OPSAWG H. Song, Ed. Internet-Draft Futurewei Intended status: Informational F. Qin Expires: June 6, 2020 China Mobile H. Chen China Telecom J. Jin LG U+ J. Shin SK Telecom December 4, 2019 In-situ Flow Information Telemetry draft-song-opsawg-ifit-framework-09 Abstract Efficient network operation increasingly relies on data-plane telemetry. As networks increase in scale and network operations become more sophisticated, traditional Operation, Administration and Maintenance (OAM) methods, which include proactive and reactive techniques, running in active and passive modes, become more susceptible to measurement accuracy and misconfiguration errors. With the advent of programmable data-plane, emerging on-path telemetry techniques provide unprecedented flow insight and realtime notification of network issues (e.g., jitter, increased latency, packet loss, significant bit error variations, and unequal load- balancing). This document enumerates several key deployment challenges and requirements for on-path telemetry techniques, especially in carrier operator networks. To address these issues, this document outlines a high-level framework, In-situ Flow Information Telemetry (iFIT). iFIT provides several essential components that can be assembled to achieve a complete and efficient solution for on-path telemetry. As a reference and open framework, iFIT only describes the basic functions of each identified component and suggests possible applications. It does not specify the implementation of the components and the interfaces between the components. The compliance of iFIT framework is not mandated either. This informational document aims to clarify the problem domain, and summarize the best practices and sensible system design considerations. The iFIT framework helps to guide the analysis on the current standard status and gaps, and motivate new works to complete the ecosystem. It also Song, et al. Expires June 6, 2020 [Page 1] Internet-Draft IFIT Framework December 2019 helps to inspire innovative network telemetry applications supporting advanced network operations. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on June 6, 2020. Copyright Notice Copyright (c) 2019 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 (https://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. Song, et al. Expires June 6, 2020 [Page 2] Internet-Draft IFIT Framework December 2019 Table of Contents 1. Requirements and Challenges . . . . . . . . . . . . . . . . . 3 2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. iFIT Framework Overview . . . . . . . . . . . . . . . . . . . 6 3.1. Passport vs. Postcard . . . . . . . . . . . . . . . . . . 8 3.2. Relationship with Network Telemetry Framework (NTF) . . . 9 4. Key Components of iFIT . . . . . . . . . . . . . . . . . . . 9 4.1. Smart Flow and Data Selection . . . . . . . . . . . . . . 9 4.1.1. Example: Sketch-guided Elephant Flow Selection . . . 10 4.1.2. Example: Adaptive Packet Sampling . . . . . . . . . . 10 4.2. Smart Data Export . . . . . . . . . . . . . . . . . . . . 10 4.2.1. Example: Event-based Anomaly Monitor . . . . . . . . 11 4.3. Dynamic Network Probe . . . . . . . . . . . . . . . . . . 12 4.3.1. Examples . . . . . . . . . . . . . . . . . . . . . . 12 4.4. Encapsulation and Tunneling . . . . . . . . . . . . . . . 12 4.5. On-demand Technique Selection and Integration . . . . . . 13 5. iFIT for Reflective Telemetry . . . . . . . . . . . . . . . . 13 5.1. Example: Intelligent Multipoint Performance Monitoring . 14 5.2. Example: Intent-based Network Monitoring . . . . . . . . 15 6. Standard Status and Gap Analysis . . . . . . . . . . . . . . 16 7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 17 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 12.1. Normative References . . . . . . . . . . . . . . . . . . 17 12.2. Informative References . . . . . . . . . . . . . . . . . 18 12.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 1. Requirements and Challenges Efficient network operation increasingly relies on data-plane telemetry. Traditional Operation, Administration and Maintenance (OAM) methods, which include proactive and reactive techniques, running in active and passive modes, become more susceptible to measurement accuracy and misconfiguration errors, as networks increase in scale and network operations become more sophisticated. The sheer complexity of today's networks requires radical rethinking of existing methods used for network monitoring and troubleshooting. Current dynamic networks require new traffic monitoring and measurement solutions for a wide range of use cases requiring better traffic visibility. Furthermore, the ability to expedite failure detection, fault localization, and recovery mechanisms, particularly Song, et al. Expires June 6, 2020 [Page 3] Internet-Draft IFIT Framework December 2019 in the case of soft failures or path degradation are expected, without causing service disruption. Future networks must also support application-aware networking. Application-aware networking is an emerging industry term and typically used to describe the capacity of an intelligent network to maintain current information about user and application connections that use network resources and, as a result, the operator can optimize the network resource usage and monitoring to ensure application and traffic optimality. On-path telemetry refers to the data-plane telemetry techniques that directly tap and measure network traffic by embedding instructions or metadata into user packets. These techniques are especially suitable for network operations that need user SLA compliance, service path enforcement, fault diagnosis, and network resource optimization. A family of on-path telemetry techniques, including In-situ OAM (IOAM) [I-D.brockners-inband-oam-data], Postcard Based Telemetry (PBT) [I-D.song-ippm-postcard-based-telemetry], In-band Flow Analyzer (IFA) [I-D.kumar-ippm-ifa], Enhanced Alternate Marking (EAM) [I-D.zhou-ippm-enhanced-alternate-marking], and Hybrid Two Steps (HTS) [I-D.mirsky-ippm-hybrid-two-step], have been proposed, which can provide flow information on the entire forwarding path on a per- packet basis in real time. These on-path telemetry techniques are very different from the previous active and passive OAM schemes in that they directly modify the user packets and can guarantee 100% accuracy. These on-path telemetry techniques can be classified as the hybrid OAM type III, supplementing the classification defined in [RFC7799]. On-path telemetry is invaluable for application-aware networking operations not only in data center and enterprise networks but also in carrier networks which may cross multiple domains. Carrier network operators have shown strong interest in utilizing such techniques for various purposes. For example, it is vital for the operators who offer bandwidth intensive, latency and loss sensitive services such as video streaming and online gaming to closely monitor the relevant flows in real time as the indispensable first step for any further measure. However, successfully applying such techniques in carrier networks needs to consider performance, deployability, and flexibility. Specifically, several practical challenges need to be addressed: o C1: On-path telemetry incurs extra packet processing which may strain the network data plane. The potential impact on the forwarding performance creates an unfavorable "observer effect" Song, et al. Expires June 6, 2020 [Page 4] Internet-Draft IFIT Framework December 2019 which not only damages the fidelity of the measurement but also defies the purpose of the measurement. o C2: On-path telemetry can generate a huge amount of OAM data which may claim too much transport bandwidth and inundate the servers for data collection, storage, and analysis. Increasing the data handling capacity is technically viable but expensive. For example, assume IOAM is applied to all the traffic. One node will collect a few tens of bytes as telemetry data for each packet. The whole forwarding path might accumulate a data trace with a size similar to or even exceeding that of the original packet. Transporting the telemetry data alone will consume almost half of the network bandwidth. o C3: The collectible data defined currently are essential but limited. As the network operation evolves to be declarative (intent-based) and automated, and the trends of network virtualization, network convergence, and packet-optical integration continue, more data will be needed in an on-demand and interactive fashion. Flexibility and extensibility on data defining, aggregation, acquisition, and filtering, must be considered. o C4: If we were to apply some on-path telemetry technique in today's carrier networks, we must provide solutions to tailor the provider's network deployment base and support an incremental deployment strategy. That is, we need to support established encapsulation schemes for various predominant protocols such as Ethernet, IPv4, and MPLS with backward compatibility and properly handle various transport tunnels. o C5: Applying only a single underlying on-path telemetry technique may lead to defective result. For example, packet drop can cause the loss of the flow telemetry data and the packet drop location and reason remains unknown if only In-situ OAM trace option is used. A comprehensive solution needs the flexibility to switch between different underlying techniques and adjust the configurations and parameters at runtime. o C6: Development of simplified on-path telemetry primitives and models, including: telemetry data (e.g., nodes, links, ports, paths, flows, timestamps) query primitives. These may be used by an API-based telemetry service for external applications, for monitoring end-to-end latency measurement of network paths and application latency calculation. Song, et al. Expires June 6, 2020 [Page 5] Internet-Draft IFIT Framework December 2019 2. Glossary This section defines and explains some acronyms and terms used in this document. On-path Telemetry: Remotely acquiring OAM data about a packet on its forwarding path. The term refers to a class of data plane telemetry techniques which collect data about user flows and packets along their forwarding paths. IOAM, PBT, IFA, EAM, and HTS are all on-path telemetry techniques. Such techniques may need to mark user packets, or insert instruction or metadata to the headers of user packets. iFIT: In-situ Flow Information Telemetry, pronounced as "I-FIT". iFIT Framework: A high-level reference framework that supports network data-plane OAM applications to apply on-path telemetry techniques. iFIT Application: A network OAM application that fits in the iFIT framework. iFIT Domain: The network domain that participates in an iFIT application. iFIT Node: A network node that is in an iFIT domain and is capable of iFIT-specific functions. iFIT Head Node: A special iFIT node. It is the entry node to an iFIT domain. Usually the instruction header encapsulation, if needed, happens here. iFIT End Node: A special iFIT node. It is the exit node of an iFIT domain. Usually the instruction header decapsulation, if needed, happens here. Reflective Telemetry: The telemetry functions in a dynamic and interactive fashion. New telemetry action is provisioned as a result of self-knowledge acquired through prior telemetry actions. 3. iFIT Framework Overview To address the aforementioned challenges, we present a high-level framework based on multiple network operators' requirements and common industry practice, which can help to build a workable and efficient on-path telemetry solution. We name the framework "In-situ Flow Information Telemetry" (iFIT) to reflect the fact that this framework is dedicated to on-path telemetry data about user/ Song, et al. Expires June 6, 2020 [Page 6] Internet-Draft IFIT Framework December 2019 application traffic. As a reference framework for building a complete solution, iFIT covers a class of on-path telemetry techniques and works a level higher than any specific technique. The framework is built up on a few functional components (Section 4). By assembling these components, iFIT supports reflective telemetry that enables autonomous network operations (Section 5). iFIT is an open and loose framework. It does not enforce any specific implementation on each component, neither does it define interfaces (e.g., API, protocol) between components. The choice of underlying on-path telemetry techniques and other implementation details is determined by application implementer. The network architecture that applies iFIT is shown in Figure 1. The iFIT domain is confined between the iFIT head nodes and the iFIT end nodes. An iFIT domain may cross multiple network domains. An iFIT application uses a controller to configure the iFIT nodes. The configuration determines which underlying technique is used, what telemetry data are interested, which flows and packets are concerned, how the telemetry data are collected, etc. After the telemetry data processing and analyzing, the iFIT application may instruct the controller to modify the iFIT node configuration and affect the future telemetry data collection. How applications communicate with the controller is out of scope for this document iFIT supports two basic on-path telemetry modes: passport mode (e.g., IOAM trace option and IFA), in which telemetry data are carried in user packets and only exported at the iFIT end nodes, and postcard mode (e.g., PBT), in which each node in the iFIT domain may export telemetry data through independent OAM packets. An on-path telemetry application may need to mix or switch between the two modes. Song, et al. Expires June 6, 2020 [Page 7] Internet-Draft IFIT Framework December 2019 +-------------------------------------+ | iFIT Application | | +------------+ +-----------+ | | | | | | | | | Controller |<-------| Collector | | | | | | | | | +-----:------+ +-----------+ | | : ^ | +-------:---------------------|-------+ :configuration |telemetry data : | ...............:.....................|.......... : : : | : : +---------:---+-------------:---++---------:---+ : | : | : | : | V | V | V | V | +------+-+ +-----+--+ +------+-+ +------+-+ packets| iFIT | | Path | | Path | | iFIT | ==>| Head |====>| Node |==//==>| Node |====>| End |==> | Node | | A | | B | | Node | +--------+ +--------+ +--------+ +--------+ |<--- iFIT Domain --->| Figure 1: iFIT Network Architecture 3.1. Passport vs. Postcard [passport-postcard] first uses the analogy of passport and postcard to describe how the packet trace data can be collected and exported. In the passport mode, each node on the path adds the telemetry data to the user packets. The accumulated data trace is exported at a configured end node. In the postcard mode, each node directly exports the telemetry data using an independent packet while the user packets are intact. A prominent advantage of the passport mode is that it naturally retains the telemetry data correlation along the entire path. The passport mode also reduces the number of data export packets. These help to simplify the data collector and analyzer's work. On the other hand, the passport mode requires more processing on the user packets and increases the size of user packets, which can cause various problems. Some other issues are documented in [I-D.song-ippm-postcard-based-telemetry]. Song, et al. Expires June 6, 2020 [Page 8] Internet-Draft IFIT Framework December 2019 The postcard mode provides a perfect complement to the passport mode. It addresses most of the issues faced by the passport mode, at a cost of needing extra effort to correlate the postcard packets. 3.2. Relationship with Network Telemetry Framework (NTF) [I-D.ietf-opsawg-ntf] describes a Network Telemetry Framework (NTF). One dimension used by NTF to partition network telemetry techniques and systems is based on the three planes in networks plus external data sources. iFIT framework fits in the data-plane telemetry category and deals with the specific on-path technical branch of the data-plane telemetry. 4. Key Components of iFIT The high-level components of iFIT are listed as follows: o Smart flow and data selection policy, addressing the challenge C1 described in Section 1. o Smart data export, addressing the challenge C2. o Dynamic network probe, addressing C3. o Encapsulation and tunneling, addressing C4. o On-demand technique selection and integration, addressing C5. Note that this document does not directly address the challenge C6 which is open for future standard proposals and left as a concern of application implementers. Next we provide a detailed description of each component. 4.1. Smart Flow and Data Selection In most cases, it is impractical to enable the data collection for all the flows and for all the packets in a flow due to the potential performance and bandwidth impact. Therefore, a workable solution usually need to select only a subset of flows and flow packets to enable the data collection, even though this means the loss of some information and accuracy. In the data plane, the Access Control List (ACL) provides an ideal means to determine the subset of flow(s). [I-D.song-ippm-ioam-data-validation-option] describes how one can set a sample rate or probability to a flow to allow only a subset of flow packets to be monitored, how one can collect a different set of data Song, et al. Expires June 6, 2020 [Page 9] Internet-Draft IFIT Framework December 2019 for different packets, and how one can disable or enable data collection on any specific network node. It further introduces an enhancement to IOAM to allow any node to accept or deny the data collection in full or partially. Based on these flexible mechanisms, iFIT allows applications to apply smart flow and data selection policies to suit the requirements. The applications can dynamically change the policies at any time based on the network load, processing capability, focus of interest, and any other criteria. 4.1.1. Example: Sketch-guided Elephant Flow Selection Network operators are usually more interested in elephant flows which consume more resource and are sensitive to changes in network conditions. A CountMin Sketch [CMSketch] can be used on the data path of the head nodes, which identifies and reports the elephant flows periodically. The controller maintains a current set of elephant flows and dynamically enables the on-path telemetry for only these flows. 4.1.2. Example: Adaptive Packet Sampling Applying on-path telemetry on all packets of selected flows can still be out of reach. A sample rate should be set for these flows and only enable telemetry on the sampled packets. However, the head nodes have no clue on the proper sampling rate. An overly high rate would exhaust the network resource and even cause packet drops; An overly low rate, on the contrary, would result in the loss of information and inaccuracy of measurements. An adaptive approach can be used based on the network conditions to dynamically adjust the sampling rate. Every node gives user traffic forwarding higher priority than telemetry data export. In case of network congestion, the telemetry can sense some signals from the data collected (e.g., deep buffer size, long delay, packet drop, and data loss). The controller may use these signals to adjust the packet sampling rate. In each adjustment period (i.e., RTT of the feedback loop), the sampling rate is either decreased or increased in response of the signals. An AIMD policy similar to the TCP flow control mechanism for the rate adjustment can be used. 4.2. Smart Data Export The flow telemetry data can catch the dynamics of the network and the interactions between user traffic and network. Nevertheless, the data inevitably contain redundancy. It is advisable to remove the Song, et al. Expires June 6, 2020 [Page 10] Internet-Draft IFIT Framework December 2019 redundancy from the data in order to reduce the data transport bandwidth and server processing load. In addition to efficient export data encoding (e.g., IPFIX [RFC7011] or protobuf [1]), iFIT nodes have several other ways to reduce the export data by taking advantage of network device's capability and programmability. iFIT nodes can cache the data and send the accumulated data in batch if the data is not time sensitive. Various deduplication and compression techniques can be applied on the batch data. From the application perspective, an application may only be interested in some special events which can be derived from the telemetry data. For example, in case that the forwarding delay of a packet exceeds a threshold, or a flow changes its forwarding path is of interest, it is unnecessary to send the original raw data to the data collecting and processing servers. Rather, iFIT takes advantage of the in-network computing capability of network devices to process the raw data and only push the event notifications to the subscribing applications. Such events can be expressed as policies. An policy can request data export only on change, on exception, on timeout, or on threshold. 4.2.1. Example: Event-based Anomaly Monitor Network operators are interested in the anomalies such as path change, network congestion, and packet drop. Such anomalies are hidden in raw telemetry data (e.g., path trace, timestamp). Such anomalies can be described as events and programmed into the device data plane. Only the triggered events are exported. For example, if a new flow appears at any node, a path change event is triggered; if the packet delay exceeds a predefined threshold in a node, the congestion event is triggered; if a packet is dropped due to buffer overflow, a packet drop event is triggered. The export data reduction due to such optimization is substantial. For example, given a single 5-hop 10Gbps path, assume a moderate number of 1 million packets per second are monitored, and the telemetry data plus the export packet overhead consume less than 30 bytes per hop. Without such optimization, the bandwidth consumed by the telemetry data can easily exceed 1Gbps (>10% of the path bandwidth), When the optimization is used, the bandwidth consumed by the telemetry data is negligible. Moreover, the pre-processed telemetry data greatly simplify the work of data analyzers. Song, et al. Expires June 6, 2020 [Page 11] Internet-Draft IFIT Framework December 2019 4.3. Dynamic Network Probe Due to limited data plane resource and network bandwidth, it is unlikely one can monitor all the data all the time. On the other hand, the data needed by applications may be arbitrary but ephemeral. It is critical to meet the dynamic data requirements with limited resource. Fortunately, data plane programmability allows iFIT to dynamically load new data probes. These on-demand probes are called Dynamic Network Probes (DNP) [I-D.song-opsawg-dnp4iq]. DNP is the technique to enable probes for customized data collection in different network planes. When working with IOAM or PBT, DNP is loaded to the data plane through incremental programming or configuration. The DNP can effectively conduct data generation, processing, and aggregation. DNP introduces enough flexibility and extensibility to iFIT. It can implement the optimizations for export data reduction motioned in the previous section. It can also generate custom data as required by today and tomorrow's applications. 4.3.1. Examples Following are some possible DNPs that can be dynamically deployed to support iFIT applications. On-demand Flow Sketch: A flow sketch is a compact online data structure for approximate flow statistics which can be used to facilitate flow selection. The aforementioned CountMin Sketch is such an example. Since a sketch consumes data plane resources, it should only be deployed when needed. Smart Flow Filter: The policies that choose flows and packet sampling rate can change during the lifetime of an application. Smart Statistics: An application may need to interactively count flows based on different flow granularity or maintain hit counters for selected flow table entries. Smart Data Reduction: DNP can be used to program the events that conditionally trigger data export. 4.4. Encapsulation and Tunneling Since the introduction of IOAM, the IOAM option header encapsulation schemes in various network protocols have been proposed with the omission of some protocols, such as MPLS and IPv4, which are still prevalent in carrier networks. iFIT provides solutions to apply the Song, et al. Expires June 6, 2020 [Page 12] Internet-Draft IFIT Framework December 2019 on-path flow telemetry techniques in such networks. PBT-M [I-D.song-ippm-postcard-based-telemetry] does not introduce new headers to the packets so the trouble of encapsulation for a new header is avoided. In case a technique that requires a new header is preferred, [I-D.song-mpls-extension-header] provides a means to encapsulate the extra header using an MPLS extension header. As for IPv4, it is possible to encapsulate the new header in an IP option. For example, RAO [RFC2113] can be used to indicate the presence of the new header. A recent proposal [I-D.herbert-ipv4-eh] that introduces the IPv4 extension header may lead to a long term solution. In carrier networks, it is common for user traffic to traverse various tunnels for QoS, traffic engineering, or security. iFIT supports both the uniform mode and the pipe mode for tunnel support as described in [I-D.song-ippm-ioam-tunnel-mode]. With such flexibility, the operator can either gain a true end-to-end visibility or apply a hierarchical approach which isolates the monitoring domain between customer and provider. 4.5. On-demand Technique Selection and Integration With multiple underlying data collection and export techniques at its disposal, iFIT can flexibly adapt to different network conditions and different application requirements. For example, depending on the types of data that are of interest, iFIT may choose either IOAM or PBT to collect the data; if an application needs to track down where the packets are lost, it may switch from IOAM to PBT. iFIT can further integrate multiple data plane monitoring and measurement techniques together and present a comprehensive data plane telemetry solution to network operating applications. 5. iFIT for Reflective Telemetry The iFIT components can work together to support reflective telemetry, as shown in Figure 2. Song, et al. Expires June 6, 2020 [Page 13] Internet-Draft IFIT Framework December 2019 +---------------------+ | | +------+ iFIT Applications |<------+ | | | | | +---------------------+ | | Technique Selection | | and Integration | | | |Smart Flow Smart | |and Data reflection-loop Data | |Selection Export| | | | +----+----+ V +---------+| +----------+ Encapsulation +---------+|| | iFIT | and Tunneling | iFIT ||| | Head |----------------------->| ||+ | Node | | Nodes |+ +----------+ +---------+ DNP DNP Figure 2: iFIT-based Reflective Telemetry An iFIT application may pick a suite of telemetry techniques based on its requirements and apply an initial technique to the data plane. It then configures the iFIT head nodes to decide the initial target flows/packets and telemetry data set, the encapsulation and tunneling scheme based on the underlying network architecture, and the iFIT- capable nodes to decide the initial telemetry data export policy. Based on the network condition and the analysis results of the telemetry data, the iFIT application can change the telemetry technique, the flow/data selection policy, and the data export approach in real time without breaking the normal network operation. Many of such dynamic changes can be done through loading and unloading DNPs. The reflective telemetry enabled by the iFIT framework allows numerous new applications suitable for future network operation architecture. 5.1. Example: Intelligent Multipoint Performance Monitoring [I-D.ietf-ippm-multipoint-alt-mark] describes an intelligent performance management based on the network condition. The idea is to split the monitoring network into clusters. The cluster partition that can be applied to every type of network graph and the possibility to combine clusters at different levels enable the so- Song, et al. Expires June 6, 2020 [Page 14] Internet-Draft IFIT Framework December 2019 called Network Zooming. It allows a controller to calibrate the network telemetry, so that it can start without examining in depth and monitor the network as a whole. In case of necessity (packet loss or too high delay), an immediate detailed analysis can be reconfigured. In particular, the controller, that is aware of the network topology, can set up the most suited cluster partition by changing the traffic filter or activate new measurement points and the problem can be localized with a step-by-step process. An iFIT application on top of the controllers can manage such mechanism and iFIT's architecture allows its dynamic and reflective operation. 5.2. Example: Intent-based Network Monitoring User Intents | V Per-packet +------------+ Telemetry ACL | | Data +--------+ Controller |<--------+ | | | | | +--+---------+ | | | ^ | | |DNPs |Network | | | |Information| | V | | +------+-------------------+-----------+---+ | | | | V +------+ | | +-------+ +------+| | | | iFIT | iFIT Domain +------+|| | | | Head | |iFIT ||+ | | | Node | |Nodes |+ | | +-------+ +------+ | +------------------------------------------+ Figure 3: Intent-based Monitoring In this example, a user can express high level intents for network monitoring. The controller translates an intent and configure the corresponding DNPs in iFIT nodes which collect necessary network information. Based on the real-time information feedback, the controller runs a local algorithm to determine the suspicious flows. It then deploys ACLs to the iFIT head node to initiate the high precision per-packet on-path telemetry for these flows. Song, et al. Expires June 6, 2020 [Page 15] Internet-Draft IFIT Framework December 2019 6. Standard Status and Gap Analysis A complete iFIT solution needs standard interfaces for configuration and data extraction, and standard encapsulation on various transport protocols. It may also need standard API and primitives for application programming and deployment. The draft [I-D.brockners-opsawg-ioam-deployment] summarizes some current proposals on encapsulation and data export for IOAM. However, these works can be extended or modified to support other types of on-path telemetry techniques and other transport protocols. The high level iFIT framework helps to develop coherent and universal standard encapsulation and data export approaches. In addition, standard approaches for function configuration, capability query and advertisement, either in a centralized fashion or a distributed fashion, are still immature. The draft [I-D.zhou-ippm-ioam-yang] provides the YANG model for IOAM configuration. Similar models needs to be defined for other techniques. It is helpful to provide standard approaches for distributed configuration in various network environments. To realize the potential of iFIT, programming and deploying DNPs are important. Currently some related works such as [I-D.wwx-netmod-event-yang] and [I-D.bwd-netmod-eca-framework] have proposed to use YANG model to define the smart policies which can be used to implement DNPs. In the future, other approaches can be development to enhance the programmability and flexibility. 7. Summary iFIT is a high level and open framework for applying on-path telemetry techniques. Combining with algorithmic and architectural schemes that fit into the framework components, iFIT enables a practical telemetry solution based on two basic on-path traffic data collection modes: passport and postcard. The operation of iFIT differs from both active OAM and passive OAM as defined in [RFC7799]. It does not generate any active probe packets or passively observe unmodified user packets. Instead, it modifies selected user packets to collect useful information about them. Therefore, the iFIT operation can be considered the hybrid OAM type III mode, which can provide more flexible and accurate network OAM. iFIT addresses the key challenges for operators to deploy a complete on-path telemetry solution. However, as a reference and open framework, iFIT only describes the basic functions of each identified component and suggests possible applications. It has no intention of specifying the implementation of the components and the interfaces Song, et al. Expires June 6, 2020 [Page 16] Internet-Draft IFIT Framework December 2019 between the components. The compliance of iFIT framework is by no means mandated either. Instead, this informational document aims to clarify the problem domain, and summarize the best practices and sensible system design considerations. The iFIT framework can guide the analysis of the current standard status and gaps, and motivate new works to complete the ecosystem. It also helps to inspire innovative data-plane reflective telemetry applications supporting advanced network operations. Having a framework covering a class of related techniques also promotes a holistic approach for standard development and helps to avoid duplicated efforts and piecemeal solutions that only focus on a specific technique while omitting the compatibility and extensibility issues. To foster a healthy ecosystem for network telemetry, we consider this essential. 8. Security Considerations Specific security issues are discussed in each individual draft on on-path telemetry. 9. IANA Considerations This document includes no request to IANA. 10. Contributors Other major contributors of this document include Giuseppe Fioccola, Daniel King, Zhenqiang Li, Zhenbin Li, Tianran Zhou, and James Guichard. 11. Acknowledgments We thank Diego Lopez, Shwetha Bhandari, Joe Clarke, Adrian Farrel, and Frank Brockners for their constructive suggestions for improving this document. 12. References 12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Song, et al. Expires June 6, 2020 [Page 17] Internet-Draft IFIT Framework December 2019 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, May 2016, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 12.2. Informative References [CMSketch] Cormode, G. and S. Muthukrishnan, "An improved data stream summary: the count-min sketch and its applications", 2005, . [I-D.brockners-inband-oam-data] Brockners, F., Bhandari, S., Pignataro, C., Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov, P., Chang, R., and d. daniel.bernier@bell.ca, "Data Fields for In-situ OAM", draft-brockners-inband-oam-data-07 (work in progress), July 2017. [I-D.brockners-opsawg-ioam-deployment] Brockners, F., Bhandari, S., and d. daniel.bernier@bell.ca, "In-situ OAM Deployment", draft- brockners-opsawg-ioam-deployment-00 (work in progress), October 2019. [I-D.bwd-netmod-eca-framework] Boucadair, M., WU, Q., Wang, Z., King, D., and C. Xie, "Framework for Use of ECA (Event Condition Action) in Network Self Management", draft-bwd-netmod-eca- framework-00 (work in progress), November 2019. [I-D.herbert-ipv4-eh] Herbert, T., "IPv4 Extension Headers and Flow Label", draft-herbert-ipv4-eh-01 (work in progress), May 2019. [I-D.ietf-ippm-multipoint-alt-mark] Fioccola, G., Cociglio, M., Sapio, A., and R. Sisto, "Multipoint Alternate Marking method for passive and hybrid performance monitoring", draft-ietf-ippm- multipoint-alt-mark-03 (work in progress), November 2019. [I-D.ietf-opsawg-ntf] Song, H., Qin, F., Martinez-Julia, P., Ciavaglia, L., and A. Wang, "Network Telemetry Framework", draft-ietf-opsawg- ntf-02 (work in progress), October 2019. Song, et al. Expires June 6, 2020 [Page 18] Internet-Draft IFIT Framework December 2019 [I-D.kumar-ippm-ifa] Kumar, J., Anubolu, S., Lemon, J., Manur, R., Holbrook, H., Ghanwani, A., Cai, D., Ou, H., and L. Yizhou, "Inband Flow Analyzer", draft-kumar-ippm-ifa-01 (work in progress), February 2019. [I-D.mirsky-ippm-hybrid-two-step] Mirsky, G., Lingqiang, W., and G. Zhui, "Hybrid Two-Step Performance Measurement Method", draft-mirsky-ippm-hybrid- two-step-04 (work in progress), October 2019. [I-D.song-ippm-ioam-data-validation-option] Song, H. and T. Zhou, "In-situ OAM Data Validation Option", draft-song-ippm-ioam-data-validation-option-02 (work in progress), April 2018. [I-D.song-ippm-ioam-tunnel-mode] Song, H., Li, Z., Zhou, T., and Z. Wang, "In-situ OAM Processing in Tunnels", draft-song-ippm-ioam-tunnel- mode-00 (work in progress), June 2018. [I-D.song-ippm-postcard-based-telemetry] Song, H., Zhou, T., Li, Z., Shin, J., and K. Lee, "Postcard-based On-Path Flow Data Telemetry", draft-song- ippm-postcard-based-telemetry-06 (work in progress), October 2019. [I-D.song-mpls-extension-header] Song, H., Li, Z., Zhou, T., and L. Andersson, "MPLS Extension Header", draft-song-mpls-extension-header-02 (work in progress), February 2019. [I-D.song-opsawg-dnp4iq] Song, H. and J. Gong, "Requirements for Interactive Query with Dynamic Network Probes", draft-song-opsawg-dnp4iq-01 (work in progress), June 2017. [I-D.wwx-netmod-event-yang] Wang, Z., WU, Q., Xie, C., Bryskin, I., Liu, X., Clemm, A., Birkholz, H., and T. Zhou, "A YANG Data model for ECA Policy Management", draft-wwx-netmod-event-yang-05 (work in progress), November 2019. [I-D.zhou-ippm-enhanced-alternate-marking] Zhou, T., Fioccola, G., Li, Z., Lee, S., and M. Cociglio, "Enhanced Alternate Marking Method", draft-zhou-ippm- enhanced-alternate-marking-04 (work in progress), October 2019. Song, et al. Expires June 6, 2020 [Page 19] Internet-Draft IFIT Framework December 2019 [I-D.zhou-ippm-ioam-yang] Zhou, T., Guichard, J., Brockners, F., and S. Raghavan, "A YANG Data Model for In-Situ OAM", draft-zhou-ippm-ioam- yang-04 (work in progress), June 2019. [passport-postcard] Handigol, N., Heller, B., Jeyakumar, V., Mazieres, D., and N. McKeown, "Where is the debugger for my software-defined network?", 2012, . [RFC2113] Katz, D., "IP Router Alert Option", RFC 2113, DOI 10.17487/RFC2113, February 1997, . [RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, September 2013, . 12.3. URIs [1] https://developers.google.com/protocol-buffers/ Authors' Addresses Haoyu Song (editor) Futurewei 2330 Central Expressway Santa Clara USA Email: haoyu.song@futurewei.com Fengwei Qin China Mobile No. 32 Xuanwumenxi Ave., Xicheng District Beijing, 100032 P.R. China Email: qinfengwei@chinamobile.com Song, et al. Expires June 6, 2020 [Page 20] Internet-Draft IFIT Framework December 2019 Huanan Chen China Telecom P. R. China Email: chenhuan6@chinatelecom.cn Jaehwan Jin LG U+ South Korea Email: daenamu1@lguplus.co.kr Jongyoon Shin SK Telecom South Korea Email: jongyoon.shin@sk.com Song, et al. Expires June 6, 2020 [Page 21]