One-way delay measurement method based on Digital Twin Network
draft-yc-nmrg-dtn-owd-measurement-00
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| Authors | Hongwei Yang , Danyang Chen | ||
| Last updated | 2022-07-03 | ||
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draft-yc-nmrg-dtn-owd-measurement-00
Internet Research Task Force H. Yang
Internet-Draft D. Chen
Intended status: Informational China Mobile
Expires: 2 January 2023 1 July 2022
One-way delay measurement method based on Digital Twin Network
draft-yc-nmrg-dtn-owd-measurement-00
Abstract
This document implements an accurate network delay measurement method
based on the digital twin network. This method does not need to send
measurement packets, change the physical network configuration,
change the format of service packets, and do not require physical
network elements to support the time synchronization protocol. Two-
way delay and one-way delay measurement of any service packet.The
digital twin network architecture of this document follows the NMRG
working group paper draft-irtf-nmrg-network-digital-twin-arch-00.
Status of This Memo
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This Internet-Draft will expire on 2 January 2023.
Copyright Notice
Copyright (c) 2022 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Method Introduction . . . . . . . . . . . . . . . . . . . . . 4
4. Implementation Process . . . . . . . . . . . . . . . . . . . 6
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Digital twin network is a virtual representation of the physical
network. Such virtual representation of the network is meant to be
used to analyze, diagnose, emulate, and then control the physical
network based on data, models, and interfaces. The DTN architecture
diagram is shown in Figure 1.
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+---------------------------------------------------------+
| +-------+ +-------+ +-------+ |
| | App 1 | | App 2 | ... | App n | Application|
| +-------+ +-------+ +-------+ |
+-------------^-------------------+-----------------------+
|Capability Exposure| Intent Input
| |
+-------------+-------------------v-----------------------+
| Instance of Digital Twin Network |
| +--------+ +------------------------+ +--------+ |
| | | | Service Mapping Models | | | |
| | | | +------------------+ | | | |
| | Data +---> |Functional Models | +---> Digital| |
| | Repo- | | +-----+-----^------+ | | Twin | |
| | sitory | | | | | | Network| |
| | | | +-----v-----+------+ | | Mgmt | |
| | <---+ | Basic Models | <---+ | |
| | | | +------------------+ | | | |
| +--------+ +------------------------+ +--------+ |
+--------^----------------------------+-------------------+
| |
| data collection | control
+--------+----------------------------v-------------------+
| Physical Network |
| |
+---------------------------------------------------------+
Figure 1: Figure1:Reference Architecture of Digital Twin Network
The digital twin layer forms a network element model by modeling
physical network elements, and the network element model forms a twin
network element through instantiation, that is, each physical network
element in the physical network has a corresponding twin network
element in the digital twin layer. Similarly, each physical flow of
the physical network also has a corresponding twin flow at the
digital twin layer.
Traditional network delay measurement methods include active
measurement, passive measurement, hybrid measurement, etc., but they
all have some disadvantages:
1) It is necessary to inject measurement packets into the physical
network, but this will affect the forwarding behavior of actual
service traffic, affect the accuracy of delay measurement, and
increase the network burden and occupy network resources;
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2) It is impossible to perform accurate delay measurement on the
packets of all network protocols. For example, it is difficult to
measure the one-way delay for UDP packets;
3) Some solutions need to change the format of service packets and
insert measurement parameters, but this requires upgrading the
physical network, which is difficult to implement, and affects the
normal forwarding behavior of service packets and affects the
measurement accuracy;
4) The time synchronization protocol is required to measure the one-
way delay of the network, and the physical network is required to
support this protocol, which increases the difficulty of implementing
the solution.
2. Conventions Used in This Document
2.1. Terminology
NTP Network Time Protocol
PTP Precision Time Protocol
DTN Digital Twin Network
2.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14[RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Method Introduction
The delay measurement method based on DTN is as follows:
1) According to the digital twin network architecture, build a
digital twin layer, including twin network elements corresponding to
physical network elements, such as twin switches, twin routers, etc.;
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2) Time synchronization is maintained between each twin network
element in the digital twin layer. a) If multiple twin NEs are in the
same physical entity, such as the NFV-based modeling method, where
multiple twin NEs are deployed in one server and share the same local
clock, the twin NEs themselves is time-synchronized; b) If multiple
twin NEs are deployed in different physical entities, use PTP
(Precise Time Protocol) [IEEE.1588.2008]or NTP (Network Time
Protocol) [RFC5905]to achieve time synchronization between physical
entities to ensure time synchronization of all twin NEs;
3) The data transmission from the physical network layer to the
digital twin layer uses a delay deterministic network (Detnet) to
ensure that the data transmission delay between each physical network
element and the twin network element is deterministic or pre-
calculable, as shown in the figure 2. T1~Tn is the delay of data
transmission; the delay deterministic network can be based on TSN or
DIP technology;
4) When a flow of the physical network is input from the physical
network element 1, passes through the physical network elements 2 and
3, and finally is output from the physical network element n. When
physical network element 1 receives the data packet, it will normally
forward the data to physical network element 2 and transmit the data
to twin network element 1 at the same time. At this time, the local
time of the twin NE 1 is t1, and the deterministic network
transmission delay is T1, then the arrival time of the traffic
information recorded by the twin NE is t1-T1; similarly, the arrival
time of the data packet recorded by other twin NEs is tn- Tn.
5) Finally, according to the arrival time of the data packet at the
twin network elements, its one-way transmission delay between
physical network elements can be calculated.
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+--------------------------------------------------------------+
| Digital Twin Network +----------+ |
| +---------+ Twin NE 3+----------+ |
| | +----------+ | |
| | | |
| -----------+ +-----+----+ +----------+ +-----+----+ |
| | Twin NE 1+----+ Twin NE 2+----+ Twin NE 4+----+ Twin NE n| |
| -----------+ +----------+ +----------+ +----------+ |
+--------------------------------------------------------------+
|
+-------------------------------+------------------------------+
| Delay Deterministic Networking |
+-------------------------------^------------------------------+
|
+---------------------------------+---------------------------------+
| Phsical Network +------------+ |
| +----------+Physical NE3+----------+ |
| | +------------+ | |
| | | |
| +------------+ +-----+------+ +------------+ +------+-----+ |
| |Physical NE1+---+Physical NE2+---+Physical NE4+---+Physical NEn| |
| +------------+ +------------+ +------------+ +------------+ |
+-------------------------------------------------------------------+
Figure 2: Figure 2: Between the physical network and the twin
network is a delay deterministic network
4. Implementation Process
The detailed calculation process is shown in Figure 3:
(1) When the traffic data to be measured reaches physical network
element 1, physical network element 1 forwards the traffic to
physical network element 2, but also transmits the data to twin
network element 1, and the transmission delay is T1. The local time
of network element 1 is t1, and the arrival time of the data recorded
by twin network element 1 is t1-T1;
(2) When the data packet is forwarded to physical network element 2,
physical network element 2 will also forward it to physical network
element 3 normally, but also to twin network element 2, and the delay
to reach twin network element 2 is T2 , at this time, the local time
of twin network element 2 is t2, and the arrival time of data packet
information recorded by twin network element 2 is t2-T2, then
(t2-T2)-(t1-T1) is the data packet from physical network element 1 to
One-way delay of physical network element 2.
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(3) Similarly, when the data packet reaches the nth physical network
element, the nth physical network element will also transmit the data
packet to the twin network element n. The data transmission time is
Tn, and the local time of the twin network element n is tn, then
record tn. -Tn is the time when the packet reaches the twin network
element n, then (tn-Tn)-(t1-T1) is the one-way transmission delay of
the data packet from physical network element 1 to physical network
element n;
So far, the one-way transmission delay of data packets between
physical NEs is obtained by calculating the time when the data packet
to be tested reaches the twin NEs. During the measurement process,
only time synchronization between twin NEs is required, but no
physical network is required. Inter-meta time synchronization. The
accuracy of delay measurement depends on the time synchronization
accuracy of the twin network elements and the time synchronization
accuracy of the delay deterministic network. If both use the PTP
synchronization protocol, the delay measurement accuracy can reach
the nanosecond level.
+--------+ +--------+ +--------+ +------+ +------+ +------+ +------+
|Physical| |Physical| |Physical| |Detnet| | Twin | | Twin | | Twin |
| NE1 | | NE2 | | NEn | | | | NE1 | | NE2 | | NEn |
+----+---+ +----+---+ +----+---+ +---+--+ +---+--+ +---+--+ +---+--+
| | | | | | |
|1.The packet is sent from physical NE1 to twin NE1, |
|and twin NE1 records the arri^al time of|the packet |
+----------+----------+---------+------->+ | |
| | | | | | |
| |2.The packet is sent|from physical NE2|to twin NE2,
| |and twin NE2 records|the arri^al time of the packet
| +----------+---------------------------> |
| | | | | | |
| | | | | | |
| | n.The packet is sent from physical NEn to twin NEn,
| | and twin NEn records the arri^al time of the|packet
| | +---------+--------+--------+-------->
| | | | | | |
| | | | | | |
| | | | | | |
Figure 3: Figure 3: Delay Measurement Process
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5. Conclusion
This method can realize segment-by-segment or end-to-end one-way
delay measurement in the physical network. The advantages of this
method include: no need to send measurement packets, all traffic
protocol types can be measured, physical network configuration is not
changed, and traffic data format is not changed. , It does not need
the physical network to support the time synchronization protocol,
and the measurement accuracy is high.
6. Security Considerations
TBD.
7. IANA Considerations
TBD.
8. Normative References
[IEEE.1588.2008]
IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
July 2008.
[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>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Authors' Addresses
Hongwei Yang
China Mobile
Beijing
100053
China
Email: yanghongwei@chinamobile.com
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Danyang Chen
China Mobile
Beijing
100053
China
Email: chendanyang@chinamobile.com
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