Multicast Address Research Articles

A dynamic active multicast group access control framework based on trust management system

The current multicast model provides no access control mechanism. Any host can send data directly to a multicast address or join a multicast group to become a member, which brings safety problems to multicast. In this paper, we present a new active multicast group access control mechanism that is founded on trust management. This structure can solve the problem that exists in multicast members' access control and distributing authorization of traditional IP multicast.

Network for Video Distribution between Preceding and Succeeding Vehicles on the Same Route

The Future Vision Distribution Service (FVDS) (Sato, et al., 2004) is an innovative video delivery service concept based on the Internet ITS (Intelligent Transport System) area, and Source Mobility Support Multicasting (SMM) (Sato, et al., 2004) consists of new multicasting techniques needed to realize FVDS. However, FVDS and SMM lack sufficient application-level protocols to manage preceding and following vehicles on the same route, and have a drawback of topological constraints in the access network to accommodate micro-mobility. To solve these problems, this paper presents two new protocols. The Mobile Vehicle Management (MVM) protocol is an application-level protocol that discovers a preceding vehicle on the same route and provides its multicast address to following vehicles by using information from the global positioning system (GPS) and a route-guiding function. The Self-Organizing Tree (SOT) protocol is a network-level protocol for use in the access network that organizes radio base-stations into a logical tree topology in a self-forming and self-healing manner. This eliminates the topological constraints and provides the network with robustness against failures and flexibility for network design. To show how these protocols further the implementation of FVDS and SMM, this paper also gives details of a software implementation model for each network node system; specifically, we have designed a software architecture, composition elements for each protocol and their relations, and internal state-machines for each element.

Multicast-Based Mobility: A Novel Architecture for Efficient Micromobility

Handover performance is very important when evaluating IP mobility protocols. If not performed efficiently, handover delays, jitters, and packet loss directly impact application performance. We propose a new architecture for providing efficient handover, while being able to coexist with other protocols. We propose a paradigm for multicast-based micromobility (M&M), where a visiting mobile is assigned a multicast address to use while moving within a domain. The multicast address is obtained using algorithmic mapping, and handover is achieved using multicast join/prune mechanisms. This paper outlines a framework for the design and evaluation of micromobility protocols. We define a suite of protocols (called candidate access router set) to enable multiple-access routers to receive traffic for the mobile node. By changing the number of such routers, timing, and buffering parameters, the protocol may be fine-tuned for specific technologies (e.g., 802.11) and handover scenarios. Extensive NS-2 simulations are used to compare M&M with other micromobility schemes-cellular Internet protocol (CIP) and handoff-aware wireless access Internet infrastructure (HAWAII). For proactive handover scenarios, our results show that M&M and CIP show lower handover delay and packet reordering than HAWAII. M&M, however, handles multiple border routers in a domain, where CIP fails. Also, for scenarios of reactive handover and coverage gaps M&M clearly outperforms CIP and HAWAII.

The multicast address allocation problem: theory and practice

In this paper, we perform the first comprehensive study of the multicast address allocation problem. We analyze this problem both within its context as a classic resource allocation problem and with respect to its practical use for multicast address assignment. We define a framework for the problem, introduce complexity results, and formulate several new allocation algorithms. Despite the theoretical superiority of these algorithms, our performance evaluation demonstrates that a common, prefix-based algorithm is better under a range of workloads. We conclude by illustrating the conditions under which dynamic address allocation should be used and provide insight into how to further improve the performance of prefix-based allocation.

End system multicast: an architectural infrastructure and topological optimization

Although IP multicast has been proposed and investigated for years, there are major problems inherent in the IP multicasting technique, e.g. difficulty to scale up the system, difficulty in allocating a globally unique multicast address, complexity in supporting higher level features such as reliable data transfer and congestion/flow control, more importantly, difficulty to deploy on the current Internet infrastructure due to necessity to change many core routers. Recently, end-system multicast (ESM) has been proposed as an alternative solution so that multicasting services can be quickly deployed. In this paper, we consider the‘architectural’ and ‘optimization’ issues on designing an ESM-tree. Specifically, we present a distributed algorithm on how to create and maintain an ESM-tree. We propose a distributed algorithm to perform tree optimization (TO) so that an ESM-tree can dynamically adapt to the changing network condition (e.g. drop in transfer bandwidth) so that the nodes within an ESM-tree can receive data more efficiently. The distributed algorithm has the important theoretical properties that at all times, a tree topology can be maintained and any node joining, leaving, as well as any TO operation will not ‘partition’ the underlying ESM-tree. Therefore, our work can be used to provide an efficient architectural infrastructure for ESM services. We have implemented a prototype ESM system and carried out experiments to illustrate the effectiveness and the performance gains of our ESM optimization protocol.

주문형 멀티캐스팅 기법을 사용한 새로운 MOD 시스템의 구현

본 논문은 멀티캐스트 전송을 이용한 MOD 시스템을 구현하였다. 기존의 시스템은 서버 지향적인 멀티캐스트 시스템을 제공하였지만 구현된 시스템은 사용자 요구 지향적인 멀티캐스트 시스템을 제공한다. 스케줄러는 사용자의 요구를 수집하고 요구된 비디오 아이템과 서비스 시간에 따라서 멀티캐스트 그룹 주소와 포트 번호를 발생한다. 그러면 스케줄러는 MOD 서버와 서비스를 요구한 사용자에게 즉시 멀티캐스트 주소와 포트 번호를 전송한다. .그리고 MOD 서버는 멀티캐스트 그룹 주소로 요구한 스트림을 전송하고, 사용자는 자동으로 그룹 주소에 가입한다. 스케줄러는 같은 스케줄링 시간 안에 있는 다른 사용자들이 동일한 비디오를 요구하였을 때 같은 멀티캐스트 그룹 주소를 할당한다. 구현된 MOD 시스템은 동시에 많은 사용자에게 서비스할 뿐 아니라 서버의 부하를 크게 줄일 수 있음을 확인하였다. This paper implements MOD system using multicast delivery. Conventional system provide server-based system in multicast delivery but implemented system provides on-demand client-based multicast system. The scheduler aggregates clients' request and it generate multcast group addresses and port numbers according to requested video items and service request time. Then it transmits immediately multicast address to MOD server and client who request service. And then MOD server transmits requested streams with a multicast group address and the client joins the group automatically. The scheduler assigns the same multicast group address when other clients request an identical video within the same scheduling duration. The system can reduce load of server and support many clients at the same time.

오버레이 멀티캐스팅에서 트리의 스위칭을 고려한 빠른 멤버 가입 방안에 관한 연구

인터넷 멀티캐스팅 기술은 지난 10여년간의 기술 발전에도 불구하고 아직 본격적인 서비스 보급이 이루어지지 못하고 있다. 주된 이유는 멀티캐스트 라우팅에서의 트래픽 제어, 글로벌 인터넷에서의 멀티캐스트 주소 할당, 멀티캐스트 신뢰전송 기법 등의 문제가 아직 해결되지 않았기 때문이다. 최근 인터넷 방송, 실시간 증권정보 서비스 등의 멀티캐스트 응용 서비스에 대한 요구가 급격히 증가함에 따라, 새로운 인터넷 멀티캐스팅 기술로써 오버레이 멀티캐스팅이 개발되고 있다 본 논문은 오버레이 멀티캐스팅 기술을 살펴보고, 새로운 멤버가 그룹에 가입하는데 걸리는 시간을 단축하는 방안을 제안한다. 기존의 방식은 잠재적인 부모 노드를 발견하기 위해서 한번에 트리의 한 레벨씩을 검색해 내려갔으며, 이로 인하여 긴 가입 지연 시간이 야기되었다. 또한, 트리의 매 레벨에서 자신과 가까운 노드를 잠재적인 부모 노드로 지적함으로써, 최적의 부모 노드를 선택하려고 노력하였지만 실제로 노드의 제한 차수로 인하여 자신과 가장 가까운 잠재적인 부모 노드를 선택하지 못하였으며, 이로 인해 트리의 효율성이 떨어졌다. 본 논문에서는 이러한 가입 지연 시간을 감소시키고, 생성된 트리의 효율성을 높이기 위해서, 트리의 두 레벨씩 검색하는 방안을 제안한다. 이 방식은 가입 요청 메시지를 자신의 자식 노드에게 전달하는 방식으로, 평상시에 트리 유지를 위한 추가적인 오버헤드 없이, 가입 요청이 왔을 때 검색 메시지의 수를 증가시켜서, 빠르게 가입을 완료한다. 또한, 더 많은 노드를 검색함으로써 좀 더 효율적인 트리를 생성하게 도와준다. 제안하늘 방안의 성능을 평가하기 위해서, 그룹의 멤버 수와 제한 차수를 기준으로 검색 시간 및 검색한 노드의 수 그리고 트리 스위칭 횟수를 측정하였다. 시뮬레이션 결과에서 제안한 기법이 기존의 방식에 비해서 가입 지연 시간을 단축시켰으며, 좀 더 효율적인 트리를 생성하는 것을 볼 수 있었다.본 연구결과 이소플라본은 전립선암 환자의 혈중 지질 패턴과 항산화체계를 개선시키는 효과를 보였다. 따라서 이소플라본이 지질대사에 미치는 영향과 항산화작용기전에 대한 보다 심층적인 연구가 이루어져야 할 것이며, 보다 많은 전립선암 환자를 대상으로 이소플라본 섭취에 따른 장기적인 임상실험연구가 이루어져 이소플라본이 전립선암 환자의 삶의 질을 향상시킬 수 있는지에 대한 다각적인 검토가 필요하다고 본다. 중 참가성 , 흥미성, 지속성, 대인관계 4개의 측정항목에서 높은 증가율을 보여 치료효과가 큰 것으로 판단된다. 원예 치료 실시 후의 자체설문지 평가결과 원예 활동을 통해서 달라진 점은 개인적으로 가족, 이웃 간의 긍정적인 변화를 이끌어내고 있다는 것을 발견할 수 있었고 다양한 원예프로그램이 인상깊었다고 하였으며 다음진행에 추가적으로 야외에서 진행할 프로그램에 대한 욕구가 표출되었다. 이것을 통해 개인적 치료경험과 가족, 이웃 간의 지지망 형성이 중요하며 긍정적인 영향을 주었다는 것을 볼 수 있었다. 또한 다양한 원예치료프로그램의 적용과 야외 활동을 조화롭게 적용한다면 성공적인 프로그램 진행에 도움을 될 것으로 판단된다. 이상의 결과를 종합하면 정신지체장애인에게 원예치료 프로그램을 실시한 이후에 원예에 대한 관심이 높고 자아존중 감이 향상되었으며 원예치료 프로그램에 대한 높은 만족도를 보였고 원예치료에 대한 참가성, 흥미성, 지속성, 대인관계성에서 높은 증가율을 보여 치료프로그램의 개입이 유의미한 효과가 있는 것으로 나타났다. 이러한 결과들 볼 때 의도적인 원예치료활동을 통해서 심신의 치료를 경험하<TEX>$\infty$</TEX>I 자존감이 향상되며 회원 상호관계를 통한 사회부적응문제를 치료하여 사회성이 향상될 것이라는 목표에 대한 높은 달성정도를 볼 수 있다. 또한 지속적이고 흥미를 유발하는 원예치 료 프로그램을 적용한다면 심리적, 신체적, 정서적 치료효과가 높은 향상을 보이고 자신감과 More than a decade after its initial proposal, deployment of IP Multicast has been limited due to the problem of traffic control in multicast routing, multicast address allocation in global internet, reliable multicast transport techniques etc. Lately, according to increase of multicast application service such as internet broadcast, real time security information service etc., overlay multicast is developed as a new internet multicast technology. In this paper, we describe an overlay multicast protocol and propose fast join mechanism that considers switching of the tree. To find a potential parent, an existing search algorithm descends the tree from the root by one level at a time, and it causes long joining latency. Also, it is try to select the nearest node as a potential parent. However, it can't select the nearest node by the degree limit of the node. As a result, the generated tree has low efficiency. To reduce long joining latency and improve the efficiency of the tree, we propose searching two levels of the tree at a time. This method forwards joining request message to own children node. So, at ordinary times, there is no overhead to keep the tree. But the joining request came, the increasing number of searching messages will reduce a long joining latency. Also searching more nodes will be helpful to construct more efficient trees. In order to evaluate the performance of our fast join mechanism, we measure the metrics such as the search latency and the number of searched node and the number of switching by the number of members and degree limit. The simulation results show that the performance of our mechanism is superior to that of the existing mechanism.

Network design for streaming service on IP multicast over ATM

AbstractThis paper considers streaming service, which is an application of multicast communications, and discusses the network configuration used in providing IP multicast over ATM. In IP multicast over ATM, conversion from the IP multicast address to the ATM address is required. One of the methods of making this conversion is to use a multicast address resolution server (MARS). In this system, the MARS manages the member information of the multicast group. When there is a change in the membership of the group because a host joins or leaves, that host sends an information renewal message to the MARS. In streaming service, there arises a time zone in which many renewal messages to MARS are generated due to program changes and the like, so that the MARS is heavily burdened. This paper considers the case in which streaming service is introduced via MARS, and analytically derives the transmission frequency of the information renewal messages. The relations between the transmission frequency, the characteristics of the program, and the network scale are identified. Based on the results of analysis and a consideration of the effect of other traffic on the network, an adequate network design principle capable of reducing the control traffic to the MARS is presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(10): 51–59, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10188

Efficient micro-mobility using intra-domain multicast-based mechanisms (M&amp;M)

One very important metric in evaluation of IP mobility protocols is handover performance. Handover occurs when a mobile node changes its network point-of-attachment. If not performed efficiently, handover delays, jitters and packet loss directly impact applications and services. With the Internet growth and heterogeneity, it becomes crucial to design efficient handover protocols that are scalable, robust and incrementally deployable. Mobile IP (MIP) has been shown to exhibit poor handover performance during micro-mobility. We propose a new architecture for providing efficient and smooth handover, while being able to coexist and inter-operate with other technologies. Specifically, we propose an intra-domain multicast-based mobility architecture, where a visiting mobile is assigned a multicast address to use while moving within a domain. Efficient handover is achieved using standard multicast join/prune mechanisms.Two approaches are proposed and contrasted. The first introduces the concept of proxy-based mobility, while the other uses algorithmic mapping to obtain the multicast address of visiting mobiles. We show that the algorithmic mapping approach has several advantages over the proxy approach, and provide mechanisms to support it.Simulations used to evaluate our scheme and compare it to other micro-mobility schemes - CIP and HAWAII. The proactive handover results show that both M&amp;M and CIP show low handoff delay and packet reordering depth as compared to HAWAII. The reason for M&amp;M's comparable performance with CIP is that both use bi-cast in proactive handover. M&amp;M, however, handles multiple border routers in a domain, where CIP fails. Also using a proactive path setup mechanism, we show that M&amp;M clearly outperforms CIP in case of reactive handover.

Optimal branching factor for tree-based reliable multicast protocols

In recent years, many reliable multicast protocols on transport layer have been proposed. Previous analysis and simulation studies gave evidence for the superiority of tree-based approaches in terms of throughput and bandwidth requirements. In many tree-based protocols, the nodes of the tree are formed of multicast group members. In this case, the branching factor, i.e. the maximum number of child nodes is adjustable. In this paper, we analyze the influence of the branching factor on a protocol's throughput and bandwidth consumption. This knowledge is important to configure protocols for best performance and to optimize the tree creation process. Our results show that the optimal branching factor depends mainly on the probability for receiving messages from other local groups. If local groups are assigned to a separate multicast address, the optimal branching factor is small. On the other hand, if TTL scoping is used and therefore the probability for receiving messages from other local groups is greater than zero, larger local groups provide better performance.

Scalable multicast forwarding

The goal of this work is to develop efficient algorithms and data structures suitable for software-based forwarding of multicast datagrams. The algorithms should scale to very large numbers of simultaneously activemulticast groups. In an example configuration with 32 interfaces a new algorithm can forward 20,000 simultaneously active multicast groups using only 64Kbytes of memory and a leak probability of . This algorithm can perform almost 10 million forwarding decisions per second on a 800MHz Pentium III processor The task of a multicast-forwarding engine is to forward packets along branches of a distribution tree. The branches of the tree consists of network segments and the nodes in the tree are routers. There are a few different classes of distribution trees. For simplicity only bidirectional trees will be considered in this discussion. Abstractly, a bidirectional-distribution tree is a bidirectional acyclic graph. It has a root called center, core or, rendez-vous point. Forwarding is performed by having traffic flow up the tree towards the center, and down the tree towards the receivers. A router must for each distribution tree maintain a list of interfaces that connect the tree. To forward a packet, first find the interface list corresponding to the group. If the packet arrived on an interface in the list, then, forward the packet over the remaining interfaces in the list. It is possible to perform this forwarding function using probabilistic methods. Observe that forwarding will be successfully performed if the interface list includes at least all interfaces that the packet must be forwarded over. Since the interface list can potentially be to long, a packet will occasionally leak out the wrong interface. However, at a minimum, packets will always be forwarded over the distribution tree. Since the leak probability can be made arbitrarily small, this may not be a problem in practice. Assume a network configuration where packets are allowed to leak with a maximum probability . The probability that a leaked packet will leak through the next router is , and through a third . Thus, leak probability decays exponentially as we travel down (or up) the tree. Also, hosts configure their network adaptors to filter out unwanted multicasts. If a packet should sneak through this hardware filter, then software filtering sets in. Thus, hosts on leaf networks are already prepared to handle the problem with traffic leaks. The suggested probabilistic-forwardingalgorithm has an efficient implementation based on Bloom filters. The algorithm uses a fixed small number of memory references (e.g eight) and a small number of multiplications and shift instructions. Memory requirements scale linearly with the maximum allowed number of groups and is also independent of the number of interfaces. Surprisingly, memory requirements are independent of group address length. This is a result of that addresses are not stored in the data structure. Thus, 112 bit IPv6 addresses use no more forwarding memory than 28 bit IPv4 addresses. An important quality of the algorithm is that it is independent of address-space usage. Performance is unchanged if addresses are picked uniformly random or from some other distribution. This is important since it is impossible to predict how a future multicast address space will be utilized. There is always a downside to using probabilisticmethods. In this case we introduce traffic leakage, i.e traffic will with a small probability leave the distribution tree. The probability that a group will leak through an interface is . Here represents the number of active groups, is the number of bits in the filter, and is the number of memory references used per lookup. Outline of algorithm: Recall that multicast routing is basically about finding the appropriate interface list and then forward the packet over all those interfaces. This mapping from group to interface list can be implemented using a number of parallel Bloom filters. For each interface wemaintain one Bloom filter. If a group is active with respect to an interface, then the corresponding Bloom filter includes this group. Bloom filters are essentially arrays of bits. By organizing these bit arrays as columns in a bit matrix it is possible to evaluate all filters in parallel using word operations. Thus, a 32 bit micro processor can efficiently calculate a 32 interface list in parallel.

Distributed core multicast (DCM)

We present a multicast routing protocol called Distributed Core Multicast (DCM). It is intended for use within a large single Internet domain network with a very large number of multicast groups with a small number of receivers. Such a case occurs, for example, when multicast addresses are allocated to mobile hosts, as a mechanism to manage Internet host mobility or in large distributed simulations. For such cases, existing dense or sparse mode multicast routing algorithms do not scale well with the number of multicast groups. DCM is based on an extension of the centre-based tree approach. It uses several core routers, called Distributed Core Routers (DCRs) and a special control protocol among them. DCM aims: (1) avoiding multicast group state information in backbone routers, (2) avoiding triangular routing across expensive backbone links, (3) scaling well with the number of multicast groups. We evaluate the performance of DCM and compare it to an existing sparse mode routing protocol when there is a large number of small multicast groups. We also analyse the behaviour of DCM when the number of receivers per group is not a small number.

IP-address lookup using LC-tries

There has been a notable interest in the organization of routing information to enable fast lookup of IP addresses. The interest is primarily motivated by the goal of building multigigabit routers for the Internet, without having to rely on multilayer switching techniques. We address this problem by using an LC-trie, a trie structure with combined path and level compression. This data structure enables us to build efficient, compact, and easily searchable implementations of an IP-routing table. The structure can store both unicast and multicast addresses with the same average search times. The search depth increases as /spl Theta/(log log n) with the number of entries in the table for a large class of distributions, and it is independent of the length of the addresses. A node in the trie can be coded with four bytes. Only the size of the base vector, which contains the search strings, grows linearly with the length of the addresses when extended from 4 to 16 bytes, as mandated by the shift from IP version 4 to IP version 6. We present the basic structure as well as an adaptive version that roughly doubles the number of lookups/s. More general classifications of packets that are needed for link sharing, quality-of-service provisioning, and multicast and multipath routing are also discussed. Our experimental results compare favorably with those reported previously in the research literature.

Multicast address management and connection control based on hierarchical autonomous structure

Multicast capability, including multicast address and multicast routing mechanisms, at the network layer is necessary in order to reduce the bandwidth requirements of multiparty, multicast applications. Based on hierarchical autonomous structure in accordance with the self-organization topologies of Internet, the paper puts forward a multicast address management scheme that is shown to be robust and scalable. Connection control hierarchy (CCH) based on master/slave relationship and a simple efficient building algorithm of multi-point connection is also built. The paper also describes the normal operations of multicast address management and multi-point connection controller. Through simulation experiment, HAM, CM and DDM of Multicast Address Allocation are compared. HAM integrates the merits of CM and DDM, which is efficient as a whole, robust and scalable. CCH raises the efficiency of connection control, and is highly robust, flexible and scalable.

Improving the WWW: caching or multicast?

We consider two schemes for the distribution of popular Web documents. In the first scheme the sender repeatedly transmits the Web document into a multicast address, and receivers asynchronously join the corresponding multicast tree to receive a copy. In the second scheme, the document is distributed to the receivers through a hierarchy of Web caches. We develop analytical models for both schemes, and use the models to compare the two schemes in terms of latency and bandwidth usage. We find that except for documents that change very frequently, hierarchical caching gives lower latency and uses less bandwidth than multicast. For rapidly changing documents, multicast distribution reduces latency, saves network bandwidth, and reduces the load on the origin server. Furthermore, if a document is updated randomly rather than periodically, the relative performance of CMP improves. Therefore, the best overall performance is achieved when the Internet implements both solutions, hierarchical caching and multicast.

The MASC/BGMP architecture for inter-domain multicast routing

Multicast routing enables efficient data distribution to multiple recipients. However, existing work has concentrated on extending single-domain techniques to wide-area networks, rather than providing mechanisms to realize inter-domain multicast on a global scale in the Internet.We describe an architecture for inter-domain multicast routing that consists of two complementary protocols. The Multicast Address-Set Claim (MASC) protocol forms the basis for a hierarchical address allocation architecture. It dynamically allocates to domains multicast address ranges from which groups initiated in the domain get their multicast addresses. The Border-Gateway Multicast Protocol (BGMP), run by the border routers of a domain, constructs inter-domain bidirectional shared trees, while allowing any existing multicast routing protocol to be used within individual domains. The resulting shared tree for a group is rooted at the domain whose address range covers the group's address; this domain is typically the group initiator's domain. We demonstrate the feasibility and performance of these complementary protocols through simulation.This architecture, together with existing protocols operating within each domain, is intended as a framework in which to solve the problems facing the current multicast addressing and routing infrastructure.

Session directories and scalable Internet multicast address allocation

A multicast session directory is a mechanism by which users can discover the existence of multicast sessions. In the Mbone, session announcements have also served as multicast address reservations - a dual purpose that is efficient, but which may cause some side-affects as session directories scale.In this paper we examine the scaling of multicast address allocation when it is performed by such a multicast session directory. Despite our best efforts to make such an approach scale, this analysis ultimately reveals significant scaling problems, and suggests a new approach to multicast address allocation in the Internet environment.

IP multicast routing through ATM networks

The purpose of this paper is to have a closer look at the ‘core’ technology providing interworking between connectionless TCP/IP internetworks and switched ATM networks. The scope of the paper is IP multicast, while the main focus is on the network side of multicast, more precisely, on layers three and two of Internet architecture dealing with IP multicast routing. The paper analyses both practically available solutions and those being currently under discussion in IETF as Internet drafts. As a background of this comparison, the possible convergence of IP and ATM multicast service models is discussed. Major conclusions, based on simulation studies and scalability analysis are: (i) the high mapping overhead requires a separate address resolution service for unicast and multicast addresses; and (ii) efficient convergence has to make obsolete classical IP over ATM (M. Laubach, Classical IP and ARP over ATM, Network Working Group, Request for Comments: 1577, Category: Standards Track, January, 1994 [1]) in order to permit ‘cut-through’ within the ATM domain.

Distributed multicast address management in the global Internet

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 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, the 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). >

Identifying migrated objects using multicast addresses

All objects in a distributed system must be associated with some form of identifier if they are to communicate with other objects. Should an object migrate between a pair of processors, it then becomes necessary to institute measures to ensure that communication can continue. Seven object identification techniques are examined here, and their application to object migration and communication is considered. The use of multicast addresses to identify objects is then proposed. Data from an experimental Ethernet illustrates the benefits of using multicast addresses, including a reduction in identifier management overheads, lower transmission times, and less network traffic.