Internet Draft Tanja Zseby Document: Elisa Boschi Expires: August 2005 Fraunhofer FOKUS Nevil Brownlee CAIDA Benoit Claise Cisco Systems February 2005 IPFIX Applicability draft-ietf-ipfix-as-04.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. 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. Copyright Notice Copyright (C) The Internet Society (2005). Zseby, Boschi, Brownlee, Claise [Page 1] IPFIX Applicability February 2005 Abstract This document describes what type of applications can use the IP Flow Information Export (IPFIX) protocol and how they can use the information provided by IPFIX. It furthermore shows how the IPFIX framework relates to other architectures and frameworks. Zseby, Boschi, Brownlee, Claise [Page 2] IPFIX Applicability February 2005 Table of Contents 1. Introduction.............................................3 2. Applications of IPFIX....................................4 2.1 Accounting...............................................4 2.1.1 Example.................................................5 2.2 Security Analysis and Intrusion Detection with IPFIX.....6 2.3 Network Planning.........................................7 2.4 Peering Agreements.......................................7 2.5 Traffic Engineering......................................7 2.6 Data Warehousing and Mining..............................8 2.7 SLA validation...........................................8 2.8 Traffic Monitoring.......................................8 2.8.1 Measurement of Round-trip-time (RTT)....................9 2.8.2 Measurement of One-way-delay (OWD)......................9 2.8.3 Measurement of One-way-loss (OWL)......................10 2.8.4 Measurement of IP delay variation (IPDV)...............10 3. Relation of IPFIX to other frameworks and protocols.....10 3.1 IPFIX and AAA...........................................10 3.1.1 Connecting via an AAA Client...........................11 3.1.2 Connecting via an Application Specific Module (ASM)....12 3.2 IPFIX and RTFM..........................................13 3.2.1 Flow Definition........................................13 3.2.2 Configuration and Management...........................13 3.2.3 Data Model Details.....................................14 3.2.4 Application/Transport Protocol.........................14 3.2.5 RTFM Summary...........................................15 3.3 IPFIX and IPPM..........................................15 3.4 IPFIX and PSAMP.........................................15 3.5 IPFIX and RMON..........................................15 3.6 IPFIX and IDMEF.........................................16 4. Limitations.............................................16 4.1 IPFIX and IPv6..........................................17 5. Security Considerations.................................17 6. Normative References....................................17 7. Informative References..................................17 8. Acknowledgements........................................19 9. Author's Addresses......................................19 10. Full Copyright Statement................................20 11. Intellectual Property Statement.........................20 12. Copyright Statement.....................................21 13. Disclaimer..............................................21 1. Introduction The IPFIX protocol defines how IP Flow information can be exported from routers, measurement probes or other devices. It is intended to provide this information as input for various Zseby, Boschi, Brownlee, Claise [Page 3] IPFIX Applicability February 2005 applications. IPFIX is a general data transport protocol, easily extensible to suit the needs of different applications. This document describes what applications can use the IPFIX protocol and how they can use it. Furthermore, the relationship of IPFIX to other frameworks and architectures is described. 2. Applications of IPFIX IPFIX data enables several critical customer applications. This section describes how different applications can use IPFIX. 2.1 Accounting Usage based accounting is one of the major applications for which the IPFIX protocol has been developed. IPFIX data provide fine-grained metering (for example, flow records include details such as IP addresses, packet and byte counts, timestamps, Type of Service (ToS), application ports, etc.) for highly flexible and detailed resource usage accounting. ISPs can use this information to migrate from single fee, flat-rate billing to more flexible charging mechanisms based on time of day, bandwidth usage, application usage, quality of service, etc. Enterprise customers can use this information for departmental chargeback or cost allocation for resource usage. In order to realize usage-based accounting with IPFIX the flow definition has to be chosen in accordance to the tariff model. A tariff can, for instance, be based on individual end-to-end streams. In that case accounting can be realized with a flow definition determined by the quintuple that consists of source address, destination address, protocol and port numbers. Another example is a class-dependent tariff (e.g. in a DiffServ network). For this flows could be distinguished just by DiffServ codepoint (DSCP) and source address. The essential elements needed for accounting are the number of transferred packets and bytes per flow which are contained in IPFIX flow records. Furthermore IPFIX provides a very flexible definition of flows, so arbitrary flow-based accounting models can be realized without any extensions to the IPFIX protocol. Nevertheless the configuration of flow definitions is out of scope of the IPFIX definition. For accounting purposes, it would be advantageous to have the ability to use IPFIX flow records as accounting input in an AAA infrastructure. AAA servers then could provide the mapping between user and flow information. Zseby, Boschi, Brownlee, Claise [Page 4] IPFIX Applicability February 2005 2.1.1 Example Letªs suppose someone has a Service Level Agreement (SLA) in a DiffServ network and has to be accounted based on the traffic volume. The information to export in this case is: - The source IP address (IPv4), so the length is 4 - Type of Service - The number of bytes of the Flow The template set (in case we use only IETF specified Information Elements) will look like: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Set ID = 2 | Length = 17 bytes | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Template ID 256 | Field Count = 3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IP_SRC_ADDR = 0x0008 | Field Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CLASS_OF_SERVICEIPv4 = 0x0005 | Field Length = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IN_BYTES = 0x0001 | Field Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The information to be exported is listed in the following table: Source IP address | Type of service | Bytes Number | | --------------------------------------------------------------- 192.181.17.0 | 101110 | 8987410 192.180.17.8 | 101110 | 170205 192.129.9.2 | 101110 | 33113 The field ªªType of serviceªª contains the DiffServ Codepoint in the first six bits while the last two are currently unused. In the example we use Codepoint 101110, recommended for the EF PHB (Expedited Forwarding Per Hop Behavior)[RFC2598] The Flow Records will then look like: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Zseby, Boschi, Brownlee, Claise [Page 5] IPFIX Applicability February 2005 | Set ID = 256 | Length = 32 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 192.181.17.0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 101110 00 | 8987410 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 192.180.17.8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 101110 00 | 170205 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 192.129.9.2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 101110 00 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 33113 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2.2 Security Analysis and Intrusion Detection with IPFIX Intrusion detection systems (IDS) monitor and control security incidents. A typical IDS system includes components like sensor, event collector, and management stations. Sensors monitor network and system traffic for attacks and other security- related events. Sensors respond to and notify the administrator about these events as they occur. Event collectors are a middle- tier component responsible for transmitting events from sensors to the console and database. The management component serves the following purposes: - visually monitors events (with a console) - collects data from sensors (with one or more event collectors) - stores data from sensors (in a database) IPFIX can report events of interest to the sensor either by the collecting process or directly by the exporting process. Which approach is best depends on the scenario and the events of interest. Getting information directly from the exporting process has the advantage that the sensor gets the information faster. It does not need to wait for collector processing time or until the collector has all relevant data. Getting the information from a collector allows correlating data from different exporting processes (e.g. from different routers) to get a better picture of what is going on in the network. IPFIX provides useful input data for basic intrusion detection functions (e.g. detecting unusually high loads) such as details on source and destination addresses, along with the start time Zseby, Boschi, Brownlee, Claise [Page 6] IPFIX Applicability February 2005 of flows, TCP flags, application ports and flow volume. This data can be used to analyze network security incidents and identify attacks. Nevertheless, for some scenarios intrusion detection may require further insight into packet content. Since IPFIX allows a flexible report definition, the metering process and the IPFIX report format could be extended to support other data needed for intrusion detection systems. Detecting security incidents in real-time would require the pre- processing of data already at the measurement device and immediate data export in case a possible incident has been identified. This means that IPFIX reports must be generated upon incident detection events and not only upon flow end or fixed time intervals. 2.3 Network Planning IPFIX data captured over a long period of time can be used to track and anticipate network growth and plan upgrades to increase the number of routing devices, ports, or higher- bandwidth interfaces. IPFIX data optimizes both strategic network planning (peering, backbone upgrade planning, and routing policy planning) as well as tactical network engineering decisions (upgrading the router or link capacity). This helps to minimize the total cost of network operations while maximizing network performance, capacity, and reliability. 2.4 Peering Agreements IPFIX data enables ISP peering partners to measure the volume and characteristics of traffic exchanged with other ISP peers. ISP peering partners, consortia, or business coalitions can use IPFIX to exchange data between different domains. Having a means to share measurement data allows for more accurate end-to-end measurements. Through IPFIX data measured with different (often domain specific) tools can be exchanged and compared with data belonging to other domains. This is especially useful for inter-domain SLA validation where, in order to be able to provide accurate data, an ISP has to obtain measurements from other ISPs crossed in the end-to-end path. 2.5 Traffic Engineering IPIFX data provides traffic engineering details for a set of prefixes. This data can be used in network optimization for load Zseby, Boschi, Brownlee, Claise [Page 7] IPFIX Applicability February 2005 balancing traffic across alternate paths, or for forwarding traffic of a certain set of prefixes on a preferred route. 2.6 Data Warehousing and Mining IPFIX data (or derived information) can be stored for later retrieval and analysis to support proactive marketing and customer service programs. An example of this would be to determine which applications and services are being used by internal and external users and then target them for improved services such as advertising. This is especially useful for ISPs because IPFIX data enables them to create better service packaging. 2.7 SLA validation Performing QoS monitoring is one target application of the IPFIX protocol. QoS monitoring is the passive observation of transmission quality for single flows or traffic aggregates in the network. One example of its usefulness is the validation of QoS guarantees in service level agreements (SLAs). Some QoS metrics require the correlation of data from multiple measurement points. For this the clocks of the involved exporting devices must be synchronized. Furthermore, such measurements would benefit from post-processing functions (e.g. packet ID generation and mapping) at the exporter and/or collector. 2.8 Traffic Monitoring IPFIX data can be used for extensive near real-time traffic monitoring. Traffic patterns associated with routing devices and switches on an individual or network wide basis can be displayed enabling proactive problem detection, efficient troubleshooting, and rapid problem resolution. IPFIX data enables content and service providers to perform a detailed, time-based, and application-based usage analysis of a network. They also provide detailed information for understanding customer or end-user usage of network and application resources. This information can then be used to efficiently plan and allocate access, backbone, and application resources, as well as to detect and resolve potential security and policy violations. This section describes how the monitoring of different metrics can be performed with IPFIX. All of the metrics require at least Zseby, Boschi, Brownlee, Claise [Page 8] IPFIX Applicability February 2005 an extension of the IPFIX information model because the necessary information such as round-trip-time, packet Ids, etc., is currently not part of the model. However given the extensibility and flexibility of IPFIX the missing attributes can be easily defined. 2.8.1 Measurement of Round-trip-time (RTT) The passive measurement of round-trip-times (RTT) can be performed by using packet pair matching techniques as described in [Brow00]. For the measurements, request/response packet pairs from protocols such as DNS, ICMP, SNMP or TCP (syn/syn-ack, data/ack) are utilized to passively observe the RTT [Brow00]. As always, this only works for passive measurements if the required traffic of interest is actually present in the network. Furthermore, if the observed protocol supports retransmissions (e.g. TCP) the RTT is not the network RTT but rather the RTT of the network and the protocol stack of the receiver. In case the reply packet is lost or can not be observed the RTT can not be calculated. In order to use this measurement technique, the IPFIX metering process needs to measure in both directions. A classification of the protocols mentioned above has to be done. That means parts of the transport header are used for the classification. Since a differentiation of flows in accordance to the transport header is one of the requirements for IPFIX, such classification can be performed without extensions. Nevertheless, the meter needs to recognize request and response packets for the given protocols and therefore needs to look further into the packets. The capability to do this analysis is not part of the IPFIX requirements but can be achieved by optional extensions to the classification process. The exporting device needs to assign a timestamp for the arrival of the packets. The calculation of the RTT can be done directly at the exporter or at the collector. In the first case IPFIX would transfer the calculated RTT to the collector. In the second case IPFIX needs to send the observed packet types and the timestamps to the collector. The round- trip-time-delay metric is defined in [RFC2681]. 2.8.2 Measurement of One-way-delay (OWD) Passive one-way-delay measurements require the collection of data at two measurement points. It is necessary to recognize packets at the second measurement point to correlate packet arrival events from both points. This can be done by capturing packet header and parts of the packet that can be used to recognize the same packet at the subsequent measurement point. Zseby, Boschi, Brownlee, Claise [Page 9] IPFIX Applicability February 2005 To reduce the amount of measurement data a unique packet ID can be calculated from the header and part and/of the content e.g. by using a CRC or hash function [GrDM98, DuGr00, ZsZC01]. The capability of using content information is out of scope of IPFIX but can be achieved by an optional extension. Nevertheless, in some scenarios it might even be sufficient to calculate a packet ID based on header fields (including datagram ID and maybe sequence numbers from transport protocols) without looking at parts of the packet content. If packet IDs need to be unique only for a certain time interval or a certain amount of packet ID collisions is tolerable this is a sufficient solution. The second issue is the export of packet IDs. IPFIX exports per flow information. However, it is possible to extend IPFIX with a scheme to export per-packet information by providing special templates for that purpose. The one way delay metric is defined in [RFC2679]. 2.8.3 Measurement of One-way-loss (OWL) Passive loss measurements for single flows can be performed at one measurement point by using sequence numbers that are present in protocols (e.g. IP identification, TCP sequence numbers) similar to the approach described in section 2.8.1. This requires the capturing of the sequence numbers of subsequent packets of the observed flow by the IPFIX metering process. An alternative to this is to perform a two-point measurement as described in section 2.8.2 and consider packets as lost that do not arrive at the second measurement point in a given time frame. This approach assumes that a packet observed at the first point should also be observed at the second point (known routing). The one-way loss metric is defined in [RFC2680]. 2.8.4 Measurement of IP delay variation (IPDV) IP Delay variation is defined as the difference of one-way-delay values for selected packets [RFC3393]. Therefore, this metric can be calculated by performing passive measurement of one-way- delay for subsequent packets (e.g. of a flow) and then calculating the differences. 3. Relation of IPFIX to other frameworks and protocols 3.1 IPFIX and AAA AAA defines a protocol and architecture for authentication, authorization and accounting for service usage. The DIAMETER Zseby, Boschi, Brownlee, Claise [Page 10] IPFIX Applicability February 2005 protocol is used for AAA communication for network access services (Mobile IP, NASREQ, and ROAMOPS). The AAA architecture [RFC2903] provides a framework for extending the AAA support also for other services. DIAMETER defines the exchange of messages between AAA entities, e.g. between AAA clients at access devices and AAA servers and among AAA servers. It is used also for the transfer of accounting records. Usage-based accounting requires measurement data from the network. IPFIX defines a protocol to export such data from routers, measurement probes and other devices. The provisioning of accounting with IPFIX can be realized without an AAA infrastructure. The collector can directly forward the measurement information to an accounting application. Nevertheless, if an AAA infrastructure is in place, IPFIX can provide the input for the generation of accounting records and several features of the AAA architecture can be used. Features include the mapping of a user ID to the flow information (by using authentication information), the generation of DIAMETER accounting records and the secure exchange of accounting records between domains with DIAMETER. Two possibilities to connect IPFIX and AAA can be distinguished: 3.1.1 Connecting via an AAA Client One possibility means of connecting IPFIX and AAA is to run an AAA client on the IPFIX collector. This client can generate DIAMETER accounting messages and send them to an AAA server. The mapping of the flow information to a user ID can be done in the AAA server by using data from the authentication process. DIAMETER accounting messages can be sent to the accounting application or to other AAA servers (e.g. in roaming scenarios). Zseby, Boschi, Brownlee, Claise [Page 11] IPFIX Applicability February 2005 +---------+ DIAMETER +---------+ | AAA-S |------------->| AAA-S | +---------+ +---------+ ^ | DIAMETER | | +--+--------+--+ | | AAA-C | | + +--------+ | | | | Collector | +--------------+ ^ | IPFIX | +------------+ | Exporter | +------------+ Figure 2: IPFIX collector connects to AAA server via AAA client 3.1.2 Connecting via an Application Specific Module (ASM) Another possibility is to directly connect the IPFIX collector with the AAA server via an application specific module (ASM). Application specific modules have been proposed by the IRTF AAA architecture research group (AAARCH) in [RFC2903]. They act as an interface between AAA server and service equipment. In this case the IPFIX collector is part of the ASM. The ASM acts as an interface between the IPFIX protocol and the input interface of the AAA server. The ASM translates the received IPFIX data into an appropriate format for the AAA server. The AAA server then can add information about the user ID and generate a DIAMETER accounting record. This accounting record can be sent to an accounting application or to other AAA servers. Zseby, Boschi, Brownlee, Claise [Page 12] IPFIX Applicability February 2005 +---------+ DIAMETER +---------+ | AAA-S |------------->| AAA-S | +---------+ +---------+ ^ | +------------------+ | ASM | | +------------+ | | | Collector | | +------------------+ ^ | IPFIX | +------------+ | Exporter | +------------+ Figure 3: IPFIX connects to AAA server via ASM 3.2 IPFIX and RTFM This section compares the Real-time Traffic Flow Measurement (RTFM) framework with the IPFIX framework. 3.2.1 Flow Definition RTFM and IPFIX both use the same definition of flow; a flow is a set of packets which share a common set of end-point address attribute values. A flow is therefore completely specified by that set of values, together with an inactivity timeout. A flow is considered to have ended when no packets are seen for at least the inactivity time. RTFM flows, however, are bidirectional, i.e. an RTFM meter matches packets from B to A and A to B as separate parts of a single flow, and maintains two sets of packet and byte counters, one for each direction. IPFIX flow are unidirectional; users needing bidirectional flows will need to match the two directions in post-processing. 3.2.2 Configuration and Management In RTFM, remote configuration (using an SNMP MIB) is the only way to configure a meter. IPFIX, however, makes no provision for remote configuration - meters must be configured locally by Zseby, Boschi, Brownlee, Claise [Page 13] IPFIX Applicability February 2005 a System Administrator. IPFIX meters export their configuration, i.e. the layout of data within their templates, from time to time. IPFIX collectors use that template information to determine how they should interpret the IPFIX flow data they receive. An IPFIX meter must normally be configured to export data to a specified list of IPFIX collectors, i.e. data is pushed out by the meter. In contrast, an RTFM meter reader pulls data from a meter; SNMP security (data view) on the meter determines whether a reader is allowed to pull data from it. 3.2.3 Data Model Details RTFM defines all its attributes in the RTFM Meter MIB [RFC 2720], and IPFIX defines its information elements in the IPFIX Information Model document. In IPFIX, fields such as ToPDUs and FromPDUs are stored in 64- bit counters. Exported flows carry such counter values as they were after the flow's last packet. Long-running flows may be broken into a sequence of shorter flows; in that case the flow counters are zeroed when the flow is exported. RTFM uses continuously-incrementing 64-bit counters, which are never reset. Instead, flows can be read at any time; the difference between counter readings gives the counts for activity in the interval between readings. 3.2.4 Application/Transport Protocol RTFM has a standards-track Meter MIB [RFC 2720], which can be used both to configure a meter and to read flow data from it. The MIB provides a way to read lists of attributes with a single Object Identifier (called a 'package'), which dramatically reduces the SNMP overhead for flow data collection. SNMP, of course, normally uses UDP as its transport protocol. Since RTFM requires a reliable flow data transport system, an RTFM meter reader must time out and resend unanswered SNMP requests. Apart from being clumsy, this can limit the maximum data transfer rate from meter to meter reader. IPFIX is designed to work over a variety of different transport protocols. The preferred protocol is SCTP (either reliable or partially reliable) or TCP. In addition, the IPFIX protocol Zseby, Boschi, Brownlee, Claise [Page 14] IPFIX Applicability February 2005 encodes data much more efficiently than does SNMP, hence IPFIX will have lower data transport overheads than RTFM. A need for high flow data rates highlights the need for careful systems design when building a flow data collection system. When data rates are high, and it is not possible to use a high level of aggregation, then it makes sense to have the collectors very close to their exporters. Once the data is safely on a dedicated host machine, large volumes of it can be moved using 'background' techniques such as FTP. 3.2.5 RTFM Summary IPFIX is designed to be a simple, high-performance system for exporting flow data from a meter, making it highly suitable for that purpose. RTFM provides bi-directional flows, dynamic configuration, and the ability to work with much more general definitions of flow end-points. It may continue to be more suitable in 'research' situations which need those features. Another difference between the two systems is that while RTFM works in ªpullª mode, IPFIX uses ªpushª mode. 3.3 IPFIX and IPPM The IPFIX protocol can be used to carry IPPM network performance metrics or information that can be used to calculate those metrics (see section 2.8). 3.4 IPFIX and PSAMP There is currently a very dynamic relation between IPFIX and PSAMP. PSAMP defines, between others, the information to be reported on sampled packets, describes the protocol by which this information is reported and the protocol by which the packet reporting is configured. The major difference between IPFIX and PSAMP protocols is that while the former exports flow records, the latter exports packet records. The Working Group describes in [PSAMP-FM] a set of requirements that affect directly the export protocol. In [PSAMP-PROTOCOL] the requirements have been analyzed with respect to IPFIX and the conclusion is that IPFIX is an exporting protocol general enough to be suitable for PSAMP. If needed, the information model can be easily extended. 3.5 IPFIX and RMON Zseby, Boschi, Brownlee, Claise [Page 15] IPFIX Applicability February 2005 RMON [RFC 3577] is a widely used monitoring system that gathers traffic data from RMON Agents in network devices in a general way using SNMP. The RMON MIB is divided into sections, each section providing different monitoring functions. For example, the 'Hosts' section gathers statistics for hosts which are active on the network being monitored. RMON does not cover flow measurement at all. To do so, one would need to extend RMON by adding a MIB module to handle flows. Further, one would need to devise a scheme for exporting high volumes of flow data. In short, IPFIX is designed to provide effective flow export: RMON is not. 3.6 IPFIX and IDMEF The Intrusion Detection Message Exchange Format (IDMEF) [CuDF04] is a standard data format developed within the IDWG Working Group to exchange data alerts between automated Intrusion Detection Systems (IDS). IDMEF provides a standard representation of the alert information that an Intrusion Detection analyzer reports when a suspicious event is detected. These alerts may be simple or complex depending on analyzers capabilities, commercial vendor objectives, and intrusion detection environments. IDMEF messages are implemented in XML and composed by a basic schema and extension modules to define alerts that are more complex. Once the kind of alert that should be sent has been determined by the analyzer, it must be formatted following the IDMEF rules. Generally, alerts are sent when analyzers detect an event that they have been configured to look for. The IPFIX protocol can be used complementarily to IDMEF for providing detailed information of intrusions traffic, suspect events or anomalous traffic that differs from normal network behavior. 4. Limitations The goal of this section is to give recommendations where not to use IPFIX. While the protocol is general enough to be adequate for exporting flow data in many applications, it still has limitations. SCTP is the preferred protocol for IPFIX, i.e. a conforming implementation must work over SCTP. Although IPFIX can also work Zseby, Boschi, Brownlee, Claise [Page 16] IPFIX Applicability February 2005 over TCP or UDP - - users make sure they have good reasons for using protocols other than SCTP. IPFIX works in ªpushª mode that is data are automatically exported without waiting for a request. It is therefore a sub- optimal solution when the monitoring configuration needs to be changed often. ªPullª modewould be in that case more appropriate. In case of many exports, requiring many different templates, the Template IDs could not be enough 4.1 IPFIX and IPv6 There is no problem in reporting IPv6 data with IPFIX, provided only that the transport protocol being used to carry IPFIX (SCTP is preferred) is running on the IPv6 network. 5. Security Considerations This document describes the usage of IPFIX in various scenarios. The security requirements for the IPFIX target applications are addressed in the IPFIX requirements draft. These requirements must be considered for the specification of the IPFIX protocol. The IPFIX extensions proposed in this document do not induce further security hazards. Section 3 of this document describes how IPFIX can be used in combination with other frameworks. New security hazards can arise when two individually secure frameworks are combined. For the combination of AAA with IPFIX an ASM or an IPFIX collector can function as transit point for the messages. It has to be ensured that at this point the applied security mechanisms (e.g. encryption of messages) are maintained. 6. Normative References [RFC3917] J. Quittek, T. Zseby, B. Claise, S. Zander, ªªRequirements for IP Flow Information Export ", October 2004 7. Informative References [Awdu02] Daniel O. Awduche, et. al.," Overview and Principles of Internet Traffic Engineering", (work in progress), Internet Draft, Internet Engineering Zseby, Boschi, Brownlee, Claise [Page 17] IPFIX Applicability February 2005 Task Force, draft-ietf-tewg-principles-02.txt, May 2002 [Brow00] Nevil Brownlee: Packet Matching for NeTraMet Distributions,http://www2.auckland.ac.nz/net//Inter net/rtfm/meetings/47-adelaide/pp-dist/ [CuDF04] D.Curry, H. Debar, H. Feinstein: ªªThe Intrusion Detection Message Exchange Formatªª,(work in progress), Internet Draft, Internet Engineering Task Force, , January 2004 [DuGr00] Nick Duffield, Matthias Grossglauser: "Trajectory Sampling for Direct Traffic Observation", Proceedings of ACM SIGCOMM 2000, Stockholm, Sweden, August 28 - September 1, 2000. [GrDM98] Ian D. GRAHAM, Stephen F. DONNELLY, Stele MARTIN, Jed MARTENS, John G. CLEARY: Nonintrusive and Accurate Measurement of Unidirectional Delay and Delay Variation on the Internet, INET'98, Geneva, Switzerland, 21-24 July, 1998 [PSAMP-FW] Nick Duffield (Ed.): A Framework for Packet Selection and Reporting, Internet Draft draft-ietf- psamp-framework-08, work in progress, January 2005 [RFC2598] V. Jacobson, K. Nichols, K. Poduri, An Expedited Forwarding PHB, Request for Comments: 2598, June 1999 [RFC2679] G. Almes, S. Kalidindi, M. Zekauskas: A One-way Delay Metric for IPPM, Request for Comments: 2679, September 1999 [RFC2680] G. Almes, S. Kalidindi, M. Zekauskas: A One-way Packet Loss Metric for IPPM, September 1999 [RFC2681] G. Almes, S. Kalidindi, M. Zekauskas, "A Round-trip Delay Metric for IPPM.", RFC 2681, September 1999 [RFC2903] C. de Laat, G. Gross, L. Gommans, J. Vollbrecht, D. Spence, "Generic AAA Architecture", RFC 2903, August 2000 [RFC3393] C. Demichelis, P. Cimento: IP Packet Delay Variation Metric for IPPM, RFC 3393, November 2002 Zseby, Boschi, Brownlee, Claise [Page 18] IPFIX Applicability February 2005 [RFC3577] S. Waldbusser, R. Cole, C. Kalbfleisch, D.Romascanu: Introduction to the Remote Monitoring (RMON) Family of MIB Module, RFC 3577, [ZsZC01] Tanja Zseby, Sebastian Zander, Georg Carle: Evaluation of Building Blocks for Passive One-way- delay Measurements, Proceedings of Passive and Active Measurement Workshop (PAM 2001), Amsterdam, The Netherlands, April 23-24, 2001 8. Acknowledgements We would like to thank the following persons for their contribution, discussion on the mailing list and valuable comments: Sebastian Zander Robert Loewe Reinaldo Penno Part of the work has been developed in the research project 6QM co-funded with support from the European Commission. 9. Author's Addresses Tanja Zseby Fraunhofer Institute for Open Communication Systems (FOKUS) Kaiserin-Augusta-Allee 31 10589 Berlin, Germany Phone: +49 30 3463 7153 Email: zseby@fokus.fhg.de Elisa Boschi Fraunhofer Institute for Open Communication Systems (FOKUS) Kaiserin-Augusta-Allee 31 10589 Berlin, Germany Phone: +49 30 3463 7366 Email: boschi@fokus.fhg.de Nevil Brownlee CAIDA (UCSD/SDSC) 9500 Gilman Drive La Jolla, CA 92093-0505 Phone : +1 858 534 8338 Email : nevil@caida.org Zseby, Boschi, Brownlee, Claise [Page 19] IPFIX Applicability February 2005 Benoit Claise Cisco Systems De Kleetlaan 6a b1 1831 Diegem Belgium Phone: +32 2 704 5622 Email: bclaise@cisco.com 10.Full Copyright Statement "Copyright (C) The Internet Society (2005). All Rights Reserved. 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Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this Zseby, Boschi, Brownlee, Claise [Page 20] IPFIX Applicability February 2005 specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. 12. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 13. Disclaimer This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Zseby, Boschi, Brownlee, Claise [Page 21]