Independent Submission Zhou Ying Internet Draft Wu Mingzhen Intended status: Informational Expires: September 10, 2024 Beijing Jiaotong University April 18, 2024 A Method for Exploring Latency Correlation in Multipath Networks draft-zhou-pce-latency-00 Abstract The exploration of latency correlation patterns is of great significance for characterizing network states. However, existing measurement approaches have to confront multiple challenges in detecting latency correlation factors, such as probing speed, routing hops and geographical locations. In this paper, we conduct three tasks to handle these issues. The first is to construct relative latency measurement strategies for individual machines without any time synchronization and control plane requirements. The probing speed has been increased by 14.3% in the same hardware conditions. In 4G/5G heterogeneous edges enabled by different mobile operators, worldwide 5003 target servers are selected to acquire more than 1TB network datasets. The second is to reveal the potential modes between latency and routing hops. Surprisingly, 91.2% available targets present non-positive characteristics in extreme cases. The third is to analyze the fine-grained relationship between latency and geographical locations. We found that the significance of mean backward receiving delay is higher than other parameters, with a maximum of 33%. Finally, we also made optimizations regarding latency compression and time accuracy in multipath networks. The experimental data have been released to an open-source community for further investigations. 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), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents Zhou, et al. Expires September 10, 2024 [Page 1] Internet-Draft Latency Correlation April 2024 at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on September 10, 2024. Zhou, et al. Expires September 10, 2024 [Page 2] Internet-Draft Latency Correlation April 2024 Copyright Notice Copyright (c) 2024 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....................................................... 4 2. Scheme Design...................................................... 4 3. Transmission Optimization.......................................... 7 3.1. Path Selection ............................................... 7 3.2. Speed Improvement ............................................ 7 3.3. Accuracy Improvement ......................................... 8 4. Conclusion......................................................... 8 5. Unresolved Issues.................................................. 8 6. Security Considerations............................................ 8 7. References......................................................... 9 8. Acknowledgments.................................................... 9 Zhou, et al. Expires September 10, 2024 [Page 3] Internet-Draft Latency Correlation April 2024 1. Introduction With the increasing adoption of new network devices and communication technologies, understanding the changes in network Quality of Service (QoS) is crucial. Among various QoS metrics, one- way latency has gained significant attention for ensuring QoS provisioning, verifying Service Level Agreements (SLAs), and detecting network anomalies. However, exploring the variation patterns of one-way delay (OWD) faces several challenges, including unsynchronized device clocks, difficulty in controlling server targets, and security concerns. To address these challenges, we propose an end-to-end relative latency measurement scheme capable of probing 5003 global servers and gathering 1TB datasets in heterogeneous network environments. The relationship between relative one-way latency, routing hops and geographical location has been established. The contributions of this paper are as follows: • A new network measurement strategy has been constructed: A relative OWD measurement is designed to avoid the requirements of time synchronisation, software-defined networks (SDN), operating licences or other limitations for latency parameter measurement. • Correlation analysis of latency and routing hop count: Through the measured data, it is revealed that there is a non-positive correlation between relative OWD and routing hop count in 91.2% of measurement points in extreme cases. • Correlation analysis of latency and geographical location: The experiment displays a latency-geographic distance relationship indicator. The correlation between average backward receiving delay and distance is significantly higher than other average latency parameters, with a maximum increase in significance of 33%. 2. Scheme Design In this section, we explain the mathematical model of measurement strategies, which includes measuring the structure and sending method of the message, obtaining the target, data processing, and keyframe algorithms. Additionally, a fourth timestamp, TW ireshark, is acquired by utilising network packet capture software. ⚫ Mathematical Model This research utilise NTP as the primary measurement protocol. The data packet comprises three essential timestamps, namely TOriginate, TReceive and TT ransmit. Zhou, et al. Expires September 10, 2024 [Page 4] Internet-Draft Latency Correlation April 2024 ⚫ Message Structure Measurement message structure design: In order to gain comprehensive network measurement performance, more targeted modifications must be made to network packets. An innovative network measurement message format was developed based on NTP [20]. +-------------------------------------------------------------+ | 4-bit | 4-bit | 8-bit Type | 16-bit Total Length | | version | IHL | Of Service | | +-------------------------------------------------------------+ | 16-bit Identification |3-bit | 16-bit Total Length | | |Flags | | +-------------------------------------------------------------+ | 8-bit Time To | 8-bit | 16-bit Header Checksum | | Live TTL=1…30 | Protocol | | +-------------------------------------------------------------+ |32-bit Source Address Source Address={5G IP address(Telecom);| | 4G IP address(Mobile) ; 4G IP address(Telecom)} | +-------------------------------------------------------------+ | 32-bit Destination Address | | Destination Address={NTP server IP addresses worldwide} | +-------------------------------------------------------------+ | 16-bit Source Port | 16-bit Destination Port | | S Port=49152…65535 | | +-------------------------------------------------------------+ | 16-bit Length | 16-bit Checksum | | | | +-------------------------------------------------------------+ | NTP message | +-------------------------------------------------------------+ Fig. 1. Network packet structure for measurement, modified port number, source address, destination address, etc As shown in Fig. 1, the image represents the ip and user datagram protocol (UDP) header of the measurement message. The red field has been modified, and we have changed the Time To Live (TTL) to 1-30 to detect forward routing information. In addition, based on heterogeneous network environments, inorder to bind network measurement messages to different networks and send multiple measurement points, we modified the source and destination addresses of the message. We also made modifications to the source port number, gradually increasing it from 49152 to 65535. Finally, we mainly extracted three timestamps from the NTP message, namely the original timestamp, the receive timestamp, and the transmit timestamp. Zhou, et al. Expires September 10, 2024 [Page 5] Internet-Draft Latency Correlation April 2024 ⚫ Obtain Measurement Targets We use the multi-location DNS resolution method. Alibaba and Tencent Cloud servers in Beijing, Shanghai and Shenzhen are used for DNS resolution of measurement targets. In this process, the server queries the local name server, root name server,top-level name resolution server and the right name server.Through this method, the data obtained from different locations are not the same. After deduplication and cleaning of the data, this study can collect as many NTP servers as possible to ensure the reliability and effectiveness of the network measurement dataset. ⚫ Relative OWD Measurement Method The construction timestamp interval is too large: In order to obtain meaningful relative latency parameters, it is required that three packets transmitted through different networks be sent simultaneously, and the interval between the construction times of the three packets should be as small as possible. Since the message transmission method based on the ntplib library is difficult to meet the time interval requirements of the experiment,1‘ it is urgent to improve and optimize the network measurement method. Transmitting and receiving rounds: To overcome this difficulty, the present work employs two distinct approaches for message transmission, one of which is the transmitting and receiving rounds method. After the data message is transmitted, the current contracting process won’t finish until the reply data packet is received or the predefined waiting time limit is surpassed, at which point the next contracting process will begin. Parallel receiving and sending: We use a parallel receiving and sending method. This method can quickly gather several actual and available data packets. However, since the disordered method of sending and receiving may cause data packet dislocation, it is necessary to require secondary data processing and cleaning before it can be used for data analysis, which is not ideal for online and real-time data processing. Message sending method that meets time accuracy: This study has developed a raw socket sending method for parallel sending and receiving packets. Experimental comparisons show that the socket sending method has a smaller packet time interval and better timestamp accuracy. Through this method, messages from three different networks can be created and sent in 0.001 ms, satisfying the experiment’s time period. ⚫ Keyframe Algorithms Zhou, et al. Expires September 10, 2024 [Page 6] Internet-Draft Latency Correlation April 2024 In a small round of packet sending, a total of 30 network measurement messages were sent. The corresponding response message only needs to extract one packet with the smallest TTL value to obtain all network performance measurement information in this round of message sending, which is called a ”keyframe”. The program blocks the dataset in order of network type, original address, and destination address, so that we can conveniently obtain the data of each individual network for each measurement target. Then, by sorting the time and port number information, the keyframe data for each measurement round can be extracted. It contains all the information required for network measurement in this experiment, including the relative total delay, OWD, one-way routing hops, etc. 3. Transmission Optimization This section introduces network optimization based on measurement data, including reducing total latency, improving message sending rate, and improving time accuracy. 3.1. Path Selection Through the network measurement method proposed in this draft, the one-way delay performance of multiple networks for a single device can be obtained, and the delay performance of different networks can be compared for different communication targets. Some networks have good one-way latency performance, which provides optimization space for path selection. By simultaneously using multiple networks to connect to the destination device and filtering out networks with better forward latency and networks with better backward latency, packets can be sent and received through these two networks. This allows for the simultaneous use of the network with the shortest forward latency and the network with the shortest backward latency, thereby compressing the overall round-trip latency. 3.2. Speed Improvement By using the network measurement message format mentioned in Fig. 1, the separation of message sending and receiving can be achieved, thereby accelerating the collection speed of measurement data. In the normal one-time message sending process, both the sender and receiver must establish sockets to listen for message replies. However, if the port number is used as an identifier to identify the order of message sending, there is no need to listen for the message process. Zhou, et al. Expires September 10, 2024 [Page 7] Internet-Draft Latency Correlation April 2024 3.3. Accuracy Improvement The network measurement method using the NTP protocol has a benefit, as it allows for device time synchronization during network measurements, which greatly improves the time accuracy of wide area network devices. At the same time, there is also room for optimization in multiple network measurements, such as using the least squares method to optimize time synchronization differences. 4. Conclusion We aim to explore the changes in large-scale unidirectional latency and propose a network measurement strategy that does not require SDN architecture, time synchronization, and extra equipment. Through analysis of measurement data, our experimental results has verified that latency at some targeted sites and route hops meets the negative correlation. It is speculated that the real-time change of the routing table makes the packets forward from the path with a lower latency. Although route hops is large, the one-way latency is low. In addition, the correlation analysis between geographical location and latency shows that compared to RTT, backward receiving delay is more significant in the calculation, fitting, and prediction tasks of the correlation due to its lower volatility. Among them, due to the unknowability of the lowest latency, in scenarios with high real-time requirements, the average backward receiving delay is the optimal choice. In this measurement process, we completed the optimal network selection under asymmetric paths, reduced the total delay and fluctuation of the time synchronisation difference. 5. Unresolved Issues The data can be used for simulation experiments to establish traffic delay models for different routing jump numbers in different geographical locations. The measurement method can also be used to optimize multiple time- related network service functions. 6. Security Considerations This document does not contain any security considerations. Zhou, et al. Expires September 10, 2024 [Page 8] Internet-Draft Latency Correlation April 2024 7. References PCEP Extensions for Signaling Multipath Information [draft-ietf-pce- multipath-11]. PCEP extensions for p2mp sr policy [draft-ietf-pce-sr-p2mp-policy- 05] Inter Stateful Path Computation Element (PCE) Communication Procedures. [draft-ietf-pce-state-sync-07] 8. Acknowledgments Many thanks to all who discussed this with us in DINRG in 2023 and 2024. This document was prepared using 2-Word-v2.0.template.dot. Authors’ Addresses Ying Zhou Beijing Jiaotong University (BJTU) Beijing, 100044, P.R.China Email: 22110019@bjtu.edu.cn Mingzhen Wu Beijing Jiaotong University (BJTU) Beijing, 100044, P.R.China Email: 23125063@bjtu.edu.cn Zhou, et al. Expires September 10, 2024 [Page 9]