A number of mobile hosts might be densely staying in an area caused by traffic congestions. The greater part of the mobile hosts will require commonly useful data, such as traffic information, parking information and other driving related information in such environment. Simultaneous data transmission broadcasts using a common link are regarded as a suitable means to distribute this location-dependent information. However, there is no guarantee that mobile hosts can finish receiving the information completely within a limited time. In this paper, we propose a data retransmission method for communications between a base station and mobile hosts and a data recovery processing method for use between base stations. The data retransmission method called "TOA" (The Order of Arrival) schedules retransmission data specified in the first NACK request received after retransmission processing. We have proposed "Advanced" Join system in which a base station makes consolidated join requests to a multicast group on behalf of mobile hosts. Applying the TOA method to resending in the Advanced Join system, data-receiving efficiency is higher than with the simple Advanced Join system and the absolute number of completed mobile host data reception is higher. Using the TOA method, even with the base station disposition rate of 50% the number of completed reception is higher than with the Advanced Join system at 80%. The proposed reliable multicasting system to the DSRC-based ITS network can realize an efficient base station arrangement in the ITS network infrastructure and contribute to the deployment of a superior ITS.

In this paper, to investigate the processing requirements at each node and offered network load of receiver-based and router-based protocols, we analyze the number of packet transmissions on each link until all receivers receive a packet for an arbitrary multicast-tree topology and packet loss probability considering the correlation between loss events of a packet for different receivers. In order to show the effectiveness of the analytical results, we demonstrate the numerical examples for various conditions. The numerical results show that local recovery protocols, especially router-based protocol can reduce the offered network load due to data packets and their acknowledgements, and can decentralize processing requirement of sending nodes effectively. Further, we reveal the influence of the locations of group senders on the performance of both protocols.

In this paper, how the new service of non-authenticated multicasting can be implemented on the AWA system is described. The AP is forced to send IGMP packets periodically in order to keep transmitting IP multicast data grams. The program tables of the non-authenticated multicast are transmitted as IP multicast data to allow the all clients to receive the material. Furthermore, the list of program tables which shows the pairs of the ID of the AP and the IP address of the program table are used so that different APs can offer different program tables and programs. Experiments on non-authenticated multicasting were successfully conducted and we confirmed that the proposed service works well.

The IETF Mobile IP defines two multicast options: remote subscription (RS) and bi-direction tunneling (BT). In order to synthesize the strong points of these two IETF multicast options, we propose a hybrid approach, mMOM, which selectively uses two IETF multicast options based on the mobility of mobile hosts. Whenever a mobile host requests its first registration to a certain foreign agent, the corresponding foreign agent starts the service using the BT option. Afterwards, if it requests re-registration to the same foreign agent, the foreign agent considers it to be relatively immobile and continues services using the RS option. We propose a new metric to compare heterogeneous algorithms. Simulation results show that our approach outperforms all others.

The multicast ATM switch has been developed for the purpose of the point-to-multipoint cell transmission. The basic structure of conventional multicast ATM switches is mainly based on a T. T. Lee's multicast switch, since it has a very simple and expandable structure. However, in spite of these benefits, it requires excessive hardware for the loss-free cell transmission, since it employs the blocking network, i.e., the banyan network as a copy network and a routing network. In this paper, we propose a new network for the multicast ATM switching. In proposed copy network, we adopt a new structure, the parallel broadcast banyan network with bypass links between switch planes, to offer the maximum cell transmission capacity and the fault tolerance. All conflict cells, which are blocked during the cell routing process, are bypassed to the next switch plane through bypass links and try to be routed. And to support the highly efficient cell transmission, we propose Alternate Path Scheme (APS) and copy-number (CN) comparator in the proposed copy network. APS is a kind of cell transmission schemes and guarantees multicasting capability to achieve a high performance. To estimate the performance of a proposed copy network, we provide several simulation results.

Multicast is an efficient way to send messages to a group of members. It is becoming the basis for a number of applications, such as teleconferencing, news groups, and on-line games. Security is one of the main issues in realizing multicast communications. A working group within IETF dedicated to multicast security has been formed and RFCs and working drafts concerning multicast security are proposed. This letter analyzes the security of a scheme proposed in [1] for securely establishing a shared, secret key in a large, dynamic group. We show that it fails to provide forward and backward security.

In this paper, we propose an efficient dual-tree-based multicasting scheme with three destination-switch partition strategies on irregular switch-based networks. The dual-tree-based routing scheme supports adaptive, distributed, and deadlock-free multicast on irregular networks with double channels. We first describe a dual-tree structure constructed from the irregular networks and prove that the multicasting based on such a structure is deadlock-free. Then, an efficient multicast routing algorithm with three destination-switch partition strategies: source-switch-based partition, destination-switch-based partition, and all-switches-based partition, is proposed. Finally, we perform simulations to evaluate our proposed algorithm under various impact parameters: system size, message length, and startup time. The experimental results show that the improved tree-based multicasting scheme outperforms the usual tree-based multicasting scheme. The dual-tree-based multicasting scheme with destination-switch-based partition is shown to be the best for all situations.

In this paper, we propose and analytically evaluate the use of punctured convolutional codes for recovering packets lost in multicast transmission. An independent erasure channel is assumed for packets transmission over a star topology. The analysis provides a method for determining the recoverability and the post-reconstruction receiving rate for a given convolutional code. We theoretically evaluate the effectiveness of the proposed approach taking into account two different parameters: the number of transmissions per packet and the number of packets needed to be sent to guarantee the reception of data. Finally, we compare the proposed approach with the scheme when parity packets are generated based on Reed-Solomon codes.

This paper proposes a scheme for joint synchronization between stored media with interactive control and live media in multicast communications. We deal with visual search control, such as fast-forward and fast-reverse, as interactive control. The proposed scheme enables visual search by enhancing the virtual-time rendering (VTR) media synchronization algorithm, which the authors previously proposed, and adjusts the timing of changing the visual search mode among destinations by carrying out group synchronization control. We also demonstrate the effectiveness of the scheme by experiment.

This paper proposes a credit-based congestion control scheme for multicast communication which employs application-specific processing at intermediate network nodes. The control scheme was designed not only to take advantage of credit-based flow control for unicast communication, but also to achieve flexibility supported by active network technology. The resultant active multicast congestion control scheme is able to meet the different requirements of various multicast applications in terms of reliability and end-to-end latency. The performance of the proposed control scheme was evaluated using both discrete-event simulations and experiments on a prototype active network implementation. The results show that the proposed scheme performs very well in terms of fairness, responsiveness, and scalability. The implementation experiences also confirmed the feasibility of the scheme in practice.

Anonymous communication essentially involves two difficulties; 1) How does the sender send a message anonymously? 2) How does the receiver send a reply to the anonymous sender? In this paper, we propose an anonymous communication method named Rivulet that overcomes both of the difficulties by using group communication. Moreover, anonymous communication holds two dilemmas; 1) Strong anonymity or good performance? 2) Protect the privacy or promote the crime? Rivulet provides a solution for the former dilemma. The latter one is hard and important problem for all privacy protection schemes, therefore, we have to keep discussing this dilemma.

We present a simple framework for multicasting video in an active network, in which we overcome heterogeneity in the quality requests by filtering the video stream at some properly located active nodes. The framework includes the requirements for the underlying active network and outlines the video multicast application. We then introduce a heuristic algorithm for electing the filtering nodes to conform a multicast distribution tree, in which we use an objective function to, for example, minimize the required bandwidth. We evaluate the performance of our algorithm comparing it with simulcast and layered encoded transmission through simulation experiments, showing some advantages of using active filtering.

In this paper we addresses the problem of finding feasible solutions for the Group Multicast Routing Problem (GMRP). This problem is a generalization of the multicast routing problem whereby every member of the group is allowed to multicast messages to other members from the same group. The routing problem involves the construction of a set of low cost multicast trees with bandwidth requirements for all the group members in the network. We first prove that the problem of finding feasible solutions to GMRP is NP-complete. Following that we propose a new heuristic algorithm for constructing feasible solutions for GMRP. Simulation results show that our proposed algorithm is able to achieve good performance in terms of its ability of finding feasible solutions whenever one exist.

In the paper, we propose a congestion control scheme for reliable multicast communication which enables TCP fairness and prevents a drop-to-zero problem. The proposed congestion control scheme is rate-based one based on NAKs from receivers and cooperatively works with a flow control scheme. The congestion control scheme consists of two components of a rate-based controller and a selection mechanism of a representative. The rate-based controller runs between the sender and the representative and achieves TCP fairness and fast response to losses at the representative. The selection mechanism of the representative allows the sender to select the representative in a scalable manner, in which the sender makes use of NAKs from receivers to select it. In the paper, we also propose the switchover mechanism of the flow and congestion control schemes which enables the sender to use either of them adaptively based on network situations. When the network is congested, the congestion control scheme works to share network resources fairly with competing TCP flows. Otherwise, the flow control scheme works to adapt the transmission rate to the slowest receiver. We verify the performance of our proposed schemes by using computer simulation.

We propose an efficient, low cost, multicast ATM switch which is fair to all inputs. The switch consists of a novel copy network which creates unicast packets in a fair manner, followed by a network that routes packets to their correct Address Translation Tables (ATT's) and ultimately a unicast routing network which ensures sequencing. The copy and routing networks are based on deflection routing. We show that our switch requires O(log N) stages and can be designed for any arbitrarily low level of packet loss. The theoretical results are backed up by simulations. Switching elements in both the copying and routing networks have O(1) bit complexity, making the overall bit level hardware complexity of the network O(N log N). The latency of the switch is proportional to the number of stages O(log N). Unlike other existing copy networks, our copy network drops packets in a fair manner and hence can provide quality of service (QoS) support. The switch is output queued and allows the delivery of multiple packets to the same destination during a time slot.

Layered multicast approach enables IP multicast to adapt to heterogeneous networks. In layered multicast, each layer of a session is sent to separate multicast groups. These layers will be transmitted on the same route, or on different routes. However, traditional congestion control schemes of layered multicast do not consider the case when layers of a session are transmitted on different routes. In this paper, at first we show that in sparse-mode routing protocols like PIM-SM and CBT, layers of a session can be mapped to different Rendezvous Points or cores due to the bootstrap mechanism. It means that layers of a session can be transmitted on different routes. We then show that traditional congestion control schemes of layered multicast do not work properly in sparse-mode routing regions. At last we introduce Rendezvous Point based Layered Multicast (RPLM), a novel congestion control scheme suitable for sparse-mode routing regions, and show that RPLM works efficiently in regions using sparse mode routing protocols. RPLM uses per-RP packet loss rate instead of the overall one to detect congestion on each route, and can react to congestion quickly by dropping the highest layer on the congested route. In addition, RPLM simultaneously drops all the layers those are useless in quality's improvement to prevent bandwidth waste.

Telepresentations will be popular in the future of ubiquitous digital media. To realize a telepresentation easily over the Internet, we design a communication protocol to control a remote material (digital media) used in a telepresentation. We describe our proposed protocol; RMOP (Remote Material Operation Protocol) in this paper. This protocol specifies commands for material operations such as synchronization of slides, drawing, and pointing. Since this protocol just specifies the common formats through IP networks independent of special functions of presentation tools, it can be applied to various presentation tools. To design the protocol, we consider the trade-off between reliability of IP multicast and practical availability in the actual Internet. We adopt the reliable multicast mechanism to improve reliability but not to lose practicality in the protocol. Also, we describe an implementation of our prototype system using RMOP for a telepresentation. Then we show some evaluations such as the protocol overhead and comparisons with the other existing systems. Last, we show a case study of a telepresentation over the Internet using our system.

Tree-based approach has been proven to be most scalable for one-to-many reliable multicast. It efficiently combines distributed recovery with local recovery over a logical tree of the sender and receivers. It has also been known that the performance of the tree-based protocols heavily depends upon the quality of the logical tree. In this paper, we propose an end-to-end scheme to further enhance the scalability of the tree-based approach. By exchanging packet loss information observed at the end hosts, the scheme constructs and maintains a logical tree congruent with the underlying multicast routing tree even in the presence of session membership and multicast route changes. The scheme also groups the tree nodes and assigns separate multicast addresses to them in order to enable efficient multicast retransmission for reducing both delay and exposure. We compare the proposed scheme with Tree-based Multicast Transport Protocol (TMTP), a static tree-based protocol. Extensive simulations up to 300 node sessions reveal that the proposed scheme reduces implosion and exposure more than 20% and 50%, respectively. The results also indicate that the scheme is highly scalable such that the improvement gets more significant as the size of the session increases.

Focusing on a distributed control service-control-node (SCP) that houses a database (DB) distributed across multiple modules, this paper proposes an autonomous distributed SCP architecture using multicasting access to the distributed DB, and highlights its application areas. We assume as a basic condition that neither the network nor the other modules in the system are aware of the DB configuration. Based on this condition, we propose two basic methods: a unicast approach in which the DB management module that is selected at random by the network routes the DB access request to the module where the target data resides (Method A), and a multicast method in which DB access requests are broadcast to all modules (Method B). A quantitative evaluation is made of the number of required modules and required communications performance between modules which is determined by the capacity of the main memory and processing capacity of the processors. Based on the results, we conclude that Method B better exploits the advantages of module autonomous distribution technology within the limits that the economy of inter-module communication overhead is not impaired. Furthermore, in the event a module fails in Method B, a scheme is proposed in which the defective module is cut out of the multicast group, and multicasting continues. This could be implemented most effectively using a separate route under hardware control that is independent of the on-line communications route between modules.

In this paper, we are concerned in obtaining multicast trees in packet-switched networks such as ATM nets, when there exist constraints on the packet (cell)-replication capabilities of the individual switching nodes. This problem can be formulated as the Steiner tree problem with degree bounds on the nodes, so we call it the Degree-Constrained Steiner Tree problem (DCST). Four heuristic algorithms are proposed: the first is a combined version of two well-known Steiner tree algorithms, heuristic Naive and the shortest path heuristic (SPH), and the second is a relaxation algorithm based on a mathematical formulation of the DCST, and the last two use a tree reconfiguration scheme based on the concept of 'logical link. ' We experimentally compare our algorithms with the previous ones in three respects; number of solved instances, objective value or tree cost, and computation time. The experimental results show that there are few instances unsolved by our algorithms, and the objective values are mostly within 5% of optimal. Computation times are also acceptable.