Network Working Group P. Kim Internet-Draft Korea Polytechnic University Intended status: Experimental Expires: May 3, 2020 November 4, 2019 Grasping Network Situation for Improving End-to-End Throughput draft-pskim-grasping-network-situation-00.txt Abstract In this draft, a mechanism to grasp the network situation is proposed for improving end-to-end path throughput. The proposed mechanism is based on the active packet-train probing based estimation. The proposed mechanism defines three cases of the difference between the average output gap and the input gap, and then reflects fully them. Since three cases are handled respectively by appropriate corresponding manners, the proposed mechanism can be expected to reduce the detection error for the turning point. Therefore, through the proposed mechanism, the available bandwidth can be estimated more reliably. 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 May 3, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect Kim Expires May 3, 2020 [Page 1] Internet-Draft Grasping Network Situation November 2019 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. A Grasping Network Situation via Bandwidth Estimation . . . . 3 2.1 Existing Active Packet-train Probing Based Estimation . . . . 3 2.2 An Alternative Active Packet-train Probing Based Estimation . 4 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 4. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Traffic jams on narrow roads can be one of the main causes of traffic congestion, which also applies to communication networks. If there are more data traffic than the available network bandwidth, communication latency appears. This can adversely affect 5G-based Internet services such as self-driving cars, autonomous robots, etc. Communication latency is the term used to indicate any kind of delay that happens in data communication over a network. In particular, high latency creates bottlenecks in any network communication. It prevents the data from taking full advantage of the network pipe and effectively decreases the communication bandwidth. The impact of latency on network bandwidth can be temporary or persistent based on the source of the delays. Recently, in order to reduce the communication latency, grasping the network situation and adjusting the data transmission amount have been researched as shown in BBR(Congestion-based congestion control) [1] and ExLL(An ultra low-latency congestion protocol for mobile cellular network)[2]. BBR has been designed to prevent bottlenecks before they happen. For a given network connection, BBR uses recent measurements of the network's transmission rate and round-trip time to build an explicit model that includes both the maximum recent bandwidth available to that connection, and its minimum recent round-trip delay. ExLL has been designed to elaborate the allowed network bandwidth for an efficient low-latency transmission protocol. If data is sent only as much as the network bandwidth allowed by the mobile communication terminal, the data will not be unnecessarily accumulated. To do this, the pattern of packets received by the mobile communication terminal is observed. As shown in above observations, understanding the dynamic properties of the end-to-end Internet performance metrics such as available network bandwidth is beneficial for the proper resource management in Kim Expires May 3, 2020 [Page 2] Internet-Draft Grasping Network Situation November 2019 emerging wireless Internet services that required low-latency data transmission. Therefore, the area of end-to-end available bandwidth estimation has attracted considerable interest. As a result, several mechanisms for the available bandwidth estimation have been developed based on active measurements[3]. Among existing mechanisms for available bandwidth estimation, the active packet-train probing mechanism such as initial gap increasing and packet transmission rate was used successfully. The ultimate objective is to experimentally determine the input gap value at some point for which the average output gap is equal to the input gap. At this point, the probing packets are considered to interleave nicely with the competing traffic, and the average rate of the packet train equals the available bandwidth on the bottleneck link. This point is called the "turning point". At the turning point, the input gap value for which the average output gap is equal to the input gap is the right value to use for estimating the available bandwidth. However, there are some issues in the existing active packet-train probing mechanism. After performing a measurement, three cases can be defined according to the difference between the average output gap and the input gap. These three cases have respectively different relationship between the average rate of the probing packet train and the available bandwidth. However, the existing mechanism did not reflect fully these three cases in order to reduce the detection latency of the turning point. That is, two of three cases are handled in the same way, which can introduce the detection error for the turning point since these two cases handled in the same way are absolutely different. Thus, the available bandwidth can be estimated inaccurately although the measurement latency can be reduced. Therefore, to reduce the detection error of the turning point and enhance the accuracy of the available bandwidth estimation, a new mechanism is proposed based on the active packet-train probing mechanism. The proposed mechanism reflects fully three cases, while the existing mechanism reflected only two cases. Since three cases are handled respectively by appropriate corresponding manners, the proposed mechanism can be expected to reduce the detection error for the turning point. Therefore, the end-to-end available bandwidth can be estimated more reliably. 2. A Grasping Network Situation via Bandwidth Estimation 2.1 Existing Active Packet-train Probing Based Estimation The active packet-train probing mechanism was proposed for the available bandwidth estimation and shown to be much faster than existing mechanisms with similar measurement accuracy but with shorter measurement latency. This mechanism is based on a single-hop gap model that captures the relationship between the competing traffic and the probing packet train. As a sequence of probing packet trains from the source travel through the network, packets belonging to the competing traffic may be inserted between them, thus Kim Expires May 3, 2020 [Page 3] Internet-Draft Grasping Network Situation November 2019 increasing the gap at the destination. As a result, the average output gap value at the destination may be a function of the competing traffic rate, making it possible to estimate the amount of competing traffic. That is, the average output gap can be used to determine the competing traffic bandwidth and hence the available bandwidth on the end-to-end path assuming that the bottleneck link bandwidth along the end-to-end path is known. At some point, the average output gap equals the input gap as gaps in a probing packet train increase. This point is called the "turning point". At the turning point, the input gap value for which the average output gap is equal to the input gap is the right value to use for estimating the available bandwidth. However, there are some issues in the existing active packet-train probing mechanism. After performing the measurement, three cases are defined according to the difference between the average output gap and the input gap. These three cases mean that the average output gap at the destination is (a) larger than, (b) equal to, (c) less than the input gap at the source. These three cases have respectively different relationship between the average rate of the probing packet train and the available bandwidth. However, the existing mechanism did not reflect fully these three cases in order to reduce the measurement latency. That is, both (b) and (c) cases are handled in the same way, which can introduce the detection error for the turning point since (b) and (c) cases are absolutely different. Therefore, the available bandwidth can be estimated inaccurately although the measurement latency can be reduced. In this draft, a new mechanism for available bandwidth estimation mechanism is proposed to improve the estimation accuracy compared with the existing mechanism. As mentioned before, since (b) and (c) cases handled in the same way are absolutely different, they should be handled by respectively. 2.2 An Alternative Active Packet-train Probing Based Estimation As shown in [3], the end-to-end available bandwidth is defined as the difference between the bottleneck link bandwidth along an end-to-end path and the competing traffic. The bottleneck link bandwidth in the path determines the end-to-end bandwidth which is the maximum IP layer rate that the path can transfer from source to destination. In other words, the bandwidth of a path establishes an upper bound on the IP layer throughput that a user can expect to get from that path. There are diverse measurement mechanisms for the bottleneck link bandwidth. Therefore, the bottleneck link bandwidth can measured from one of existing mechanisms. There are several important probing parameters such as probing packet size, number of probing packet in packet train, and input gap to get correct measurement. Among them, input gap in a probing Kim Expires May 3, 2020 [Page 4] Internet-Draft Grasping Network Situation November 2019 packet train is the most important parameter to control for accurate available bandwidth estimation. The source sends a sequence of probing packet trains with adjusting input gap. The difference between the average output gap and the input gap is observed for each train. Then, the turning point is detected for estimating the available bandwidth. After performing a measurement, three cases are defined according to the difference between the average output gap and the input gap. Three cases are called 'Red', 'Yellow', 'Green' cases which have respectively different relationship between the average rate of the probing packet train and the available bandwidth as follows: - Red : The average rate of the packet train is more than the available bandwidth with the following condition: average output gap > input gap + delta/2. - Yellow : The average rate of the packet train is similar to the available bandwidth with the following condition: |average output gap - input gap | < delta. - Green : The average rate of the packet train is less than the available bandwidth with the following condition: average output gap < input gap - delta/2. Above three cases are handled respectively as follows: (1) Handling of 'Red' case The measurement is repeated with the increased input gap. After then, three cases observed once again. For each case, the measurement is repeated with adjusting input gap as follows: - Red : increased input gap - Yellow : same input gap as previous measurement - Green : decreased input gap In the existing mechanism, the measurement is repeated with the same input gap as previous measurement for 'Green' case. (2) Handling of 'Yellow' case The measurement is repeated with the same input gap as previous measurement. After then, three cases are observed once again and then handled respectively as follows: - Red : measurement with increased input gap - Yellow : measurement finished (turning point detected) Kim Expires May 3, 2020 [Page 5] Internet-Draft Grasping Network Situation November 2019 - Green : measurement with decreased input gap In the existing mechanism, the measurement is finished for 'Green' case. (3) Handling of 'Green' case The measurement is repeated with the decreased input gap. In the existing mechanism, the measurement is repeated with the same input gap in this case. After then, three cases are observed once again and then handled respectively as follows: - Red : measurement with increased input gap - Yellow : measurement finished (turning point detected) - Green : measurement with decreased input gap In the existing mechanism, the measurement is finished for 'Green' case. As shown in three cases, the proposed mechanism handles 'Yellow' and 'Green' cases respectively while the existing mechanism handles them in the same way. When the turning point is detected, the measurement is finished and then the end-to-end available bandwidth can be estimated as follows. The end-to-end available bandwidth is obtained by subtracting the competing traffic bandwidth from the bottleneck link bandwidth. As mentioned before, the bottleneck link bandwidth can be measured from one of existing mechanisms. Then, the competing traffic bandwidth can be computed using the average output gap and the input gap at the turning point, and the bottleneck link bandwidth. 3. IANA Considerations This document has no IANA actions. 4. References [1] N. Cardwell et al., "BBR v2 : A Model-based Congestion Control", ICCRG, IETF 104, Mar 2019 [2] S. Park et al., "ExLL: An Extremely Low-latency Congestion Control for Mobile Cellular Networks," Proc. of the 14th International Conference on Emerging Networking EXperiments and Technologies(CoNEXT'18) pp. 307-319, 2018. [3] N. Hu and P. Steenkiste, "Evaluation and characterization of available bandwidth probing techniques," IEEE JSAC, Vol. 21, No. 6, pp. 879-894, 2003. Kim Expires May 3, 2020 [Page 6] Internet-Draft Grasping Network Situation November 2019 Author's Address Pyungsoo Kim Department of Electronics Engineering, Korea Polytechnic University, 2121 Jungwang-Dong, Shiheung City, Gyeonggi-Do 429-793 KOREA Phone: +82 31 8041 0489 EMail: pskim@kpu.ac.kr Kim Expires May 3, 2020 [Page 7]