Network Telemetry Framework
draft-ietf-opsawg-ntf-13
| Document | Type | Active Internet-Draft (opsawg WG) | |
|---|---|---|---|
| Authors | Haoyu Song , Fengwei Qin , Pedro Martinez-Julia , Laurent Ciavaglia , Aijun Wang | ||
| Last updated | 2022-04-19 (Latest revision 2021-12-03) | ||
| Replaces | draft-opsawg-ntf | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Informational | ||
| Formats | plain text html xml htmlized pdfized bibtex | ||
| Reviews |
RTGDIR Telechat review
(of
-10)
Has Issues
INTDIR Telechat review
(of
-10)
Almost Ready
TSVART Last Call review
(of
-09)
Ready with Issues
GENART Last Call review
(of
-09)
Ready with Nits
|
||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Alexander Clemm | ||
| Shepherd write-up | Show Last changed 2021-03-11 | ||
| IESG | IESG state | RFC Ed Queue | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Robert Wilton | ||
| Send notices to | ludwig@clemm.org | ||
| IANA | IANA review state | IANA OK - No Actions Needed | |
| IANA action state | No IANA Actions | ||
| RFC Editor | RFC Editor state | AUTH48-DONE | |
| Details |
draft-ietf-opsawg-ntf-13
OPSAWG H. Song
Internet-Draft Futurewei
Intended status: Informational F. Qin
Expires: 6 June 2022 China Mobile
P. Martinez-Julia
NICT
L. Ciavaglia
Rakuten Mobile
A. Wang
China Telecom
3 December 2021
Network Telemetry Framework
draft-ietf-opsawg-ntf-13
Abstract
Network telemetry is a technology for gaining network insight and
facilitating efficient and automated network management. It
encompasses various techniques for remote data generation,
collection, correlation, and consumption. This document describes an
architectural framework for network telemetry, motivated by
challenges that are encountered as part of the operation of networks
and by the requirements that ensue. This document clarifies the
terminologies and classifies the modules and components of a network
telemetry system from different perspectives. The framework and
taxonomy help to set a common ground for the collection of related
work and provide guidance for related technique and standard
developments.
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 6 June 2022.
Song, et al. Expires 6 June 2022 [Page 1]
Internet-Draft Network Telemetry Framework December 2021
Copyright Notice
Copyright (c) 2021 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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Applicability Statement . . . . . . . . . . . . . . . . . 4
1.2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Telemetry Data Coverage . . . . . . . . . . . . . . . . . 7
2.2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3. Challenges . . . . . . . . . . . . . . . . . . . . . . . 9
2.4. Network Telemetry . . . . . . . . . . . . . . . . . . . . 11
2.5. The Necessity of a Network Telemetry Framework . . . . . 13
3. Network Telemetry Framework . . . . . . . . . . . . . . . . . 14
3.1. Top Level Modules . . . . . . . . . . . . . . . . . . . . 15
3.1.1. Management Plane Telemetry . . . . . . . . . . . . . 18
3.1.2. Control Plane Telemetry . . . . . . . . . . . . . . . 18
3.1.3. Forwarding Plane Telemetry . . . . . . . . . . . . . 19
3.1.4. External Data Telemetry . . . . . . . . . . . . . . . 21
3.2. Second Level Function Components . . . . . . . . . . . . 22
3.3. Data Acquisition Mechanism and Type Abstraction . . . . . 24
3.4. Mapping Existing Mechanisms into the Framework . . . . . 26
4. Evolution of Network Telemetry Applications . . . . . . . . . 27
5. Security Considerations . . . . . . . . . . . . . . . . . . . 28
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 29
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
9. Informative References . . . . . . . . . . . . . . . . . . . 29
Appendix A. A Survey on Existing Network Telemetry Techniques . 35
A.1. Management Plane Telemetry . . . . . . . . . . . . . . . 35
A.1.1. Push Extensions for NETCONF . . . . . . . . . . . . . 35
A.1.2. gRPC Network Management Interface . . . . . . . . . . 36
A.2. Control Plane Telemetry . . . . . . . . . . . . . . . . . 36
A.2.1. BGP Monitoring Protocol . . . . . . . . . . . . . . . 36
A.3. Data Plane Telemetry . . . . . . . . . . . . . . . . . . 36
A.3.1. The Alternate Marking (AM) technology . . . . . . . . 36
Song, et al. Expires 6 June 2022 [Page 2]
Internet-Draft Network Telemetry Framework December 2021
A.3.2. Dynamic Network Probe . . . . . . . . . . . . . . . . 38
A.3.3. IP Flow Information Export (IPFIX) Protocol . . . . . 38
A.3.4. In-Situ OAM . . . . . . . . . . . . . . . . . . . . . 38
A.3.5. Postcard Based Telemetry . . . . . . . . . . . . . . 39
A.3.6. Existing OAM for Specific Data Planes . . . . . . . . 39
A.4. External Data and Event Telemetry . . . . . . . . . . . . 39
A.4.1. Sources of External Events . . . . . . . . . . . . . 39
A.4.2. Connectors and Interfaces . . . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction
Network visibility is the ability of management tools to see the
state and behavior of a network, which is essential for successful
network operation. Network Telemetry revolves around network data
that can help provide insights about the current state of the
network, including network devices, forwarding, control, and
management planes, and that can be generated and obtained through a
variety of techniques, including but not limited to network
instrumentation and measurements, and that can be processed for
purposes ranging from service assurance to network security using a
wide variety of data analytical techniques. In this document,
Network Telemetry refer to both the data itself (i.e., "Network
Telemetry Data"), and the techniques and processes used to generate,
export, collect, and consume that data for use by potentially
automated management applications. Network telemetry extends beyond
the classical network Operations, Administration, and Management
(OAM) techniques and expects to support better flexibility,
scalability, accuracy, coverage, and performance.
However, the term "network telemetry" lacks an unambiguous
definition. The scope and coverage of it cause confusion and
misunderstandings. It is beneficial to clarify the concept and
provide a clear architectural framework for network telemetry, so we
can articulate the technical field, and better align the related
techniques and standard works.
To fulfill such an undertaking, we first discuss some key
characteristics of network telemetry which set a clear distinction
from the conventional network OAM and show that some conventional OAM
technologies can be considered a subset of the network telemetry
technologies. We then provide an architectural framework for network
telemetry which includes four modules, each concerned with a
different category of telemetry data and corresponding procedures.
All the modules are internally structured in the same way, including
components that allow the operator to configure data sources in
regard to what data to generate and how to make that available to
client applications, components that instrument the underlying data
Song, et al. Expires 6 June 2022 [Page 3]
Internet-Draft Network Telemetry Framework December 2021
sources, and components that perform the actual rendering, encoding,
and exporting of the generated data. We show how the network
telemetry framework can benefit the current and future network
operations. Based on the distinction of modules and function
components, we can map the existing and emerging techniques and
protocols into the framework. The framework can also simplify
designing, maintaining, and understanding a network telemetry system.
In addition, we outline the evolution stages of the network telemetry
system and discuss the potential security concerns.
The purpose of the framework and taxonomy is to set a common ground
for the collection of related work and provide guidance for future
technique and standard developments. To the best of our knowledge,
this document is the first such effort for network telemetry in
industry standards organizations. This document does not define
specific technologies.
1.1. Applicability Statement
Large-scale network data collection is a major threat to user privacy
and may be indistinguishable from pervasive monitoring [RFC7258].
The network telemetry framework presented in this document must not
be applied to generating, exporting, collecting, analyzing, or
retaining individual user data or any data that can identify end
users or characterize their behavior without consent. Based on this
principle, the network telemetry framework is not applicable to
networks whose endpoints represent individual users, such as general-
purpose access networks.
1.2. Glossary
Before further discussion, we list some key terminology and acronyms
used in this document. We make an intended differentiation between
the terms of network telemetry and OAM. However, it should be
understood that there is not a hard-line distinction between the two
concepts. Rather, network telemetry is considered as an extension of
OAM. It covers all the existing OAM protocols but puts more emphasis
on the newer and emerging techniques and protocols concerning all
aspects of network data from acquisition to consumption.
AI: Artificial Intelligence. In the network domain, AI refers to
the machine-learning based technologies for automated network
operation and other tasks.
AM: Alternate Marking, a flow performance measurement method,
specified in [RFC8321].
BMP: BGP Monitoring Protocol, specified in [RFC7854].
Song, et al. Expires 6 June 2022 [Page 4]
Internet-Draft Network Telemetry Framework December 2021
DPI: Deep Packet Inspection, referring to the techniques that
examines packet beyond packet L3/L4 headers.
gNMI: gRPC Network Management Interface, a network management
protocol from OpenConfig Operator Working Group, mainly
contributed by Google. See [gnmi] for details.
GPB: Google Protocol Buffer, an extensible mechanism for serializing
structured data. See [gpb] for details.
gRPC: gRPC Remote Procedure Call, an open source high performance
RPC framework that gNMI is based on. See [grpc] for details.
IPFIX: IP Flow Information Export Protocol, specified in [RFC7011].
IOAM: In-situ OAM [I-D.ietf-ippm-ioam-data], a dataplane on-path
telemetry technique.
JSON: An open standard file format and data interchange format that
uses human-readable text to store and transmit data objects,
specified in [RFC8259].
MIB: Management Information Base, a database used for managing the
entities in a network.
NETCONF: Network Configuration Protocol, specified in [RFC6241].
NetFlow: A Cisco protocol for flow record collecting, described in
[RFC3954].
Network Telemetry: The process and instrumentation for acquiring and
utilizing network data remotely for network monitoring and
operation. A general term for a large set of network visibility
techniques and protocols, concerning aspects like data generation,
collection, correlation, and consumption. Network telemetry
addresses the current network operation issues and enables smooth
evolution toward future intent-driven autonomous networks.
NMS: Network Management System, referring to applications that allow
network administrators to manage a network.
OAM: Operations, Administration, and Maintenance. A group of
network management functions that provide network fault
indication, fault localization, performance information, and data
and diagnosis functions. Most conventional network monitoring
techniques and protocols belong to network OAM.
PBT: Postcard-Based Telemetry, a dataplane on-path telemetry
Song, et al. Expires 6 June 2022 [Page 5]
Internet-Draft Network Telemetry Framework December 2021
technique. A representative technique is described in
[I-D.ietf-ippm-ioam-direct-export].
RESTCONF: An HTTP-based protocol that provides a programmatic
interface for accessing data defined in YANG, using the datastore
concepts defined in NETCONF, as specified in [RFC8040].
SMIv2: Structure of Management Information Version 2, defining MIB
objects, specified in [RFC2578].
SNMP: Simple Network Management Protocol. Version 1, 2, and 3 are
specified in [RFC1157], [RFC3416], and [RFC3411], respectively.
XML: Extensible Markup Language is a markup language for data
encoding that is both human-readable and machine-readable,
specified by W3C [xml].
YANG: YANG is a data modeling language for the definition of data
sent over network management protocols such as the NETCONF and
RESTCONF. YANG is defined in [RFC6020] and [RFC7950].
YANG ECA: A YANG model for Event-Condition-Action policies, defined
in [I-D.wwx-netmod-event-yang].
YANG-Push: A mechanism that allows subscriber applications to
request a stream of updates from a YANG datastore on a network
device. Details are specified in [RFC8641] and [RFC8639].
2. Background
The term "big data" is used to describe the extremely large volume of
data sets that can be analyzed computationally to reveal patterns,
trends, and associations. Networks are undoubtedly a source of big
data because of their scale and the volume of network traffic they
forward. When a network's endpoints do not represent individual
users (e.g. in industrial, datacenter, and infrastructure contexts),
network operations can often benefit from large-scale data collection
without breaching user privacy.
Today one can access advanced big data analytics capability through a
plethora of commercial and open source platforms (e.g., Apache
Hadoop), tools (e.g., Apache Spark), and techniques (e.g., machine
learning). Thanks to the advance of computing and storage
technologies, network big data analytics gives network operators an
opportunity to gain network insights and move towards network
autonomy. Some operators start to explore the application of
Artificial Intelligence (AI) to make sense of network data. Software
tools can use the network data to detect and react on network faults,
Song, et al. Expires 6 June 2022 [Page 6]
Internet-Draft Network Telemetry Framework December 2021
anomalies, and policy violations, as well as predicting future
events. In turn, the network policy updates for planning, intrusion
prevention, optimization, and self-healing may be applied.
It is conceivable that an autonomic network [RFC7575] is the logical
next step for network evolution following Software Defined Networking
(SDN), aiming to reduce (or even eliminate) human labor, make more
efficient use of network resources, and provide better services more
aligned with customer requirements. The IETF ANIMA working group is
dedicated to developing and maintaining protocols and procedures for
automated network management and control of professionally-managed
networks. The related technique of Intent-based Networking (IBN)
[I-D.irtf-nmrg-ibn-concepts-definitions] requires network visibility
and telemetry data in order to ensure that the network is behaving as
intended.
However, while the data processing capability is improved and
applications require more data to function better, the networks lag
behind in extracting and translating network data into useful and
actionable information in efficient ways. The system bottleneck is
shifting from data consumption to data supply. Both the number of
network nodes and the traffic bandwidth keep increasing at a fast
pace. The network configuration and policy change at smaller time
slots than before. More subtle events and fine-grained data through
all network planes need to be captured and exported in real time. In
a nutshell, it is a challenge to get enough high-quality data out of
the network in a manner that is efficient, timely, and flexible.
Therefore, we need to survey the existing technologies and protocols
and identify any potential gaps.
In the remainder of this section, first we clarify the scope of
network data (i.e., telemetry data) relevant in this document. Then,
we discuss several key use cases for today's and future network
operations. Next, we show why the current network OAM techniques and
protocols are insufficient for these use cases. The discussion
underlines the need for new methods, techniques, and protocols, as
well as the extensions of existing ones, which we assign under the
umbrella term - Network Telemetry.
2.1. Telemetry Data Coverage
Any information that can be extracted from networks (including data
plane, control plane, and management plane) and used to gain
visibility or as basis for actions is considered telemetry data. It
includes statistics, event records and logs, snapshots of state,
configuration data, etc. It also covers the outputs of any active
and passive measurements [RFC7799]. In some cases, raw data is
processed in network before being sent to a data consumer. Such
Song, et al. Expires 6 June 2022 [Page 7]
Internet-Draft Network Telemetry Framework December 2021
processed data is also considered telemetry data. The value of
telemetry data varies. In some cases, if the cost is acceptable,
less but higher quality data are preferred than lots of low quality
data. A classification of telemetry data is provided in Section 3.
To preserve the privacy of end-users, no user packet content should
be collected. Specifically, the data objects generated, exported,
and collected by a network telemetry application should not include
any packet payload from traffic associated with end-users systems.
2.2. Use Cases
The following set of use cases is essential for network operations.
While the list is by no means exhaustive, it is enough to highlight
the requirements for data velocity, variety, volume, and veracity,
the attributes of big data, in networks.
* Security: Network intrusion detection and prevention systems need
to monitor network traffic and activities and act upon anomalies.
Given increasingly sophisticated attack vectors coupled with
increasingly severe consequences of security breaches, new tools
and techniques need to be developed, relying on wider and deeper
visibility into networks. The ultimate goal is to achieve
security with no, or only minimal, human intervention, and without
disrupting legitimate traffic flows.
* Policy and Intent Compliance: Network policies are the rules that
constrain the services for network access, provide service
differentiation, or enforce specific treatment on the traffic.
For example, a service function chain is a policy that requires
the selected flows to pass through a set of ordered network
functions. Intent, as defined in
[I-D.irtf-nmrg-ibn-concepts-definitions], is a set of operational
goals that a network should meet and outcomes that a network is
supposed to deliver, defined in a declarative manner without
specifying how to achieve or implement them. An intent requires a
complex translation and mapping process before being applied on
networks. While a policy or intent is enforced, the compliance
needs to be verified and monitored continuously by relying on
visibility that is provided through network telemetry data. Any
violation must be reported immediately, potentially resulting in
updates to how the policy or intent is applied in the network to
ensure that it remains in force, or otherwise alerting the network
administrator to the policy or intent violation.
* SLA Compliance: A Service-Level Agreement (SLA) is a service
contract between a service provider and a client, which include
the metrics for the service measurement and remedy/penalty
procedures when the service level misses the agreement. Users
Song, et al. Expires 6 June 2022 [Page 8]
Internet-Draft Network Telemetry Framework December 2021
need to check if they get the service as promised and network
operators need to evaluate how they can deliver services that can
meet the SLA based on realtime network telemetry data, including
data from network measurements.
* Root Cause Analysis: Many network failure can be the effect of a
sequence of chained events. Troubleshooting and recovery require
quick identification of the root cause of any observable issues.
However, the root cause is not always straightforward to identify,
especially when the failure is sporadic and the number of event
messages, both related and unrelated to the same cause, is
overwhelming. While technologies such as machine learning can be
used for root cause analysis, it is up to the network to sense and
provide the relevant diagnostic data which are either actively fed
into, or passively retrieved by, the root cause analysis
applications.
* Network Optimization: This covers all short-term and long-term
network optimization techniques, including load balancing, Traffic
Engineering (TE), and network planning. Network operators are
motivated to optimize their network utilization and differentiate
services for better Return On Investment (ROI) or lower Capital
Expenditures (CAPEX). The first step is to know the real-time
network conditions before applying policies for traffic
manipulation. In some cases, micro-bursts need to be detected in
a very short time-frame so that fine-grained traffic control can
be applied to avoid network congestion. Long-term planning of
network capacity and topology requires analysis of real-world
network telemetry data that is obtained over long periods of time.
* Event Tracking and Prediction: The visibility into traffic path
and performance is critical for services and applications that
rely on healthy network operation. Numerous related network
events are of interest to network operators. For example, Network
operators want to learn where and why packets are dropped for an
application flow. They also want to be warned of issues in
advance, so proactive actions can be taken to avoid catastrophic
consequences.
2.3. Challenges
For a long time, network operators have relied upon SNMP [RFC3416],
Command-Line Interface (CLI), or Syslog [RFC5424] to monitor the
network. Some other OAM techniques as described in [RFC7276] are
also used to facilitate network troubleshooting. These conventional
techniques are not sufficient to support the above use cases for the
following reasons:
Song, et al. Expires 6 June 2022 [Page 9]
Internet-Draft Network Telemetry Framework December 2021
* Most use cases need to continuously monitor the network and
dynamically refine the data collection in real-time. Poll-based
low-frequency data collection is ill-suited for these
applications. Subscription-based streaming data directly pushed
from the data source (e.g., the forwarding chip) is preferred to
provide sufficient data quantity and precision at scale.
* Comprehensive data is needed, ranging from packet processing
engines to traffic manager, from line cards to main control board,
from user flows to control protocol packets, from device
configurations to operations, and from physical layer to
application layer. Conventional OAM only covers a narrow range of
data (e.g., SNMP only handles data from the Management Information
Base (MIB)). Classical network devices cannot provide all the
necessary probes. More open and programmable network devices are
therefore needed.
* Many application scenarios need to correlate network-wide data
from multiple sources (i.e., from distributed network devices,
different components of a network device, or different network
planes). A piecemeal solution is often lacking the capability to
consolidate the data from multiple sources. The composition of a
complete solution, as partly proposed by Autonomic Resource
Control Architecture(ARCA)
[I-D.pedro-nmrg-anticipated-adaptation], will be empowered and
guided by a comprehensive framework.
* Some conventional OAM techniques (e.g., CLI and Syslog) lack a
formal data model. The unstructured data hinder the tool
automation and application extensibility. Standardized data
models are essential to support the programmable networks.
* Although some conventional OAM techniques support data push (e.g.,
SNMP Trap [RFC2981][RFC3877], Syslog, and sFlow [RFC3176]), the
pushed data are limited to only predefined management plane
warnings (e.g., SNMP Trap) or sampled user packets (e.g., sFlow).
Network operators require the data with arbitrary source,
granularity, and precision which are beyond the capability of the
existing techniques.
* The conventional passive measurement techniques can either consume
excessive network resources and produce excessive redundant data,
or lead to inaccurate results; on the other hand, the conventional
active measurement techniques can interfere with the user traffic
and their results are indirect. Techniques that can collect
direct and on-demand data from user traffic are more favorable.
Song, et al. Expires 6 June 2022 [Page 10]
Internet-Draft Network Telemetry Framework December 2021
These challenges were addressed by newer standards and techniques
(e.g., IPFIX/Netflow, Packet Sampling (PSAMP), IOAM, and YANG-Push)
and more are emerging. These standards and techniques need to be
recognized and accommodated in a new framework.
2.4. Network Telemetry
Network telemetry has emerged as a mainstream technical term to refer
to the network data collection and consumption techniques. Several
network telemetry techniques and protocols (e.g., IPFIX [RFC7011] and
gRPC [grpc]) have been widely deployed. Network telemetry allows
separate entities to acquire data from network devices so that data
can be visualized and analyzed to support network monitoring and
operation. Network telemetry covers the conventional network OAM and
has a wider scope. For instance, it is expected that network
telemetry can provide the necessary network insight for autonomous
networks and address the shortcomings of conventional OAM techniques.
Network telemetry usually assumes machines as data consumers rather
than human operators. Hence, the network telemetry can directly
trigger the automated network operation, while in contrast some
conventional OAM tools were designed and used to help human operators
to monitor and diagnose the networks and guide manual network
operations. Such a proposition leads to very different techniques.
Although new network telemetry techniques are emerging and subject to
continuous evolution, several characteristics of network telemetry
have been well accepted. Note that network telemetry is intended to
be an umbrella term covering a wide spectrum of techniques, so the
following characteristics are not expected to be held by every
specific technique.
* Push and Streaming: Instead of polling data from network devices,
telemetry collectors subscribe to streaming data pushed from data
sources in network devices.
* Volume and Velocity: The telemetry data is intended to be consumed
by machines rather than by human being. Therefore, the data
volume can be huge and the processing is optimized for the needs
of automation in realtime.
* Normalization and Unification: Telemetry aims to address the
overall network automation needs. Efforts are made to normalize
the data representation and unify the protocols, so as to simplify
data analysis and provide integrated analysis across heterogeneous
devices and data sources across a network.
Song, et al. Expires 6 June 2022 [Page 11]
Internet-Draft Network Telemetry Framework December 2021
* Model-based: The telemetry data is modeled in advance which allows
applications to configure and consume data with ease.
* Data Fusion: The data for a single application can come from
multiple data sources (e.g., cross-domain, cross-device, and
cross-layer) based on common naming/ID and needs to be correlated
to take effect.
* Dynamic and Interactive: Since the network telemetry means to be
used in a closed control loop for network automation, it needs to
run continuously and adapt to the dynamic and interactive queries
from the network operation controller.
In addition, an ideal network telemetry solution may also have the
following features or properties:
* In-Network Customization: The data that is generated can be
customized in network at run-time to cater to the specific need of
applications. This needs the support of a programmable data plane
which allows probes with custom functions to be deployed at
flexible locations.
* In-Network Data Aggregation and Correlation: Network devices and
aggregation points can work out which events and what data needs
to be stored, reported, or discarded thus reducing the load on the
central collection and processing points while still ensuring that
the right information is ready to be processed in a timely way.
* In-Network Processing: Sometimes it is not necessary or feasible
to gather all information to a central point to be processed and
acted upon. It is possible for the data processing to be done in
network, allowing reactive actions to be taken locally.
* Direct Data Plane Export: The data originated from the data plane
forwarding chips can be directly exported to the data consumer for
efficiency, especially when the data bandwidth is large and the
real-time processing is required.
* In-band Data Collection: In addition to the passive and active
data collection approaches, the new hybrid approach allows to
directly collect data for any target flow on its entire forwarding
path [I-D.song-opsawg-ifit-framework].
It is worth noting that a network telemetry system should not be
intrusive to normal network operations by avoiding the pitfall of the
"observer effect". That is, it should not change the network
behavior and affect the forwarding performance. Moreover, high-
volume telemetry traffic may cause network congestion unless proper
Song, et al. Expires 6 June 2022 [Page 12]
Internet-Draft Network Telemetry Framework December 2021
isolation or traffic engineering techniques are in place, or
congestion control mechanisms ensure that telemetry traffic backs off
if it exceeds the network capacity. [RFC8084] and [RFC8085] are
relevant Best Current Practices (BCP) in this space.
Although in many cases a system for network telemetry involves a
remote data collecting and consuming entity, it is important to
understand that there are no inherent assumptions about how a system
should be architected. While a network architecture with centralized
controller (e.g., SDN) seems a natural fit for network telemetry,
network telemetry can work in distributed fashions as well. For
example, telemetry data producers and consumers can have a peer-to-
peer relationship, in which a network node can be the direct consumer
of telemetry data from other nodes.
2.5. The Necessity of a Network Telemetry Framework
Network data analytics (e.g., machine learning) is applied for
network operation automation, relying on abundant and coherent data
from networks. Data acquisition that is limited to a single source
and static in nature will in many cases not be sufficient to meet an
application's telemetry data needs. As a result, multiple data
sources, involving a variety of techniques and standards, will need
to be integrated. It is desirable to have a framework that
classifies and organizes different telemetry data source and types,
defines different components of a network telemetry system and their
interactions, and helps coordinate and integrate multiple telemetry
approaches across layers. This allows flexible combinations of data
for different applications, while normalizing and simplifying
interfaces. In detail, such a framework would benefit the
development of network operation applications for the following
reasons:
* Future networks, autonomous or otherwise, depend on holistic and
comprehensive network visibility. The use cases and applications
are better to be supported uniformly and coherently using an
integrated, converged mechanism and common telemetry data
representations wherever feasible. Therefore, the protocols and
mechanisms should be consolidated into a minimum yet comprehensive
set. A telemetry framework can help to normalize the technique
developments.
* Network visibility presents multiple viewpoints. For example, the
device viewpoint takes the network infrastructure as the
monitoring object from which the network topology and device
status can be acquired; the traffic viewpoint takes the flows or
packets as the monitoring object from which the traffic quality
and path can be acquired. An application may need to switch its
Song, et al. Expires 6 June 2022 [Page 13]
Internet-Draft Network Telemetry Framework December 2021
viewpoint during operation. It may also need to correlate a
service and its impact on user experience to acquire the
comprehensive information.
* Applications require network telemetry to be elastic in order to
make efficient use of network resources and reduce the impact of
processing related to network telemetry on network performance.
For example, routine network monitoring should cover the entire
network with a low data sampling rate. Only when issues arise or
critical trends emerge should telemetry data sources be modified
and telemetry data rates boosted as needed.
* Efficient data aggregation is critical for applications to reduce
the overall quantity of data and improve the accuracy of analysis.
A telemetry framework collects together all the telemetry-related
works from different sources and working groups within IETF. This
makes it possible to assemble a comprehensive network telemetry
system and to avoid repetitious or redundant work. The framework
should cover the concepts and components from the standardization
perspective. This document describes the modules which make up a
network telemetry framework and decomposes the telemetry system into
a set of distinct components that existing and future work can easily
map to.
3. Network Telemetry Framework
The top level network telemetry framework partitions the network
telemetry into four modules based on the telemetry data object source
and represents their relationship. Once the network operation
applications acquire the data from these modules, they can apply data
analytics and take actions. At the next level, the framework
decomposes each module into separate components. Each of the modules
follows the same underlying structure, with one component dedicated
to the configuration of data subscriptions and data sources, a second
component dedicated to encoding and exporting data, and a third
component instrumenting the generation of telemetry related to the
underlying resources. Throughout the framework, the same set of
abstract data acquiring mechanisms and data types (Section 3.3) are
applied. The two-level architecture with the uniform data
abstraction helps accurately pinpoint a protocol or technique to its
position in a network telemetry system or disaggregate a network
telemetry system into manageable parts.
Song, et al. Expires 6 June 2022 [Page 14]
Internet-Draft Network Telemetry Framework December 2021
3.1. Top Level Modules
Telemetry can be applied on the forwarding plane, the control plane,
and the management plane in a network, as well as other sources out
of the network, as shown in Figure 1. Therefore, we categorize the
network telemetry into four distinct modules (management plane,
control plane, forwarding plane, and external data and event
telemetry) with each having its own interface to Network Operation
Applications.
+------------------------------+
| |
| Network Operation |<-------+
| Applications | |
| | |
+------------------------------+ |
^ ^ ^ |
| | | |
V V | V
+--------------+-----------|---+ +-----------+
| | Control | | | |
| | Plane | | | External |
| <---> | | | Data and |
| | Telemetry | | | Event |
| Management | ^ V | | Telemetry |
| Plane +-------|-------+ | |
| Telemetry | V | +-----------+
| | Forwarding |
| | Plane |
| <---> |
| | Telemetry |
| | |
+--------------+---------------+
Figure 1: Modules in Layer Category of NTF
The rationale of this partition lies in the different telemetry data
objects which result in different data source and export locations.
Such differences have profound implications on in-network data
programming and processing capability, data encoding and transport
protocol, and required data bandwidth and latency. Data can be sent
directly, or proxied via the control and management planes. There
are advantages/disadvantages to both approaches.
Note that in some cases the network controller itself may be the
source of telemetry data that is unique to it or derived from the
telemetry data collected from the network elements. Some of the
principles and taxonomy specific to the control plane and management
Song, et al. Expires 6 June 2022 [Page 15]
Internet-Draft Network Telemetry Framework December 2021
plane telemetry could also be applied to the controller when it is
required to provide the telemetry data to Network Operation
Applications hosted outside. The scope of the document is focused on
the network elements telemetry and further details related to
controllers are thus out of scope.
We summarize the major differences of the four modules in the
following table. They are compared from six angles:
* Data Object
* Data Export Location
* Data Model
* Data Encoding
* Telemetry Application Protocol
* Data Transport Method
Data Object is the target and source of each module. Because the
data source varies, the location where data is mostly conveniently
exported also varies. For example, forwarding plane data mainly
originates as data exported from the forwarding Application-Specific
Integrated Circuits (ASICs), while control plane data mainly
originates from the protocol daemons running on the control CPU(s).
For convenience and efficiency, it is preferred to export the data
off the device from locations near the source. Because the locations
that can export data have different capabilities, different choices
of data model, encoding, and transport method are made to balance the
performance and cost. For example, the forwarding chip has high
throughput but limited capacity for processing complex data and
maintaining state, while the main control CPU is capable of complex
data and state processing, but has limited bandwidth for high
throughput data. As a result, the suitable telemetry protocol for
each module can be different. Some representative techniques are
shown in the corresponding table blocks to highlight the technical
diversity of these modules. Note that the selected techniques just
reflect the de facto state of the art and are by no means exhaustive
(e.g., IPFIX can also be implemented over TCP and SCTP, but that is
not recommended for forwarding plane). The key point is that one
cannot expect to use a universal protocol to cover all the network
telemetry requirements.
Song, et al. Expires 6 June 2022 [Page 16]
Internet-Draft Network Telemetry Framework December 2021
+-----------+-------------+-------------+--------------+----------+
| Module |Management |Control |Forwarding |External |
| |Plane |Plane |Plane |Data |
+-----------+-------------+-------------+--------------+----------+
|Object |config. & |control |flow & packet |terminal, |
| |operation |protocol & |QoS, traffic |social & |
| |state |signaling, |stat., buffer |environ- |
| | |RIB |& queue stat.,|mental |
| | | |ACL, FIB | |
+-----------+-------------+-------------+--------------+----------+
|Export |main control |main control |fwding chip |various |
|Location |CPU |CPU, |or linecard | |
| | |linecard CPU |CPU; main | |
| | |or forwarding|control CPU | |
| | |chip |unlikely | |
+-----------+-------------+-------------+--------------+----------+
|Data |YANG, MIB, |YANG, |YANG |YANG, |
|Model |syslog |custom |custom, |custom |
+-----------+-------------+-------------+--------------+----------+
|Data |GPB, JSON, |GPB, JSON, |plain text |GPB, JSON |
|Encoding |XML |XML, | |XML, plain|
| | |plain text | |text |
+-----------+-------------+-------------+--------------+----------+
|Application|gRPC,NETCONF,|gRPC,NETCONF,|IPFIX, traffic|gRPC |
|Protocol |RESTCONF |IPFIX,traffic|mirroring, | |
| | |mirroring |gRPC, NETFLOW | |
+-----------+-------------+-------------+--------------+----------+
|Data |HTTP(S), TCP |HTTP(S), TCP,|UDP |HTTP(S), |
|Transport | |UDP | |TCP, UDP |
+-----------+-------------+-------------+--------------+----------+
Figure 2: Comparison of the Data Object Modules
Note that the interaction with the applications that consume network
telemetry data can be indirect. Some in-device data transfer is
possible. For example, in the management plane telemetry, the
management plane will need to acquire data from the data plane. Some
operational states can only be derived from data plane data sources
such as the interface status and statistics. As another example,
obtaining control plane telemetry data may require the ability to
access the Forwarding Information Base (FIB) of the data plane.
On the other hand, an application may involve more than one plane and
interact with multiple planes simultaneously. For example, an SLA
compliance application may require both the data plane telemetry and
the control plane telemetry.
Song, et al. Expires 6 June 2022 [Page 17]
Internet-Draft Network Telemetry Framework December 2021
The requirements and challenges for each module are summarized as
follows (note that the requirements may pertain across all telemetry
modules; however, we emphasize those that are most pronounced for a
particular plane).
3.1.1. Management Plane Telemetry
The management plane of network elements interacts with the Network
Management System (NMS), and provides information such as performance
data, network logging data, network warning and defects data, and
network statistics and state data. The management plane includes
many protocols, including the classical SNMP and syslog. Regardless
the protocol, management plane telemetry must address the following
requirements:
* Convenient Data Subscription: An application should have the
freedom to choose which data is exported (see section 4.3) and the
means and frequency of how that data is exported (e.g., on-change
or periodic subscription).
* Structured Data: For automatic network operation, machines will
replace human for network data comprehension. Data modeling
languages, such as YANG, can efficiently describe structured data
and normalize data encoding and transformation.
* High Speed Data Transport: In order to keep up with the velocity
of information, a data source needs to be able to send large
amounts of data at high frequency. Compact encoding formats or
data compression schemes are needed to reduce the quantity of data
and improve the data transport efficiency. The subscription mode,
by replacing the query mode, reduces the interactions between
clients and servers and helps to improve the data source's
efficiency.
* Network Congestion Avoidance: The application must protect the
network from congestion by congestion control mechanisms or at
least circuit breakers. [RFC8084] and [RFC8085] provide some
solutions in this space.
3.1.2. Control Plane Telemetry
The control plane telemetry refers to the health condition monitoring
of different network control protocols at all layers of the protocol
stack. Keeping track of the operational status of these protocols is
beneficial for detecting, localizing, and even predicting various
network issues, as well as network optimization, in real-time and
with fine granularity. Some particular challenges and issues faced
by the control plane telemetry are as follows:
Song, et al. Expires 6 June 2022 [Page 18]
Internet-Draft Network Telemetry Framework December 2021
* One challenging problem for the control plane telemetry is how to
correlate the End-to-End (E2E) Key Performance Indicators (KPI) to
a specific layer's KPIs. For example, IPTV users may describe
their User Experience (UE) by the video smoothness and definition.
Then in case of an unusually poor UE KPI or a service
disconnection, it is non-trivial to delimit and pinpoint the issue
in the responsible protocol layer (e.g., the Transport Layer or
the Network Layer), the responsible protocol (e.g., ISIS or BGP at
the Network Layer), and finally the responsible device(s) with
specific reasons.
* Conventional OAM-based approaches for control plane KPI
measurement include Ping (L3), Traceroute (L3), Y.1731 [y1731]
(L2), and so on. One common issue behind these methods is that
they only measure the KPIs instead of reflecting the actual
running status of these protocols, making them less effective or
efficient for control plane troubleshooting and network
optimization.
* An example of the control plane telemetry is the BGP monitoring
protocol (BMP). It is currently used for monitoring the BGP
routes and enables rich applications, such as BGP peer analysis,
AS analysis, prefix analysis, and security analysis. However, the
monitoring of other layers, protocols and the cross-layer, cross-
protocol KPI correlations are still in their infancy (e.g., IGP
monitoring is not as extensive as BMP), which require further
research.
* The requirement and solutions for network congestion avoidance are
also applicable to the control plane telemetry.
3.1.3. Forwarding Plane Telemetry
An effective forwarding plane telemetry system relies on the data
that the network device can expose. The quality, quantity, and
timeliness of data must meet some stringent requirements. This
raises some challenges to the network data plane devices where the
first-hand data originates.
* A data plane device's main function is user traffic processing and
forwarding. While supporting network visibility is important, the
telemetry is just an auxiliary function, and it should strive to
not impede normal traffic processing and forwarding (i.e., the
forwarding behavior should not be altered and the trade-off
between forwarding performance and telemetry should be well-
balanced).
Song, et al. Expires 6 June 2022 [Page 19]
Internet-Draft Network Telemetry Framework December 2021
* Network operation applications require end-to-end visibility
across various sources, which can result in a huge volume of data.
However, the sheer quantity of data must not exhaust the network
bandwidth, regardless of the data delivery approach (i.e., whether
through in-band or out-of-band channels).
* The data plane devices must provide timely data with the minimum
possible delay. Long processing, transport, storage, and analysis
delay can impact the effectiveness of the control loop and even
render the data useless.
* The data should be structured and labeled, and easy for
applications to parse and consume. At the same time, the data
types needed by applications can vary significantly. The data
plane devices need to provide enough flexibility and
programmability to support the precise data provision for
applications.
* The data plane telemetry should support incremental deployment and
work even though some devices are unaware of the system.
* The requirement and solutions for network congestion avoidance are
also applicable to the forwarding plane telemetry.
Although not specific to the forwarding plane, these challenges are
more difficult to the forwarding plane because of the limited
resource and flexibility. Data plane programmability is essential to
support network telemetry. Newer data plane forwarding chips are
equipped with advanced telemetry features and provide flexibility to
support customized telemetry functions.
Technique Taxonomy: concerning about how one instruments the
telemetry, there can be multiple possible dimensions to classify the
forwarding plane telemetry techniques.
Song, et al. Expires 6 June 2022 [Page 20]
Internet-Draft Network Telemetry Framework December 2021
* Active, Passive, and Hybrid: This dimension concerns about the
end-to-end measurement. Active and passive methods (as well as
the hybrid types) are well documented in [RFC7799]. Passive
methods include TCPDUMP, IPFIX [RFC7011], sFlow, and traffic
mirroring. These methods usually have low data coverage. The
bandwidth cost is very high in order to improve the data coverage.
On the other hand, active methods include Ping, OWAMP [RFC4656],
TWAMP [RFC5357], STAMP [RFC8762], and Cisco's SLA Protocol
[RFC6812]. These methods are intrusive and only provide indirect
network measurements. Hybrid methods, including in-situ OAM
[I-D.ietf-ippm-ioam-data], Alternate-Marking (AM) [RFC8321], and
Multipoint Alternate Marking [RFC8889], provide a well-balanced
and more flexible approach. However, these methods are also more
complex to implement.
* In-Band and Out-of-Band: Telemetry data carried in user packets
before being exported to a data collector is considered in-band
(e.g., in-situ OAM [I-D.ietf-ippm-ioam-data]). Telemetry data
that is directly exported to a data collector without modifying
user packets is considered out-of-band (e.g., the postcard-based
approach described in Appendix A.3.5). It is also possible to
have hybrid methods, where only the telemetry instruction or
partial data is carried by user packets (e.g., AM [RFC8321]).
* End-to-End and In-Network: End-to-End methods start from, and end
at, the network end hosts (e.g., Ping). In-Network methods work
in networks and are transparent to end hosts. However, if needed,
In-Network methods can be easily extended into end hosts.
* Data Subject: Depending on the telemetry objective, the methods
can be flow-based (e.g., in-situ OAM [I-D.ietf-ippm-ioam-data]),
path-based (e.g., Traceroute), and node-based (e.g., IPFIX
[RFC7011]). The various data objects can be packet, flow record,
measurement, states, and signal.
3.1.4. External Data Telemetry
Events that occur outside the boundaries of the network system are
another important source of network telemetry. Correlating both
internal telemetry data and external events with the requirements of
network systems, as presented in
[I-D.pedro-nmrg-anticipated-adaptation], provides a strategic and
functional advantage to management operations.
Song, et al. Expires 6 June 2022 [Page 21]
Internet-Draft Network Telemetry Framework December 2021
As with other sources of telemetry information, the data and events
must meet strict requirements, especially in terms of timeliness,
which is essential to properly incorporate external event information
into network management applications. The specific challenges are
described as follows:
* The role of the external event detector can be played by multiple
elements, including hardware (e.g., physical sensors, such as
seismometers) and software (e.g., Big Data sources that can
analyze streams of information, such as Twitter messages). Thus,
the transmitted data must support different shapes but, at the
same time, follow a common but extensible schema.
* Since the main function of the external event detectors is to
perform the notifications, their timeliness is assumed. However,
once messages have been dispatched, they must be quickly collected
and inserted into the control plane with variable priority, which
is higher for important sources and events and lower for secondary
ones.
* The schema used by external detectors must be easily adopted by
current and future devices and applications. Therefore, it must
be easily mapped to current data models, such as in terms of YANG.
* As the communication with external entities outside the boundary
of a provider network may be realized over the Internet, the risk
of congestion is even more relevant in this context and proper
counter-measures must be taken. Solutions such as network
transport circuit breakers are needed as well.
Organizing both internal and external telemetry information together
will be key for the general exploitation of the management
possibilities of current and future network systems, as reflected in
the incorporation of cognitive capabilities to new hardware and
software (virtual) elements.
3.2. Second Level Function Components
The telemetry module at each plane can be further partitioned into
five distinct conceptual components:
* Data Query, Analysis, and Storage: This component works at the
network operation application block in Figure 1. It is normally a
part of the network management system at the receiver side. On
the one hand, it is responsible for issuing data requirements.
The data of interest can be modeled data through configuration or
custom data through programming. The data requirements can be
queries for one-shot data or subscriptions for events or streaming
Song, et al. Expires 6 June 2022 [Page 22]
Internet-Draft Network Telemetry Framework December 2021
data. On the other hand, it receives, stores, and processes the
returned data from network devices. Data analysis can be
interactive to initiate further data queries. This component can
reside in either network devices or remote controllers. It can be
centralized and distributed, and involve one or more instances.
* Data Configuration and Subscription: This component manages data
queries on devices. It determines the protocol and channel for
applications to acquire desired data. This component is also
responsible for configuring the desired data that might not be
directly available from data sources. The subscription data can
be described by models, templates, or programs.
* Data Encoding and Export: This component determines how telemetry
data is delivered to the data analysis and storage component with
access control. The data encoding and the transport protocol may
vary due to the data export location.
* Data Generation and Processing: The requested data needs to be
captured, filtered, processed, and formatted in network devices
from raw data sources. This may involve in-network computing and
processing on either the fast path or the slow path in network
devices.
* Data Object and Source: This component determines the monitoring
objects and original data sources provisioned in the device. A
data source usually just provides raw data which needs further
processing. Each data source can be considered a probe. Some
data sources can be dynamically installed, while others will be
more static.
Song, et al. Expires 6 June 2022 [Page 23]
Internet-Draft Network Telemetry Framework December 2021
+----------------------------------------+
+----------------------------------------+ |
| | |
| Data Query, Analysis, & Storage | |
| | +
+-------+++ -----------------------------+
||| ^^^
||| |||
||V |||
+--+V--------------------+++------------+
+-----V---------------------+------------+ |
+---------------------+-------+----------+ | |
| Data Configuration | | | |
| & Subscription | Data Encoding | | |
| (model, template, | & Export | | |
| & program) | | | |
+---------------------+------------------| | |
| | | |
| Data Generation | | |
| & Processing | | |
| | | |
+----------------------------------------| | |
| | | |
| Data Object and Source | |-+
| |-+
+----------------------------------------+
Figure 3: Components in the Network Telemetry Framework
3.3. Data Acquisition Mechanism and Type Abstraction
Broadly speaking, network data can be acquired through subscription
(push) and query (poll). A subscription is a contract between
publisher and subscriber. After initial setup, the subscribed data
is automatically delivered to registered subscribers until the
subscription expires. There are two variations of subscription. The
subscriptions can be either pre-defined, or the subscribers are
allowed to configure and tailor the published data to their specific
needs.
In contrast, queries are used when a client expects immediate and
one-off feedback from network devices. The queried data may be
directly extracted from some specific data source, or synthesized and
processed from raw data. Queries work well for interactive network
telemetry applications.
Song, et al. Expires 6 June 2022 [Page 24]
Internet-Draft Network Telemetry Framework December 2021
In general, data can be pulled (i.e., queried) whenever needed, but
in many cases, pushing the data (i.e., subscription) is more
efficient, and can reduce the latency of a client detecting a change.
From the data consumer point of view, there are four types of data
from network devices that a telemetry data consumer can subscribe or
query:
* Simple Data: The data that are steadily available from some
datastore or static probes in network devices.
* Derived Data: The data need to be synthesized or processed in
network from raw data from one or more network devices. The data
processing function can be statically or dynamically loaded into
network devices.
* Event-triggered Data: The data are conditionally acquired based on
the occurrence of some events. An example of event-triggered data
could be an interface changing operational state between up and
down. Such data can be actively pushed through subscription or
passively polled through query. There are many ways to model
events, including using Finite State Machine (FSM) or Event
Condition Action (ECA) [I-D.wwx-netmod-event-yang].
* Streaming Data: The data are continuously generated. It can be
time series or the dump of databases. For example, an interface
packet counter is exported every second. The streaming data
reflect realtime network states and metrics and require large
bandwidth and processing power. The streaming data are always
actively pushed to the subscribers.
The above telemetry data types are not mutually exclusive. Rather,
they are often composite. Derived data is composed of simple data;
Event-triggered data can be simple or derived; streaming data can be
based on some recurring event. The relationships of these data types
are illustrated in Figure 4.
Song, et al. Expires 6 June 2022 [Page 25]
Internet-Draft Network Telemetry Framework December 2021
+----------------------+ +-----------------+
| Event-triggered Data |<----+ Streaming Data |
+-------+---+----------+ +-----+---+-------+
| | | |
| | | |
| | +--------------+ | |
| +-->| Derived Data |<--+ |
| +------+------ + |
| | |
| V |
| +--------------+ |
+------>| Simple Data |<------+
+--------------+
Figure 4: Data Type Relationship
Subscription usually deals with event-triggered data and streaming
data, and query usually deals with simple data and derived data. But
the other ways are also possible. Advanced network telemetry
techniques are designed mainly for event-triggered or streaming data
subscription, and derived data query.
3.4. Mapping Existing Mechanisms into the Framework
The following table shows how the existing mechanisms (mainly
published in IETF and with the emphasis on the latest new
technologies) are positioned in the framework. Given the vast body
of existing work, we cannot provide an exhaustive list, so the
mechanisms in the tables should be considered as just examples.
Also, some comprehensive protocols and techniques may cover multiple
aspects or modules of the framework, so a name in a block only
emphasizes one particular characteristic of it. More details about
some listed mechanisms can be found in Appendix A.
+-------------+-----------------+---------------+--------------+
| | Management | Control | Forwarding |
| | Plane | Plane | Plane |
+-------------+-----------------+---------------+--------------+
| data config.| gNMI, NETCONF, | gNMI, NETCONF,| NETCONF, |
| & subscribe | RESTCONF, SNMP, | RESTCONF, | RESTCONF, |
| | YANG-Push | YANG-Push | YANG-Push |
+-------------+-----------------+---------------+--------------+
| data gen. & | MIB, | YANG | IOAM, PSAMP |
| process | YANG | | PBT, AM, |
+-------------+-----------------+---------------+--------------+
| data encode.| gRPC, HTTP, TCP | BMP, TCP | IPFIX, UDP |
| & export | | | |
+-------------+-----------------+---------------+--------------+
Song, et al. Expires 6 June 2022 [Page 26]
Internet-Draft Network Telemetry Framework December 2021
Figure 5: Existing Work Mapping
Although the framework is generally suitable for any network
environments, the multi-domain telemetry has some unique challenges
which deserve further architectural consideration, which is out of
the scope of this document.
4. Evolution of Network Telemetry Applications
Network telemetry is an evolving technical area. As the network
moves towards the automated operation, network telemetry applications
undergo several stages of evolution which add new layer of
requirements to the underlying network telemetry techniques. Each
stage is built upon the techniques adopted by the previous stages
plus some new requirements.
Stage 0 - Static Telemetry: The telemetry data source and type are
determined at design time. The network operator can only
configure how to use it with limited flexibility.
Stage 1 - Dynamic Telemetry: The custom telemetry data can be
dynamically programmed or configured at runtime without
interrupting the network operation, allowing a trade-off among
resource, performance, flexibility, and coverage.
Stage 2 - Interactive Telemetry: The network operator can
continuously customize and fine tune the telemetry data in real
time to reflect the network operation's visibility requirements.
Compared with Stage 1, the changes are frequent based on the real-
time feedback. At this stage, some tasks can be automated, but
human operators still need to sit in the middle to make decisions.
Stage 3 - Closed-loop Telemetry: The telemetry is free from the
interference of human operators, except for generating the
reports. The intelligent network operation engine automatically
issues the telemetry data requests, analyzes the data, and updates
the network operations in closed control loops.
Existing technologies are ready for stage 0 and stage 1. Individual
stage 2 and stage 3 applications are also possible now. However, the
future autonomic networks may need a comprehensive operation
management system which works at stage 2 and stage 3 to cover all the
network operation tasks. A well-defined network telemetry framework
is the first step towards this direction.
Song, et al. Expires 6 June 2022 [Page 27]
Internet-Draft Network Telemetry Framework December 2021
5. Security Considerations
The complexity of network telemetry raises significant security
implications. For example, telemetry data can be manipulated to
exhaust various network resources at each plane as well as the data
consumer; falsified or tampered data can mislead the decision-making
and paralyze networks; wrong configuration and programming for
telemetry is equally harmful. The telemetry data is highly
sensitive, which exposes a lot of information about the network and
its configuration. Some of that information can make designing
attacks against the network much easier (e.g., exact details of what
software and patches have been installed), and allows an attacker to
determine whether a device may be subject to unprotected security
vulnerabilities.
Given that this document has proposed a framework for network
telemetry and the telemetry mechanisms discussed are more extensive
(in both message frequency and traffic amount) than the conventional
network OAM concepts, we must also reflect that various new security
considerations may also arise. A number of techniques already exist
for securing the forwarding plane, the control plane, and the
management plane in a network, but it is important to consider if any
new threat vectors are now being enabled via the use of network
telemetry procedures and mechanisms.
This document proposes a conceptual architectural for collecting,
transporting, and analyzing a wide variety of data sources in support
of network applications. The protocols, data formats, and
configurations chosen to implement this framework will dictate the
specific security considerations. These considerations may include:
* Telemetry framework trust and policy model;
* Role management and access control for enabling and disabling
telemetry capabilities;
* Protocol transport used for telemetry data and its inherent
security capabilities;
* Telemetry data stores, storage encryption, methods of access, and
retention practices;
* Tracking telemetry events and any abnormalities that might
identify malicious attacks using telemetry interfaces.
* Authentication and integrity protection of telemetry data to make
data more trustworthy.
Song, et al. Expires 6 June 2022 [Page 28]
Internet-Draft Network Telemetry Framework December 2021
* Segregating the telemetry data traffic from the data traffic
carried over the network (e.g., historically management access and
management data may be carried via an independent management
network).
Some security considerations highlighted above may be minimized or
negated with policy management of network telemetry. In a network
telemetry deployment it would be advantageous to separate telemetry
capabilities into different classes of policies, i.e., Role Based
Access Control and Event-Condition-Action policies. Also, potential
conflicts between network telemetry mechanisms must be detected
accurately and resolved quickly to avoid unnecessary network
telemetry traffic propagation escalating into an unintended or
intended denial of service attack.
Further study of the security issues will be required, and it is
expected that the security mechanisms and protocols are developed and
deployed along with a network telemetry system.
6. IANA Considerations
This document includes no request to IANA.
7. Contributors
The other contributors of this document are Tianran Zhou, Zhenbin Li,
Zhenqiang Li, Daniel King, Adrian Farrel, and Alexander Clemm
8. Acknowledgments
We would like to thank Rob Wilton, Greg Mirsky, Randy Presuhn, Joe
Clarke, Victor Liu, James Guichard, Uri Blumenthal, Giuseppe
Fioccola, Yunan Gu, Parviz Yegani, Young Lee, Qin Wu, Gyan Mishra,
Ben Schwartz, Alexey Melnikov, Michael Scharf, Dhruv Dhody, Martin
Duke, Roman Danyliw, Warren Kumari, Sheng Jiang, Lars Eggert, Eric
Vyncke, Jean-Michel Combes, Erik Kline, Benjamin Kaduk, and many
others who have provided helpful comments and suggestions to improve
this document.
9. Informative References
[gnmi] "gNMI - gRPC Network Management Interface",
<https://github.com/openconfig/reference/tree/master/rpc/
gnmi>.
[gpb] "Google Protocol Buffers",
<https://developers.google.com/protocol-buffers>.
Song, et al. Expires 6 June 2022 [Page 29]
Internet-Draft Network Telemetry Framework December 2021
[grpc] "gPPC, A high performance, open-source universal RPC
framework", <https://grpc.io>.
[I-D.ietf-grow-bmp-local-rib]
Evens, T., Bayraktar, S., Bhardwaj, M., and P. Lucente,
"Support for Local RIB in BGP Monitoring Protocol (BMP)",
Work in Progress, Internet-Draft, draft-ietf-grow-bmp-
local-rib-13, 31 August 2021,
<https://www.ietf.org/archive/id/draft-ietf-grow-bmp-
local-rib-13.txt>.
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
for In-situ OAM", Work in Progress, Internet-Draft, draft-
ietf-ippm-ioam-data-16, 8 November 2021,
<https://www.ietf.org/archive/id/draft-ietf-ippm-ioam-
data-16.txt>.
[I-D.ietf-ippm-ioam-direct-export]
Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
OAM Direct Exporting", Work in Progress, Internet-Draft,
draft-ietf-ippm-ioam-direct-export-07, 13 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-ippm-ioam-
direct-export-07.txt>.
[I-D.ietf-netconf-distributed-notif]
Zhou, T., Zheng, G., Voit, E., Graf, T., and P. Francois,
"Subscription to Distributed Notifications", Work in
Progress, Internet-Draft, draft-ietf-netconf-distributed-
notif-02, 6 May 2021, <https://www.ietf.org/archive/id/
draft-ietf-netconf-distributed-notif-02.txt>.
[I-D.ietf-netconf-udp-notif]
Zheng, G., Zhou, T., Graf, T., Francois, P., Feng, A. H.,
and P. Lucente, "UDP-based Transport for Configured
Subscriptions", Work in Progress, Internet-Draft, draft-
ietf-netconf-udp-notif-04, 21 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-netconf-udp-
notif-04.txt>.
[I-D.irtf-nmrg-ibn-concepts-definitions]
Clemm, A., Ciavaglia, L., Granville, L. Z., and J.
Tantsura, "Intent-Based Networking - Concepts and
Definitions", Work in Progress, Internet-Draft, draft-
irtf-nmrg-ibn-concepts-definitions-05, 2 September 2021,
<https://www.ietf.org/archive/id/draft-irtf-nmrg-ibn-
concepts-definitions-05.txt>.
Song, et al. Expires 6 June 2022 [Page 30]
Internet-Draft Network Telemetry Framework December 2021
[I-D.pedro-nmrg-anticipated-adaptation]
Martinez-Julia, P., "Exploiting External Event Detectors
to Anticipate Resource Requirements for the Elastic
Adaptation of SDN/NFV Systems", Work in Progress,
Internet-Draft, draft-pedro-nmrg-anticipated-adaptation-
02, 29 June 2018, <https://www.ietf.org/archive/id/draft-
pedro-nmrg-anticipated-adaptation-02.txt>.
[I-D.song-ippm-postcard-based-telemetry]
Song, H., Mirsky, G., Filsfils, C., Abdelsalam, A., Zhou,
T., Li, Z., Shin, J., and K. Lee, "In-Situ OAM Marking-
based Direct Export", Work in Progress, Internet-Draft,
draft-song-ippm-postcard-based-telemetry-11, 15 November
2021, <https://www.ietf.org/archive/id/draft-song-ippm-
postcard-based-telemetry-11.txt>.
[I-D.song-opsawg-dnp4iq]
Song, H. and J. Gong, "Requirements for Interactive Query
with Dynamic Network Probes", Work in Progress, Internet-
Draft, draft-song-opsawg-dnp4iq-01, 19 June 2017,
<https://www.ietf.org/archive/id/draft-song-opsawg-dnp4iq-
01.txt>.
[I-D.song-opsawg-ifit-framework]
Song, H., Qin, F., Chen, H., Jin, J., and J. Shin, "In-
situ Flow Information Telemetry", Work in Progress,
Internet-Draft, draft-song-opsawg-ifit-framework-16, 21
October 2021, <https://www.ietf.org/archive/id/draft-song-
opsawg-ifit-framework-16.txt>.
[I-D.wwx-netmod-event-yang]
Wu, Q., Bryskin, I., Birkholz, H., Liu, X., and B. Claise,
"A YANG Data model for ECA Policy Management", Work in
Progress, Internet-Draft, draft-wwx-netmod-event-yang-10,
1 November 2020, <https://www.ietf.org/archive/id/draft-
wwx-netmod-event-yang-10.txt>.
[RFC1157] Case, J., Fedor, M., Schoffstall, M., and J. Davin,
"Simple Network Management Protocol (SNMP)", RFC 1157,
DOI 10.17487/RFC1157, May 1990,
<https://www.rfc-editor.org/info/rfc1157>.
[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information
Version 2 (SMIv2)", STD 58, RFC 2578,
DOI 10.17487/RFC2578, April 1999,
<https://www.rfc-editor.org/info/rfc2578>.
Song, et al. Expires 6 June 2022 [Page 31]
Internet-Draft Network Telemetry Framework December 2021
[RFC2981] Kavasseri, R., Ed., "Event MIB", RFC 2981,
DOI 10.17487/RFC2981, October 2000,
<https://www.rfc-editor.org/info/rfc2981>.
[RFC3176] Phaal, P., Panchen, S., and N. McKee, "InMon Corporation's
sFlow: A Method for Monitoring Traffic in Switched and
Routed Networks", RFC 3176, DOI 10.17487/RFC3176,
September 2001, <https://www.rfc-editor.org/info/rfc3176>.
[RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
DOI 10.17487/RFC3411, December 2002,
<https://www.rfc-editor.org/info/rfc3411>.
[RFC3416] Presuhn, R., Ed., "Version 2 of the Protocol Operations
for the Simple Network Management Protocol (SNMP)",
STD 62, RFC 3416, DOI 10.17487/RFC3416, December 2002,
<https://www.rfc-editor.org/info/rfc3416>.
[RFC3877] Chisholm, S. and D. Romascanu, "Alarm Management
Information Base (MIB)", RFC 3877, DOI 10.17487/RFC3877,
September 2004, <https://www.rfc-editor.org/info/rfc3877>.
[RFC3954] Claise, B., Ed., "Cisco Systems NetFlow Services Export
Version 9", RFC 3954, DOI 10.17487/RFC3954, October 2004,
<https://www.rfc-editor.org/info/rfc3954>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<https://www.rfc-editor.org/info/rfc4656>.
[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
Circuit Connectivity Verification (VCCV): A Control
Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
December 2007, <https://www.rfc-editor.org/info/rfc5085>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<https://www.rfc-editor.org/info/rfc5357>.
[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424,
DOI 10.17487/RFC5424, March 2009,
<https://www.rfc-editor.org/info/rfc5424>.
Song, et al. Expires 6 June 2022 [Page 32]
Internet-Draft Network Telemetry Framework December 2021
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6812] Chiba, M., Clemm, A., Medley, S., Salowey, J., Thombare,
S., and E. Yedavalli, "Cisco Service-Level Assurance
Protocol", RFC 6812, DOI 10.17487/RFC6812, January 2013,
<https://www.rfc-editor.org/info/rfc6812>.
[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,
<https://www.rfc-editor.org/info/rfc7011>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>.
[RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
Weingarten, "An Overview of Operations, Administration,
and Maintenance (OAM) Tools", RFC 7276,
DOI 10.17487/RFC7276, June 2014,
<https://www.rfc-editor.org/info/rfc7276>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>.
[RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking: Definitions and Design Goals", RFC 7575,
DOI 10.17487/RFC7575, June 2015,
<https://www.rfc-editor.org/info/rfc7575>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
Song, et al. Expires 6 June 2022 [Page 33]
Internet-Draft Network Telemetry Framework December 2021
[RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
Monitoring Protocol (BMP)", RFC 7854,
DOI 10.17487/RFC7854, June 2016,
<https://www.rfc-editor.org/info/rfc7854>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8084] Fairhurst, G., "Network Transport Circuit Breakers",
BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017,
<https://www.rfc-editor.org/info/rfc8084>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate-Marking Method for Passive and Hybrid
Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
January 2018, <https://www.rfc-editor.org/info/rfc8321>.
[RFC8639] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
E., and A. Tripathy, "Subscription to YANG Notifications",
RFC 8639, DOI 10.17487/RFC8639, September 2019,
<https://www.rfc-editor.org/info/rfc8639>.
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
September 2019, <https://www.rfc-editor.org/info/rfc8641>.
[RFC8671] Evens, T., Bayraktar, S., Lucente, P., Mi, P., and S.
Zhuang, "Support for Adj-RIB-Out in the BGP Monitoring
Protocol (BMP)", RFC 8671, DOI 10.17487/RFC8671, November
2019, <https://www.rfc-editor.org/info/rfc8671>.
Song, et al. Expires 6 June 2022 [Page 34]
Internet-Draft Network Telemetry Framework December 2021
[RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
Two-Way Active Measurement Protocol", RFC 8762,
DOI 10.17487/RFC8762, March 2020,
<https://www.rfc-editor.org/info/rfc8762>.
[RFC8889] Fioccola, G., Ed., Cociglio, M., Sapio, A., and R. Sisto,
"Multipoint Alternate-Marking Method for Passive and
Hybrid Performance Monitoring", RFC 8889,
DOI 10.17487/RFC8889, August 2020,
<https://www.rfc-editor.org/info/rfc8889>.
[RFC8924] Aldrin, S., Pignataro, C., Ed., Kumar, N., Ed., Krishnan,
R., and A. Ghanwani, "Service Function Chaining (SFC)
Operations, Administration, and Maintenance (OAM)
Framework", RFC 8924, DOI 10.17487/RFC8924, October 2020,
<https://www.rfc-editor.org/info/rfc8924>.
[xml] "Extensible Markup Language (XML) 1.0 (Fifth Edition)",
<https://www.w3.org/TR/2008/REC-xml-20081126/>.
[y1731] "ITU-T Y.1731: OAM Functions and Mechanisms for Ethernet
based networks, 2015",
<https://www.itu.int/rec/T-REC-Y.1731/en>.
Appendix A. A Survey on Existing Network Telemetry Techniques
In this non-normative appendix, we provide an overview of some
existing techniques and standard proposals for each network telemetry
module.
A.1. Management Plane Telemetry
A.1.1. Push Extensions for NETCONF
NETCONF [RFC6241] is a popular network management protocol
recommended by IETF. Its core strength is for managing
configuration, but can also be used for data collection. YANG-Push
[RFC8641] [RFC8639] extends NETCONF and enables subscriber
applications to request a continuous, customized stream of updates
from a YANG datastore. Providing such visibility into changes made
upon YANG configuration and operational objects enables new
capabilities based on the remote mirroring of configuration and
operational state. Moreover, distributed data collection mechanism
[I-D.ietf-netconf-distributed-notif] via UDP based publication
channel [I-D.ietf-netconf-udp-notif] provides enhanced efficiency for
the NETCONF based telemetry.
Song, et al. Expires 6 June 2022 [Page 35]
Internet-Draft Network Telemetry Framework December 2021
A.1.2. gRPC Network Management Interface
gRPC Network Management Interface (gNMI) [gnmi] is a network
management protocol based on the gRPC [grpc] RPC (Remote Procedure
Call) framework. With a single gRPC service definition, both
configuration and telemetry can be covered. gRPC is an HTTP/2
[RFC7540]-based open-source micro-service communication framework.
It provides a number of capabilities which are well-suited for
network telemetry, including:
* Full-duplex streaming transport model combined with a binary
encoding mechanism provides good telemetry efficiency.
* gRPC provides higher-level features consistency across platforms
that common HTTP/2 libraries typically do not. This
characteristic is especially valuable for the fact that telemetry
data collectors normally reside on a large variety of platforms.
* The built-in load-balancing and failover mechanism.
A.2. Control Plane Telemetry
A.2.1. BGP Monitoring Protocol
BGP Monitoring Protocol (BMP) [RFC7854] is used to monitor BGP
sessions and is intended to provide a convenient interface for
obtaining route views.
The BGP routing information is collected from the monitored device(s)
to the BMP monitoring station by setting up the BMP TCP session. The
BGP peers are monitored by the BMP Peer Up and Peer Down
Notifications. The BGP routes (including Adjacency_RIB_In [RFC7854],
Adjacency_RIB_out [RFC8671], and Local_Rib
[I-D.ietf-grow-bmp-local-rib]) are encapsulated in the BMP Route
Monitoring Message and the BMP Route Mirroring Message, providing
both an initial table dump and real-time route updates. In addition,
BGP statistics are reported through the BMP Stats Report Message,
which could be either timer triggered or event-driven. Future BMP
extensions could further enrich BGP monitoring applications.
A.3. Data Plane Telemetry
A.3.1. The Alternate Marking (AM) technology
The Alternate Marking method enables efficient measurements of packet
loss, delay, and jitter both in IP and Overlay Networks, as presented
in [RFC8321] and [RFC8889].
Song, et al. Expires 6 June 2022 [Page 36]
Internet-Draft Network Telemetry Framework December 2021
This technique can be applied to point-to-point and multipoint-to-
multipoint flows. Alternate Marking creates batches of packets by
alternating the value of 1 bit (or a label) of the packet header.
These batches of packets are unambiguously recognized over the
network and the comparison of packet counters for each batch allows
the packet loss calculation. The same idea can be applied to delay
measurement by selecting ad hoc packets with a marking bit dedicated
for delay measurements.
Alternate Marking method needs two counters each marking period for
each flow under monitor. For instance, by considering n measurement
points and m monitored flows, the order of magnitude of the packet
counters for each time interval is n*m*2 (1 per color).
Since networks offer rich sets of network performance measurement
data (e.g., packet counters), conventional approaches run into
limitations. The bottleneck is the generation and export of the data
and the amount of data that can be reasonably collected from the
network. In addition, management tasks related to determining and
configuring which data to generate lead to significant deployment
challenges.
The Multipoint Alternate Marking approach, described in [RFC8889],
aims to resolve this issue and make the performance monitoring more
flexible in case a detailed analysis is not needed.
An application orchestrates network performance measurements tasks
across the network to allow for optimized monitoring. The
application can choose how roughly or precisely to configure
measurement points depending on the application's requirements.
Using Alternate Marking, it is possible to monitor a Multipoint
Network without in depth examination by using the Network Clustering
(subnetworks that are portions of the entire network that preserve
the same property of the entire network, called clusters). So in the
case that there is packet loss or the delay is too high then the
specific filtering criteria could be applied to gather a more
detailed analysis by using a different combination of clusters up to
a per-flow measurement as described in Alternate-Marking (AM)
[RFC8321].
In summary, an application can configure end-to-end network
monitoring. If the network does not experience issues, this
approximate monitoring is good enough and is very cheap in terms of
network resources. However, in case of problems, the application
becomes aware of the issues from this approximate monitoring and, in
order to localize the portion of the network that has issues,
configures the measurement points more extensively, allowing more
Song, et al. Expires 6 June 2022 [Page 37]
Internet-Draft Network Telemetry Framework December 2021
detailed monitoring to be performed. After the detection and
resolution of the problem, the initial approximate monitoring can be
used again.
A.3.2. Dynamic Network Probe
Hardware-based Dynamic Network Probe (DNP) [I-D.song-opsawg-dnp4iq]
proposes a programmable means to customize the data that an
application collects from the data plane. A direct benefit of DNP is
the reduction of the exported data. A full DNP solution covers
several components including data source, data subscription, and data
generation. The data subscription needs to define the derived data
which can be composed and derived from the raw data sources. The
data generation takes advantage of the moderate in-network computing
to produce the desired data.
While DNP can introduce unforeseeable flexibility to the data plane
telemetry, it also faces some challenges. It requires a flexible
data plane that can be dynamically reprogrammed at run-time. The
programming API is yet to be defined.
A.3.3. IP Flow Information Export (IPFIX) Protocol
Traffic on a network can be seen as a set of flows passing through
network elements. IP Flow Information Export (IPFIX) [RFC7011]
provides a means of transmitting traffic flow information for
administrative or other purposes. A typical IPFIX enabled system
includes a pool of Metering Processes that collects data packets at
one or more Observation Points, optionally filters them and
aggregates information about these packets. An Exporter then gathers
each of the Observation Points together into an Observation Domain
and sends this information via the IPFIX protocol to a Collector.
A.3.4. In-Situ OAM
Classical passive and active monitoring and measurement techniques
are either inaccurate or resource-consuming. It is preferable to
directly acquire data associated with a flow's packets when the
packets pass through a network. In-situ OAM (iOAM)
[I-D.ietf-ippm-ioam-data], a data generation technique, embeds a new
instruction header to user packets and the instruction directs the
network nodes to add the requested data to the packets. Thus, at the
path end, the packet's experience gained on the entire forwarding
path can be collected. Such firsthand data is invaluable to many
network OAM applications.
Song, et al. Expires 6 June 2022 [Page 38]
Internet-Draft Network Telemetry Framework December 2021
However, iOAM also faces some challenges. The issues on performance
impact, security, scalability and overhead limits, encapsulation
difficulties in some protocols, and cross-domain deployment need to
be addressed.
A.3.5. Postcard Based Telemetry
The postcard-based telemetry, as embodied in IOAM DEX
[I-D.ietf-ippm-ioam-direct-export] and IOAM Marking
[I-D.song-ippm-postcard-based-telemetry], is a complementary
technique to the passport-based IOAM. PBT directly exports data at
each node through an independent packet. At the cost of higher
bandwidth overhead and the need for data correlation, PBT shows
several unique advantages. It can also help to identify packet drop
location in case a packet is dropped on its forwarding path.
A.3.6. Existing OAM for Specific Data Planes
Various data planes raise unique OAM requirements. IETF has
published OAM technique and framework documents (e.g., [RFC8924] and
[RFC5085]) targeting different data planes such as Multi-Protocol
Label Switching (MPLS), L2 Virtual Private Network (L2-VPN), Network
Virtualization Overlays (NVO3), Virtual Extensible LAN (VXLAN), Bit
Indexed Explicit Replication (BIER), Service Function Chaining (SFC),
Segment Routing (SR), and Deterministic Networking (DETNET). The
aforementioned data plane telemetry techniques can be used to enhance
the OAM capability on such data planes.
A.4. External Data and Event Telemetry
A.4.1. Sources of External Events
To ensure that the information provided by external event detectors
and used by the network management solutions is meaningful for
management purposes, the network telemetry framework must ensure that
such detectors (sources) are easily connected to the management
solutions (sinks). This requires the specification of a list of
potential external data sources that could be of interest in network
management and match it to the connectors and/or interfaces required
to connect them.
Categories of external event sources that may be of interest to
network management include::
* Smart objects and sensors. With the consolidation of the Internet
of Things~(IoT) any network system will have many smart objects
attached to its physical surroundings and logical operation
environments. Most of these objects will be essentially based on
Song, et al. Expires 6 June 2022 [Page 39]
Internet-Draft Network Telemetry Framework December 2021
sensors of many kinds (e.g., temperature, humidity, presence) and
the information they provide can be very useful for the management
of the network, even when they are not specifically deployed for
such purpose. Elements of this source type will usually provide a
specific protocol for interaction, especially one of those
protocols related to IoT, such as the Constrained Application
Protocol (CoAP).
* Online news reporters. Several online news services have the
ability to provide enormous quantity of information about
different events occurring in the world. Some of those events can
impact on the network system managed by a specific framework and,
therefore, such information may be of interest to the management
solution. For instance, diverse security reports, such as the
Common Vulnerabilities and Exposures (CVE), can be issued by the
corresponding authority and used by the management solution to
update the managed system if needed. Instead of a specific
protocol and data format, the sources of this kind of information
usually follow a relaxed but structured format. This format will
be part of both the ontology and information model of the
telemetry framework.
* Global event analyzers. The advance of Big Data analyzers
provides a huge amount of information and, more interestingly, the
identification of events detected by analyzing many data streams
from different origins. In contrast with the other types of
sources, which are focused on specific events, the detectors of
this source type will detect generic events. For example, during
a sport event some unexpected movement makes it fascinating and
many people connect to sites that are reporting on the event. The
underlying networks supporting the services that cover the event
can be affected by such situation, so their management solutions
should be aware of it. In contrast with the other source types, a
new information model, format, and reporting protocol is required
to integrate the detectors of this type with the management
solution.
Additional types of detector types can be added to the system, but
they will be generally the result of composing the properties offered
by these main classes.
Song, et al. Expires 6 June 2022 [Page 40]
Internet-Draft Network Telemetry Framework December 2021
A.4.2. Connectors and Interfaces
For allowing external event detectors to be properly integrated with
other management solutions, both elements must expose interfaces and
protocols that are subject to their particular objective. Since
external event detectors will be focused on providing their
information to their main consumers, which generally will not be
limited to the network management solutions, the framework must
include the definition of the required connectors for ensuring the
interconnection between detectors (sources) and their consumers
within the management systems (sinks) are effective.
In some situations, the interconnection between the external event
detectors and the management system is via the management plane. For
those situations there will be a special connector that provides the
typical interfaces found in most other elements connected to the
management plane. For instance, the interfaces could accomplish this
with a specific data model (YANG) and specific telemetry protocol,
such as NETCONF, YANG-Push, or gRPC.
Authors' Addresses
Haoyu Song
Futurewei
United States of America
Email: haoyu.song@futurewei.com
Fengwei Qin
China Mobile
P.R. China
Email: qinfengwei@chinamobile.com
Pedro Martinez-Julia
NICT
Japan
Email: pedro@nict.go.jp
Laurent Ciavaglia
Rakuten Mobile
France
Email: laurent.ciavaglia@rakuten.com
Song, et al. Expires 6 June 2022 [Page 41]
Internet-Draft Network Telemetry Framework December 2021
Aijun Wang
China Telecom
P.R. China
Email: wangaj.bri@chinatelecom.cn
Song, et al. Expires 6 June 2022 [Page 42]