UDP based Publication Channel for Streaming Telemetry
draft-ietf-netconf-udp-pub-channel-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|
|---|---|---|---|
| Authors | Guangying Zheng , Tianran Zhou , Alexander Clemm | ||
| Last updated | 2017-11-13 | ||
| Replaces | draft-zheng-netconf-udp-pub-channel | ||
| Replaced by | draft-unyte-netconf-udp-notif, draft-unyte-netconf-udp-pub-channel | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Additional resources | Mailing list discussion | ||
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draft-ietf-netconf-udp-pub-channel-01
NETCONF G. Zheng
Internet-Draft T. Zhou
Intended status: Standards Track A. Clemm
Expires: May 15, 2018 Huawei
November 11, 2017
UDP based Publication Channel for Streaming Telemetry
draft-ietf-netconf-udp-pub-channel-01
Abstract
This document describes a UDP-based publication channel for streaming
telemetry use to collect data from devices. A new shim header is
proposed to facilitate the distributed data collection mechanism
which directly pushes data from line cards to the collector. Because
of the lightweight UDP encapsulation, higher frequency and better
transit performance can be achieved.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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
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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 May 15, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 4
4. UDP Transport for Publication Channel . . . . . . . . . . . . 5
4.1. Design Overview . . . . . . . . . . . . . . . . . . . . . 5
4.2. Data Format of the Message Header . . . . . . . . . . . . 6
4.3. Options . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3.1. Reliability Option . . . . . . . . . . . . . . . . . 8
4.4. Data Encoding . . . . . . . . . . . . . . . . . . . . . . 9
5. Congestion Control . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 10
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Streaming telemetry refers to sending a continuous stream of
operational data from a device to a remote receiver. This provides
an ability to monitor a network from remote and to provide network
analytics. Devices generate telemetry data and push that data to a
collector for further analysis. By streaming the data, much better
performance, finer-grained sampling, monitoring accuracy, and
bandwidth utilization can be achieved than with polling-based
alternatives.
Sub-Notif [I-D.ietf-netconf-subscribed-notifications] and YANG-Push
[I-D.ietf-netconf-yang-push] defines a mechanism that allows a
collector to subscribe to updates of YANG-defined data that is
maintained in a YANG [RFC7950] datastore. The mechanism separates
the management and control of subscriptions from the transport that
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is used to actually stream and deliver the data. Two transports have
been defined so far, NETCONF [RFC6241] and RESTCONF [RFC8040].
While powerful in its features and general in its architecture, in
its current form the mechanism needs to be extended to stream
telemetry data at high velocity from devices that feature a
distributed architecture. The transports that have been defined so
far, NETCONF and RESTCONF, are ultimately based on TCP (Transmission
Control Protocol) and lack the efficiency needed to stream data
continuously at high velocity. A lighter-weight, more efficient
transport, e.g. a transport based on UDP (User Datagram Protocol) is
needed.
o Firstly, data collector will suffer a lot of TCP connections from,
for example, many line cards equipped on different devices.
o Secondly, as no connection state needs to be maintained, UDP
encapsulation can be easily implemented by hardware which will
further improve the performance.
o Thirdly, because of the lightweight UDP encapsulation, higher
frequency and better transit performance can be achieved, which is
important for streaming telemetry.
This document specifies a higher-performance transport option for
YANG-Push that leverages UDP. Specifically, it facilitates the
distributed data collection mechanism described in
[I-D.zhou-netconf-multi-stream-originators]. In the case of data
originating from multiple line cards, the design requires data to be
internally forwarded from those line cards to the push server,
presumably on a main board, which then combines the individual data
items into a single consolidated stream. The centralized data
collection mechanism can result in a performance bottleneck,
especially when large amounts of data are involved. What is needed
instead is the support for a distributed mechanism that allows to
directly push multiple individual substreams, e.g. one from each line
card, without needing to first pass them through an additional
processing stage for internal consolidation, but still allowing those
substreams to be managed and controlled via a single subscription.
The proposed UDP publication channel natively supports the
distributed data collection mechanism.
While this document will focus on the data publication channel, the
subscription can be used in conjunction with the mechanism proposed
in [I-D.ietf-netconf-yang-push] with necessary extensions
[I-D.zhou-netconf-multi-stream-originators].
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2. Terminology
Streaming telemetry: refers to sending a continuous stream of
operational data from a device to a remote receiver. This provides
an ability to monitor a network from remote and to provide network
analytics.
3. Solution Overview
The typical distributed data collection solution is shown in Fig. 1.
The Subscriber cannot see the Agents directly, so it will send the
Global Subscription information to the Master (e.g., main board).
When receiving a Global Subscription, the Subscription Server
decomposes the subscription request into multiple Component
Subscriptions, each involving data from a separate internal telemetry
source, for example a line card. The Component Subscriptions are
distributed to the Component Subscription Server located in Agents.
Subsequently, each Agent generates its own stream of telemetry data,
collecting and encapsulating the packets per the Component
Subscription and streaming them to the designated Collector.This
distributed data collection mechanism may form multiple Publication
Channels between the data originators and the Collector. The
Collector is able to assemble many pieces of data associated with one
Global Subscription.
The Publication Channel supports the reliable data streaming, for
example for some alarm events. The Collector has the option of
deducing the packet loss and the disorder based on the information
carried by the notification data. And the Collector will decide the
behavior to request retransmission. The Collector can send the
retransmission request to the subscriber server for further
processing.
The rest of the draft describes the UDP based publication channel.
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retransmission + + Global
request | | Subscription
+------------------------+
| | | Master |
| +--v----v--------+ |
| | Subscription | |
| | Server | |
| +--+----+-----+--+ |
| | | | | internal
Component +------------------------+ subscription
Subscription | | | distribution
+---------------+ | +--------------+
| | |
+------------------+ +------------------+ +------------------+
| | | | | | | | |
| +-------v------+ | | +------v-------+ | | +-----v--------+ |
| | Component | | | | Component | | | | Component | |
| | Subscription | | | | Subscription | | | | Subscription | |
| | Server | | | | Server | | | | Server | |
| +--------------+ | | +--------------+ | | +--------------+ |
| Agent 1 | | Agent 2 | | Agent n |
+---------+--------+ +--------+---------+ +----------+-------+
| | |
| | Publication Channel |
+--------------+ | +-----------------+
| | |
+-v-----v-----v-+
| |
| Collector |
| |
+---------------+
Fig. 1 Distributed Data Collection
4. UDP Transport for Publication Channel
4.1. Design Overview
As specified in YANG-Push, the telemetry data is encapsulated in the
NETCONF/RESTCONF notification message, which is then encapsulated and
carried in the transport protocols, e.g. TLS, HTTP2. The following
figure shows the overview of the UDP publication message structure.
o Next to the UDP encapsulation, the DTLS layer is to provide
reusable security and authentication functions over UDP.
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o The Message Header contains information that can facilitate the
message transmission before de-serializing the notification
message.
o Notification Message is the encoded content that the publication
channel transports. The common encoding method includes GPB [1],
CBOR [RFC7049], JSON, and XML.
[I-D.ietf-netconf-notification-messages] describes the structure
of the Notification Message for both single notification and
multiple bundled notifications.
+--------------+
| Notification |
| Message |
+--------------+
+--------------+
| Message |
| Header |
+--------------+
+--------------+
| DTLS |
+--------------+
+--------------+
| UDP |
+--------------+
Fig. 2 UDP Publication Message Overview
4.2. Data Format of the Message Header
The Message Header contains information that can facilitate the
message transmission before de-serializing the notification message.
The data format is shown as follows.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------+---------------+-------+-------------------------------+
| Vers. | Flag | ET | Length |
+-------+---------------+-------+-------------------------------+
| Notification-Time |
+---------------------------------------------------------------+
| Message-Generator-ID |
+---------------------------------------------------------------+
~ Options ~
+---------------------------------------------------------------+
Fig. 3 Message Header Format
The Message Header contains the following field:
o Vers.: represents the PDU (Protocol Data Unit) encoding version.
The initial version value is 0.
o Flag: is a bitmap indicating what features this packet has and the
corresponding options attached. Each bit associates to one
feature and one option data. When the bit is set to 1, the
associated feature is enabled and the option data is attached.
The sequence of the presence of the options follows the bit order
of the bitmap. In this document, the flag is specified as
follows:
* bit 0, the reliability flag;
* other bits are reserved.
o ET: is a 4 bits identifier to indicate the encoding type used for
the Notification Message. 16 types of encoding can be expressed:
* 0: GPB;
* 1: CBOR;
* 2: JSON;
* 3: XML;
* others are reserved.
o Length: is the total length of the message, measured in octets,
including message header.
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o Message-Generator-ID: is a 32-bit identifier of the process which
created the message notification. This allows disambiguation of
an information source, such as the identification of different
line cards sending the notification messages.
o Notification-Time: is the time at which the message leaves the
exporter, expressed in seconds since the UNIX epoch of 1 January
1970 at 00:00 UTC, encoded as an unsigned 32-bit integer.
o Options: is a variable-length field. The details of the Options
will be described in the respective sections below.
4.3. Options
The order of packing the data fields in the Options field follows the
bit order of the Flag field.
4.3.1. Reliability Option
The UDP based publication transport described in this document
provides two streaming modes, the reliable mode an the unreliable
mode, for different SLA (Service Level Agreement) and telemetry
requirements.
In the unreliable streaming mode, the line card pushes the
encapsulated data to the data collector without any sequence
information. So the subscriber does not know whether the data is
correctly received or not. Hence no retransmission happens.
The reliable streaming mode provides sequence information in the UDP
packet, based on which the subscriber can deduce the packet loss and
disorder. Then the subscriber can decide whether to request the
retransmission of the lost packets.
In most case, the unreliable streaming mode is preferred. Because
the reliable streaming mode will cost more network bandwidth and
precious device resource. Different from the unreliable streaming
mode, the line card cannot remove the sent reliable notifications
immediately, but to keep them in the memory for a while. Reliable
notifications may be pushed multiple times, which will increase the
traffic. When choosing the reliable streaming mode or the unreliable
streaming mode, the operate need to consider the reliable requirement
together with the resource usage.
When the reliability flag bit is set to 1 in the Flag field, the
following option data will be attached
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------------------------------------------------------+
| Notification ID |
+---------------------------------------------------------------+
| Previous Notification ID |
+---------------------------------------------------------------+
Fig. 4 Reliability Option Format
The notification ID is generated continuously by the message
generator. Different subscribers share the same notification ID
sequence. Current ID and previous ID will be added in the packets.
For example, there are two subscriber A and B,
o Notification IDs for the generator are : [1, 2, 3, 4, 5, 6, 7, 8,
9], in which Subscriber A subscribes [1,2,3,6,7] and Subscriber B
subscribes [1,2,4,5,7,8,9].
o Subscriber A will receive : [0,1][1,2][2,3][3,6][6,7].
o Subscriber B will receive : [0,1][1,2][2,4][4,5][5,7][7,8].
4.4. Data Encoding
Subscribed data can be encoded in GPB, CBOR, XML or JSON format. It
is conceivable that additional encodings may be supported as options
in the future. This can be accomplished by augmenting the
subscription data model with additional identity statements used to
refer to requested encodings.
Implementation may support different encoding method per
subscription. When bundled notifications is supported between the
publisher and the receiver, only subscribed notifications with the
same encoding can be bundled as one message.
5. Congestion Control
While efficient, UDP has no build-in congestion control mechanism.
It is not recommended to use the UDP based publication channel over
congestion-sensitive network paths. The deployments require the
communications from exporters to collectors are always congestion
controllable, i.e., the transport is over dedicated links or the
streaming rate can be limited.
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6. IANA Considerations
TBD
7. Security Considerations
TBD
8. Acknowledgements
The authors of this documents would like to thank Eric Voit, Tim
Jenkins, and Huiyang Yang for the initial comments.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[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>.
9.2. Informative References
[I-D.ietf-netconf-notification-messages]
Voit, E., Bierman, A., Clemm, A., and T. Jenkins,
"Notification Message Headers and Bundles", draft-ietf-
netconf-notification-messages-02 (work in progress),
October 2017.
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[I-D.ietf-netconf-subscribed-notifications]
Voit, E., Clemm, A., Prieto, A., Nilsen-Nygaard, E., and
A. Tripathy, "Custom Subscription to Event Streams",
draft-ietf-netconf-subscribed-notifications-07 (work in
progress), October 2017.
[I-D.ietf-netconf-yang-push]
Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
Nygaard, E., Bierman, A., and B. Lengyel, "YANG Datastore
Subscription", draft-ietf-netconf-yang-push-11 (work in
progress), October 2017.
[I-D.zhou-netconf-multi-stream-originators]
Zhou, T., Zheng, G., Voit, E., Clemm, A., and A. Bierman,
"Subscription to Multiple Stream Originators", draft-zhou-
netconf-multi-stream-originators-00 (work in progress),
October 2017.
9.3. URIs
[1] https://developers.google.com/protocol-buffers/
Appendix A. Change Log
(To be removed by RFC editor prior to publication)
A.1. draft-ietf-zheng-udp-pub-channel-00 to v00
o Modified the telemetry header format.
o Add a section on the Authentication Option.
o Cleaned up the text and removed unnecessary TBDs.
A.2. v01
o Removed the detailed description on distributed data collection
mechanism from this document. Mainly focused on the description
of a UDP based publication channel for telemetry use.
o Modified the telemetry header format.
Authors' Addresses
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Guangying Zheng
Huawei
101 Yu-Hua-Tai Software Road
Nanjing, Jiangsu
China
Email: zhengguangying@huawei.com
Tianran Zhou
Huawei
156 Beiqing Rd., Haidian District
Beijing
China
Email: zhoutianran@huawei.com
Alexander Clemm
Huawei
2330 Central Expressway
Santa Clara, California
USA
Email: alexander.clemm@huawei.com
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