TCP/IPoverATM的性能研究

 本文讨论将传统的TCP拥塞控制机制和CIPOA用于采用ER(FB)算法和EFCI(CCR)算法的ATM网络时可用比特率业务(ABR)和未确定比特率业务(UBR)的性能.仿真结果表明,无论在缓冲区的需求、带宽分配的公平性、吞吐量和链路利用率方面ABR业务的TCP性能均明显优于UBR业务.对于较简单的网络模型ER(FB)算法的TCP性能优于EFCI(CCR)算法,更优于传统的EFCI算法.     

TCP/IP performance over satellite links

Achieving high data rates using TCP/IP over satellite networks can be difficult. This article explains some of the reasons TCP/IP has difficulty with satellite links. We present solutions to some problems, and describe the state of the research on some the unsolved problems     

Traffic management for TCP/IP over satellite ATM networks

Several Ka-band satellite systems have been proposed that will use ATM technology to seamlessly transport Internet traffic. The ATM UBR, GFR, and ABR service categories have been designed for data. However, several studies have reported poor TCP performance over satellite ATM networks. We describe techniques to improve TCP performance over satellite ATM networks. We first discuss the various design options available for TCP end systems, IP-ATM edge devices, as well as ATM switches for long-latency connections. We discuss buffer management policies, guaranteed rate services, and the virtual source/virtual destination option in ATM. We present a comparison of ATM service categories for TCP transport over satellite links. The main goal of this article is to discuss design and performance issues for the transport of TCP over UBR, GFR, and ABR services for satellite ATM networks     

A new ATM adaptation layer for TCP/IP over wireless ATM networks

This paper describes the design and performance of a new ATM adaptation layer protocol (AAL‐T) for improving TCP performance over wireless ATM networks. The wireless links are characterized by higher error rates and burstier error patterns in comparison with the fiber links for which ATM was introduced in the beginning. Since the low performance of TCP over wireless ATM networks is mainly due to the fact that TCP always responds to all packet losses by congestion control, the key idea in the design is to push the error control portion of TCP to the AAL layer so that TCP is only responsible for congestion control. The AAL‐T is based on a novel and reliable ARQ mechanism to support quality‐critical TCP traffic over wireless ATM networks. The proposed AAL protocol has been validated using the OPNET tool with the simulated wireless ATM network. The simulation results show that the AAL‐T provides higher throughput for TCP over wireless ATM networks compared to the existing approach of TCP with AAL 5. This revised version was published online in July 2006 with corrections to the Cover Date.     

Transport of IP controlled-load service over ATM networks

A hot topic in the research community is the interworking of integrated IP services, defined by the IETF, with ATM, a technology designed for the transport of multimedia traffic. In particular, the IETF recommends the ATM CBR, nrt-VBR, and ABR service classes for the transport of controlled-load service (CLS) over ATM. In this work the first two alternatives are examined and compared, in order to determine which is the most convenient for CLS. The comparison is carried out in terms of QoS and amount of buffering required at the IP/ATM routers. These performance parameters strongly depend on the parameters of the CLS token bucket shaper, that is, the token bucket depth and token bucket input buffer capacity. A nrt-VBR connection is able to offer a given performance level over a range of values of the token bucket parameters wider than that permitted by a CBR connection. Moreover, in all the examined cases the nrt-VBR connection needs a relatively small ATM buffer at the IP/ATM routers. Since, in order to guarantee acceptable performance, some CLS requests must be rejected, the utilization of the ATM link can be relatively low; this drawback can be overcome by serving the rejected CLS requests as classic best-effort traffic     

Guaranteed frame rate: a better service for TCP/IP in ATM networks

Guaranteed frame rate, approved by the ATM Forum, is expected to become an important service category to efficiently support TCP/IP traffic in ATM networks. We first describe the GFR traffic contract in detail. We then present different types of switch implementations that have been proposed to support GFR. We analyze the performance of three of these switch implementations by simulations in two different network environments. These simulations show that the scheduler-based implementations provide a much better performance than the simple switch implementation. However, we also show that coupling an active packet discard mechanism to a scheduler-based switch implementation does not produce a performance gain when many TCP connections are multiplexed inside one ATM VC     

Improving and managing multimedia performance over TCP/IP nets

The TCP/IP-based Internet and, consequently corporate Intranets, were not designed for multimedia traffic. This article discusses the several ways of improving multimedia performance, finding that data compression techniques are no longer the most important factor. © 1998 John Wiley & Sons, Ltd.     

IP/ATM over xDSL技术

随着Internet和Intranet的发展,人们对访问速度的要求越来越高,出现了多种接入技术来满足用户对高速数据接入的需求,如:数字用户环路(xDSL)、混合光纤同轴电缆网(HFC)、基于ATM的无源光网络(APON)、多点分配系统(xMDS)等.     

TCP／IP协议对ATM网的适配

当前在Ｉｎｔｅｒｎｅｔ和其他计算机网上广泛使用的ＴＣＰ／ＩＰ协议与未来准备在Ｂ－ＩＳＤＮ上应用的ＡＴＭ技术之间的有机结合，是一个战略性的技术课题。本文以ＴＣＰ／ＩＰ协议的体系结构及其作用、ＡＴＭ信号元结构与ＡＴＰ适应层为依据，对ＩＰ与ＡＴＭ适配的种种构想（其中包括协议复用、封装、地址分辨和连接管理等项功能的实现）做了轮廓性的探讨。     

Design and evaluation of multicast GFR for supporting TCP/IP over hybrid wired/wireless ATM

The major challenges of designing multicast traffic control protocols for a combined wired/wireless network are the varying transmission characteristics (bandwidth, error, and propagation delay) of the wireless and wired media, and the different, possibly conflicting frame rate requests from multiple sources. To address these issues, in this paper we design and evaluate new unicast and multicast guaranteed frame rate (GFR) schemes for supporting TCP/IP traffic over a combined wired/wireless ATM network. We first propose a new, flexible weighted buffer management, and a frame‐based virtual spacing (VS) mechanism implementing weighted fair queueing. The unicast GFR scheme is based on the integration of the new weighted buffer management, and either cell‐based or frame‐based VS. It is then extended to support multicast GFR flows. The multicast scheme presented in this paper is the first multicast GFR scheme appeared in the literature. These schemes are carefully evaluated over several network configuration, supporting heterogeneous TCP/IP traffic with various frame rates. Simulation results show that the new schemes guarantee the minimum rates requested, provide excellent fairness, and achieve reasonably high efficiency. The new schemes may be extended to provide differentiated service in both IP and mobile IP frame work. This revised version was published online in July 2006 with corrections to the Cover Date.     

Voice service interworking for PSTN and IP networks

This article presents an overview of the main technical problems to be addressed for the provision of interoperable services between IP telephony and the PSTN. The pivotal element of the solution resides in an interworking function. This function is typically implemented in a gateway whose requirements and behavior are here analyzed in terms of signaling and control protocols (control plane) as well as user data transfer (user plane). The presentation is structured around these two planes. The control plane defines the set of signaling protocols to be used in each networking context and the translation between them. Detailed scenarios illustrate the signal translation in the gateway allowing for the establishment of a hybrid phone call. The user plane is responsible for adapting the user data to the properties of each network channel and determines the quality of service of the voice call in terms of delay and speech quality     

Multimedia service interworking over heterogeneous networkingenvironments

This article discusses technical issues related to delivery of multimedia services, such as video-on-demand, over heterogeneous networking environments. In particular, it describes the design and implementation of an experimental system for multimedia service interworking between a DAVIC (Digital Audio Visual Council) domain and an Internet domain. The system, called MIDDLEMEN (middlemen for multimedia environment), consists of the broker and the interworking unit, which work together to provide multimedia services across different types of networks in a seamless manner. The broker acts as a guide to multimedia services, and complements servers or clients that are not equipped with full functionality. The broker also controls the resources in MIDDLEMEN. The interworking unit performs various translation functions under the control of the broker, including stream transport protocol conversion, traffic monitoring and bit-rate control, service gateway conversion, and stream control conversion. Current implementation supports the delivery of a DAVIC-compliant VOD service from an ATM network to an IP network     

IP over SDH和IP over ATM技术

随着Internet的快速发展,对广域网的带宽提出了更高的要求,目前在广域上采用的两种技术是IP over ATM和IP over SDH。本文简要介绍了SDH和ATM以及实现IP over ATM和IP over SDH所需的协议栈,着重比较了这两技术在协议开销,宽带管理,服务质量（QoS),寻址选路以及流量控制等技术。     

SS7 over IP: signaling interworking vulnerabilities

Public telephony - the preferred choice for two-way voice communication over a long time - has enjoyed remarkable popularity for providing acceptable voice quality with negligible connection delays, perhaps due to its circuit-switched heritage. Recently, IP telephony, a packet-based telephone service that runs as an application over the IP protocol, has been gaining popularity. To provide seamless interconnectivity between these two competing services, the Internet Engineering Task Force (IETF) has designed a signaling interface commonly referred to as SIGTRAN. This seamless intersignaling provided by SIGTRAN facilitates any subscriber in one network to reach any other subscriber in the other network, passing through any heterogeneous maze of networks consisting of either of these. Unfortunately, the same intersignaling potentially can be exploited from either side to disrupt the services provided on the other side. We show how this can be done and propose a solution based on access control, signal screening, and detecting anomalous signaling. We argue that to be effective, the latter two should consider syntactic correctness, semantic validity of the signal content, and the appropriateness of a particular signal in the context of earlier exchanged messages     

Unicast and multicast IP error performance over an ATM satellitelink

IP multicast using ATM-based satellites provides the potential to support multimedia applications, including audio/video streaming and information distribution, at a large scale. This article considers the impact of satellite channel errors, and equations are derived for the probability of IP datagram loss in the presence of burst errors on the satellite link. When there are a large number of multicast receivers per spotbeam there is a significant probability that one or more recipients will not receive the data, and this has implications particularly for the design of reliable multicast network protocols     

Impact of mobility on TCP/IP: an integrated performance study

This paper presents a simulation analysis of the impact of mobility on TCP/IP augmented with features to support host mobility in wide area networks. Our results show that the existing version of TCP can yield low throughput in highly mobile environments due to the fact that TCP cannot discriminate packets dropped due to hand-offs with those dropped due to congestion in one or more network resources. As a result, TCP invokes a congestion recovery process when packets are lost during internetwork hand-offs of the mobile host. We investigate a proposal in which the transport layer explicitly receives information from the network layer of any ongoing mobility. We show that by effectively capitalizing this information, TCP can appropriately extend the slow-start phase in the recovery process and achieve higher throughput. Based on the simulation analysis we also show the robustness of this scheme in the presence of both host mobility and network congestion     

ATM与IP技术的融合分析

分别从ATM和IP技术特点出发,讨论了IPoverATM技术的2种模型及其中几种方案,然后分析了IP与ATM结合的性能以及发展前景.     

一种用于TCP/IP减荷的体系结构

TCP/IP减荷的目的是为了将系统主处理器从用于协议处理的繁重的内核中断服务中解脱出来。笔者从对TCP/IP减荷的需求出发,分析了TCP/IP减荷在设计方面的要求,进而提出了一种用于TCP/IP减荷的体系结构。     

Transparent bridging support for Bluetooth–IP service interworking

A PC‐based transparent gateway for interconnecting Bluetooth Piconets and IP local area networks (LAN) was designed in our research. The essential function of this designed Bluetooth‐IP gateway is to achieve a seamless integration among home appliances, networking elements and multi‐systems using the address resolution protocol (ARP) and connection management scheme. The key techniques developed, as well as the performance analysis in terms of queue length, loss rate, throughput and transmission delay are explored in this research. The results allow us to determine the value of the optimal command and infer the maximum queue length requirements such that the service quality is kept at an acceptance level. Copyright © 2002 John Wiley & Sons, Ltd.     

IP multicasting over ATM networks

The Internet protocol (IP) multicast model involves a combination of intrasubnet and intersubnet multicast mechanisms. Technologies supporting a given subnet are expected to have native mechanisms for supporting intrasubnet forwarding of packets sent to multicast destinations. Multicast routers attach to subnets and provide intersubnet forwarding of multicast packets, using interdomain multicast routing protocols developed by the Internet Engineering Task Force (IETF). Unfortunately, ATM networks based on UNI 3.0 or UNI 3.1 signaling service do not provide the native multicast support expected by IP. This has led the IETF to develop the “MARS model”-a fairly complex mechanism for emulating intrasubnet multicast support required when running IPs over ATMs. This paper takes a high level look at the IP multicast service, examines the limitations of the ATM point-to-multipoint virtual channel service, and describes the major architectural points of the MARS model