TCP Response to Lower-Layer Connectivity-Change Indications (original) (raw)

TCP and explicit congestion notification

ACM SIGCOMM Computer Communication Review, 1994

This paper discusses the use of Explicit Congestion Notification (ECN) mechanisms in the TCP/IP protocol. The first part proposes new guidelines for TCP's response to ECN mechanisms (e.g., Source Quench packets, ECN fields in packet headers). Next, using simulations, we explore the benefits and drawbacks of ECN in TCP/IP networks. Our simulations use RED gateways modified to set an ECN bit in the IP packet header as an indication of congestion, with Reno-style TCP modified to respond to ECN as well as to packet drops as indications of congestion. The simulations show that one advantage of ECN mechanisms is in avoiding unnecessary packet drops, and therefore avoiding unnecessary delay for packets from low-bandwidth delay-sensitive TCP connections. A second advantage of ECN mechanisms is in networks (generally LANs) where the effectiveness of TCP retransmit timers is limited by the coarse granularity of the TCP clock. The paper also discusses some implementation issues concerning ...

Improving TCP Network Performance by Detecting and Reacting to Packet Reordering

2003

There are many factors governing the performance of TCP-basec applications traversing satellite channels. The end-to-end performance of TCP is known to be degraded by the reordering, delay, noise and asymmetry inherent in geosynchronous systems. This result has been largely based on experiments that evaluate the performance of TCP in single flow tests. While single flow tests are useful for deriving information on the theoretical behavior of TCP and allow for easy diagnosis of problems they do not represent a broad range of realistic situations and therefore cannot be used to authoritatively comment on performance issues. The experiments discussed in this report test TCP's performance in a more dynamic environment with competing traffic flows from hundreds of TCP connections running simultaneously across the satellite channel. Another aspect we investigate is TCP's reaction to bit errors on satellite channels. TCP interprets loss as a sign of network congestion. This causes TCP to reduce its transmission rate leading to reduced performance when loss is due to corruption. We allowed the bit error rate on our satellite channel to vary widely and tested the performance of TCP as a function of these bit error rates. Our results show that the average performance of TCP on satellite channels is good even under conditions of loss as high as bit error rates of

On TCP reaction to Explicit Congestion Notification

Journal of High Speed Networks, 2004

We investigate the behavior of a new response strategy to TCP Explicit Congestion Notification (ECN). The new strategy is more aggressive in the short term, but preserves TCP long term behavior-without modifying the router ECN marking rate. A more aggressive short term behavior gives incentives for hosts to become ECN-compliant. ECN serves as an early warning sign in this case. Our analysis demonstrates the effectiveness of the new TCP ECN behavior. Simulation results with short/long lived FTP, UDP and HTTP connections, multiple bottleneck configurations, and various TCP flavors and parameters, demonstrate higher throughput and reduced oscillations with the new response strategy.

Delay-based congestion avoidance for TCP

IEEE/ACM Transactions on Networking, 2003

The set of TCP congestion control algorithms associated with TCP/Reno (e.g., slow-start and congestion avoidance) have been crucial to ensuring the stability of the Internet. Algorithms such as TCP/NewReno (which has been deployed) and TCP/Vegas (which has not been deployed) represent incrementally deployable enhancements to TCP as they have been shown to improve a TCP connection's throughput without degrading performance to competing flows. Our research focuses on delay-based congestion avoidance algorithms (DCA), like TCP/Vegas, which attempt to utilize the congestion information contained in packet round-trip time (RTT) samples. Through measurement and simulation, we show evidence suggesting that a single deployment of DCA (i.e., a TCP connection enhanced with a DCA algorithm) is not a viable enhancement to TCP over high-speed paths. We define several performance metrics that quantify the level of correlation between packet loss and RTT. Based on our measurement analysis we find that although there is useful congestion information contained within RTT samples, the level of correlation between an increase in RTT and packet loss is not strong enough to allow a TCP/Sender to reliably improve throughput. While DCA is able to reduce the packet loss rate experienced by a connection, in its attempts to avoid packet loss, the algorithm will react unnecessarily to RTT variation that is not associated with packet loss. The result is degraded throughput as compared to a similar flow that does not support DCA.

Abstract— Traditional Tcp Implementations Are Tuned To

work well over wired networks. A packet loss is occurred in a wired network mainly due to network congestion. On the other hand in a wireless link packet losses are caused mainly due to bit errors resulted from noise, interference, and various kinds of fadings. TCP performance in these environments is impacted by three path characteristics, not normally present in wired environments: high bandwidth delay product, packet losses due to corruption and bandwidth asymmetry. Wireless TCP has no idea whether a packet loss is caused by congestion or bit error. TCP assumes loss is caused by congestion and turns on its congestion control algorithms to slow down the amount of data it transmits as well as adopts retransmission policy. Invoking congestion control for bit errors in wireless channel reduces TCP throughput drastically. We propose an empirical architecture to recover these bit errors at Data Link Layer dynamically before entering the frame into buffer which reduces the number of ret...

Improving performance of delay-based TCPs with rerouting

IEEE Communications Letters, 2000

Delay-based TCPs detect network congestion in the early stage and successfully prevent periodic packet loss that usually occurs in loss-based mechanisms. It has been demonstrated that delay-based algorithms outperform loss-based schemes in many aspects. However, a delay-based TCP may not prevent unnecessary throughput degradation when rerouting occurs and in mobile IP networks and mobile ad hoc networks because it could not differentiate whether the increased RTT is due to route change or network congestion. This work investigates how to improve the performance of delay-based TCPs with rerouting and proposes a mechanism for delay-based TCPs. The proposed mechanism is able to re-measure the BaseRTT if necessary by detecting the change of TTL value of two end-hosts. Based on the simulation results, we demonstrate the effectiveness and utilities.

A fast adaptation mechanism for TCP vertical handover

2008 International Conference on Advanced Technologies for Communications, 2008

In this paper we propose a vertical handover mechanism for TCP to deal with the delay and bandwidth change during the handover. The proposed mechanism relies on the interaction between the sender and the receiver during the handover and requires no a prior information of the new path. The adaptation is triggered by a handover notification at the receiver and finishes in about two round-trip time. Furthermore, it solves the problem of packet reordering and spurious retransmission timeout as well which are also common during vertical handovers. Simulation results show that our mechanism improves TCP performance in various vertical handover scenarios.

On the prevalence and evaluation of recent TCP enhancements

IEEE Global Telecommunications Conference, 2004. GLOBECOM '04., 2004

In recent years several enhancements to TCP congestion control and loss recovery mechanisms have been proposed and accepted as Internet standards. While each proposal has been accompanied with related research, a number of questions remain to be answered both in the research and the implementer community: (i) What is the current deployment status of these TCP enhancements in the Internet, (ii) What is the effect of TCP enhancements on web based transfers, and (iii) How do bulk data transfers benefit from the cumulative addition of these TCP enhancements. In this paper, we attempt to answer these questions. We consider five TCP enhancements:

TCP vs. TCP: A systematic study of adverse impact of short-lived TCP flows on long-lived TCP flows

Proceedings IEEE 24th Annual Joint Conference of the IEEE Computer and Communications Societies., 2005

While earlier studies have pointed out that short-lived TCP flows (mice) may hurt long-lived TCP flows (elephants) in the long term, they provide insufficient insight for developing scenarios leading to drastic drop in throughputs of long-lived TCP flows. We have systematically developed TCP adversarial scenarios where we use short-lived TCP flows to adversely influence long-lived TCP flows. Our scenarios are interesting since, (a) they point out the increased vulnerabilities of recently proposed scheduling, AQM and routing techniques that further favor short-lived TCP flows, and (b) they are more difficult to detect when intentionally found to target long-lived TCP flows.

A Diagnosis-Based Soft Vertical Handoff Mechanism for TCP Performance Improvement

2010

Most existing soft handoff approaches lead to plenty of out-of-order packets during downward vertical handoffs (VHOs). We have presented a soft VHO scheme, called SHORDER, to avoid packet reordering caused by downward VHOs. In this paper, we analyze the effects of our SHORDER scheme and another typical existing soft VHO method on the handoff latency and the received data size during a downward VHO for TCP applications. Then, we approximately derive the applicable conditions of the two approaches, and further propose a diagnosis-based soft vertical handoff (DSVH) mechanism which can self-adaptively deal with reordering packets. The mechanism has practical advantages of no changes to correspondent nodes and compatibility with various enhanced TCP variants. With numerical analysis and test-bed experiments, we show that the DSVH mechanism has better performance than the SHORDER scheme and the typical existing method. Furthermore, experimental and analytical results are consistent with each other.