Joseph P. Macker

Mobile ad hoc networking and the IETF

This article is part of a continuing series to discuss ongoing activities within the mobile ad hoc networking (MANET) working group (WG) of the IETF. This article provides a brief overview of recent events.

Mobile and wireless Internet services: putting the pieces together

There are a variety of emerging technologies and protocol enhancements designed to extend Internet services to mobile users, including operation over more dynamic, heterogeneous wireless interconnections. Many different approaches and protocols have been proposed, and there are even multiple standardization efforts within the Internet Engineering Task Force that address portions of the overall goal. This article highlights some of the emerging technology efforts and provides insight into how some of these pieces may fit together to realize seamless Internet services for users on the move or in application spaces with little to no preexisting communications infrastructure.

Techniques and issues in multicast security

Multicast networking support is becoming an increasingly important future technology area for both commercial and military distributed and group-based applications. Integrating a multicast security solution involves numerous engineering tradeoffs. The end goal of effective operational performance and scalability over a heterogeneous internetwork is of primary interest for widescale adoption and application of such a capability. Various techniques that have been proposed to support multicast security are discussed and their relative merits are explored.

Simplified multicast forwarding in mobile ad hoc networks

We implemented a working IP multicast forwarding prototype for use in mobile ad hoc networks (MANET) based upon flooding mechanisms. We present the design of a working experimental prototype and some initial performance results using the NRL mobile network emulation system and various optional flooding approaches within the design framework. In addition, we present supplemental analytical examination of several implemented flooding algorithms for MANET environments and discuss related performance tradeoffs. We conclude by presenting further technical considerations and future work issues.

Anycast routing for mobile networking

This paper considers the problem of locating and forwarding network traffic to any one of a set of distributed servers or service points-primarily in the context of mobile ad hoc networks. The advantages of providing such a capability in mobile networks through the use of anycast routing techniques at the network layer are discussed. The results of a simulation study are highlighted to demonstrate how anycast routing techniques can provide a one-to any communication capability with greater efficiency than traditional unicast based techniques. The simulation results also indicate anycast routing simplifies required configuration and management and reduces connection setup latency and overall message packet delay. Potential applications of anycast routing technology in military networks are presented and related issues are discussed.

Quantitative prediction of NACK-oriented reliable multicast (norm) feedback

We have applied the concept of truncated exponential timers for efficient reliable multicast feedback suppression for cases of both multicast and unicast feedback channels. Unicast feedback operation for multicast transport is becoming a more prevalent concern with the advent of source specific multicast routing and asymmetric networks of offering forward-based multicast (e.g., satellite distribution network). We discuss our approach to the design and its integration with a working reliable multicast protocol. We then present simulation results demonstrating that observed implementation performance matches the analytically predicted performance. Finally, we formulate a quantitative predictor of reliable multicast protocol feedback traffic levels.

Evaluation of distributed cover set algorithms in mobile ad hoc network for simplified multicast forwarding

This paper presents design issues and performance analysis of optimized cover set algorithms supporting Simplified Multicast Forwarding (SMF) of data plane traffic within mobile ad hoc network (MANET) environments. SMF is presently being developed within the Internet Engineering Task Force (IETF) as an experimental specification to provide simplified multicast data dissemination among multi-hop, wireless nodes within peer MANET routing neighborhoods. The SMF protocol allows for a variety of cover set reduction techniques to optimize the simplified data flooding and relaying process amongst routing peers. A variety of distributed algorithms for forming connected dominating sets (CDS) are being considered as mechanisms to reduce the cover set. This paper presents modeling and analysis work of various CDS relay set algorithms and demonstrates working code within an SMF implementation. We provide a brief problem background, discuss models and scenarios, compare various algorithms, and then summarize observations as well as discuss future work. A main purpose of the paper is to begin examining the robustness of the algorithms to mobility and increasing multicast traffic load. We examine the results against a classical flooding baseline for comparison. We observe similar efficiency and robustness performance for several forwarding algorithms of interest.

The multicast dissemination protocol (MDP) toolkit

The multicast dissemination protocol (MDP) provides reliable multicast file and data delivery on top of the generic UDP/IP multicast transport. Early work on MDP was deployed across the global Internet multicast backbone (Mbone) as part of the publicly available image multicaster (IMM) application. This paper describes more recent work on MDP resulting in the MDP version 2 (MDPv2) toolkit. This effort has significantly modified and generalized the MDP protocol and the associated software interface. Enhancements made to the protocol are suitable for a wide range of network environments. Additionally, integrated erasure-based repairing improves reliable multicast efficiency and robustness. We briefly discuss the protocol design, general performance characteristics, and ongoing MDP work including: initial rate-based congestion control design and results, network simulation and modeling, and asymmetric satellite operation.

Perceptive admission control for wireless network quality of service

As wireless networks become more widely used, there is a growing need to support advanced services, such as multimedia streaming and voice over IP. Traditional approaches to guarantee quality of service (QoS) work well only with predictable channel and network access. In wireless mobile networks, where conditions dynamically change as nodes move about the network, a stateless, high level approach is required. Since shared wireless resources are easily over-utilized, the load in the network must be controlled so that an acceptable QoS for real-time applications can be maintained. If minimum real-time requirements are not met, these unusable packets waste scarce bandwidth and hinder other traffic, compounding the problem. To enable high QoS for all admitted traffic, we propose the Perceptive Admission Control (PAC) protocol. PAC monitors the wireless channel and dynamically adapts admission control decisions to enable high network utilization while preventing congestion. Through discussion, simulations and testbed experiments, we demonstrate that PAC ensures low packet loss and delay for all admitted flows.

A low-cost, IP-based mobile network emulator (MNE)

The Naval Research Laboratory (NRL) mobile network emulator (MNE) is a low-cost, flexible wireless mobile internetwork protocol (IP) test environment that provides flexible, dynamic topology control and manipulation for testing of both IPv4 and IPv6 dynamic network scenarios, direct and indirect software support for network node motion modeling is supported. The emulation design and various software and hardware support components are described. A case example of how the mobile emulation system has been applied is also provided with a set of ancillary visualization tools, motion generators, and network analysis tools. Finally, it is discussed how such an emulation environment provides a valuable engineering tool supplementing more abstract simulation studies and costly, time-consuming field trials of mobile network systems and software.