Improving the performance of interactive TCP applications using service differentiation

Abstract

Abstract-Interactive TCP applications, such as Telnet and the Web, are particularly sensitive to network congestion. Indeed, congestion-induced queuing and packet loss can be a significant cause of large delays and variability, thereby decreasing user-perceived quality. We consider addressing these effects using service differentiation, by giving priority to interactive applications' traffic in the network. We study different packet marking schemes and handling mechanisms (packet dropping and scheduling) in the network. For marking packets, two approaches are considered. First, we look into application-based marking, and show how the protection of Telnet traffic against loss can eliminate large echo delays caused by retransmit timeouts, and how, by limiting packet loss for Web page downloads, their delays can be significantly reduced, resulting in enhanced interactivity. Second, we consider differentiation based on TCP state, where we present a marking algorithm that prioritizes packets at the source, based on each connection's window size. In addition, we describe the shaping mechanisms required for conformance to agreements with the network. We show how this marking results in good response times for short transfers, which are characteristic of interactive applications, without significantly affecting longer ones.

Network schemes for TCP elastic traffic in the Internet

“…Its value depends on users' desires and the specific application. For example (see [5] and references therein), a typical user browsing small web pages expects a maximum response time of a few seconds (e.g., 5 s); in ftp, where files are typically larger, the maximum response times are also larger, and users would be willing to wait in proportion to the file size; or in telnet, the echo delays should be smaller than 150 ms. Moreover, some demanding users can want better performance than others, e.g., users using the web for business applications (e-commerce, online trading, etc.)…”

“…This scheme [5]  Packets are marked in the host by TCP sources as high, med or low. The marking algorithm depends on the TCP state, i.e., on the actual value of the window and on the identification of some "important" packets, as we describe below in more detail.…”

Service Differentiation in the Internet to Support Multimedia Traffic

“…This allows the elimination of excessive delay of character echoes (1 sec), which result from retransmits due to packet loss. Without service differentiation, these delays occur for about one out of ten typed characters (more details can be found in [20]). In conclusion, it is possible to use multiple drop priorities to the advantage of interactive applications, in order to improve the user-perceived performance of such applications.…”

Evaluating performance among different TCP flows in a differentiated services enabled network

“…Some studies concerning the interaction among flows with different characteristics in a DS capable network have been recently presented in [6,8,10,11,12,13,14,15,16], but most of them suffer from the same problem. They have mainly focused on achieving targeted throughputs and performance guarantees for long TCP transfers (i.e., they analysed steady-state performance of TCP flow) in the presence of competing UDP flows in the same bottleneck link.…”

“…Web browsing) have much different characteristics and behavior than bulk FTP transfers. Some studies [14,17,18] have investigated the fairness problem between short-lived and long-lived TCP flows. As argued in [18], short-lived TCP flows, which transmit small documents, suffer from reduced throughput compared with long-lived ones, which transmit large documents.…”