A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> In this paper, we explore end-to-end loss differentiation algorithms (LDAs) for use with congestion-sensitive video transport protocols for networks with either backbone or last-hop wireless links. As our basic video transport protocol, we use UDP in conjunction with a congestion control mechanism extended with an LDA. For congestion control, we use the TCP-Friendly Rate Control (TFRC) algorithm. We extend TFRC to use an LDA when a connection uses at least one wireless link in the path between the sender and receiver. We then evaluate various LDAs under different wireless network topologies, competing traffic, and fairness scenarios to determine their effectiveness. In addition to evaluating LDAs derived from previous work, we also propose and evaluate a new LDA, ZigZag, and a hybrid LDA, ZBS, that selects among base LDAs depending upon observed network conditions. We evaluate these LDAs via simulation, and find that no single base algorithm performs well across all topologies and competition. However, the hybrid algorithm performs well across topologies and competition, and in some cases exceeds the performance of the best base LDA for a given scenario. All of the LDAs are reasonably fair when competing with TCP, and their fairness among flows using the same LDA depends on the network topology. In general, ZigZag and the hybrid algorithm are the fairest among all LDAs. <s> BIB001 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> This article proposes the Implicit Packet Meta Header (IPMH) as a standard method to compute and represent common QoS properties of the Application Data Units (ADU) of multimedia streams using legacy and proprietary streams' headers (e.g. Real-time Transport Protocol headers). The use of IPMH by mechanisms located at different layers of the communication architecture will allow implementing fine per-packet self-optimization of communication services regarding the actual application requirements. A case study showing how IPMH is used by error control mechanisms in the context of wireless networks is presented in order to demonstrate the feasibility and advantages of this approach. <s> BIB002 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Multipath TCP, as proposed by the IETF working group mptcp, allows a single data stream to be split across multiple paths. This has obvious benefits for reliability, and it can also lead to more efficient use of networked resources. We describe the design of a multipath congestion control algorithm, we implement it in Linux, and we evaluate it for multihomed servers, data centers and mobile clients. We show that some 'obvious' solutions for multipath congestion control can be harmful, but that our algorithm improves throughput and fairness compared to single-path TCP. Our algorithmis a drop-in replacement for TCP, and we believe it is safe to deploy. <s> BIB003 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> The IETF is developing a new transport layer solution, MultiPath TCP (MPTCP), which allows to efficiently exploit several Internet paths between a pair of hosts, while presenting a single TCP connection to the application layer. From an implementation viewpoint, multiplexing flows at the transport layer raises several challenges. We first explain how this major TCP extension affects the Linux TCP/IP stack when considering the establishment of TCP connections and the transmission and reception of data over multiple paths. Then, based on our implementation of MultiPath TCP in the Linux kernel, we explain how such an implementation can be optimized to achieve high performance and report measurements showing the performance of receive buffer tuning and coupled congestion control. <s> BIB004 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Multipath transport protocols such as Multipath TCP can concurrently use several subflows to transmit a TCP flow over potentially different paths. Since more than one subflow is used, an efficient multipath scheduling algorithm is needed at the sender. The objective of the scheduler is to identify the subflow over which the current data packet should be sent. This paper compares the most important types of schedulers for multipath transfers. We model their performance analytically and derive key metrics, most notably the resulting end-to-end delay over heterogeneous paths. Our results show that a scheduler minimizing the packet delivery delay yields the best overall performance, but it is complex to realize. An alternative scheduler based on the sender queue size is simpler and has sufficient performance for relatively small asymmetry between the multiple paths. Our model results are confirmed by measurements with a real multipath transport protocol. <s> BIB005 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> The increasing number of interfaces using different access technologies in modern devices gives opportunities for enhancing the Quality of Service (QoS) delivered to multimedia and interactive data transfers involved in distributed applications. In the current Internet, the presence of "middleboxes" such as Network Address Translators (NAT) or firewalls hardly lets applications use any Transport protocol but the well-known Transmission Control Protocol (TCP). Currently under standardization at the IETF, the new Multipath-TCP (MPTCP) protocol uses several TCP flows to make use of the multiple interfaces available on the end terminals, thus improving both network availability and QoS, still being capable to cross over middle boxes. Although originally being fully reliable and fully ordered, its two sub-layers architecture gives opportunity to use QoS techniques over fully reliable paths. This paper studies the QoS benefits induced by the implementation of the "partial reliability" concept in MPTCP for interactive video applications. Two different mechanisms are experimented with the aim to enhance global quality of video transmission over paths close to 3G networks characteristics. The Internet Engineering Task Force (IETF) MPTCP working group's ns-2 implementation is used for the experimentations. The Evalvid toolkit over ns-2 is used to measure the QoS benefits expressed in terms of Peak Signal to Noise Ratio (PSNR). <s> BIB006 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Besides the traditional routers and switches, middleboxes such as NATs, firewalls, IDS or proxies have a growing importance in many networks, notably in entreprise and wireless access networks. Many of these middleboxes modify the packets that they process. For this, they to implement (a subset of) protocols like TCP. Despite the deployment of these middleboxes, TCP continues to evolve on the endhosts and little is known about the interactions between TCP extensions and the middleboxes. In this paper, we experimentally evaluate the interference between middleboxes and the Linux TCP stack. For this, we first propose MBtest, a set of Click elements that model middlebox behavior. We use it to experimentally evaluate how three TCP extensions interact with middleboxes. We also analyzes measurements of the interference between Multipath TCP and middleboxes in fifty different networks. <s> BIB007 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Today many end hosts are equipped with multiple interfaces. These interfaces can be utilized simultaneously by multipath protocols to pool resources of the links in an efficient way while also providing resilience to eventual link failures. However how to schedule the data segments over multiple links is a challenging problem, and highly influences the performance of multipath protocols. In this paper, we focus on different schedulers for Multipath TCP. We first design and implement a generic modular scheduler framework that enables testing of different schedulers for Multipath TCP. We then use this framework to do an in-depth analysis of different schedulers by running emulated and real-world experiments on a testbed. We consider bulk data transfer as well as application limited traffic and identify metrics to quantify the scheduler's performance. Our results shed light on how scheduling decisions can help to improve multipath transfer. <s> BIB008 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Over the past two or three years, wireless cellular networks have become faster than before, most notably due to the deployment of LTE, HSPA+, and other similar networks. LTE throughputs can reach many megabits per second and can even rival WiFi throughputs in some locations. This paper addresses a fundamental question confronting transport and application-layer protocol designers: which network should an application use? WiFi, LTE, or Multi-Path TCP (MPTCP) running over both? We compare LTE and WiFi for transfers of different sizes along both directions (i.e. the uplink and the downlink) using a crowd-sourced mobile application run by 750 users over 180 days in 16 different countries. We find that LTE outperforms WiFi 40\% of the time, which is a higher fraction than one might expect at first sight. We measure flow-level MPTCP performance and compare it with the performance of TCP running over exclusively WiFi or LTE in 20 different locations across 7 cities in the United States. For short flows, we find that MPTCP performs worse than regular TCP running over the faster link; further, selecting the correct network for the primary subflow in MPTCP is critical in achieving good performance. For long flows, however, selecting the proper MPTCP congestion control algorithm is equally important. To complement our flow-level analysis, we analyze the traffic patterns of several mobile apps, finding that apps can be categorized as "short-flow dominated" or "long-flow dominated". We then record and replay these patterns over emulated WiFi and LTE links. We find that application performance has a similar dependence on the choice of networks as flow-level performance: an application dominated by short flows sees little gain from MPTCP, while an application with longer flows can benefit much more from MPTCP --- if the application can pick the right network for the primary subflow and the right choice of MPTCP congestion control. <s> BIB009 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Multipathing in communication networks is gaining momentum due to its attractive features of increased reliability, throughput, fault tolerance, and load balancing capabilities. In particular, wireless environments and datacenters are envisioned to become largely dependent on the power of multipathing for seamless handovers, virtual machine (VM) migration and in general, pooling less proficient resources together for achieving overall high proficiency. The transport layer, with its knowledge about end-to-end path characteristics, is well placed to enhance performance through better utilization of multiple paths. Realizing the importance of transport-layer multipath, this paper investigates the modernization of traditional connection establishment, flow control, sequence number splitting, acknowledgement, and flow scheduling mechanisms for use with multiple paths.Multipath rate control defines the fundamental feature of the transport layer. Thus, we study the restructuring of classical utility maximization framework and analyze its stability and convergence. We also examine the topic of multipath congestion control in the light of TCP fairness. To the best of our knowledge, this is the first in-depth survey paper that has chronicled the evolution of the transport layer of the Internet from the traditional single-path TCP to the recent development of the modern multipath TCP (MPTCP) protocol. Along with describing the history of this evolution, we also highlight in this paper the remaining challenges and research issues. Graphical abstractDisplay Omitted <s> BIB010 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Transport protocols that can exploit multiple paths, especially MPTCP, do not match the requirements of video streaming: high average transmission delay, too strict reliability, and frequent head-of-line phenomenons resulting in abrupt throughput drops. In this paper, we address this mismatch by introducing a cross-layer scheduler, which leverages information from both application and transport layers to re-order the transmission of data and prioritize the most significant parts of the video. Our objective is to maximize the amount of video data that is received in time at the client. We show that current technologies enable the implementation of this cross-layer scheduler without much overhead. We then demonstrate the validity of our approach by studying the performance of an optimal cross-layer scheduler. The gap between the performance of the traditional scheduler versus the optimal scheduler justifies our motivation to implement a cross-layer scheduler in practice. We propose one implementation with basic cross-layer awareness. To evaluate the performance of our proposal, we aggregate a dataset of real MPTCP sessions and we use video stream encoded with HEVC. Our results show that our cross-layer proposal outperforms the traditional scheduler. Viewers not only benefit from the inherent advantages of using MPTCP (such as a better resilience to path failure) but also get a better QoE compared to the traditional scheduler. <s> BIB011 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> MPTCP (MultiPath TCP) boosts application network performance by aggregating bandwidth over multiple paths. However, it may cause poor performance due to the large number of out-of-order packets especially when the paths have different delays. To resolve this issue, we propose to dynamically add or remove MPTCP paths with the leverage of software-defined networking (SDN). The key idea is to track the available capacity of connected paths and pick the most appropriate paths depending on varying network conditions. To show the feasibility of our approach, we create an SDN platform using Mininet over Wi-Fi networks. Our analysis shows that a faster download and improved quality of experience (QoE) in adaptive rate video streaming is possible with our dynamic MPTCP path control mechanism using SDN. <s> BIB012 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> The proliferating wireless infrastructures with complementary characteristics prompt the bandwidth aggregation for concurrent video transmission in heterogeneous access networks. Multipath TCP (MPTCP) is an important transport-layer protocol recommended by IETF to integrate different access medium (e.g., Cellular and Wi-Fi). This paper investigates the problem of mobile video delivery using MPTCP in heterogeneous wireless networks with multihomed terminals. To achieve the optimal quality of real-time video streaming, we have to seriously consider the path asymmetry in different access networks and the disadvantages of the data retransmission mechanism in MPTCP. Motivated by addressing these critical issues, this study presents a novel quAlity-Driven MultIpath TCP (ADMIT) scheme that integrates the utility maximization based Forward Error Correction (FEC) coding and rate allocation. We develop an analytical framework to model the MPTCP-based video delivery quality over multiple communication paths. ADMIT is able to effectively integrate the most reliable access networks with FEC coding to minimize the end-to-end video distortion. The performance of ADMIT is evaluated through extensive semi-physical emulations in Exata involving H.264 video streaming. Experimental results show that ADMIT outperforms the reference transport protocols in terms of video PSNR (Peak Signal-to-Noise Ratio), end-to-end delay, and goodput. Thus, we recommend ADMIT for streaming high-quality mobile video in heterogeneous wireless networks with multihomed terminals. <s> BIB013 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> One major concern when applying Multipath TCP (MPTCP) to the real-time multimedia applications is related to MPTCP's fully-reliable and fully-ordered service nature, which will inevitably degrade users' Quality of Experience (QoE) for multimedia streaming services in a heterogeneous wireless network environment because asymmetric wireless links are commonly with different transmission characteristics and sensitive to variations. In this paper, we first discuss the design considerations of partially reliable-MPTCP associated with the real-time constraint of multimedia streaming. Then we propose a context-aware QoE-oriented MPTCP Partial Reliability extension (PR-MPTCP+) for providing partially reliable multimedia streaming service to an upper layer protocol. Finally, we evaluate the proposed PR-MPTCP+ solution using a wide range of multimedia quality metrics. <s> BIB014 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Compared with using only a single wireless path such as WiFi, leveraging multipath (e.g., WiFi and cellular) can dramatically improve users' quality of experience (QoE) for mobile video streaming. However, Multipath TCP (MPTCP), the de-facto multipath solution, lacks the support to prioritize one path over another. When applied to video streaming, it may cause undesired network usage such as substantial over-utilization of the metered cellular link. In this paper, we propose MP-DASH, a multipath framework for video streaming with the awareness of network interface preferences from users. The basic idea behind MP-DASH is to strategically schedule video chunks' delivery and thus satisfy user preferences. MP-DASH can work with a wide range of off-the-shelf video rate adaptation algorithms with very small changes. Our extensive field studies at 33 locations in three U.S. states suggest that MP-DASH is very effective: it can reduce cellular usage by up to 99% and radio energy consumption by up to 85% with negligible degradation of QoE, compared with off-the-shelf MPTCP. <s> BIB015 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> Recent technological advancements in wireless infrastructures and handheld devices enable mobile users to concurrently receive multimedia contents with different radio interfaces (e.g., cellular and Wi-Fi). However, multipath video transport over the resource-limited and error-prone wireless networks is challenged with key technical issues: 1) conventional multipath protocols are throughput-oriented, and video data are scheduled in a content-agnostic fashion and 2) high-quality real-time video is bandwidth-intensive and delay-sensitive. To address these critical problems, this paper proposes a bandwidth-efficient multipath streaming (BEMA) protocol featured by the priority-aware data scheduling and forward error correction-based reliable transmission. First, we present a mathematical framework to formulate the delay-constrained distortion minimization problem for concurrent video transmission over multiple wireless access networks. Second, we develop a joint Raptor coding and data distribution framework to achieve target video quality with minimum bandwidth consumption. The proposed BEMA is able to effectively mitigate packet reordering and path asymmetry to improve network utilization. We conduct performance evaluation through extensive emulations in Exata involving real-time H.264 video streaming. Compared with the existing multipath protocols, BEMA achieves appreciable improvements in terms of video peak signal-to-noise ratio, end-to-end delay, bandwidth utilization, and goodput. Therefore, BEMA is recommended for streaming high-quality real-time video to multihomed terminals in heterogeneous wireless networks. <s> BIB016 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> This document describes, surveys, and classifies the protocol ::: mechanisms provided by existing IETF protocols, as background for ::: determining a common set of transport services. It examines the ::: Transmission Control Protocol (TCP), Multipath TCP, the Stream Control ::: Transmission Protocol (SCTP), the User Datagram Protocol (UDP), UDP- ::: Lite, the Datagram Congestion Control Protocol (DCCP), the Internet ::: Control Message Protocol (ICMP), the Real-Time Transport Protocol ::: (RTP), File Delivery over Unidirectional Transport / Asynchronous ::: Layered Coding (FLUTE/ALC) for Reliable Multicast, NACK- Oriented ::: Reliable Multicast (NORM), Transport Layer Security (TLS), Datagram ::: TLS (DTLS), and the Hypertext Transport Protocol (HTTP), when HTTP is ::: used as a pseudotransport. This survey provides background for the ::: definition of transport services within the TAPS working group. <s> BIB017 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 4) MPTCP: <s> This memo presents an extension to the Multipath Transmission Control ::: Protocol (MPTCP) that allows MPTCP endpoints in which case both sender ::: side and receiver side support this function to provide partially ::: reliable data transmission service to the upper layer applications. In ::: order to achieve the above goal, this memo extents MPTCP by adding two ::: new subtypes which are expressed as "PR_CAPABLE" and "ACK_NOTIFY" and ::: the corresponding processes are also introduced. The extension can ::: provide the backward-compatibility with MPTCP if the new features are ::: not available. <s> BIB018
Multipath TCP (MPTCP)  ,  is a prominent protocol for multipath transmission developed at IETF since 2009. MPTCP has been implemented in the Linux kernel  , and also as an experimental kernel patch for FreeBSD-10.x [175] . Industry has also adopted MPTCP on smartphones  ,  . Two major deployments are voice recognition (SIRI) application  since 2013, and for any application on iOS11  . Another major MPTCP deployment in high-end Android smartphones (e.g., Samsung Galaxy S6 and Galaxy S6 Edge smartphones) relies on network-operated SOCKS proxies, reaching bandwidth of 1 Gbps by KT Corporation, in Korea 2015  . In the following, we first provide an overview of MPTCP. Then, we discuss performance problems. Finally, we survey relevant works based on this protocol. MPTCP overview. MPTCP was designed to use multiple paths for data transmission. In particular, MPTCP establishes multiple subflows for a single MPTCP session. A subflow is a TCP flow over an individual path and looks similar to a regular TCP connection. Besides, there is a MP CAPABLE option to identify that the connection is MPTCP rather than TCP. Further, a token is associated to the MPTCP session. This token is used for subflows to add to this particular session. In MPTCP, application layer sees MPTCP connections as unique, as shown in Figure 10 . Therefore, sender's transport layer packetizes data to TCP packets and receiver's transport layer reorders and recreates the byte stream without application layer knowing about it. As a result, application layer stays unmodified and a standard socket API is used. Regarding data transmission process, each packet contains two sequence numbers: the Subflow Sequence Number (SSN) to lost detection and an additional Data Sequence Number (DSN) to reconstruct the original data at the receiver. MPTCP also utilizes ACKs for subflow and connection level. SACK/Cumulative ACKs are used at subflow level and DSNACKs are used at connection level BIB010 . For data transmission protection, MPTCP uses retransmission mechanism as in regular TCP. Besides, in the case of packet loss over a subflow, retransmission could be over another subflow. Default MPTCP uses coupled congestion control (each MPTCP connection has its own congestion control) to avoid an unfair TCP connection. This algorithm provides better congestion balancing than just using TCP congestion control over each subflow (uncoupled) BIB003 ,  because MPTCP over regular TCP connections could behave unfairly. A shared MPTCP receiving buffer is used at the receiver side to receive and reorder packets of different paths BIB011 . In other words, there is a single window shared by all subflows at the receiver side. Because in multipath approaches, packet scheduling strategy has an important role, there are different strategies introduced for MPTCP. Performance comparison of scheduling methods for multipath transfer is analyzed in BIB005 and different schedulers are implemented and evaluated in BIB008 for MPTCP. Default MPTCP packet scheduling strategy selects the packets in First-In First-Out (FIFO) order and maps them to the different paths according to RTT-based policy. MPTCP supports middleboxes and is compatible with the current network infrastructure BIB010 . This is due to this fact that SSN contains a consecutive sequence number for each subflow packet. Therefore, it can pass through middleboxes BIB004 . However, in case of conflict, MPTCP handles middleboxes by fallback to the regular TCP BIB007 . Moreover, MPTCP provides resilience, mobility and load balancing BIB017 . Performance challenges. Studies in BIB009 and BIB005 show that MPTCP presents performance issues most critically in the case of heterogeneous paths. The reasons of MPTCP performance limitations are discussed below: • Out-of-order packets: MPTCP suffers from out-of-order packet problem. A comparison between Single Path TCP (SPTCP) and MPTCP in BIB012 shows that SPTCP outperforms MPTCP when paths are heavily imbalanced in terms of throughput. MPTCP operates poorly in this case due to a large number of out-of-order delivered packets. Such imbalance throughput could also happen frequently in the case of using 5G network simultaneously with other wireless networks. In our surveyed works, the approach proposed in BIB012 introduced a dynamic MPTCP path control to remedy out-of-order problem. • HOL blocking due to ARQ mechanism: Using ARQ mechanism by MPTCP causes frequently HOL blocking problem, even more than a single TCP connection BIB011 . As previously explained in Section I, HOL incurs large End-to-End delay and low performance. In our surveyed works, the proposed approaches in AD-MIT BIB013 , BIB006 , BIB018 and BIB014 attempted to solve the retransmission problem in order to decrease End-to-End delay. • Frequent throughput fluctuation and unnecessary fast retransmission: MPTCP uses AdditiveIncrease/Multiplicative-Decrease (AIMD) congestion control algorithm to set congestion window sizes. The problem is that AIMD causes frequent throughput fluctuation and significant End-to-End delay BIB013 ,  . For example, out-of-order packet delivery, which is common in multipath transmission, and losses, which could be wireless loss and not congestion loss, could trigger unnecessary fast retransmission, which impacts undesirable reduction in the size of congestion window and waste useful bandwidth BIB010 . In our surveyed works, ADMIT BIB013 considered the packet loss differentiation to mitigate this problem. • Content-agnostic traffic scheduling: In MPTCP, availability of multipath connections is unknown to the application. Therefore, MPTCP is unaware of application information and video content features. The approaches proposed in BIB011 and BIB015 introduced cross layer solutions to access the video content and deadlines, respectively. • Fully reliable and ordered service: MPTCP is an extension of TCP protocol with inherited fully reliable and ordered services, which are not required by video streaming. In our surveyed works, there are some efforts BIB006 , BIB018 , PR-MPTCP + BIB014 applying the concept of partial reliability in MPTCP for real-time video delivery. This concept avoids retransmission for acceptable loss rates and provides partial reliable video data transmission to the upper layers BIB006 , BIB018 , BIB014 . Partial reliability leads to improved network performance parameters (e.g., delay, bandwidth), and consequently, better QoE BIB006 . Improved scheduling mechanisms. There are several proposals to improve MPTCP regarding the above mentioned problems through scheduling functions that define the multipath decision. Next, we briefly review them and next we provide more details. Cross layer works to adapt application/network layer protocols with MPTCP (e.g., BIB015 , BIB011 and BIB012 ) will be presented later in Section IV-D. Wu J. et al. proposed quAlity-Driven MultIpath TCP (ADMIT) protocol BIB013 for streaming high-quality mobile video with multipath TCP in heterogeneous wireless networks. ADMIT is an extension of MPTCP with inheriting basic mechanisms from it, including coupled congestion control, the same connection, subflow level acknowledgments, and retransmission mechanism. The authors claimed that ADMIT is the first MPTCP scheme that incorporates the qualitydriven FEC coding and rate allocation to mitigate End-toEnd video streaming distortion. The proposed FEC Coding in ADMIT, adaptively chooses FEC redundancy and FEC packet sizes according to the network situations (e.g., RTT, bandwidth and, packet loss rate) and delay constraint. This adaptive FEC coding leads to remedy the shortcomings of packet retransmission (e.g., serious delay and performance degradation BIB016 ) by protecting video data. Besides that, the proposed rate allocator algorithm is responsible for load balancing. ZigZag scheme BIB001 is also used in ADMIT. ZigZag has high effect on the FEC coding and rate allocator results due to distinguishing congestion losses from wireless losses. Finally, packet scheduling strategy maps FEC packets to the different paths according to the rate allocation vector. However, there is no mechanism to ACK for reconstructed lost packets in FEC unit. Therefore, the ADMIT protocol keeps sending retransmissions of the lost packets until receiving the ACK. Besides, the packet scheduling strategy is not aware of the frames different priorities. Another problem is that all packets of the Group of Pictures (GoP) and redundant packets must be received before the GoP frames are processed. Each video unit may consist of several packets and it may also depend on other units. The works BIB006 , BIB018 , and PR-MPTCP + BIB014 apply the concept of partial reliability in MPTCP. These works demonstrate that capability of partial reliability for MPTCP outperforms the default MPTCP for real-time video streaming. As a comparison among these works, one can note that the approach in PR-MPTCP + BIB014 defines that switching between MPTCP and partial reliable capability occurs dynamically based on the network situation. However, in BIB018 , partial reliability is only activated in the initial handshake, and there is no explanation about how switching occurs in BIB006 . Besides, the works in BIB006 and PR-MPTCP + BIB014 used old versions of MPTCP. Finally, these works defined different methods for applying partial reliability, which are explained in more details below. Diop et al. BIB006 introduced QoS-ORIENTED MPTCP in order to improve QoS in terms of End-to-End delay. In this work, two QoS-aware mechanisms are implemented with the concept of partial reliability in MPTCP for interactive video applications. The first one, MPTCP-SD (selective discarding), eliminates the least important packets (B-frames) at the sender side. This could decrease the network traffic and avoid latency and loss of I and P frames. The capability of gathering priority information for MPTCP is implemented by using Implicit Packet Meta Header (IPMH) interface BIB002 . In the second mechanism, a time-aware policy is used. In MPTCP-PR (time constrained partial reliability), delay of each queued packet on the receiver side is calculated and whenever it gets close to a time limit (400 ms), packets are sent to the application, and acknowledge would be sent for the missed packets. In addition, delivered packets after a specific time limit are considered as losses, but acknowledgments are sent for them to the sender. The results show that MPTCP-SD provides better video QoS than MPTCP-PR and MPTCP. Another MPTCP Partial Reliability extension is introduced in BIB018 to provide different required reliability level and recommended for video streaming. There is a threshold for the maximum number of retransmission attempts, or maximum delay of transmission for each packet. In this approach, the sender and receiver negotiate about partial reliability function in the initializing phase. During data transmission whenever a packet exceeds the defined threshold, the sender informs it to the receiver. Therefore, the receiver will not wait anymore to receive that packet. Consequently, the receiver will send a forced acknowledgment and sender eliminates that packet from its buffer similar to the time the packet delivered successfully. The forced acknowledgment also shows losses and congestion in the network and triggers the congestion control algorithm. Cao et al. BIB014 proposed Context-aware QoE-oriented MPTCP Partial Reliability extension (PR-MPTCP + ). In this work, sender monitors network congestion and receiver buffer blocking to determine when it should enable partial reliability. In order to detect network congestion, a function of RTT for each path is proposed and to detect the buffer blocking, advertised receiver window (rwnd) is used. In the case of a congested network, only the packets with enough deadline to play would be sent and the packets with the highest priority could be retransmitted. In particular, in this work, the concept of context is used to refer to the video content where I-frames have the highest priority. Whenever buffer blocking is detected, a subset of paths are adaptively selected based on their quality (e.g., bandwidth). The approach switches to the full MPTCP mode (standard MPTCP) when there is no buffer blocking. Authors of PR-MPTCP + demonstrate that this method outperforms the proposed approach in BIB006 in terms of video performance metric.