per-SCTP-stream extension, then the first Data Record received
        by the Collecting Process will disable the extension for the
        specific Exporter on the Collecting side.
     
        The Collecting Process MUST accept other non-scope Information
        Elements in the Data Record Reliability Options Template.
     
        As specified in [RFC5101], the IPFIX protocol has a Sequence
        Number field in the IPFIX Message header that increases with the
        number of IPFIX Data Records in the IPFIX Message.  A Collector
        may detect out-of-sequence, dropped, or duplicate IPFIX Messages
        by tracking the Sequence Number.
     
        When one or more sequential IPFIX Messages are considered lost,
        the number of lost Data Records is equal to the Sequence Number
        of the first IPFIX Message Header following the lost packets
        (S2) minus the Sequence Number of the first lost IPFIX Message
        (S1).  The Sequence Number of the first lost IPFIX Message can
        be calculated as the Sequence Number of the last IPFIX Message
        before the sequence of lost IPFIX Messages (S0) plus the number
        of Data Records in that IPFIX Message (N0).
     
            S1   = S0 + N0
            loss = S2 - S1 = S2 - (S0 + N0)
     
     
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        As this Sequence Number is incremented per SCTP stream, the loss
        of Data Records sent in that SCTP stream can be calculated in
        case of partially-reliable export.  This loss can be attributed
        to the Data Records sent for the (Options) Template(s) whose
        records are being sent unreliably within that SCTP stream.
     
        Once the Collecting Process receives a Data Record Reliability
        Options Data Record for a particular Template, if the Collecting
        Process receives a Data Record or a Template Withdrawal Message
        for the same Template on a different SCTP stream, then the
        Collecting Process SHOULD log an error message and 'disable'
        this extension for the SCTP association.
     
     
     5. Performance Impact
     
        Although adding the new SCTP streams requires a message
        exchange, it is more lightweight to set up additional SCTP
        streams than to set up a new SCTP association since the only
        overhead of adding SCTP stream(s) to an existing SCTP
        association is the addition of 16-24 more bytes (allocated in
        the SCTP association, a single time), whereas setting up a new
        SCTP association implies more overhead.
     
        In terms of throughput impact, the fact that these
        specifications discourage multiplexing Templates and Data
        Records of different Template IDs may lead to a slightly larger
        IPFIX Message overhead.  If the Data Record rate is low for a
        specific Template (hence a specific SCTP stream), the Exporting
        Process might not be able to fill the IPFIX Messages with Data
        Records associated with other Templates.  In such a situation,
        there is a potential overhead due to additional IPFIX Message
        headers and SCTP chunk headers.
     
        Finally, with respect to the processing overhead on the
        Exporter, a lot of state information must be stored when a large
        number of SCTP streams are used within an SCTP association.
        However, no comparison of the performance impact of multiple
        streams within an SCTP association versus opening the same
        number of independent SCTP associations is available.
     
     
     6. Examples
     
        Figure 1 shows an example where SCTP stream 10 carries a
        Template Record with the Template ID 256 transmitted with full
     
     
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        reliability (FR), together with associated Data Records
        transmitted with partial reliability (PR).  The Data Record
        Reliability Options Template with Template ID 257 is transmitted
        with full reliability (FR).  Its corresponding Data Set contains
        one Data Record.
        Record 1:
     
             o Scope:     Template ID = 256
             o Non-scope: dataRecordsReliability = False
     
     
                      +--------+       +---------+   +--------+
                      |        |       |         |   |        |
        stream 10 ----| Data   | . . . |  Data   |---| Data   |---...
                      |   256  |       |    256  |   |   257  |
                      |      PR|       |       PR|   |      FR|
                      +--------+       +---------+   +--------+
     
     
     
     
     
                             +----------+       +------------+
                             |          |       | Options    |
                             |          |       | Reliability|
                       ...---| Template |-------| Template   |------>
                             |     256  |       |        257 |
                             |        FR|       |          FR|
                             +----------+       +------------+
     
                                  Figure 1
     
        Note that Template 256 will always be processed before the Data
        Records by the Collecting Process because all IPFIX Messages are
        sent in order within an SCTP stream. Therefore, the Collecting
        Process job is simplified. Furthermore, the Data Record loss for
        the Template 256 can easily be calculated on the Collecting
        Process.
     
     
        If an Options Template is necessary to understand the content of
        a Data Record (i.e., the scope in the Options Template Record is
        an Information Element contained in the Data Record or
        associated with the Data Record), the Options Template Record
        should be sent in the same SCTP stream, as displayed in figure
        2.
     
     
     
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                         +--------+   +--------+     +--------+
                         |        |   |        |     |        |
           stream 20 ----| Data   |...| Data   |-----| Data   |--- ...
                         |   260  |   |   260  |     |   259  |
                         |      PR|   |      PR|     |      FR|
                         +--------+   +--------+     +--------+
     
                                +--------+       +----------+
                                |        |       |          |
                          ...---| Data   |-------| Template |---...
                                |   258  |       |     260  |
                                |      FR|       |        FR|
                                +--------+       +----------+
     
     
                             +----------+       +-------------+
                             | Options  |       | Options     |
                             | Template |       | Reliability |
                       ...---|          |-------| Template    |------>
                             |     259  |       |        258  |
                             |        FR|       |           FR|
                             +----------+       +-------------+
     
     
     
                                     Figure 2
     
        Figure 2 shows an example where SCTP stream 20 carries:
        -  a Data Record Reliability Options Template with Template ID
           258, transmitted with full reliability (FR)
        -  an Options Template Record with Template ID 259 transmitted
           with full reliability.  This Options Template Record contains
           additional information related to the subsequent Data Records
           based on Template ID 260.  Typical examples are the Common
           Properties information [RFC5473] or a Selector Report
           Interpretation [RFC5476].
        -  a Template Record with Template ID 260, transmitted with full
           reliability.
        -  a Data Set specified by the Reliability Options Template with
           Template ID 258 transmitted with full reliability.
           The Data Set contains three Data Records.
           Record 1:
             o Scope:     Template ID = 258
             o Non-scope: dataRecordsReliability = True
           Record 2:
             o Scope:     Template ID = 259
     
     
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             o Non-scope: dataRecordsReliability = True
           Record 3:
             o Scope:     Template ID = 260
             o Non-scope: dataRecordsReliability = False
           These Data Records inform the Collector that the Data Records
           for Template ID 258 and 259 are sent reliably, while the Data
           Records for Template ID 260 are not.
        -  a Data Record specified by Template ID 259, transmitted with
           full reliability
        -  a Data Record specified by Template ID 260, transmitted with
           partial reliability
     
        If the Collector observes some Data Record loss using the
        Sequence Number, the loss can only stem from the Data Records
        associated with Template ID 260, as these are the only Data
        Records not exported reliably.  Therefore, the calculation of
        loss per Template ID 260 is possible.
     
        Note that the Options Templates 258, 259, and 260 will always
        arrive before their associated Data Records, respectively,
        because all IPFIX Messages must be sent in order within an SCTP
        stream.
     
        Figure 3 shows an example where SCTP stream 30 carries a
        Template Record with Template ID 262 transmitted with full
        reliability (FR), an associated Data Record transmitted with
        full reliability (PR), a Template Withdrawal Message, followed
        by a redefinition of the Template ID 262, and finally the Data
        Record associated with the new Template transmitted with partial
        reliability.  The Template Withdrawal Message and the new
        definition of the Template ID 262 are sent immediately, without
        waiting for the Template Reuse Delay.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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                         +--------+   +----------+     +----------+
                         |        |   |Data      |     |          |
        stream 30 ... ---| Data   |...|  257     |-----| Template |---
                         |   262  |   |tmpID: 261|     |    262   |
                         |      PR|   |dRR: false|     |        FR|
                         +--------+   +----------+     +----------+
     
                   +----------+     +--------+       +----------+
                   | Template |     |        |       | Data     |
                ...| Withdraw |-----| Data   |-------|   261    |---...
                   |    262   |     |   262  |       |tmpID: 262|
                   |        FR|     |      FR|       |dRR:  true|
                   +----------+     +--------+       +----------+
     
     
                             +----------+       +-------------+
                             |          |       | Options     |
                             | Template |       | Reliability |
                       ...---|          |-------| Template    |------>
                             |     262  |       |        261  |
                             |        FR|       |           FR|
                             +----------+       +-------------+
     
                                     Figure 3
     
        The second Data Record associated with the Data Record
        Reliability Options Template shows that the Data Records
        associated with the newly specified Template ID 262, will be
        sent unreliably.
     
     
     7. IANA Considerations
     
        According to the process defined in [RFC5102], IANA will
        allocate the dataRecordsReliability Information element defined
        in Section 4.1.  in the IANA IPFIX Information Elements
        registry.
     
     
     8. Security Considerations
     
        The same security considerations as for the IPFIX Protocol
        [RFC5101] apply.
     
     
     
     
     
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     9. References
     
     9.1. Normative References
     
        [RFC2119] S. Bradner, Key words for use in RFCs to Indicate
                Requirement Levels, BCP 14, RFC 2119, March 1997
     
        [RFC3758] Stewart, R., Ramalho, M, Xie, Q., Tuexen, M., and P.
                Conrad, "Stream Control Transmission Protocol (SCTP),
                Partial Reliability Extension", May 2004
     
        [RFC4960] Stewart, R., Ed., "Stream Control Transmission
                Protocol", RFC 4960, September 2007.
     
        [RFC5101] Claise, B., Ed., "Specification of the IP Flow
                Information Export (IPFIX) Protocol for the Exchange of
                IP Traffic Flow Information", RFC 5101, January 2008.
     
        [RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and
                J. Meyer, "Information Model for IP Flow Information
                Export", RFC 5102, January 2008.
     
        [RFC5475] Zseby, T., Molina, M., Duffield, N., Niccolini S., and
                F. Raspall, "Sampling and Filtering Techniques for IP
                Packet Selection", RFC5475, March 2009
     
        [SCTP-RESET] Stewart, R., Lei, P., Tuexen, M, "Stream Control
                Transmission Protocol (SCTP) Stream Reconfiguration",
                draft-ietf-tsvwg-sctp-strrst-01, Internet-Draft work in
                progress, October 2009
     
     
     9.2. Informative References
     
     
        [RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
                Requirements for IP Flow Information Export, RFC 3917,
                October 2004
     
        [RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J.
                Quittek, "Architecture Model for IP Flow Information
                Export", RFC5470, March 2009
     
        [RFC5472] Zseby, T., Boschi, E., Brownlee, N., and B. Claise,
                "IP Flow Information Export (IPFIX) Applicability", RFC
                5472, March 2009
     
     
     
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        [RFC5477] T. Dietz, F. Dressler, G. Carle, and B. Claise,
                "Information Model for Packet Sampling Exports", RFC
                5477, March 2009
     
        [RFC5476] Claise, B., Quittek, J., and A. Johnson, "Packet
                Sampling (PSAMP) Protocol Specifications", RFC 5476,
                March 2009.
     
        [RFC5474] Chiou, D., Claise, B., Duffield, N., Greenberg, A.,
                Grossglauser, M., Marimuthu, P., Rexford, J., and G.
                Sadasivan,  RFC 5474, March 2009
     
        [RFC5473] Boschi, E., Mark, L., and B. Claise, " Reducing
                Redundancy in IP Flow Information Export (IPFIX) and
                Packet Sampling (PSAMP) Reports", RFC 5473, March 2009
     
        [PSAMP-MIB] Dietz, T., and B. Claise, "Definitions of Managed
                Objects for Packet Sampling", Internet-Draft work in
                progress, June 2006
     
     
     10. Acknowledgements
     
        The authors would like to thank Brian Trammell for his expert
        feedback and continuous effort to improve the specifications,
        Elisa Boschi for her thorough reading, and Randall Stewart,
        Peter Lei, Michael Tuexen for their SCTP-related feedback and
        expertise, and Tobias Limmer.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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     11. Author's Addresses
     
        Benoit Claise
        Cisco Systems Inc.
        De Kleetlaan 6a b1
        Diegem 1813
        Belgium
     
        Phone: +32 2 704 5622
        Email: bclaise@cisco.com
     
     
        Paul Aitken
        Cisco Systems (Scotland) Ltd.
        96 Commercial Quay
        Commercial Street
        Edinburgh, EH6 6LX, United Kingdom
     
        Phone: +44 131 561 3616
        Email: paitken@cisco.com
     
     
        Andrew Johnson
        Cisco Systems (Scotland) Ltd.
        96 Commercial Quay
        Commercial Street
        Edinburgh, EH6 6LX, United Kingdom
     
        Phone: +44 131 561 3641
        Email: andrjohn@cisco.com
     
     
        Gerhard Muenz
        Technische Universitaet Muenchen
        Departement of Informatics - I8
        Boltzmannstr. 3
        Garching D-85748
        DE
     
        Phone: +49 89 289-18008
        Email: muenz@net.in.tum.de
        URI: http://www.net.in.tum.de/~muenz
     
     
     
     
     
     
     
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