A New Direction for Research on Data Origin Authentication in Group Communication

Multicasting is the data distribution from one sender to a group of receivers. Traditionally multicasting is implemented at network layer, in the way that routers perform membership management, maintain data delivery path, and replicate and forward data. IP multicast is the most efficient way for group data distribution. However, it has been shown that it is extremely difficult to deploy IP multicast at a large scale. Therefore an alternative has been proposed to shift multicast support to the application layer. This approach expects end-hosts participating in the application to perform multicast functions. This is application layer multicasting (ALM). This paper proposes a proxy-based single source ALM protocol which targets media streaming applications, where latency is the overlay building metric. A text-based message exchange application is implemented based on this protocol. Some measurements are taken both on the intranet and on the Internet. And some performance data are provided. Finally we concluded our research

Despite the availability of high bandwidth Internet access for end-users, video broadcasting over the Internet is not widely spread. Multicast communication decreases the network load by eliminating redundancy of the data transfer. However IP multicast was never widely accepted by commercial Internet service providers (ISP). Existing solutions solving this problem, like MBONE tunneling, are not available for end-users accessing the Internet via xDSL or TV cable. Application layer multicast using peer-to-peer (P2P) overlay networks could solve the problem of sparse IP multicast support in the Internet. A limitation of this approach is the lack of standardized interfaces for existing IP multicast applications. We propose a solution, which bridges application layer multicast and IP multicast and uses a P2P (overlay) network to transport multicast data. Our solution - including a proof-of-concept prototype - enables video broadcasting over the Internet using existing IP multicast applications without requiring additional service deployment.

Multicast solutions have been evolving from "bottom" to "top", i.e., from IP layer (called IP multicast) to application layer (referred to as application layer multicast). Recently, there are some new proposals (named as overlay multicast) using certain "infrastructure" (composed of proxies) in the middle. Although it is well accepted that application layer multicast and overlay multicast are easier to deploy while sacrificing bandwidth efficiency compared with IP multicast, little research has been done to systematically evaluate and compare their performance. In this paper, we conduct a comparative study of different types of multicast routing protocols. We first present a qualitative comparison of three types of protocols, and then we provide a quantitative study of four representative protocols, namely, PIM-SSM, NARADA, NICE, and POM by extensive simulations. Our studies will help to answer some of the most important questions, such as which way to go: top, bottom, or in the middle?.

Video streaming services over the Internet are growing rapidly owing to the broadbandization of various networks. However, in such systems where a large number of users simultaneously access the same contents server, the convergence of the network traffic and service requests presents a significant problem. From this point of view, application layer multicast (ALM) has recently attracted much attention due to its scalability and feasibility in the current network systems. In ALM, user nodes construct a multicast tree structure to efficiently deliver an identical video streaming content. Various techniques to construct ALM trees have been designed to achieve improved performance in terms of shorter delay and higher reliability. However, in most of the existing ALM schemes, the performance in channel switching events has not been studied sufficiently; channel switching can be considered as the combination of the procedures for departing from the current and joining the future ALM trees, respectively. In general, node joining and departure processes take a certain time, which can be increased significantly depending on the network conditions whereby users are left waiting for the start of a new program on the switched channel. Therefore, reducing the channel switching delay is a significant issue in multichannel video streaming in ALM. In this paper, we propose a multichannel streaming scheme to reduce channel switching delay in ALM. Our scheme is based on an advanced ALM method dubbed network-aware hierarchical arrangement graph, which constructs node-disjoint multicast trees by utilizing the arrangement graph theory to achieve high robustness on node departures. The performance of the proposed scheme is verified through extensive computer simulations, which demonstrate that our proposed scheme succeeds in reducing the delay in channel switching without system throughput degradation.

After a decade of research and development, IP multicast has still not been deployed widely in the global Internet due to many open technical issues: lack of admission control, poorly scaled with large number of groups, and requiring substantial infrastructure modifications. To provide the benefits of IP multicast without requiring direct router support of the presence of a physical broadcast medium, various application level multicast (ALM) models have been attempted. However, there are still several problems with ALM: unnecessary coupling between an application and its multicasting supports, bottleneck problem at network access links and considerable processing power required at the end nodes to support ALM mechanisms. This paper proposes an architecture to address these problems by delegating application-multicasting support mechanisms to smart edge devices associated with the application end nodes. The architecture gives rise to an interesting edge device any-casting technology that lies between the IP-multicasting and the application layer multicasting and enjoys the benefits of both. Furthermore, the architecture may provide sufficient cost-benefit for adoption by service providers. The paper presents initial results obtained from the implementation of a video streaming application over the testbed that implements the proposed architecture.

Native IP multicast would be the best solution to distribute live streaming contents among various destinations since the real-time nature of such applications usually imposes strict delay constraints. Application Layer Multicast (ALM) platforms are emerging as a solution to overcome the well-known lack of a globally supported native multicast. Since the development of ALM applications is slowed by complexity and portability issues, we designed an open source C library framework that takes care of RTP/RTCP technical details and fosters a modular and higher level design. Besides it frees ALM developers from spending time in porting operations from Unix to Windows operating systems.

This thesis reports on an investigation into the teletraffic modelling and performance of layered cellular networks that use overflow for new call and handover attempts in order to improve system performance It addresses the important problems how to model and analyse overflow in large cellular networks so that the overall impact across the network can be evaluated, the overflow policies that can be used with new calls and handovers to improve network performance and how these policies perform under a range of conditions. The general problem of modelling overflow in cellular networks is considered at length and from this it is concluded that the use of overflow in existing schemes such as directed retry, reuse partitioning and overlaid cells can also be described by the simple concepts of intra and inter layer overflow Using these concepts the author formulates the problem of overflow in layered networks as a subset of the general problem of overflow with multiple overflow routes and restricted overflow. This leads to the derivation of the mean and variance of the overflow traffic from a cell with multiple handover routes and restricted handover from the two-dimensional birth death model of the system. These expressions for the mean and variance are used in conjunction with the Equivalent Random Theory and splitting formulae in the development of the Splitting Formula Method or SF Method. The accuracy of three splitting formulae and a simple Poisson approximation are investigated and compared with simulation. From this we conclude that the splitting formulae of Akimaru and Takahashi and Wallstrom provide the best overall result. This method is used to solve the general problem of multiple user classes for an example two layer network. This leads to conclusions on the complex relationship between cell capacity, the proportion of uses that can access the microcells and the proportion of users that can overflow from the microcell to the macrocell. The Modified Splitting Formula Method is an extension of the SF Method that includes handovers and overflow for handovers. A user perceived measure of the effect of new call and handover blocking described by the probability of call failure augments the Modified SF method. This is then used to analyse five new call overflow policies for a three layer network under conditions of extended handover, restrictions on handover for calls in cells at the edge of layers and spatial offset between the peak of the traffic demand and the cell layout. The results give new and valuable insight into the behaviour of layered cellular networks with overflow and the trade-offs in performance that exist when designing and operating these networks.

Group communication is a one-to-many communication pattern that distributes data from one sender to multiple receivers. Multicast as a group communication method is extensively employed in content distribution scenarios, such as IP-based cable TV, live streaming, video conference, data delivery, etc. Since application-layer multicast cannot touch network elements, it suffers from inefficient network utilization. Some existing network-assisted multicast are limited by scalability issues caused by the inability to maintain a sharply increased per-flow state in individual network elements. Moreover, existing network-assisted multicast is unable to meet the newly emerging need, such as load balancing and traffic engineering. This paper presents a novel multicast technique called Carrier-Grade Minimalism Multicast (CGM2). Through a string of bits, the bitmap, nodes are instructed to locally replicate packets and forward them over several interfaces without maintaining a per-flow state. Bitmaps of nodes along the multicast path are encapsulated in the recursive format as a binary in-packet tree for explicit forwarding path.

Purpose: The purpose of this paper is to identify the workplace accommodations used by individuals who are deaf or hard of hearing, to report the perceived impact of the accommodations and to identify unmet needs with respect to workplace accommodations. Method: Individuals who are deaf or hard of hearing participated in an online survey. Respondents identified with one of four levels of functional hearing ability and selected from descriptions of workplace accommodations. Each selection was ranked according to perceived importance, satisfaction and frequency of use. Respondents also commented on unmet needs. Results: The most common accommodations were telephone aids (55%), co-worker helps (34%) and electronic communication (31%). Importance and frequency of use ranked high among most respondents (76% and 87%, respectively). However, perceived satisfaction ranked high among only 50% of respondents. The most common unmet needs were effective communication in groups and lack of co-worker support. Conclusions: Workplace accommodations are viewed as important and frequently used by individuals who are deaf or hard of hearing. However, satisfaction with the accommodations is marginal at best. Unmet needs remain in the areas of communication in meetings, support of co-workers and the development of a more universally accessible workplace environment.Implications for RehabilitationIndividuals who are deaf or hard of hearing consider their workplace accommodations to be important and frequently used.Satisfaction with workplace accommodations among individuals who are deaf or hard of hearing is relatively low, indicating room for improvement in the design and application of such accommodations.Unmet needs for individuals who are deaf or hard of hearing remain in the area of effective communication in meetings with multiple participants.Universal (or Inclusive) Design principles should be used to help reduce barriers in workplace environments and with respect to common-use tools in the workplace.

Application layer multicast (ALM) is an effective group communication method. The ALM tree is usually built in a distributed manner because of its good scalability. However, the distributed ALM solution sometimes produces a low performance delivery tree. In this paper, we propose an ALM tree optimization solution, named ALMTO, for multicast applications, in particular, those with a large number of concurrent users. ALMTO manages and optimizes the ALM tree in the following four steps: 1) periodic collection of related structure information, based on a proposed structure report domain model and special tree structure; 2) construction and maintenance of a logical ALM tree, in terms of the collected structure information; 3) central computation of the ALM tree optimization scheme, according to the logical ALM tree and optimization objective corresponding to the specific multicast application; and 4) reshaping of the real ALM tree in terms of the optimization scheme. We analyze the problem of the centralized tree optimization scheme orchestration and present an effective solution that can adapt to the dynamics of group members. We also present two approaches: 1) degree-bounded connection-keeping tree transformation and 2) ring-based data compensation to ensure that the ALM tree can be reliably transformed.

CoolStreaming is the first protocol which introduces the mesh structure into Application Layer Multicast(ALM) in media streaming application, i.e. each agent may have two or more parents instead of only one parent. However, since the agents in Mesh-based ALM(MALM) are strategy and selfish, the effect of cheating behavior may not be ignored. To solve this problem, we apply the VCG mechanism design into MALM network model, and devise a strategyproof mechanism to avoid the agent cheating. As a result, the goal to maximize the system outcome can be achieved. In addition, we design a distributed algorithm to realize our mechanism. The algorithm can dynamically adapts to form a better multicast mesh, though ALM network parameters and constraints change dynamically in reality. The correctness and performance of this distributed algorithm are verified by the following experimental results.

IPTV will be one of the main drivers of network innovation in the near future. Its bandwidth demands, especially if combined with HDTV, require smart algorithms for content distribution. One approach that is currently discussed intensively is Application Layer Multicast (ALM), which allows to scale to large node numbers by incorporating the resources of participating peers. In addition, locality-aware ALM approaches can distribute content close to the edges of the network and thus are able to relieve core networks from traffic. In this work, we propose to combine ALM with virtual routers that assist in content distribution, so-called ALM-Routers. They can be moved between distinct network positions and are inspired by current research towards a future Internet. Furthermore, we propose adaptation algorithms that operate solely on local knowledge and optimize ALM-Router positions as well as their overlay neighborhood. As our simulation results indicate, already a small fraction of such virtual nodes deployed on core network routers, decrease the overall traffic amount. Moreover, a subsequent optimization of the positions of ALM-Routers and the optimization of their overlay neighborhood induces additional considerable traffic savings compared to a static placement.

It is proved that network coding can achieve multicast capacity and therefore improves the throughput of a multicast network significantly. This chapter will focus on applying network coding to Application layer multicast(ALM). The benefits are two folds: first, ALM is built on peer-to-peer networks whose topology can be arbitrary so it is easy to tailor the topology to facilitate network coding; second, the nodes in ALM are end hosts which are powerful enough to perform complex encoding and decoding operations.

IP multicast plays a very important role in group communication. At the network level IP multicast provides an efficient one-to-many IP packets delivery but without providing any reliability guarantees. Desirable features of reliable multicast include low end-to-end delay, high throughput and scalability. Active networks open a new perspective in providing more efficient solutions to the problems of reliability. However, the existing active reliable multicast protocols are based on receiver-initiated approach for loss recovery. In this paper we propose a new active reliable multicast protocol by combining sender- initiated and receiver-initiated approaches for loss recovery. This approach helps to solve the scalability problems like acknowledgement implosion, recovery load balancing etc.

Chapter 8 - IPv6 Security