Characterization and evaluation of TCP and UDP-based transport on real networks

StandardTcp (RenoTcp) does not perform well on fast long distance networks, due to its AMD congestion control algorithm. In this paper we consider the effectiveness of various alternatives, in particular with respect to their applicability to a production environment. We then characterize and evaluate the achievable throughput, stability and intra-protocol fairness of differentTcp stacks (Scalable,Hstcp,Htcp, FastTcp, Reno,Bictcp, hstcp-lp andLtcp) and aUdp based application level transport protocol (Udtv2) on both production and testbed networks. The characterization is made with respect to both the transient traffic (entry and exit of different streams) and the steady state traffic on production Academic and Research networks, using paths withRtts differing by a factor of 10. We also report on measurements made with 10 Gbit/secNics with and withoutTcp Offload Engines, on 10 Gbit/s dedicated paths set up forSc2004.     

A study of a simple preventive transport protocol

The main qualities of a protocol for multimedia flows transportation are related to the way congestions are handled. This paper addresses the problem of end-to-end congestion control performed in the Internet transport layer. We present a simple protocol called Primo, which determines the appropriate sending rate in order to maximize network resources usage and minimize packets loss. Comparison with existing transport protocols (Tcp Reno, Sack, Vegas andTfrc) are considered, regarding various efficiency criteria such as sending and reception rates stability, loss rate, resources occupancy rate and fairness.     

Bandwidth sharing under the assured forwarding Per-Hop behavior

The DiffServ’s Assured Forwarding (af) Per-Hop Behavior (phb) Group defines a differentiated forwarding of packets in four independent classes, each class having three levels of drop precedence. Specific end-to-end services based on thisphb are still being defined. A particular type of service that could assure a given rate to a traffic aggregate has been outlined elsewhere. In such a service, a fair distribution of bandwidth is one of the main concerns. This paper presents experimental work carried out to evaluate howaf distributes bandwidth among flows under different load conditions and traffic patterns. We focused on the effect that marking mechanisms have on bandwidth sharing among flows within a singleaf class. The traffic types we used includeudp flows, individual and aggregatedtcp flows, mix oftcp andudp, tcp sessions with heterogeneous round-trip times, as well as color-blind and color-aware re-marking at the aggregation point fortcp flows. Tests were performed on real and simulated networks. We have found certain conditions under whichaf distributes bandwidth fairly among nonadaptiveudp flows andtcp aggregates. Finally, we evaluate a basic rule for setting the parameters of the two-rate Three-Color Marker conditioning algorithm (trtcm) in order to achieve a better bandwidth distribution fortcp flows.     

AIMD-based online MPLS traffic engineering for TCP flows via distributed multi-path routing

With this paper, we propose a distributed online traffic engineering architecture formpls networks. In this architecture, a primary and secondarympls lsp are established from an ingresslsr to every other egresslsr. We propose to split thetcp traffic between the primary and secondary paths using a distributed mechanism based onecn marking andaimd-based rate control. Inspired by the random early detection mechanism for active queue management, we propose a random early reroute scheme to adaptively control the delay difference between the primary and secondarylsps. Considering the adverse effect of packet reordering ontcp performance for packet-based load balancing schemes, we propose that thetcp splitting mechanism operates on a per-flow basis. Using flow-based models developed for Internet traffic and simulations, we show that flow-based distributed multi-path traffic engineering outperforms on a consistent basis the case of a single path in terms of per-flow goodputs. Due to the elimination of out-of-order packet arrivals, flow-based splitting also enhancestcp performance with respect to packet-based splitting especially for longtcp flows that are hit hard by packet reordering. We also compare and contrast two queuing architectures for differential treatment of data packets routed over primary and secondarylsps in thempls data plane, namely first-in-first-out and strict priority queuing. We show through simulations that strict priority queuing is more effective and relatively more robust with respect to the changes in the traffic demand matrix than first-in-first-out queuing in the context of distributed multi-path routing.     

Modeling of submicrometer gate GaAs field effect transistors

Before describing the mainFet modelings today available, the main technological evolutions ofMesfet andTegfet are summarized. It is brought some information on the various physical effects that occur in the devices and that must be taken into account in the models. It is shown that the different kinds of modelings (Monte Carlo, two dimensional, one dimensional) constitute a continuous chain, where the different elements appear strictly complementary. Finally, the present situation concerning modeling ofMesfet andTegfet will be presented.     

A scheduler for relative delay service differentiation

We propose a new delay-based scheduler called asRD-VC (Relative Delay VirtualClock). Since it performs a delay-based service differentiation among flow aggregates, the quality at microflow level is the same as that at aggregate level. This is not easily achievable when the service differentiation is bandwidth-based or loss-based. Unlike theEDF (Earliest Deadline First) scheduler [1], our proposed scheduler self-regulates and adapts the delays according to load changes. This characteristic permits us to implement it in an AF-likePHB providing the relative quantification service in a DiffServ network. Finally, we compare our proposedrd-vc scheduler with two important existing propositions:WTP (Waiting Time Priority) [2, 3] andex-vc (Extended VirtualClock) [4]. Both these propositions are delay-based and have self-regulation property. All three schedulers (RD-VC, WTP andEX-VC) maintain the required service differentiation among aggregates and have comparable long term average performance like mean throughput per aggregate and packet loss ratio etc. However,RD-VC and WTP take an edge overEX-VC at short-term performance like jitter. Bothrd-vc andWTP have good long term and short-term performance. Our proposedrd-vc, compared to existingWTP, has two additional characteristics, i.e. unlike WTP which is limited to architectures with one queue per Qos class, it has no limitation on implementation scope (with or without separate queues per class) and it has lower complexity. This rendersRD-VC an interesting proposition.     

A countermeasure againstDDOS attacks using active networks technologies

A Distributed Denial of Service (DDoCS) attack consumes the resources of a remote host or network by sending a massive amount ofIP packets from many distributed hosts. It is a pressing problem on the Internet as demonstrated by recent attacks on major e-commerce servers andISPs. Since the attack is distributed and the attack tools evolve at a rapid and alarming rate, an effective solution must be formulated using a distributed and adaptive approach. In this paper, we propose a countermeasure againstDDoCS attacks using a method we call Active Shaping. Our method employs the Active Networks technologies, which incorporates programmability into network nodes. The Active Networks technology enables us to deter congestion and bandwidth consumption of the backbone network caused byDDoCS attacks, and to prevent our system from dropping packets of legitimate users mistakenly. This paper introduces the concept of our method, system design and evaluates the effectiveness of our method using a prototype.     

IP-based transport of voice traffic in the UMTS radio access network: analytical study and empirical validation

In this paper, we investigate theIp protocol as a transport option for the user traffic in the UMTS Terrestrial Radio Access Network (Utran), where stringent delay bounds are to be met for both real-time and non real-time traffic. We focus on real-time voice traffic and present an analytical model for the multiplexing and transport of voice channels in theUtran usingIp. The novelty of our model is that it analytically includes and quantifies the performance of the timer used in multiplexing arriving Frame Protocol (Fp) frames into largerIp packets. We then validate our work through empirical results on a test-bed emulating theUtran transport functionalities. We show the trade-offs between performance, in terms of delay and link utilization, and quantify optimal values for the timer as well as the number ofFp frames perIp packet for a given output link capacity.     

An evaluation oftcp with explicit congestion notification

We study the effect of Explicit Congestion Notification (ecn) ontcp for relatively large but finite file transfers inip networks, and compare it to other congestion avoidance mechanisms, namely Drop Tail (dt) and Random Early Detection (red). We use simulation to measuretcp performance for transfers initiated by a varying number of end hosts. In contrast to previous work, we focus on situations in which all nodes in the network operate uniformly under the same mechanism (dt orred orecn). Our results show that under such uniform conditionsecn does not necessarily lead to significant improvement intcp goodput, although in no case does it lead to an actual degradation in performance. Our results also show that, withecn, tcp flows benefit from lower overhead for unsuccessful transmissions. Furthermore, lockouts are largely avoided. In other words, in an all-ecn network resources are shared more fairly. Finally, we show that global synchronization is no longer an issue, and argue that currenttcp versions have essentially solved the problem, regardless of the queue management scheme employed.     

Space applications of optical communications

Optical communication in Space is now a reality. In this paper we present the recent developments that were undertaken in Europe for this application. We first describe the different missions where optical communications are useful: link between two geostationary satellites (geo-geo), Data Relay Mission (leo-geo) and High Data Rate Satellite Constellation Network. Then we detail the different candidate laser technologies from the most straightforward technologies that have been developed for optical fiber applications (λ=1.55 µm) and 0.8 µm technology based on Silicon detector to the recent developments based on high power fiber amplifiers. In the last chapter we describe thesilex (Semi conductor Intersatellite Link Experiment) program which performs optical communication betweenspot4 Earth observation satellite (cnes) andartemis (esa). The excellent results based on 0.8 µm laser diode technology are considered to be a major milestone in optical intersatellite communication     

Web-based interorganizational information systems for logistics outsourcing

This article examines how web-based interorganizational information systems(ios)can efficiently support coordination mechanisms between outsourcer and third party logistics (3PL). First, we review the literature on coordination mechanisms andios. Second, we report on the methodology used for gathering information on outsourcers and 3PLs. Third, armed with limited but quality data, we identified two fundamental dimensions: 3PL involvement andios impacts on logistics outsourcing decisions. By combining the two dimensions, we propose a conceptual framework that highlights four main categories ofios that we characterize as neutralios, supply chainios, strategicios and dynamicios. After characterizing and analyzing each category, we discuss how these web basedios support outsourcers and 3PL along the supply chain. Finally, the article discusses the framework’s relevancy and its limits.     

Network-controlled mobility within radio access networks based onWLAN technologies

This article presents a network-controlled approach of user terminal mobility within anIP based WirelessLAN Access Network. In a first part, this article makes a review of the mobility support, on the subject of emergingWLAN technologies asHIPERLAN/2 andIEEE 802.11, on the one hand, and, regardingIP networks as currently studied withinIETF, on the other hand. Both types ofIP mobility protocols are presented, either global mobility protocols such as MobileIP, or local mobility management protocols (micro mobility). In the next part, the overall principles of our mobility management approach are explained; this approach is based on the implementation of a new network entity dedicated to the control of user terminal mobility. The last part details a practical implementation of this approach. The implementation is carried out on the basis of Hierarchical MobileIPv6 (HMIPv6). The experimental results confirm the importance to carefully plan and control the user terminal mobility within largeIP based Access Networks, as this brings benefit to the user as well as to the operator.     

A MC-CDMA system analysis in a software radio context

This paper presents a Multi-Carrier Code Division Multiple Access (Mc-Cdma) system analysis in a software radio context. Based on a combination of multi-carrier modulation and code division multiple access,Mc-Cdma benefits from the main advantages from both schemes: high spectral efficiency, high flexibility, multiple access capabilities, etc. It is firstly shown why, nowadays,Mc-Cdma is undoubtedly a high potential candidate for the air interface of the 4G cellular networks. TheMc-Cdma concept and the block-diagrams of the transmitter and the receiver are presented first. Afterwards, the technical issues concerning the processing devices for the implementation ofMc-Cdma systems in a software radio context are analysed. The advantages and disadvantages of Digital Signal Processors (Dsps) and Field Programmable Gate Arrays (Fgpas) components are discussed. The implementation ofMc-Cdma systems and the integration of signal processing algorithms as Fast Hadamard Transform (Fht) and Inverse Fast Fourier Transform (Ifft) are considered and analysed for the first time. Finally, implementation results with a mixed prototyping board are presented. Then, it is shown that a new combination of the flow graphs ofFht andIfft leads to interesting computation savings and that hardware structures asFgpas are more adapted thanDsps to those intensive computation functions. Finally, for the completeMc-Cdma modem implementation, the necessity of a Co-Design methodology is highlighted in order to obtain the best matching between algorithms and architecture.     

Modélisation de la technique temporelle asynchrone

The evolution towards the integrated broadband communication network is undertaken by several countries. In France, system designers ofCnet in Lannion have assembled an experimental integrated broadband communication network (Ibcn)called Prelude based upon a 4.5 Gbit/s switching matrix and a new and promising transfer mode called the asynchronous time-division technique (Atd).During the project, performance evaluation studies have been carried through, aiming to validate the Atd concepts and to dimension the switching matrix. This paper reviews the Ibcn lab experiments in the world, with operational characteristics;Atd concepts are detailed and the most important features of Ibcn modelling are given. Finally, the network dimensioning is carried through giving packet size, buffers length, loss probabilities and waiting times.     

ATM and AAL layer issues concerning multimedia applications

This paper presents an overview of the facilities that should be provided by theAtm layer and the adaptation layer (Aal) in order to support multimedia communications. From the analysis of data flows generated by well known multimedia applications and the services that could be offered byAtm networks both in the public and the private domain, we propose solutions enabling the availability of such applications onAtm networks taking into account both economical andQos parameters.     

TICP: Transport Information Collection Protocol

We present and validateTicp, a TCP-friendly reliable transport protocol to collect information from a large number of sources spread over the Internet.Ticp is a stand-alone protocol that can be used by any application requiring the reliable collection of information. It ensures two main functions: (i) the information arrives at the collector entirely and correctly, (ii) the implosion at the collector and the congestion of the network are avoided. The congestion control inTicp is done by having the collector probe the sources at a rate function of network conditions. The probing rate increases and decreases in a way similar to how TCP adapts its congestion window. We implementTicp in ns-2 and validate its performance. In particular, we show how efficientTicp is in quickly and reliably collecting information from a large number of sources, while avoiding network congestion and being fair with competing traffic.     

Analysis of flow transfer times in IEEE 802.11 wireless LANs

In this paper we present an integrated packet/flow level modelling approach for analysing flow throughputs and transfer times inieee 802.11wlans. It captures the statistical characteristics of the transmission of individual packets at themac layer and takes into account the system dynamics due to the initiation and completion of data flow transfers. In particular, at the flow level the system is modelled by a processor sharing type of queue, reflecting theieee 802.11mac design principle of distributing the transmission capacity fairly among the active flows. The integrated packet/flow level model is analytically tractable and yields a simple approximation for the throughput and flow transfer time. Extensive simulations show that the approximation is very accurate for a wide range of parameter settings. In addition, the simulation study confirms the attractive property following from our approximation that the expected flow transfer delay is insensitive to the flow size distribution (apart from its mean).     

Mobility-awareness in group key management protocols within MANETs

Several sensitive applications deployed within wireless networks require group communications. A high level of security is often required in such applications, like military or public security applications. The most suitable solution to ensure security in these services is the deployment of a group key management protocol, adapted to the characteristics ofManets, especially to mobility of nodes. In this paper, we present theOmct (Optimized Multicast Cluster Tree) algorithm for dynamic clustering of multicast group, that takes into account both nodes localization and mobility, and optimizes the energy and bandwidth consumptions. Then, we show how we integrateOmct within our group key management protocolBalade, in a sequential multi-source model. The integration ofBalade andOmct allows an efficient and fast key distribution process, validated through simulations, by applying various models of mobility (individual mobility and group mobility). The impact of the mobility model on the performance and the behaviour of the group key management protocolBalade coupled withOmct, is also evaluated.     

10 gigabit Ethernet long-haul transmission without in-line EDFAs

In this contribution, we present experimental results on optical packet transmission of two 10 gigabit ethernet channels (10Ge) over 252 km link of standard single mode fibre (Ssmf, itu-t Recommendation G.652) and 287 km long link composed of 85 km ofSsmf and 202 km of non-zero dispersion-shifted (Nz DSF, itu-t Recommendation G.655) without deployment of in-line erbium-doped fiber amplifiers (Edfas). All the active components, dispersion compensating fibre (Dcf) modules and optical band-pass filters were placed at the transmitter and at the receiver side of the link. To our best knowledge, this is the first report of pure Ethernet transmission without in-lineEdfas over such a distance. The results are encouraging especially for operators of national research and educational networks who rely on leased dark fibres and prefer as long transmission as possible without deployment of in-line amplifiers.     

Optimizing IP networks in a hybrid IGP/MPLS environment

In this paper, we consider a traffic engineering (te) approach toip networks in a hybridigp/mpls environment. Thoughigp (Interior Gateway Protocol) routing has proven its scalability and reliability, effective traffic engineering has been difficult to achieve in public IP networks because of the limited functional capabilities of conventionalip technologies.mpls (Multi-Protocol Label Switching) on the one hand enhances the possibility to engineer traffic onip networks by allowing explicit routes. But on the other hand it suffers from the scalability (n-square) problem. Hybridigp/mpls approaches rely onip native routing as much as possible and usempls only if necessary. In this work we propose a novel hybrid traffic engineering method based on genetic algorithms, which can be considered as an offlinete approach to handle long or medium-term traffic variations in the range days, weeks or months. In our approach the maximum number of hops anlsp (Label Switched Path) may take and the number oflsps which are applied solely to improve the routing performance, are treated as constraints due to delay considerations and the complexity of management. We apply our method to the German scientific network (b-win) for which a traffic matrix is available and also to some other networks with a simple demand model. We will show results comparing this hybridigp/mpls routing scenario with the result of pureigp routing and that of a full meshmpls with and without traffic splitting.