Pricing communication networks P11

MulticastingMột dịch vụ unicasting là một trong những yêu cầu mạng để cung cấp vận chuyển điểm-điểm giữa các nguồn chỉ là một thông tin và nhận một. Một dịch vụ multicasting mở rộng ý tưởng này bằng cách yêu cầu các mạng để cung cấp vận tải giữa một hoặc nhiều nguồn thông tin và một nhóm người nhận. Multicasting dịch vụ có thể được sử dụng cho teleconferencing phân phối phần mềm, và truyền dẫn của âm thanh và video. Một đặc tính quan trọng của một dịch vụ multicasting là nó có giá của nó phải là...
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Pricing communication networks P11Pricing Communication Networks: Economics, Technology and Modelling. Costas Courcoubetis and Richard Weber Copyright  2003 John Wiley & Sons, Ltd. ISBN: 0-470-85130-9 Part DSpecial Topics Pricing Communication Networks: Economics, Technology and Modelling. Costas Courcoubetis and Richard Weber Copyright  2003 John Wiley & Sons, Ltd. ISBN: 0-470-85130-911MulticastingA unicasting service is one that requires the network to provide point-to-point transportbetween just one information source and one receiver. A multicasting service extends thisidea by requiring the network to provide transport between one or more information sourcesand a group of receivers. Multicasting services can be used for teleconferencing, softwaredistribution and the transmission of audio and video. A key characteristic of a multicastingservice is that it its cost must be optimized for the particular group of receivers to which itprovides service. This poses important resource management and control problems, whichadd new complexity to pricing issues. A special case of multicasting is broadcasting. Broadcasting is simple, in that the sameinformation is continually made available to all potential receivers, and so there is no needto optimize network resources to the subset of receivers that is presently listening. Thetransmission rates and network resource allocation are fixed, and the transmission cost isindependent of the customer group. If broadcasting technology is in place, then we canmulticast information by broadcasting it, but only granting the subscribers of the multicastthe permissions to access or decode it. Multicasting over a data network such as the Internet requires far more complex resourcemanagement than does broadcasting. This is because there are different mechanismsavailable at the network level, and the identities of the end receivers can influencerouting decisions about which links of the network should carry the multicast traffic. Also,whereas satellite broadcasting typically uses constant bit rate channels, applications thatuse data network multicasting services may produce bursty data flows and have moreflexible quality of service requirements. In this chapter, we investigate the issues ofresource allocation and pricing that arise when multicasting services are to be providedover a data network like the Internet. We see that the final resource allocation maydepend upon decisions taken by a large number of participants. This contrast with unicast,where one of the two connected parties makes all the decisions about the propertiesof the connection and is responsible for paying the bill. Hence, if one is to achieveglobally efficiency by giving appropriate incentives to the various decision-makers, thereare many delicate gaming aspects that can make pricing very complex. Of course,we can always view a single unicast connection as the simplest case of a multicastservice, in which the sender and the receiver make independent decisions and so mustagree on common features of the connection, such as the bit rate and how to split thenetwork charge.264 MULTICASTING In Section 11.1 we set out some requirements for multicasting. In Section 11.2 wedescribe some basic technologies for it. Section 11.3 considers mechanisms for providingquality of service and Section 11.4 addresses flow control. Starting from a model forallocating bandwidth to elastic multicast traffic, Section 11.5 considers issues of cost sharingand the formation of the multicast tree. Section 11.6 is about settlement.11.1 The requirements of multicastingMulticasting is potentially a very promising network service for IP technology networks.Great efficiency can be achieved by arranging that only one copy of the data transversesany common paths on its way towards multiple destinations. For example, in satellitebroadcasting there is a single common path; all receivers share the same set of broadcastchannels, all of which are transmitted over the same link. Multicasting services provide positive network externalities. Since a customer sharescommon cost with other customers he can access services that he would otherwise find tooexpensive. However, there is a negative externality, since a customer may not be able tochoose the precise type and quality of the service that he desires. His choices are restrictedbecause other customers in his multicast group value service differently or have differenttechnological capabilities. These issues make the pricing of multicasting services interesting,but complex. As for unicast services, pricing plays an important role in controlling the waynetwork resources are shared. A pricing policy must fairly reflect the externality effectsand provide the right incentives for customers to join or leave a multicast session when itis economically justified from the viewpoint of the multicast group as a whole. Before looking at the economic aspects of a multicast service model, we consider thetechnology aspects. Clearly, multicast services can provide savings in network resources.Savings occur because network routers and switches can, at no cost, copy incoming packetflows and direct resulting identical flows to more than one output link. The network gainsby taking information that is destined for multiple receivers and forwarding it over pathsfor which receivers have common parts. An inefficient network could always use traditionalunicast technology to support a multicast service. However, ...