The number of devices connected to the Internet has outstripped the number of effectively assignable IPv4 addresses. In order to be globally reachable, many devices must share the same IPv4 address; current mechanisms only provide reachability when the device sharing the IPv4 address itself initiates communication. We describe a mechanism to make nodes behind a NAT globally reachable, even when communications are initiated from the global Internet. The intended application of the mechanism, denoted SIPNAT, is to allow for the first time bidirectional global reachability of IPv6 addresses by nodes in the global IPv4 Internet, in a scalable manner, thus resolving the major issue associated with IPv4-IPv6 translation. SIPNAT involves filtering flows at the gateway between the IPv4 and IPv6 domain through a combination of DNS request and timing information for the IPv4 initiated connection (the IPv6 to IPv4 connections are performed using typical NAT mechanisms, where the IPv6 domain takes the role of the private address space). We study the performance of the SIPNAT mechanism using queuing theoretic analysis, and show that our SIPNAT model is accurate on actual data traces.

We present an analytical, epidemiological, model for the overhead of information dissemination in mobile networks, which finds application in a range of settings, including resource discovery, information dissemination in sensor networks, location services and ad hoc network routing. We consider two principal information dissemination mechanisms, one for which nodes strictly relay information for other nodes, and the other for which they also take advantage of the information already being disseminated to insert their own data to share. The latter mechanism is denoted by path accumulation. We will show that the overhead with path accumulation scales as n3/2and without path accumulation as n5/4. With respect to the connection rate, both scale as radic(lambda). We also identify the cutoff point for path accumulation as xic= 1 - radic(2/radic(n)). Below that threshold, path accumulation should be preferred, while above, path accumulation does not provide substantial benefits. Our model proves extremely accurate against simulation data.

The Internet has revolutionized communication, education, commerce and information access for its users worldwide. Unfortunately, the lack of copper/fiber infrastructure in the rural areas of the developing world has prevented a large majority of the human population from reaping the benefits of the Internet. While the number of mobile subscribers in the developing world has more than quadrupled in the last five years, the adoption of the Internet has shown a slow growth pattern. Recently, there has been a growing interest in providing Internet access to rural areas by means of inexpensive long distance WiFi mesh networks. However, the expensive Internet uplink and the difficulty in troubleshooting of WiFi mesh networks has hindered their large scale deployment. In this paper, we propose Cell-Share an architecture that leverages the explosive growth in cellular network penetration in the developing world to provide rural WiFi mesh networks with an on-demand scalable Internet uplink and troubleshooting back-channel using a collaborative mobile phone framework. We implement Cell-Share on Windows Mobile and Android platforms to demonstrate the feasibility of using the infrastructure of cellular data networks to provide a back-channel for network troubleshooting as well as capacity enhancement for rural mesh networks.

We study the overhead of some mechanisms for information dissemination. We use reactive routing protocols in mobile ad hoc networks as our illustrative example. However, while reactive routing protocols are the main application for our results, they apply to different settings as well, which include publish/subscribe information dissemination mechanisms, information dissemination in sensor networks, and location services. We use a performance measure, defined in [8], which we call the efficiency xi of the information dissemination process, and use this efficiency to evaluate the overhead. The overhead is influenced by the use of a mechanism to increase the amount of information disseminated, at the cost of a higher overhead, called path accumulation. We compare the overhead of routing protocols with and without path accumulation. We observe that path accumulation is always more efficient at disseminating route information in the network, but the gain in efficiency decreases when it is normalized by the number of extra routes discovered, as more is known about the network. This means that the marginal return of path accumulation decreases over not using path accumulation. We propose a new route discovery mechanism which applies to most of the reactive protocols using a route request/route reply exchange. Our route discovery mechanism, denoted adaptive path accumulation adjusts the accumulated path in order to either: scale its bandwidth overhead down as more information is distributed in the network, or improve the network discovery by carefully selecting the routes to be propagated. We assess a range of adaptive path accumulation policies using numerical evaluation and show the effect of these policies on route discovery and packet overhead.

Despite the large amount of research in ad hoc networks, there are still several limitations on the scalability and performance of routing protocols, which require a more fundamental understanding of some of the basic mechanisms. In this paper, we focus on one of these mechanisms, which is route discovery, and analyze its extent and overhead in discovering routes to nodes in the network. Gwalani et al. (2003) has augmented route discovery in AODV with a mechanism called path accumulation, that allows additional routes to be propagated through the network. We provide detailed analysis and simulations for the potential benefits of path accumulation and apply it on one of the prominent ad hoc routing protocols, AODV. The results show that path accumulation can improve the performance of AODV and reduce its overhead significantly.

Privacy when using IP communication has become an important problem. It is a challenging problem that spans multiple layers in the OSI reference model with various constant identifiers that can be profiled. This leads to user privacy concerns. Location Privacy, on the other hand, is primarily concerned with revealing a user’s identity as a function of mobility. When a user visits a new network and uses a fixed identifier, such as a Mobile IPv6 Home Address for communication, on-lookers can determine that the user has roamed. We address this problem of location privacy and provide a Privacy-Tag for use in place of a fixed identifier to protect user privacy. Our method is readily implementable using the Mobile IPv6 Return Routability [2] protocol and the Binding Update procedure.

Current mobile ad hoc network (MANET) routing protocols operate with networks as flat address spaces, treating all nodes in the network as independent peers. However, these nodes are not always independent; they can form groups due to physical or environmental restraints. By taking advantage of these natural groupings, there is an opportunity to optimize the performance of MANET routing in these settings. This paper examines address aggregation in MANETs, focusing primarily on its ability to reduce routing overhead. We specifically describe the work necessary to implement address aggregation in the ad hoc on-demand distance vector routing protocol (AODV). We found the benefits of aggregation to be quite significant, reducing overhead and delay by 42% to 82% and 30% to 62%, respectively.

The use of dominating-set neighbor elimination as an integral part of the distribution of route requests using the ad hoc on-demand distance vector (AODV) protocol as an example of on-demand routing protocols is investigated. We use detailed simulations to show that simply applying dominant pruning (DP) to the distribution of route requests in AODV results in pruning too many route requests in the presence of mobility and cross-traffic. Accordingly, we introduce several heuristics to compensate the effects of DP and show that the resulting AODV with dominating set heuristics (AODV-DS) has comparable or better delivery ratio, network load, and packet latency than the conventional AODV. AODV-DS exhibits over 70% savings on RREQ traffic than conventional AODV, and in some situations, AODV-DS may have a lower control overhead using Hello packets than conventional AODV without Helios.

Ad hoc networks meet the demands of spontaneous network set-up. They are characterized by the use of wireless links, dynamically changing topology, multi-hop connectivity and decentralized routing mechanisms and decision-making. AODV and DSR are the two most widely studied on-demand ad hoc routing protocols. Previous studies have shown limitations of these protocols in certain network scenarios. To improve the performance of AODV, we modify AODV to include the source route accumulation feature of DSR. We call this AODV with path accumulation. This protocol optimizes AODV to perform effectively in terms of routing overhead and delay during high load. The performance of the protocol is evaluated by a simulation model under a variety of network conditions. We also compare its performance with that of unmodified AODV and DSR. We demonstrate how a small change to the AODV protocol can lead to significantly improved performance results.

A new protocol is presented for on-demand loop-free routing in ad hoc networks. The new protocol, called labeled distance routing (LDR) protocol, uses a distance invariant to establish an ordering criterion and per-destination sequence numbers to reset the invariant resulting in loop-freedom at every instant. The distance invariant allows nodes to change their next hops or distances to destinations without creating routing-table loops. The destination sequence number, which only the destination may increment, permits nodes to reset the values of their distance invariants. The performance of LDR is compared against the performance of three other protocols that are representative of the state-of-the art, namely AODV, DSR and OLSR.

Standard IP mobility management (IP-MM) commonly known as Mobile IP, presents a set of technical challenges in performance and scalability, as the mobile host (MN) varies the handoff rate, due to its mobility pattern, between successive wireless points of attachment; these manifest themselves primarily as increased signaling between the MN and its peers. In addition, they encompass sources of latency external to the mobility protocol; a significant component of this latency is induced by signaling round trip time between the communicating entities while in transit. Recently, Mobile IP has been extended by certain micro-mobility protocol mechanisms, aiming to alleviate the above performance limitations; they are identified as hierarchical/regional or more generically localised IP mobility management. This paper presents an investigation on requirements for IP localised mobility management (IP-LMM). Based on generic principles derived from the effect of localising mobility control signaling it explores the requirement space essential for robust micro-mobility protocol extensions to base IP mobility models.

Abstract The need for ad hoc networks arises when a number of mobile nodes gather in one particular location and form autonomous networks. Ad hoc networks can be adjoined to the Internet, introducing routing and addressing issues that require new features from ad hoc networking protocols. The Internet Gateway can offer global addressability and bidirectional Internet connectivity to every node in the ad hoc network. This can be done in such a way that mobile wireless nodes can migrate between wireless access points that have direct access to the wired Internet and the wireless ad hoc networks that do not have any such local access point infrastructure. Mobile IP can be employed to make such movement seamless (whenever physically possible), even though it occurs between domains with previously incompatible routing models. We believe that IPv6 and Mobile IPv6 afford important advantages for making such attachments, especially regarding router advertisement and address autoconfiguration. In this paper, we show how general ad hoc networks can be connected to the Internet by Internet Gateways, and then describe our specific experiments with Ad hoc On‐Demand Distance Vector Routing (AODV) for IPv6 (AODV6). After demonstrating the basic principles allowing access to the Internet, we then detail our further experiments using Mobile IPv6. Copyright © 2002 John Wiley & Sons, Ltd.

Abstract Since a TCP sender cannot distinguish between packet losses arising from transmission errors from those due to congestion, TCP tends to perform poorly on wireless links that are prone to transmission errors. Several techniques have previously been proposed to improve TCP performance over wireless links. Existing schemes typically require an intermediate node (typically, a base station) to be TCP‐aware. For instance, the Snoop scheme requires the base station to interpret TCP headers and take appropriate action to help improve TCP performance. This paper proposes an alternativeTCP‐unawaretechnique that attempts to mimic the behavior of the Snoop protocol. Performance evaluation shows that the proposed Delayed Dupacks scheme performs quite well. Copyright © 2001 John Wiley & Sons, Ltd.

Mobility of users in a future Internet has become a reality due to highly mobile end-systems. However, the new dimension of protocol functionality, Mobile IP, resource control, quality of service (QoS) support and AAA (authentication, authorization and accounting) features extended by charging schemes are still to be integrated effectively. Therefore, this position paper addresses these three areas of research concern, discusses basic concepts and outlines major problem fields still to be worked on.

Ad hoc networks are characterized by multi-hop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols. We compare the performance of two prominent on-demand routing protocols for mobile ad hoc networks - dynamic source routing (DSR) and ad hoc on-demand distance vector routing (AODV). A detailed simulation model with MAC and physical layer models is used to study inter-layer interactions and their performance implications. We demonstrate that even though DSR and AODV share a similar on-demand behavior the differences in the protocol mechanics can lead to significant performance differentials. The performance differentials are analyzed using varying network load, mobility and network size. Based on the observations, we make recommendations about how the performance of either protocol can be improved.

As mobile computing gains popularity, the need for ad hoc routing protocols will continue to grow. There have been numerous simulations comparing the performance of these protocols under varying conditions and constraints. One question that arises is whether the choice of MAC protocol affects the relative performance of the routing protocols being studied. This paper investigates the answer to that question by simulating the performance of three ad hoc routing protocols when run over different MAC protocols. It is determined that the choice of MAC layer protocol does, in fact, affect the relative performance of the routing protocols.

The Ad hoc On-Demand Distance Vector (AODV) routing protocol is designed for use in ad hoc mobile networks. Because of the difficulty of testing an ad hoc routing protocol in a real-world environment, a simulation was first created so that the protocol design could be tested in a variety of scenarios. Once simulation of the protocol was nearly complete, the simulation was used as the basis for an implementation in the Linux operating system. In the course of converting the simulation into an implementation, certain modifications were needed in AODV and the Linux kernel due to both simplifications made in the simulation of AODV and to incompatibilities of the Linux kernel and the IP-layer to routing in a mobile environment. This paper details many of the changes that were necessary during the development of the implementation.

Mobile IP provides mobility support for hosts connected to the Internet without changing their IP addresses. Route optimization strategies complement Mobile IP, to alleviate triangle routing, by informing correspondent hosts of the mobile host's care-of address. We propose further strategies that are compatible with route optimization and its security model. First, foreign agents buffer packets for a mobile host and send them to its new location when it leaves. Second, hierarchical foreign agent management reduces the administrative overhead of frequent local handoffs, using an extension of the Mobile IP registration process so security can be maintained. Duplicate packets due to buffer handover are eliminated with the cooperation of mobile hosts. Simulation results show substantial performance improvements in terms of throughput, registration overhead, lost and duplicate packets during a handoff, without restrictions on physical placement of foreign agents.

An ad-hoc network is the cooperative engagement of a collection of (typically wireless) mobile nodes without the required intervention of any centralized access point or existing infrastructure.To provide optimal communication ability, a routing protocol for such a dynamic self-starting network must be capable of unicast, broadcast, and multicast.In this paper we extend Ad-hoc On-Demand Distance Vector Routing (AODV), an algorithm for the operation of such ad-hoc networks, to offer novel multicast capabilities which follow naturally from the way AODV establishes unicast routes.AODV builds multicast trees as needed (i.e., on-demand) to connect multicast group members.Control of the multicast tree is distributed so that there is no single point of failure.AODV provides loop-free routes for both unicast and multicast, even while repairing broken links.We include an evaluation methodology and simulation results to validate the correct and efficient operation of the AODV algorithm.

The Dynamic Host Configuration Protocol (DHCPv6) provides a framework for passing configuration information via extensions, to IPv6 nodes. It offers the capability of automatic allocation of reusable network addresses and additional configuration flexibility. This protocol should be considered a stateful counterpart to the IPv6 Stateless Address Autoconfiguration protocol specification, and can be used separately or together with the latter to obtain configuration information.

A Service Location Protocol has been designed within the Internet Engineering Task Force to simplify or eliminate the configuration needs for users of the Internet and World-Wide Web. This is of increasing importance to mobile users, first because they experience frequently changing network service environments, and secondly because the Internet is itself becoming more service oriented. The basic Service Location Protocol is described, with detailed descriptions of the various protocol entities, messages, and ways of selecting appropriate services.

Mobile clients have unusual needs for sending and receiving multimedia data. The traditional client/server paradigm does not take into account variable network conditions; thus traditional client/server applications have no capability of responding to intermittent connectivity, changing cost structures, or the kind of fluctuations in available bandwidth which are characteristic of wireless links. Two approaches towards allowing such adaptations are presented for comparison: proxies and modifications to client and server.

Continuing advances in wireless communications and feature integration into laptop computers are creating the need to allow nomadic users to make network connections to the Internet and with each other with no loss of functionality. This requires new advances in routing protocols and application interfaces. We use Mobile-IP as the basis for providing mobility for nomadic users, and extend it to facilitate additional services for nomadic users both at the network layer and above. As an example of how Mobile-IP can be useful with other protocols at the network layer, we show how Mobile-IP can naturally extend the usefulness of ad-hoc networking. For higher level protocols, we show that, by offering a callback service, Mobile-IP can enable applications to be responsive to changing network conditions. As an example of this technique, we show how service location can benefit from interaction with Mobile-IP. We also mention some other nomadic services which will similarly benefit from a callback service from Mobile-IP.

IP version 6 (1Pv6) is being designed within the IETF as a replacement for the current version of the IP protocol used in the Internet (1Pv4).We have designed protocol enhancements for 1Pv6, known as Mobile 1Pv6, that allow transparent routing ofiPv6 packets to mobile nodes, taking advantage of the opportunities made possible by the design of a new version of IP.In Mobile IPv6, each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet.While away from its home IP subnet, a mobile node is also associated with a care-of address, which indicates the mobile node's current location.Mobile 1Pv6 enables any 1Pv6 node to learn and cache the care-of address associated with a mobile node's home address, and then to send packets destined for the mobile node directly to it at this care-of address using an 1Pv6 Routing header.

Mobile-IP and the Dynamic Host Configuration Protocol (DHCP) are two protocols which are likely to be implemented together for use with wireless computers. We explore the ways that they can be used with in mobile computers. These protocols interact in subtle ways, presenting a system architect with a variety of trade-offs that need careful analysis. We detail the important interactions and system design issues, and also explain the design and implementation of a new DHCP option for mobile computers. The difference between mobility and portability is explained; this paper only emphasizes approaches for mobility. We explore implementation issues that we have encountered.

Host mobility is becoming an important issue due to the recent proliferation of notebook and palmtop computers, the development of wireless network interfaces, and the growth in global internetworking. This paper describes the design and implementation of a mobile host protocol, called the Internet mobile host protocol (IMHP), that is compatible with the TCP/IP protocol suite, and allows a mobile host to move around the Internet without changing its identity, In particular, IMHP provides host mobility over both the local and wide area, while remaining transparent to the user and to other hosts communicating with the mobile host. IMHP features route optimization and integrated authentication of all management packets. Route optimization allows a node to cache the location of a mobile host and to send future packets directly to that mobile host. By authenticating all management packets, IMHP guards against possible attacks on packet routing to mobile hosts, including the interception or redirection of arbitrary packets within the network. A simple new authentication mechanism is introduced that preserves the level of security found in the Internet today, while accommodating the transition to stronger authentication based on public key cryptography or shared keys that may either be manually administered or provided by a future Internet key management protocol.>

An ad-hoc network is the cooperative engagement of a collection of Mobile Hosts without the required intervention of any centralized Access Point. In this paper we present an innovative design for the operation of such ad-hoc networks. The basic idea of the design is to operate each Mobile Host as a specialized router, which periodically advertises its view of the interconnection topology with other Mobile Hosts within the network. This amounts to a new sort of routing protocol. We have investigated modifications to the basic Bellman-Ford routing mechanisms, as specified by RIP [5], to make it suitable for a dynamic and self-starting network mechanism as is required by users wishing to utilize ad hoc networks. Our modifications address some of the previous objections to the use of Bellman-Ford, related to the poor looping properties of such algorithms in the face of broken links and the resulting time dependent nature of the interconnection topology describing the links between the Mobile Hosts. Finally, we describe the ways in which the basic network-layer routing can be modified to provide MAC-layer support for ad-hoc networks.