Applications running in data center networks exhibits barrier-synchronized many-to-one communication pattern. Under this pattern, multiple workers synchronously transmit data to single aggregator. Synchronized transmission from multiple workers overload small-sized buffer of switch connected to aggregator. This causes severe packet drops and leads to overall application goodput degradation. This is named as TCP Incast problem in data center network. In this paper, an application layer technique called Delayed Server Response at Application Layer (DSRAL) is proposed to mitigate TCP Incast problem. It is delay-based sequential data transmission technique. In DSRAL, aggregator first determines amount of time required by each worker to finish its data transmission. This can be done by knowing Server Request Unit (SRU) size, average Round Trip Time (RTT) and packet scheduling time. Then along with request packet, aggregator communicates distinct SRU transmission time with each worker and enforces them to transmit SRUs sequentially. Through simulation it is proved that DSRAL avoids TCP Incast problem and provides improved performance than existing application layer serialized method. It supports large number of workers and simultaneously achieves high application goodput without causing any packet loss.

在数据中心网络中运行的应用程序表现出屏障同步的多对一通信模式。在这种模式下，多个工作进程将数据同步传输到单个聚合器。来自多个工作人员的同步传输使连接到聚合器的交换机的小型缓冲区过载。这会导致严重的数据包丢失，并导致整个应用程序吞吐量下降。这在数据中心网络中被称为TCP Incast问题。在本文中，提出了一种称为应用程序延迟服务器响应（DSRAL）的应用程序层技术来缓解TCP Incast问题。它是基于延迟的顺序数据传输技术。在DSRAL中，聚合器首先确定每个工作人员完成数据传输所需的时间。这可以通过了解服务器请求单元（SRU）大小来完成，平均往返时间（RTT）和数据包调度时间。然后，与请求数据包一起，聚合器与每个工作人员通信不同的SRU传输时间，并强制他们依次传输SRU。通过仿真证明，DSRAL避免了TCP Incast问题，并提供了比现有应用程序层序列化方法更高的性能。它支持大量工作人员，同时实现高应用吞吐量，而不会造成任何数据包丢失。