Multicast Papers Appeared in 1995

Shridhar B. Shukla, Multicast Tree Construction in Network Topologies with Asymmetric Link Loads, Electrical and Computer Engineering, Naval Postgraduate School, Monterey, California, Technical Report, Jan, 1995

Abstract: "This paper addresses the problem of constructing multicast trees with reservation of resources. The main features of the approach described here are that it tolerates asymmetric traffic loads on network links and algorithmically locates data distribution centers for every multiparticipant interaction. A fast and scalable algorithm for locating distribution centers based on the network load and a priori knowledge of participants' locations and resource requirements is given. To explicitly handle cases of disjoint send and receive paths between two nodes, a protocol to build separate send-trees and receive-trees around the centers located in the above manner is given. Simulation results on various topologies are presented showing that, with the above center location mechanism, center-specific trees yield lower tree cost than source-specific trees for many concurrent senders with only a modest increase in the average path length. The use of distribution centers, a priori information, and sensitivity to load asymmetry permit effective combination of center-specific and source-specific trees for an interaction and eliminate the need for symmetry checks during resource reservation."
Keywords: "multicast tree construction; distribution centers; resource reservation; asymmetric link loads; multiparty interactions"

B. Awerbuch and Y. Azar, "Competitive multicast routing in virtual circuit environments", Wireless Networks, Jan, 1995, 1(1)

Abstract: "In this paper, we introduce and solve the multicast routing problem for virtual circuit environment without making any assumptions about the communication patterns, or about the network topology. By multicast we refer to the case where one source transmits to several destinations the same information. Also, we allow arbitrary interleaving of subscription patterns for different multicast groups, i.e. the destinations for each group arrive at an arbitrary order and may be interleaved with destinations of other groups. Our goal is to make route selection so as to minimize congestion of the bottleneck link. This is the first analytical treatment for this problem in its full generality. The main contribution of this paper is an on-line competitive routing strategy."
Keywords: "wireless networks; routing; multicast"

Hunt, Guerney Douglass Holloway, "Multicast Flow Control on Local Area Networks", Cornell University, Computer Science Department,TR95-1479, 1995

Abstract: "The primary LAN technologies in use today --- ethernet, FDDI, and token-ring --- all provide hardware support for broadcast and multicast capability. However, distributed systems have traditionally used unicast messaging exclusively, even when multicast communication patterns arise. As the number of distributed applications grows, the load on networks caused by unnecessary unicasts will increase. In addition, for some applications performance and group size are limited by using unicast technologies for multicast. If multicast technologies are exploited, the network load caused by ``redundant'' packets will be reduced. Exploiting multicast will also improve the performance and scalability of some distributed applications. However, as distributed systems move towards exploiting multicast, multicast flow control protocols are becoming more important. Finding a general, effective solution for multicast flow control will help facilitate the exploitation of the multicast primitives provided in LANs and Wide Area Networks (WANs). This dissertation presents the results of an investigation into multicast performance on local area networks. An analysis of multicast flow control is presented which distinguishes between {\it rate reservation} and {\it rate control}, followed by a discussion of the major design issues associated with multicast flow control and a presentation of a proposed protocol family. The proposed protocol family is based on send-rate control. An unreliable and a reliable multicast flow control protocol based on the proposed family are presented. A study of the performance of these protocols is also presented. This dissertation concludes with an investigation into how well the proposed reliable multicast flow control protocol performs when used to disseminate messages. This dissertation argues that direct rate control has merit as a technique for multicast flow control on local area networks"
Keywords: "Ethernet; multicast; flow control; LAN; Tokenring; FDDI"

Jacobson, Van, The MBone -- interactive multimedia on the Internet, Lawrence Berkeley Laboratory, Berkeley, California, 1995

Keywords: "MBONE; IP; Internet; multimedia; multicast; ATM; talk"

Schulzrinne, Henning, Dynamic Configuration of Conferencing Applications using Pattern-Matching Multicast, nossdav, Durham, New Hampshire, 1995,

Abstract: "Multimedia conferencing systems are usually large, complex software systems. We describe a local control architecture and communication protocols that allow to tie together media agents, controllers and auxiliary applications such as media recorders and management proxies into a single conference application. Unlike other systems, control of a single conference can be shared between several controllers. Each media can be handled by one or more independent media agents. Parts of the system have been implemented using an IP-multicast-based audio conferencing tool (NeVoT). The communicating applications disseminate state and control information through a replicator. The replicator mainly limits distribution of messages based on expressed interest of other applications, thus implementing an application-level, receiver-driven local multicast. It also automatically starts applications as needed. The same functionality was also implemented IP multicast restricted to the local host."
Keywords: "multimedia; conferencing; conference control; multicast"

Schulzrinne, Henning, Message-Based API for the Dynamic Configuration of Multimedia Conferencing Applications, GMD Fokus, Berlin, 1995

Abstract: "This working paper describes in detail the multicast message-based application programming interface used by NeVoT.", KEYWORDS="NeVoT; packet audio; operating systems; multicast; API; multimedia; CSCW"

Bernard M. Waxman, "Models for Multipoint Connections in Gigabit Networks", Proc. of Gigabit Networking Workshop, Boston, Massachusetts, 1995,

Abstract: "There is little doubt that as high speed networks become available, many applications will make use of multicast and multipoint connections. Controversy arises only when proposing suitable models for multipoint connections and the kinds of applications these connections will support. The lack of a ``good'' model has been a problem in our attempt to evaluate the performance of different routing algorithms. In order to conduct experiments using computer simulations, connection models are needed. We considered several different approaches before selecting a model for our experimental studies. Since our list is certainly not complete, we would like to encourage the exchange of ideas in this area especially among those who have an interest in multimedia applications.", REan.abstract.txt"

Bauer, Fred and Varma, Anujan, "Degree-Constrained Multicasting in Point-to-Point Networks", Infocom'95, Boston, Massachusetts, 1995

Abstract: "Establishing a multicast tree in a point-to-point network of switch nodes, such as a wide-area ATM network, is often modeled as the NP-complete Steiner problem in networks. In this paper, we study algorithms for finding efficient multicast trees in the presence of constraints on the copying ability of the individual switch nodes in the network. We refer to this problem as the degree-constrained multicast tree problem and model it as the degree-constrained Steiner problem in networks. Steiner heuristics for the degree-constrained case are proposed and their simulation results for sparse, point-to-point networks are presented. The results are compared with respect to their quality of solution, cost (running time), and the number of test cases for which no solution could be found. The results of our research indicate that efficient multicast trees can be found in large, sparse networks with small multicast groups even with limited multicast capability in the individual switches. Some of the Steiner heuristics tested yielded degree-constrained multicast trees within 5\% of the best heuristic solution found in most of the cases. Even when the fanout of each switch node was restricted to 2, the heuristics we used were able to generate efficient multicast trees in almost all our test networks. Surprisingly few test networks were unsolvable. In those cases where no solution was found by a heuristic, backtracking solved many of the remaining cases. Among the heuristics we used, degree-constrained versions of simple path-distance heuristics such as SPH and SPH-R provided the best tradeoffs between quality of solution and cost."
Keywords: "Degree-constrained multicasting, Steiner problem in networks, multicast switch design"

Law, Ka Lun Eddie and Leon-Garcia, Alberto, "Multicast and Self-Routing in ATM Radix Trees and Banyan Networks",Infocom'95, Boston, Massachusetts, 1995,

Abstract: We investigate the relationship between the structure of the routing tab and the ease of performing multicasting. We first consider a simple explicit addressing scheme that requires $(N-1)(\log_2N+1)$ routing bits. We then present an addressing filtering scheme that requires $N$ routing bits. Next we propose a new method, the Vertex Isolation Addressing (VIA) Scheme, which requires $r(N-1)/(r-1)$ bits for radix-$r$ tree networks. Thus for binary trees the routing tab is $2(N-1)$ bits longs and as $r$ approaches $N$ the routing tab approaches $N$ bits. We demonstrate that the ``excess'' bits in the VIA routing tab provide certain error detection capabilities. Encoding and decoding algorithms and hardware implementations for the VIA method are presented. Modified VIA schemes are then investigated for large tree networks. Finally we show that the VIA scheme and its modifications are applicable to Banyan networks."
Keywords: "ATM, multicast routing tab, multicast radix trees, Banyan networks, Vertex Isolation Addressing scheme, VIA, G-VIA"

Liew, Soung C., "A General Packet Replication Scheme for Multicasting in Interconnection Networks",Infocom'95, Boston, Massachusetts, 1995,

Abstract: "Multicasting in broadband packet switches and metropolitan networks can be achieved by first replicating the packets and then routing them to their destinations. This paper studies a very simple but general replication scheme that can be applied to arbitrary interconnection-network topologies. The replication process of a packet adapts itself according to the network topology and the traffic condition. Hot spots of replication activities are diffused by this scheme which automatically moves part of the replication efforts to less active network regions. The scheme can potentially be used in networks (e.g., the Manhattan-street network) in which multicasting were thought to be inherently difficult. Fundamental issues and critical problem areas are laid out, and solutions addressing them are proposed. The performance of the replication algorithm and its implementation (logic diagram level) in the shuffle-exchange copy network are investigated in detail. It is found that the performance of the algorithm improves with the increase of network dimensions."
Keywords: "Packet Replication, Multicasting, Copy Networks, ATM Switching, Packet Switching, Interconnection Networks, Shuffle-Exchange Networks, Manhattan Networks"

Hwang, Ren-Hung, "Adaptive Multicast Routing in Single Rate Loss Networks", Infocom'95, Boston, Massachusetts, 1995,

Abstract: "In this paper, we propose a new approach, based on the Maximum Free Circuit Routing (MFCR) concept, toward multicast routing in single rate loss networks. Two versions of the multicast routing problems are studied: static and dynamic. In the static version of the multicast routing problem, the identities of all destination nodes is available to the multicast routing algorithm at once. Conversely, in the dynamic version of the multicast problem, the identities of the destination nodes is revealed to the routing algorithm one by one. We studied three MFCR-based multicast routing algorithms: one for the static multicast problem and two for the dynamic multicast problem. We also propose a new performance metric, referred to as fractional reward loss, for evaluating these three multicast routing algorithms. The performance of these three multicast routing algorithms are evaluated through simulations."
Keywords: "Multicast, Routing, Single Rate Loss Network"

Eleftheriadis, A. and Pejhan, S. and Anastassiou, D., "Address Management and Connection Control for Multicast Communication Applications",Infocom'95, Boston, Massachusetts, 1995

Abstract: "An architecture and associated protocols are presented for managing multicast addresses and performing connection control for multicast communication applications. A scheme to partition the multicast address space on the basis of the network number is proposed (an underlying IP-based internetworking environment is assumed), and its performance and scaling characteristics are discussed. A protocol is then developed to provide for dynamic allocation and release of multicast addresses, as well as maintaining state information for a connection. The protocol is independent of the address partitioning scheme; it is also shown to be robust and efficient. Finally, we describe two different mechanisms that enable the use of a common port number by all session participants."

Talpade, Rajesh and Ammar, Mostafar H., Single Connection Emulation SCE: an architecture for providing a reliable multicast transport service, Georgia Institute of Technology, Technical Report, GIT-CC-94-47, 1995

Abstract: "We present a novel architecture for providing a reliable multicast transport service over existing protocol stacks. These protocol stacks ordinarily support reliable unicast transport layer connections over a network layer which is capable of providing an unreliable multicasting service. We propose the addition of a new single connection emulation (SCE) sublayer between the unicast transport layer and the multicast network layer. This added layer mimics the single destination network layer interface to the transport layer and interfaces with the multicast network layer to provide the necessary multicast functionality. The new architecture also enables interactions between applications and the SCE, thus allowing the applications to control the semantics of the reliable multicast connection. We discuss the design issues that need to be considered when such a sublayer is to be introduced. We also discuss an implementation of this new approach using the TCP/IP protocol stack, and present some preliminary experimental results."

Almeroth, K. and Ammar, M., The Role of Multicast Communication in the Provision of Scalable and Interactive Video-On-Demand Service, Nossdav'95, 1995

Abstract: "Multicast delivery can improve the scalability of Video-On-Demand (VOD) systems by allowing multiple customers to share one set of video server and network resources. In such a system, providing customer interactivity can be difficult. In this paper we overview our work which addresses how interactivity may be accomplished in a multicast delivery environment and analyzes the performance of such systems."
Keywords: "Video-On-Demand; video; multicast; interactive; scalable",

Biersack, E. and Nonnenmacher, J., WAVE: A New Multicast Routing Algorithm for Static and Dynamic Multicast Groups, Nossdav'95

Abstract: "We present a new multicast algorithm called WAVE for establishing source-specific multicast trees. WAVE meets multiple quality of service requirements (constraints) such as delay, cost, and available bandwidth, simultaneously. Simulation results show that WAVE performs very good in terms of delay and cost for both, static and dynamic multicast groups, when compared to the best multicast algorithms known."

Bettati, R. and Ferrari, D. and Gupta, A. and W. Heffner, W. Howe and Moran, M. and Nguyen, Q. and Yavatkar, R., Connection Establishment for Multi-Party Real-Time Communication , Nossdav'95, 1995

Abstract: "There is considerable interest in the network community in supporting real-time multi-party applications, such as video conferencing. The Tenet Group at UC Berkeley and ICSI has designed and implemented protocols that provide quality of service (QoS) guarantees for real-time traffic on packet switching networks. Suite 2 of the Tenet protocols provides scalable, flexible and efficient network support for real-time multi-party connections. We outline our method of connection establishment and describe the design issues and alternatives, and our decisions. Preliminary measurements confirm the viability of our approach for real-time multicast connection establishment."
Keywords: "multicast connection establishment; real-time communication; multimedia networking"

Zhang, Lixia and Shenker, Scott and Clark, Dave and Huitema, Christian and Deering, Steve and Ferrari, Domenico, Reservations or No Reservations , Infocom'95 panel-discussion slides,

Keywords: "Internet; resource reservations; admission control; multicast"

Floyd, Sally and Jacobson, Van and Liu, Ching-Gung and McCanne, Steven and Zhang, Lixia, Reliable Multicast Framework for Light-weight Sessions and Application Level Framing, Sigcomm'95, Cambridge, Massachusetts, 1995 Nossdav'95

Abstract: "This paper describes SRM (Scalable Reliable Multicast), a reliable multicast framework for application level framing and light-weight sessions. The algorithms of this framework are efficient, robust, and scale well to both very large networks and very large sessions. The framework has been prototyped in wb, a distributed whiteboard application, and has been extensively tested on a global scale with sessions ranging from a few to more than 1000 participants. The paper describes the principles that have guided our design, including the IP multicast group delivery model, an end-to-end, receiver-based model of reliability, and the application level framing protocol model. As with unicast communications, the performance of a reliable multicast delivery algorithm depends on the underlying topology and operational environment. We investigate that dependence via analysis and simulation, and demonstrate an adaptive algorithm that uses the results of previous loss recovery events to adapt the control parameters used for future loss recovery. With the adaptive algorithm, our reliable multicast delivery algorithm provides good performance over a wide range of underlying topologies."
Keywords: "reliable multicast; MBONE; whiteboard; computer supported cooperative work; retransmission"

Thyagarajan, Ajit S. and Deering, Stephen E., Hierarchical Distance-Vector Multicast Routing for the MBone, Sigcomm'95, Cambridge, Massachusetts, 1995

Abstract: "The exponential growth of the Multicast Backbone (MBone) has resulted in increased routing overhead and processing costs. In this paper we propose a two-level hierarchical routing model as a solution to this problem. This approach involves partitioning the MBone into nonoverlapping regions using DVMRP as the inter-region routing protocol; intra-region routing may be accomplished by any of a number of existing multicast protocols. Our design is flexible enough to accomodate additional levels of hierachy, and protocols other than DVMRP at the higher levels. The unique feature of this approach is the independence of the higher level routing protocol from the subnet addresses, which allows for easy incremental deployment with small changes to existing intra-region protocols."
Keywords: "multicast; MBONE; DVMRP; scaling; Internet; routing; distance vector; hierarchical routing"

Kalantar, Michael, "Issues in Ordered Multicast Performance: A Simulation Study", Cornell University, Computer Science Department, TR95-1531, 1995

Abstract: "Process groups are an increasingly popular tool for programming distributed systems. Such groups consist of collections of processes that work together to provide reliability, fault tolerance, task distribution, or some other abstraction. A combination of group actions, reliable failure detection, and ordered message delivery are used to provide group functionality. {\em Causal ordering}, one form of message ordering, is fundamental in process group systems. Its cost is therefore an important determinant of overall performance. In order to gain more insight into the behavior of causal order protocols, two simulations of process group systems were developed. The first, a detailed simulation of all system processes, groups, and interconnection networks, was used to study small systems. Using this model, a number of parameters were identified as having the greatest impact on ordered multicast performance. These parameters were used as indices to a set of precomputed probability distribution tables used by the second simulation. The second simulation focused only on key processes --- packet originators and processes in multiple overlapping groups --- and used precomputed probability tables to reduce simulation overhead. Simulations using this model showed that the delays imposed by the ordering protocols result in a tendency for packets to become ``convoyed'' together. Consequences are larger delays and greater system and network burstiness. We speculate that this tendency for systems to become more bursty, or less uniform, is a general principle. That is, any system which delays actions on a ``microscopic'' level results in burstiness at a ``macroscopic'' level. The more times such delays occur, the greater the degree of burstiness. Such a principle would imply that systems with this characteristic are limited in scale by the size of the largest burst that can be handled. It also suggests that protocols that minimize the number and length of delays and which optimize the handling of bursts should be used. In the context of process group systems, burstiness can be limited by minimizing the number of groups through which a packet is filtered and by protocol designs which minimize the number of delays used to control out-of-order message arrival."

Smirnov, Michael, Efficient Multicast Routing in High Speed Networks, First International Workshop on High Speed Networks and Open Distributed Platforms, St. Petersburg, Russia, 1995

Abstract: "The paper considers the case of multipoint routing in the high speed networking environment. Efficiency of such kind of routing, known as multicasting depends significantly on the quality of a network routing protocol establishing the multicast tree spanning all senders and receivers of the multicast flow. This quality in turn could be measured by minimal delay or minimal network resource consumption (minimal cost tree). The latter is known as Steiner problem in networks [1]. A new heuristic algorithm to solve the problem of shared multipoint minimal cost tree is presented together with it's formal background, cost calculation technique and estimation of needed checking overhead. The centralized version of the algorithm is demonstrated with a numerical example. The fitness of the algorithm for a distributed implementation is discussed."
Keywords: "multicast; routing; Steiner tree; heuristic; graph presentation; communication cost"

Smirnov, Michael, Object-Oriented Framework for the Multicast Applications Integration, Workshop on Distributed Object Oriented Computing, Frankfurt/Main, Germany, 1995

Abstract: "The paper presents an object - oriented framework aiming at integration of networked collaborative applications strongly demanding smart multicasting capabilities from the telecommunication environment. A new mediator for this support is introduced - the multicast agent (MCA), which is a software object moving across the internetwork and delivering all needed functionality for reliable and flexible participation in a multicast session to all members of the group. The MCA is an object, whose methods provide for the interoperability of heterogeneous applications, the highest achievable scalability, for individual patching of the multimedia multicast flow, and for simultaneous flows from different senders. Based on some precalculated multicast tree (MCT) spanning all dedicated receivers, it is possible to make efficient use of alternatives during the MCT development, the needed solution is presented in a form of a generic behaviour of the splitting point router. It is pointed out that the MCA implementation could be realized within the CORBA approach."
Keywords: "multicast routing; multicast agent; multicast tree; object-oriented framework; scalability; multimedia flow; routing alternatives; CORBA"

Smirnov, Michael, Object-Oriented Framework for a Scalable Multicast Call Modelling , COST 237 Conference on Multimedia Transport and Teleservices, Copenhagen, Denmark, 1995

Abstract: "The proposed approach for the Multicast Call modelling framework considers logical entities participating in the Call process and specify their interfaces as well as object' methods behind them in such a way that real design could benefit from this separation in terms of model flexibility, completeness, feasibility and, mainly, manageability. The paper considers a generic multicasting case and proposes a highly scalable decision for it: only one member of the multicast group negotiates initially with the service provider; all negotiations with the receivers could be provided at the splitting points of the multicast tree. The general idea of the approach comes out of the decomposition of the multicast tree spanning all members of the multicast session; and the decomposition of a generic MC Agent which is defined in this paper as some object capable to move across the network, clone, intercommunicate with it's instances and perform a set of specified actions. Agent's activities are described in a proposed scenario named the Multicast tree development together with the multicast Call establishment scenario components. Needed support for the multidomain networks and sender substitution is discussed as well as some performance aspects."
Keywords: "multicast agent; call modelling; primitives; object-oriented framework; multicast tree; scalability"

Salama, Hussein and Viniotis, Yannis and Reeves, Doug S. and Sheu, T. L., Evaluation of Multicast Routing Algorithms for Distributed Real-Time Applications of High-Speed Networks, Proc. of 6th IFIP Conference on High-Performance Networks (HPN'95), 1995

Abstract: "Multicast (MC) routing algorithms capable of satisfying the QoS requirements of multimedia applications will be essential for future's high-speed networks. We compare the performance of selected MC routing algorithms when applied to networks with asymmetric link loads. Each algorithm is judged based on the quality of the MC tree it generates and its efficiency in managing the network resources. Simulation results over random networks show that unconstrained algorithms are not capable of fulfilling the QoS requirements of applications utilizing networks spanning large areas. One algorithm, reverse path multicasting, is not suitable for asymmetric networks irrespective of the requirements of the application. Three constrained Steiner tree (CST) heuristics are also studied. Simulations show that all three behave similarly and that they can manage the network efficiently and construct low cost MC trees that satisfy the QoS requirements of multimedia traffic. The execution times of the CST heuristics are larger than those of unconstrained algorithms."
Keywords: "multicast routing algorithms; quality of service; high-speed networks; asynchronous transfer mode; ATM; distributed real-time applications"

K. Ravindran, A Flexible Network Architecture for Data Multicasting in ``Multiservice Networks''", IEEE JSAC, 13(8), pp.1426--1444, 1995

Abstract: "The paper describes a canonical model of data-transport architecture that offers a flexible framework for implementations of data multicasting on backbone networks to support multiservice applications (e.g., videoconferencing, digital TV broadcast). The architecture is based on acyclic graph structured communication channels that provide connectivity among data sources and destinations through switches and links in a backbone network. The paper adopts a network-wide logical addressing of communication channels, which allows data multicasting to be realized on specific backbone networks by establishing local bindings between a logical address and the information on network-specific routing of data over switches and links. The approach allows various sources to share the switches and links in a multicast path connecting to destinations. This is a desirable feature in view of the significant reduction in network routing control costs and data transfer costs when dealing with high-volume multisource data (say, in videoconferencing). In addition, logical addressing allows grouping of selected destinations to overlay different ``virtual networks'' on a base-level multicast channel (e.g., private discussion groups in a conference). As a demonstration of architectural flexibility, the paper describes the embedding of our multicast model on sample backbone networks capable of supporting multiservice applications: interconnected LAN's, ATM networks, and high-speed public data networks (viz., SMDS networks)."

Sassan Pejhan and Alexandros Eleftheriadis and Dimitris Anastassiou, Distributed Multicast Address Management in the Global Internet, IEEE JSAC, 13(8), pp.1445--1456, 1995

Abstract: "We describe a distributed architecture for managing multicast addresses in the global Internet. A multicast address space partitioning scheme is proposed, based on the unicast host address and a per-host address management entity. By noting that port numbers are an integral part of end-to-end multicast addressing we present a single, unified solution to the two problems of dynamic multicast address management and port resolution. We then present a framework for the evaluation of multicast address management schemes, and use it to compare our design with three recently proposed approaches, as well as a random allocation strategy. The criteria used for the evaluation are blocking probability and consistency, address acquisition delay, the load on address management entities, robustness against failures, and processing and communications overhead. With the distributed scheme the probability of blocking for address acquisition is reduced by several orders of magnitude, to insignificant levels, while consistency is maintained. At the same time, address acquisition delay is reduced to a minimum by serving the request within the host itself. It is also shown that the scheme generates much less control traffic, is more robust against failures, and puts much less load on address management entities as compared with the other three schemes. The random allocation strategy is shown to be attractive primarily due to its simplicity, although it does have several drawbacks stemming from its lack of consistency (addresses may be allocated more than once)."
Keywords: "multicast; address allocation; sd"

Kumar, Vinay, MBone: Interactive Multimedia On The Internet, Macmillan Publishing (Simon \& Schuster), ISBN 1-56205-397-3, 1995

Handley, Mark, The Use of Plain Text Keys for Encryption of Multimedia Conferences, Department of Computer Science, University College London, Draft V1.4, 1995

Abstract: "For reasons of privacy, multimedia conferencing tools are starting to incorporate encryption schemes. When the tools are used for one to many communication using multicast, such encryption schemes must use secret key encryption algorithms such as DES. Keys for the encryption scheme are distributed out of band. Many such key distribution schemes can be envisaged, such as PEM (Privacy Enhanced Mail), secure WWW, and additions to the existing conference control and conference setup schemes. These distribution schemes are not discussed here. It is important that all compatible tools given a key use it in the same way. It is also desirable that such keys can be plain text, as this aids key distribution in cases where the key must be entered manually, or must be remembered. However, plain text should not be used directly as an encryption key for algorithms such as DES, as the entropy in the key is unevenly distributed amongst the bits of the key, which reduces the potential key space, and thus greatly weakens the encryption scheme. Another simple but important aspect is that many tools may support multiple encryption schemes. It is important that the encryption scheme being used is specified in a standard way. Distributing this information along with the plain text key simplifies the distribution process."
Keywords: "encryption; key distribution"

McCanne, Steve and Jacobson, Van, vic: A Flexible Framework for Packet Video, Proc. of ACM Multimedia '95, 1995

Abstract: "The deployment of IP Multicast has fostered the develop ment of a suite of applications, collectively known as the MBone tools, for real-time multimedia conferencing over the Internet. Two of these tools -- nv from Xerox PARC and ivs from INRIA -- provide video transmission using software based codecs. We describe a new video tool, vic, that ex tends the groundbreaking work of nv and ivs with a more flexible system architecture. This flexibility is characterized by network layer independence, support for hardware-based codecs, a conference coordination model, an extensible user interface, and support for diverse compression algorithms. We also propose a novel compression scheme called ``Intra H.261''. Created as a hybrid of the nv and ivs codecs, Intra H.261 provides a factor of 2-3 improvement in compression gain over the nv encoder (6 dB of PSNR) as well as a sub stantial improvement in run-time performance over the ivs H.261 coder."
Keywords: "Conferencing protocols; digital video; image and video compression and processing; multicasting; networking and communication; vic; packet video; MBONE; H.261; nv; RTP"

Rathke, Bernhard K., Evaluation of a distance-vector based multicast-routing protocol for datagram internetworks , Department of Telecommunications, TU Berlin, Germany, 1995

Abstract: "This master thesis evaluates the mrouted protocol, a reverse path multicast (RPM) routing protocol which actually is used in the Internet Multicast backbone (MBone). The RPM algorithm is described using a new, graphical description technique. It is shown how a traditional distance-vector unicast algorithm is extended step by step to achieve true multicast delivery (reverse path forwarding, reverse path broadcasting, truncated reverse path broadcasting, reverse path multicasting). This description is more detailed than those found in the literature without being fixed to a specific implementation. The thesis then investigates how much traffic the mrouted protocol generates with its prune, graft and graft acknowledgement messages. By means of a discrete event simulation, the group size scalability, the internetwork size scalability and the group density scalability are evaluated for three typical multicast services: audio/video transmission (AV), teleconference (TC) and resource discovery (RD). It is found that the protocol overhead is reasonable for AV services. TC services can only be provided for dense groups and/or in small internetworks. For RD services, the mrouted protocol should not be used. Finally, several protocol extensions are proposed to improve the protocol for these TC and RD services."

Elan Amir and Steve McCanne and Hui Zhan, An Application Level Video Gateway, Proc. of ACM Multimedia, 1995

Abstract: "The current model for multicast transmission of video over the Internet assumes that a fixed average bandwidth is uniformly present throughout the network. Consequently, sources limit their transmission rates to accomodate the lowest bandwidth links, even though high-bandwidth connectivity might be available to many of the participants. We propose an architecture where a video transmission can be decomposed into multiple sessions with different bandwidth requirements using an application-level gateway. Our video gateway transparently connects pairs of sessions into a single logical conference by manipulating the data and control information of the video streams. In particular, the gateway performs bandwidth adaptation through transcoding and rate control. We describe an efficient algorithm for transcoding Motion-JPEG to H.261 that runs in real time on standard workstations. By making the Real-time Transport Protocol (RTP) an integral component of our architecture, the video gateway interoperates with the current Internet video tools in a transparent fashion. We have built a prototype of the video gateway and used it to redistribute multi-megabit JPEG video seminars from the Bay Area Gigabit Network as 128 kb/s H.261 MBone sessions."
Keywords: "RTP; translator; gateway; packet video; H.261; transcoding"

Firoiu, Victor and Towsley, Don, Call admission and resource reservation for multicast sessions, Department of Computer Science, University of Massachusetts, TR 95-17, 1995

Abstract: "Multicast applications, including audio and video, are expected to consume a large fraction of resources in forthcoming high-speed networks. Because of this, new services are needed to provide the quality of service (QoS) required by these applications. In this paper, we take a step in this direction by presenting a general framework for admission control and resource reservation for multicast sessions. Within this framework, efficient and practical algorithms that aim to efficiently utilize network resources are developed. The problem of admission control is decomposed into several subproblems that include: the division of end-to-end QoS requirements into local QoS requirements, the mapping of local QoS requirements into resource allocation, and the optimization of the resulting resource allocation for a multicast session. These are solved independently of each other yielding a set of mechanisms and policies that can be used to provide admission control and resource reservation for multicast connection establishment. A comprehensive application of an instance of the algorithms in the context of packetized voice multicast connections over the Mbone is provided to illustrate their applicability."
Keywords: "multicast algorithms; quality of service; resource allocation and optimization; admission control; Mbone; resource reservation"

Arup Acharya and Ajay Bakre and B. R. Badrinath, IP Multicast Extensions for Mobile Internetworking, Department of Computer Science, Rutgers University, New Brunswick, New Jersey, Technical Report, LCSR-TR-243, 1995

Abstract: "This paper deals with multicasting in an internetwork with mobile hosts, particularly with regard to Mobile-IP and Distance Vector Multicast Routing (DVMRP) protocols. When the source of a multicast datagram is a mobile host (MH), the datagram may not reach all group members to which the datagram is addressed, including other mobile hosts. When the source is a static host and the multicast group includes mobile hosts, a mobile group member may receive datagrams in one cell but not in another. Further, when a MH enters a cell which contains no other member of the same group, the MH will experience a delay before it starts receiving datagrams addressed to that group. Mobility between campuses, which result in a MH acquiring an additional unicast address, also has an effect on multicast routing. We propose enhancements to DVMRP executed at the Mobility Support Routers (MSR) that ensure correct forwarding of multicast change at hosts and routers unaware of mobility, i.e. the modifications are limited to MSRs and MHs. We also describe an implementation incorporating a subset of our proposals. Lastly, we show that alternate styles of multicasting or mobile networking, viz. link-state (MOSPF) and IETF proposal, will face similar problems and our proposed solutions are still valid in their context."
Keywords: "mobile IP; routing; multicast"

Stiller, Burkhard, "A Survey of UNI Signaling Systems and Protocols for ATM Networks", CCR, 25(2), 1995

Abstract: "The main aspects covered by signaling systems and protocols for ATM networks concerns the possility to manage, maintain and control a user-driven communication between arbitrary ATM end-systems connected to an ATM network. The tasks and procedures defined for, e.g., setting-up an ATM connection, are often very different concerning the relevant specifications of various working bodies (such as ITU-T or ATM-Forum) or certain vendors, although the basics to be done for maintaining ATM connections are always principally the same. The reason for this situation is, that the intentions of working bodies are different and each one of them follows specific strategies for certain scenarios (such as for point-to-point unicast or point-to-multipoint multicast). Nevertheless, various types of characteristics (such as addressing, multicast, or interworking) are requested from applications residing on top of ATM networks. Therefore, this survey of signaling systems and protocols for ATM networks identifies for serveral of selected approaches (such as Q.2931, UNI 3.1 or CMAP) important characteristics and relevant scenarios. Furthermore, a table-based comparison of some approaches has been added."

Marlow, D., "Host Group Extensions for CLNP Multicasting", RFC 1768, 1995

Abstract: "This memo documents work performed in the TUBA (TCP/UDP over Bigger Addresses) working group of IPng area prior to the July 1994 decision to utilize SIPP-16 as the basis for IPng. The TUBA group worked on extending the Internet Protocol suite by the use of ISO 8473 (CLNP) and its related routing protocols. This memo describes multicast extensions to CLNP and its related routing protocols for Internet multicast use. Publication of this memo does not imply acceptance by any IETF Working Group for the ideas expressed within."