IEEE Communications Magazine

This article outlines an approach for multicast congestion control based on an economic model that has been successfully applied to unicast congestion control. In this model, congestion signals are interpreted as prices and congestion-controlled sessions as utility maximizing agents. A naive extension of the unicast model fails to achieve a reasonable balance between providing the incentives necessary to promote the use of multicast and ensuring that multicast sessions do not interact too aggressively with unicast sessions. We extend the model by introducing a rational definition of multicast utility. The revised model provides a basis for multicast congestion control protocols that provide incentives to use multicast but are necessarily unfair to unicast traffic. We show, however, that the degree of unfairness can be controlled by appropriately setting a design parameter with a limiting case of strict fairness.

We analyze IPv6 handover over wireless LAN. Mobile IPv6 is designed to manage mobile nodes' movements between wireless IPv6 networks. Nevertheless, the active communications of a mobile node are interrupted until the handover completes. Therefore, several extensions to Mobile IPv6 have been proposed to reduce the handover latency and the number of lost packets. We describe two of them, hierarchical Mobile IPv6, which manages local movements into a domain, and fast handover protocol, which allows the use of layer 2 triggers to anticipate the handover. We expose the specific handover algorithms proposed by all these methods. We also evaluate the handover latency over IEEE 802.11b wireless LAN. We compare the layer 2 and layer 3 handover latency in the Mobile IPv6 case in order to show the saving of time expected by using anticipation. We conclude by showing how to adapt the IEEE 802.11b control frames to set up such anticipation.

It is now widely recognized that using IP as the foundation for next-generation mobile networks makes strong economic and technical sense, since it takes advantage of the ubiquitous installed IP infrastructure, capitalizes on the IETF standardization process, and benefits from both existing and emerging IP-related technologies and services. The large-scale support of data services and their integration with legacy services are the common objectives of all wireless efforts termed third generation (3G) and beyond. In these all-IP wireless networks, IP can be deployed in two modes: the transport mode and the native mode. As we show in this article, this duality in the use of IP has a significant impact on network efficiency and performance. It is the extended native use of IP in the terrestrial segment of a wireless operator's domain that more readily allows for building a converged network with multiple access technologies. We then discuss the different levels of mobility in the all-IP network. In particular, our focus is on micromobility, and on the issue of seamless localized mobility within the converged network. After reviewing the mobility schemes that have emerged in previous years, we describe a hierarchical mobility management scheme based on multiprotocol label switching (MPLS). The scheme employs an enhanced type of MPLS routers, called label edge mobility agents, and is scalable, efficient, and flexible. It directly inherits the noted capabilities of MPLS in terms of support of QoS, traffic engineering, advanced IP services, and fast restoration. This scheme does not use nodes that are specific to any given wireless technology, and is well suited for gradual deployment.

One of the biggest barriers to the development of public IP telephony services has been the lack of a universal addressing system. While IP-enabled devices have long been capable of originating phone and fax calls, it is difficult to "call" an IP device because they are hard to find. Internet Engineering Task Force (IETF) Request for Comments (RFC) 2916, "E.164 Number and DNS," seeks to solve this problem in a simple and perhaps unlikely way. Simple, in that the ENUM protocol converts existing telephone numbers into domain names.The designers of ENUM hope to foster a global megadirectory of communications users who can be reached in any number of ways by means of only one number. While theoretically any character space could be standardized in an attempt to create a universal addressing scheme, ENUM explicitly adopts telephone numbers, presumably to take advantage of their global user acceptance and mature infrastructure. This choice adds a significant public policy dimension to the story. Far from being benign and boring, telephone numbers can present significant communications policy issues, and are regulated both domestically and internationally. The top level of this hierarchy is defined by International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Recommendation E.164.

The wide deployment of wavelength-division multiplexing technology and new transmission techniques have resulted in significant increases in the transmission capacity in optical fibers, both in the number of wavelengths and the bandwidth of each wavelength channel. Meanwhile, the fast growth of the Internet demands more data switching capacity in the network in order to deliver high bandwidth to end users. Although the capacity of electronic routers has been increasing consistently in the past, optical switching appears to be a more cost-effective way to switch individual wavelengths. As the bit rate per wavelength channel continues to grow, optical subwavelength switching emerges as a new paradigm capable of dynamically delivering the vast bandwidth WDM offers. This article discusses one of such techniques, namely optical packet switching, and its performance perceived by end users in optical mesh networks. Specifically, our investigation reveals the benefit of using electrical ingress buffering and traffic aggregation to reduce packet-loss rate of optical packet-switched networks. Through simulation experiments, we present an evaluation of the network's TCP-level performance based on the proposed architecture.

The reliable multicast protocol guarantees that all receivers place the source messages in the same order. We have changed this protocol from an event-driven protocol to a timed protocol in order to also guarantee that all of the receivers have a source message by a deadline. Certain of the control messages that are transmitted by the receivers in this protocol are scheduled to occur at specified times, rather than responding to other messages. This results in short sequences of protocol states that are independent of one another, rather than a protocol machine that is recursive and runs indefinitely. It is easier to prove the properties of these short sequences of events than to prove those of many protocols that have indefinitely long sequences.

Presents the guest editorial for this issue of the publication.