We consider a resource allocation problem where individual users wish to send data across a network to maximize their utility, and a cost is incurred at each link that depends on the total rate sent through the link. It is known that as long as users do not anticipate the effect of their actions on prices, a simple proportional pricing mechanism can maximize the sum of users' utilities minus the cost (called aggregate surplus). Continuing previous efforts to quantify the effects of selfish behavior in network pricing mechanisms, we consider the possibility that users anticipate the effect of their actions on link prices. Under the assumption that the links' marginal cost functions are convex, we establish existence of a Nash equilibrium. We show that the aggregate surplus at a Nash equilibrium is no worse than a factor of 4 # 2 - 5 times the optimal aggregate surplus; thus, the efficiency loss when users are selfish is no more than approximately 34%.

The initial window MAY be two packets (instead of the current initial window of one packet). For packets of at most 1460 bytes, the initial window MAY be three packets. For packets of at most 1095 bytes, the initial window MAY be four packets. 2 The Burstiness of Current TCP in Slow-Start: cwnd = 1 packet:) send one data packet ( receive one ACK increase cwnd to 2 packets:) send two back-to-back packets ( receive one ACK (a delayed ACK) increase cwnd to 3 packets:) send three back-to-back packets 3 The Burstiness of Current TCP with a Dropped Ack: cwnd = N packets, N packets are in pipe: ( receive one ACK, acking two packets) send two back-to-back packets ( receive one ACK, acking two packets) send two back-to-back packets ONE ACK IS DROPPED IN THE NETWORK

DCCP, the Datagram Congestion Control Protocol, is a new transport protocol in the TCP/UDP family that provides a congestion-controlled flow of unreliable datagrams. Delay-sensitive applications, such as streaming media and telephony, prefer timeliness to reliability. These applications have historically used UDP and implemented their own congestion control mechanisms---a difficult task---or no congestion control at all. DCCP will make it easy to deploy these applications without risking congestion collapse. It aims to add to a UDP-like foundation the minimum mechanisms necessary to support congestion control, such as possibly-reliable transmission of acknowledgement information. This minimal design should make DCCP suitable as a building block for more advanced application semantics, such as selective reliability. We introduce and motivate the protocol and discuss some of its design principles. Those principles particularly shed light on the ways TCP's reliable byte-stream semantics influence its implementation of congestion control.

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Wireless links have intrinsic characteristics that affect the performance of transport protocols; these include variable bandwidth, corruption, channel allocation delays, and asymmetry. In this paper we review simulation models for cellular, WLAN and satellite links used in the design of transport protocols, and consider the interplay between wireless links and transport. We argue that the design and evaluation of transport protocols can be improved by providing easily available models of wireless links that strike a balance between realism, generality, and detail.

Wireless and satellite networks often have non-negligible packet corruption rates that can significantly degrade TCP performance. This is due to TCP's assumption that every packet loss is an indication of network congestion (causing TCP to reduce the transmission rate). This problem has received much attention in the literature. In this paper, we take a broad look at the problem of enhancing TCP performance under corruption losses, and include a discussion of the key issues. The main contributions of this paper are: (i) a confirmation of previous studies that show the reduction of TCP performance in the face of corruption loss, and in addition a plausible upper bound achievable with perfect knowledge of the cause of loss, (ii) a classification of the potential mitigation space, and (iii) the introduction of a promising new mitigation that employs rich cumulative information from intermediate nodes in a path to form a better congestion response.

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2006). This document describes service classes configured with Diffserv and recommends how they can be used and how to construct them using Differentiated Services Code Points (DSCPs), traffic conditioners, Per-Hop Behaviors (PHBs), and Active Queue Management (AQM) mechanisms. There is no intrinsic requirement that particular DSCPs, traffic conditioners, PHBs, and AQM be used for a certain service class, but as a policy and for interoperability it is useful to apply them consistently.

We present an improved Explicit Congestion Notification (ECN) mechanism that enables a router to signal congestion to the sender without trusting the receiver or other network devices along the signaling path. Without our mechanism, ECN-based transports can be manipulated to undermine congestion control. Web clients seeking faster downloads, for example, can trivially conceal congestion signals from Web servers. A misbehaving connection would exceed its fair bandwidth share at the expense of competing traffic by as much as an order of magnitude in our simulations. Our improved mechanism is robust because it does not depend on correct implementation at locations other than the sender and marking router, and it is practical because it admits an efficient implementation that is backwards-compatible with prior ECN and TCP/IP mechanisms. 1.

Resource allocation and accountability keep reappearing on every list of requirements for the Internet architecture. The reason we never resolve these issues is a broken idea of what the problem is. The applied research and standards communities are using completely unrealistic and impractical fairness criteria. The resulting mechanisms don’t even allocate the right thing and they don’t allocate it between the right entities. We explain as bluntly as we can that thinking about fairness mechanisms like TCP in terms of sharing out flow rates has no intellectual heritage from any concept of fairness in philosophy or social science, or indeed real life. Comparing flow rates should never again be used for claims of fairness in production networks. Instead, we should judge fairness mechanisms on how they share out the ‘cost ’ of each user’s actions on others.

One key component of recent pricing-based congestion control schemes is an algorithm for probabilistically setting the Explicit Congestion Notification bit at routers so that a receiver can estimate the sum of link congestion prices along a path. We consider two such algorithms---a well-known algorithm called Random Exponential Marking (REM) and a novel algorithm called Random Additive Marking (RAM). We show that if link prices are unbounded, a class of REM-like algorithms are the only ones possible. Unfortunately, REM computes a biased estimate of total price and requires setting a parameter for which no uniformly good choice exists in a network setting. However, we show that if prices can be bounded and therefore normalized, then there is an alternate class of feasible algorithms, of which RAM is representative and furthermore, only the REM-like and RAM-like classes are possible. For properly normalized link prices, RAM returns an optimal price estimate (in terms of mean squared error), outperforming REM even if the REM parameter is chosen optimally. RAM does not require setting a parameter like REM, but does require a router to know its position along the path taken by a packet. We present an implementation of RAM for the Internet that exploits the existing semantics of the time-to-live field in IP to provide the necessary path position information.