GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc6526

Internet Engineering Task Force (IETF) B. Claise Request for Comments: 6526 P. Aitken Category: Standards Track A. Johnson ISSN: 2070-1721 Cisco Systems, Inc.

                                                              G. Muenz
                                                           TU Muenchen
                                                            March 2012
               IP Flow Information Export (IPFIX) Per
         Stream Control Transmission Protocol (SCTP) Stream

Abstract

 This document specifies an extension to the specifications in RFC
 5101, 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 Process and Collecting
 Process, this method offers several advantages, such as the ability
 to calculate Data Record losses for PR-SCTP per Template, 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 Process or Exporting Process, then normal IPFIX
 behavior will be seen without all of the additional benefits.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6526.

Claise, et al. Standards Track [Page 1] RFC 6526 IPFIX Per SCTP Stream March 2012

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Claise, et al. Standards Track [Page 2] RFC 6526 IPFIX Per SCTP Stream March 2012

Table of Contents

 1. Introduction ....................................................3
    1.1. Relationship with IPFIX and PSAMP ..........................4
    1.2. Applicability ..............................................5
    1.3. Limitations ................................................5
 2. Terminology .....................................................6
    2.1. Conventions Used in This Document ..........................6
    2.2. IPFIX Documents Overview ...................................6
    2.3. PSAMP Documents Overview ...................................7
 3. IPFIX Protocol Specifications: Limitations and Improvements .....7
    3.1. Data Record Loss Calculated Per Template ...................7
         3.1.1. IPFIX Protocol Specifications: Limitation ...........7
         3.1.2. IPFIX Export Per SCTP Stream: Advantage .............8
    3.2. Immediate Template Withdrawal and Reuse ....................8
         3.2.1. IPFIX Protocol Specifications: Limitation ...........8
         3.2.2. IPFIX Export Per SCTP Stream: Advantages ............9
    3.3. Requirement for Data Set Buffering .........................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
         4.5.1. SCTP ...............................................14
         4.5.2. Enabling the Per-SCTP-Stream Extension .............14
         4.5.3. Disabling the Per-SCTP-Stream Extension ............15
         4.5.4. Calculating Data Record Loss Per Template ..........16
 5. Resource Impact ................................................16
 6. Examples .......................................................17
 7. IANA Considerations ............................................20
 8. Security Considerations ........................................21
 9. References .....................................................21
    9.1. Normative References ......................................21
    9.2. Informative References ....................................21
 10. Acknowledgments ...............................................22

1. Introduction

 The IPFIX protocol [RFC5101] has the goal of exporting 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

Claise, et al. Standards Track [Page 3] RFC 6526 IPFIX Per SCTP Stream March 2012

 information, as long as the relevant Information Element is specified
 in the IPFIX information model [RFC5102], registered with IANA
 [IANA], or specified as an enterprise-specific Information Element.
 The IPFIX protocol [RFC5101] specifies that 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
 specifies both ordered and 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 per Template, 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.

1.1. Relationship with IPFIX and PSAMP

 The specifications in this document apply to the IPFIX protocol
 specifications [RFC5101].  However, they only apply to the SCTP
 transport protocol [RFC4960] option of the IPFIX protocol
 specifications (see Section 10 of [RFC5101]), specifically if the
 Partial Reliability extension [RFC3758] is used.  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.

Claise, et al. Standards Track [Page 4] RFC 6526 IPFIX Per SCTP Stream March 2012

1.2. 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, where the
 Exporting Process cannot afford to export all the Flow Records
 reliably, due to limited resources to buffer a large number of Flow
 Records.  Such a situation 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(s) the lost Data Records belong.
 Exporting Processes following the specifications in this document
 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.  Since the
 specifications in this document mandate in-order transmission of
 (Options) Templates and associated Data Records, late arrival of
 (Options) Templates at the Collecting Process is avoided, which means
 that there are no Data Records that need to be dropped or buffered.

1.3. Limitations

 When multiple Templates are required, this method requires multiple
 SCTP streams in the association between the Exporting Process and
 Collecting Process, ideally one stream 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 [RFC6525] are supported.

Claise, et al. Standards Track [Page 5] RFC 6526 IPFIX Per SCTP Stream March 2012

2. 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.  A suitable default
    value is 5 seconds, as specified in [RFC5101].

2.1. 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].

2.2. IPFIX Documents Overview

 The IPFIX protocol [RFC5101] provides network administrators with
 access to Flow information.
 The architecture for the export of measured 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.
 IPFIX has a formal description of IPFIX Information Elements, their
 names, their types, and additional semantic information, as specified
 in the IPFIX information model [RFC5102].
 Finally, the IPFIX applicability statement [RFC5472] describes what
 types of applications can use the IPFIX protocol and how they can use
 the information provided.  Furthermore, it shows how the IPFIX
 framework relates to other architectures and frameworks.

Claise, et al. Standards Track [Page 6] RFC 6526 IPFIX Per SCTP Stream March 2012

2.3. 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, their types, and additional
 semantic information.  The PSAMP information model is defined in
 [RFC5477].

3. IPFIX Protocol Specifications: Limitations and Improvements

 For three specific topics ("Data Record Loss Calculated Per
 Template", "Immediate Template Withdrawal and Reuse", and
 "Requirement for Data Set Buffering"), this section explains the
 limitations of the IPFIX protocol specifications on the one hand, and
 the advantages of the method specified in this document on the other.

3.1. Data Record Loss Calculated Per Template

3.1.1. IPFIX Protocol Specifications: Limitation

 Section 6.3.2 of [RFC3917], "Requirements for IP Flow Information
 Export" 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 Collecting Process 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.

Claise, et al. Standards Track [Page 7] RFC 6526 IPFIX Per SCTP Stream March 2012

 The IPFIX protocol specifications [RFC5101] specify 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 with which Template any
 lost Data Record is associated.  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 in
 [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.

3.1.2. IPFIX Export Per SCTP Stream: Advantage

 Using the specifications 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 its corresponding Data
 Records in a separate SCTP stream from other Templates and Data
 Records, the loss pertaining to each specific Template can be deduced
 from the Sequence Number field in the IPFIX Message headers.

3.2. Immediate Template Withdrawal and Reuse

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 following:
    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 Collecting Process 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 Collecting Process, 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.

Claise, et al. Standards Track [Page 8] RFC 6526 IPFIX Per SCTP Stream March 2012

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 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 (5 seconds by default, as
 specified in [RFC5101]) does not need to be applied to 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. Requirement for Data Set Buffering

3.3.1. IPFIX Protocol Specifications: Limitation

 The fact that the protocol specifications in [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 levels of 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.

Claise, et al. Standards Track [Page 9] RFC 6526 IPFIX Per SCTP Stream March 2012

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 the Options Template and associated Data Records
 sent in different streams.  This has several advantageous
 consequences, including 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 that 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 defined
 in [RFC2119].

4.1. New Information Element

 dataRecordsReliability
    Description:
       The export reliability of Data Records, within this SCTP
       stream, for the element(s) in the Options Template scope.  A
       typical example of an element for which the export reliability
       will be reported is the Template ID, as specified in the Data
       Records Reliability Options Template.  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.

Claise, et al. Standards Track [Page 10] RFC 6526 IPFIX Per SCTP Stream March 2012

    Abstract Data Type: boolean
    Data Type Semantics: identifier
    ElementId: 276
    Status: current
 Per Section 6.1.5 of [RFC5101], the boolean data type is encoded as a
 single octet, with the value of 1 for True and the value of 2 for
 False.

4.2. Template Management

 To take advantage of per-stream export, Exporting Processes MUST
 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 Records 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.  After defining a Template ID and before
 sending any associated 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 Records
 Reliability Options Template for the Template associated with the
 Data Records to be sent.  If it does not, then the Collecting Process
 MUST disable this extension for the SCTP association.  The one
 exception to this rule is that the Data Records associated with the
 Data Records Reliability Options Template don't require an explicit
 notification, as these MUST always be sent reliably.
 The Data Records Reliability Options Template MUST contain the
 following Information Elements:
    Scope:     Template ID
    Non-scope: dataRecordsReliability
 After sending a value of 'True' for the dataRecordsReliability
 Element, the Exporting Process MUST send any Data Records associated
 with the currently defined Template ID reliably within this SCTP
 stream.  After sending a value of 'False' for the

Claise, et al. Standards Track [Page 11] RFC 6526 IPFIX Per SCTP Stream March 2012

 dataRecordsReliability Element, the Exporting Process MAY send any
 Data Records associated with the Template ID unreliably within this
 SCTP stream.
 If the Exporting Process wants to change the Data Records 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 Records Reliability Options Template MAY contain other
 non-scope Information Elements associated with the (Options)
 Template.
 When an Options Template (including the Data Records 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 Exporting Process 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 Exporting Process 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 by Options Template Records, the Data Records
 defined by the Options Template Records SHOULD be sent reliably so
 that the Collecting Process 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 MUST
 manage SCTP streams according to the specification in this section,
 in addition to Section 10.2.4.3, "Stream", of [RFC5101].

Claise, et al. Standards Track [Page 12] RFC 6526 IPFIX Per SCTP Stream March 2012

 PR-SCTP [RFC3758] MUST be implemented by all compliant
 implementations.
 All IPFIX Messages in an SCTP stream MUST be sent in order.
 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 to which it is able
 to send, per [RFC6525].  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 any Data Record loss attribution.
 An alternative that may result in the loss of Flow Records (for
 example, due to lack of buffering on the Exporter) 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 MUST 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 that are no longer in use 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.
 The Template Withdrawal Message MUST be sent reliably, using SCTP-
 ordered delivery per [RFC5101].  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 Collecting
 Process.
 The Template ID from a withdrawn Template MAY be reused on the same
 SCTP stream immediately after the Template Withdrawal Message is
 sent.  This case is equivalent to the use of a Template Reuse Delay
 value of 0.

Claise, et al. Standards Track [Page 13] RFC 6526 IPFIX Per SCTP Stream March 2012

 After reusing the Template ID, the Exporting Process MUST send a Data
 Record associated with the Data Records 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
 interval.
 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 in a fashion slightly contrary to
 [RFC5101] in order to realize the full benefits of per-stream export.
 However, the specification in this section contains a mechanism that
 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 that do not
 implement per-stream export.

4.5.1. SCTP

 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 specified in [RFC6525].

4.5.2. Enabling the Per-SCTP-Stream Extension

 In IPFIX, there is no explicit notification of the Exporting
 Process's capabilities.  There is also no return channel for the
 Collecting Process to communicate its capabilities.
 When the Exporting Process is sending according to the per-SCTP-
 stream extension, the first Data Record received by the Collecting
 Process will be associated with the Data Records Reliability Options

Claise, et al. Standards Track [Page 14] RFC 6526 IPFIX Per SCTP Stream March 2012

 Template.  In this case, the Collecting Process enables the extension
 for this Transport Session.  Otherwise, the Collecting Process MUST
 NOT enable the extension for this Transport Session.
 The Collecting Process MUST accept other non-scope Information
 Elements in the Data Records Reliability Options Template.

4.5.3. Disabling the Per-SCTP-Stream Extension

 Nothing prevents an implementation that does not meet the
 specification of the per-SCTP-stream extension from sending a
 Template that looks like a dataRecordsReliability Options Template.
 Therefore, a Collecting Process MUST detect if the Exporting Process
 fails to meet the specification fully.  If any of the conditions
 below is met, the Exporting Process does not properly use the
 per-SCTP-stream extension, and the Collecting Process MUST log an
 error message and disable this extension for the SCTP association.
    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 4.2).
       Note: Data Records associated with the Data Records Reliability
       Options Template are an exception to this rule.
    2. A Data Record associated with a Data Records Reliability
       Options Template is received on an SCTP stream for a
       (non-Options) Template that was defined on a different SCTP
       stream.
    3. A second Data Record associated with the Data Records
       Reliability Options Template is received for the same (Options)
       Template.
    4. A Data Record or a Template Withdrawal Message is associated
       with a Template that was defined on a different SCTP stream.
    5. Loss of Data Records is detected within a stream where a Data
       Record associated with the Data Records Reliability Options
       Template indicating unreliable transmission for any Template
       has not been received.
    6. 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.

Claise, et al. Standards Track [Page 15] RFC 6526 IPFIX Per SCTP Stream March 2012

4.5.4. Calculating Data Record Loss Per 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 Collecting Process 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) (mod(2^32))
         = (S2 - (S0 + N0)) (mod(2^32))
 Note that modulo 2^32 arithmetic is required, since the Sequence
 Number may wrap within the series of lost IPFIX Messages.  If less
 than 2^32 Data Records are lost in a sequence (which can be assumed
 in practice), the above equation returns the exact number of lost
 Data Records.
 Note that using an unsigned32 type for the loss would automatically
 take care of the mod(2^32) operation.
 As this Sequence Number is incremented per SCTP stream, the loss of
 Data Records sent in that SCTP stream can be calculated in the 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.

5. Resource 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 requires 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.

Claise, et al. Standards Track [Page 16] RFC 6526 IPFIX Per SCTP Stream March 2012

 If the Data Record rate is low for a specific Template (and 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 Template ID 257 transmitted with full reliability (FR),
 together with associated Data Records transmitted with partial
 reliability (PR).  The Data Records Reliability Options Template with
 Template ID 256 is transmitted with full reliability.  Its
 corresponding Data Set contains one Data Record.
 Record 1:
    o Scope:     Template ID = 257
    o Non-scope: dataRecordsReliability = False
                    +--------+       +---------+   +--------+
                    |        |       |         |   |        |
      stream 10 ----| Data   | . . . |  Data   |---| Data   |---...
                    |   257  |       |    257  |   |   256  |
                    |      PR|       |       PR|   |      FR|
                    +--------+       +---------+   +--------+
                           +----------+       +-------------+
                           |          |       | Reliability |
                           |          |       | Options     |
                     ...---| Template |-------| Template    |------>
                           |     257  |       |        256  |
                           |        FR|       |           FR|
                           +----------+       +-------------+
                               Figure 1

Claise, et al. Standards Track [Page 17] RFC 6526 IPFIX Per SCTP Stream March 2012

 Note that Template 257 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 job of the
 Collecting Process is simplified.  Furthermore, the Data Record loss
 for Template 257 can easily be calculated by 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.
                     +--------+   +--------+     +--------+
                     |        |   |        |     |        |
       stream 20 ----| Data   |...| Data   |-----| Data   |--- ...
                     |   260  |   |   260  |     |   259  |
                     |      PR|   |      PR|     |      FR|
                     +--------+   +--------+     +--------+
                            +--------+       +----------+
                            |        |       |          |
                      ...---| Data   |-------| Template |---...
                            |   258  |       |     260  |
                            |      FR|       |        FR|
                            +--------+       +----------+
                         +----------+       +-------------+
                         | Options  |       | Reliability |
                         | Template |       | Options     |
                   ...---|          |-------| Template    |------>
                         |     259  |       |        258  |
                         |        FR|       |           FR|
                         +----------+       +-------------+
                               Figure 2
 Figure 2 shows an example where SCTP stream 20 carries the following:
  1. a Data Records Reliability Options Template with Template ID 258,

transmitted with full reliability.

  1. 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 the Selector Report
    Interpretation [RFC5476].

Claise, et al. Standards Track [Page 18] RFC 6526 IPFIX Per SCTP Stream March 2012

  1. a Template Record with Template ID 260, transmitted with full

reliability.

  1. 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
       o Non-scope: dataRecordsReliability = True
    Record 3:
       o Scope:     Template ID = 260
       o Non-scope: dataRecordsReliability = False
    These Data Records inform the Collecting Process that the Data
    Records for Template IDs 258 and 259 are sent reliably, while the
    Data Records for Template ID 260 are not.  Note that the first
    Data Record associated with the Data Record Reliability Options
    Template (Template ID 258) is not required and can be omitted.
  1. a Data Record specified by Template ID 259, transmitted with full

reliability.

  1. a Data Record specified by Template ID 260, transmitted with

partial reliability.

 If the Collecting Process 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 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.

Claise, et al. Standards Track [Page 19] RFC 6526 IPFIX Per SCTP Stream March 2012

 Figure 3 shows an example where SCTP stream 30 carries a Template
 Record with Template ID 262 transmitted with full reliability, an
 associated Data Record transmitted with full reliability, and a
 Template Withdrawal Message, followed by a redefinition of 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 Template ID 262 are sent
 immediately, without waiting for the Template Reuse Delay interval.
                     +--------+   +----------+     +----------+
                     |        |   |Data      |     |          |
    stream 30 ... ---| Data   |...|  261     |-----| Template |---
                     |   262  |   |tmpID: 262|     |    262   |
                     |      PR|   |dRR: False|     |        FR|
                     +--------+   +----------+     +----------+
               +----------+     +--------+       +----------+
               | Template |     |        |       | Data     |
            ...| Withdraw |-----| Data   |-------|   261    |---...
               |    262   |     |   262  |       |tmpID: 262|
               |        FR|     |      FR|       |dRR:  True|
               +----------+     +--------+       +----------+
                         +----------+       +-------------+
                         |          |       | Reliability |
                         | Template |       | Options     |
                   ...---|          |-------| Template    |------>
                         |     262  |       |        261  |
                         |        FR|       |           FR|
                         +----------+       +-------------+
            dRR: Data Records Reliability
                               Figure 3
 The second Data Record associated with the Data Records 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 has allocated the
 dataRecordsReliability Information Element (defined in Section 4.1)
 in the "IPFIX Information Elements" registry [IANA].

Claise, et al. Standards Track [Page 20] RFC 6526 IPFIX Per SCTP Stream March 2012

8. Security Considerations

 The same security considerations as for the IPFIX protocol [RFC5101]
 apply.

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.
 [RFC3758]   Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
             Conrad, "Stream Control Transmission Protocol (SCTP)
             Partial Reliability Extension", RFC 3758, 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", RFC 5475, March 2009.
 [RFC6525]   Stewart, R., Tuexen, M., and P. Lei, "Stream Control
             Transmission Protocol (SCTP) Stream Reconfiguration",
             RFC 6525, February 2012.

9.2. Informative References

 [IANA] IPFIX Information Elements Registry,
             <http://www.iana.org/assignments/ipfix>.
 [RFC3917]   Quittek, J., Zseby, T., Claise, B., and S. Zander,
             "Requirements for IP Flow Information Export (IPFIX)",
             RFC 3917, October 2004.
 [RFC5470]   Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
             "Architecture for IP Flow Information Export", RFC 5470,
             March 2009.

Claise, et al. Standards Track [Page 21] RFC 6526 IPFIX Per SCTP Stream March 2012

 [RFC5472]   Zseby, T., Boschi, E., Brownlee, N., and B. Claise, "IP
             Flow Information Export (IPFIX) Applicability", RFC 5472,
             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.
 [RFC5474]   Duffield, N., Ed., Chiou, D., Claise, B., Greenberg, A.,
             Grossglauser, M., and J. Rexford, "A Framework for Packet
             Selection and Reporting", RFC 5474, March 2009.
 [RFC5476]   Claise, B., Ed., Johnson, A., and J. Quittek, "Packet
             Sampling (PSAMP) Protocol Specifications", RFC 5476,
             March 2009.
 [RFC5477]   Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
             Carle, "Information Model for Packet Sampling Exports",
             RFC 5477, March 2009.

10. Acknowledgments

 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; Randall Stewart, Peter Lei, and
 Michael Tuexen for their SCTP-related feedback and expertise; and
 Tobias Limmer.

Claise, et al. Standards Track [Page 22] RFC 6526 IPFIX Per SCTP Stream March 2012

Authors' 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, Inc.
 96 Commercial Quay
 Commercial Street
 Edinburgh, EH6 6LX, United Kingdom
 Phone: +44 131 561 3616
 EMail: paitken@cisco.com
 Andrew Johnson
 Cisco Systems, Inc.
 96 Commercial Quay
 Commercial Street
 Edinburgh, EH6 6LX, United Kingdom
 Phone: +44 131 561 3641
 EMail: andrjohn@cisco.com
 Gerhard Muenz
 Technische Universitaet Muenchen
 Department of Informatics - I8
 Boltzmannstr. 3
 Garching D-85748
 DE
 EMail: muenz@net.in.tum.de
 URI: http://www.net.in.tum.de/~muenz

Claise, et al. Standards Track [Page 23]

/data/webs/external/dokuwiki/data/pages/rfc/rfc6526.txt · Last modified: 2012/03/24 18:00 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki