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 Expires May 19 2010 [Page 1] Internet-Draft November 2009 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 Expires May 19, 2010 [Page 2] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 3] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 4] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 5] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 6] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 7] Internet-Draft November 2009 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 Expires May 19, 2010 [Page 8] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 9] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 10] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 11] Internet-Draft November 2009 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]. Expires May 19, 2010 [Page 12] Internet-Draft November 2009 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 Expires May 19, 2010 [Page 13] Internet-Draft November 2009 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: Expires May 19, 2010 [Page 14] Internet-Draft November 2009 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) Expires May 19, 2010 [Page 15] Internet-Draft November 2009 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 Expires May 19, 2010 [Page 16] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 17] Internet-Draft November 2009 +--------+ +--------+ +--------+ | | | | | | 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 Expires May 19, 2010 [Page 18] Internet-Draft November 2009 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. Expires May 19, 2010 [Page 19] Internet-Draft November 2009 +--------+ +----------+ +----------+ | | |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. Expires May 19, 2010 [Page 20] Internet-Draft November 2009 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 Expires May 19, 2010 [Page 21] Internet-Draft November 2009 [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. Expires May 19, 2010 [Page 22] Internet-Draft November 2009 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 Expires May 19, 2010 [Page 23]