TCP/IP performance with random loss and bidirectional congestion
TCP/IP performance with random loss and bidirectional congestion
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DOI：
10.1109/90.879342
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发表时间：
2000-10
期刊：
影响因子：
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通讯作者：
T. V. Lakshman;Upamanyu Madhow;B. Suter
中科院分区：
文献类型：
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作者：
T. V. Lakshman;Upamanyu Madhow;B. Suter
随着互联网接入服务的增长，在网络上的非对称链路，如非对称数字用户线（ADSL）和电缆为基础的接入网络，它变得至关重要的是，以评估TCP/IP的性能在系统中的瓶颈链路速度的反向路径上是相当慢的比在forward path.In本文中，我们提供了指导方针，设计网络控制机制，支持TCP/IP。我们将吞吐量确定为缓冲、往返时间和归一化不对称性（定义为反向路径中的确认（ACK）的传输时间与正向路径中的数据包的传输时间的比率）的函数。我们确定了三种模式的操作，这是依赖于前向缓冲区的大小和归一化的不对称性，并确定的条件下，前向链路被充分利用。我们还表明，从前面丢弃ACK的反向链路上的下降提供了性能优势，在使用中的其他下降机制。不对称性增加了TCP已经很高的敏感性，随机数据包丢失发生在一个时间尺度上快于连接往返时间。我们推广到现在众所周知的关系随机丢失概率的平方根获得TCP吞吐量，最初只考虑数据路径拥塞。具体地，当丢失概率、归一化不对称性和带宽延迟乘积的平方的乘积较大时，随机丢失导致显著的吞吐量恶化。当多个连接共享反向瓶颈链路时，反向路径中的拥塞会大大增加TCP的不公平性。我们将展示如何通过反向路径上的每个连接缓冲区和带宽分配来缓解这些问题。
With the growth in Internet access services over networks with asymmetric links such as asymmetric digital subscriber line (ADSL) and cable-based access networks, it becomes crucial to evaluate the performance of TCP/IP over systems in which the bottleneck link speed on the reverse path is considerably slower than that on the forward path. In this paper, we provide guidelines for designing network control mechanisms for supporting TCP/IP. We determine the throughput as a function of buffering, round-trip times, and normalized asymmetry (defined as the ratio of the transmission time of acknowledgment (ACK) in the reverse path to that of data packets in the forward path). We identify three modes of operation which are dependent on the forward buffer size and the normalized asymmetry, and determine the conditions under which the forward link is fully utilized. We also show that drop-from-front discarding of ACKs on the reverse link provides performance advantages over other drop mechanisms in use. Asymmetry increases the TCP already high sensitivity to random packet losses that occur on a time scale faster than the connection round-trip time. We generalize the by-now well-known relation relating the square root of the random loss probability to obtained TCP throughput, originally derived considering only data path congestion. Specifically, random loss leads to significant throughput deterioration when the product of the loss probability, the normalized asymmetry and the square of the bandwidth delay product is large. Congestion in the reverse path adds considerably to TCP unfairness when multiple connections share the reverse bottleneck link. We show how such problems can be alleviated by per-connection buffer and bandwidth allocation on the reverse path.