IMDEA Networks Institute Digital Repository
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Contention Resolution in Multiple-Access Channels: k-Selection in Radio Networks
Get PDFIn this paper, contention resolution among k contenders on a multiple-access channel is explored. The problem studied has been modeled as a k-Selection in Radio Networks, in
which every contender has to have exclusive access at least once to a shared communication channel. The randomized adaptive protocol presented shows that, for a probability
of error 2ε, all the contenders get access to the channel in time (e+ 1 +ξ)k+O(log 2(1/ε)), where ε ≤ 1/(n+ 1), ξ > 0 is any constant arbitrarily close to 0, and n is the total number of potential contenders. The above time complexity is asymptotically optimal for any significant ε. The protocol works even if the number of contenders k is unknown and collisions cannot be detected.TRUEpu
Biased Selection for Building Small-World Networks
Get PDFSmall-world networks are currently present in many distributed applications and can be built augmenting a base network with long-range links using a
probability distribution. Currently available distributed algorithms to select these
long-range neighbors are designed ad hoc for specific probability distributions.
In this paper we propose a new algorithm called Biased Selection (BS) that, using a uniform sampling service (that could be implemented with, for instance, a
gossip-based protocol), allows to select long-range neighbors with any arbitrary
distribution in a distributed way. This algorithm is of iterative nature and has a
parameter r that gives its number of iterations. We prove that the obtained sampling distribution converges to the desired distribution as r grows. Additionally,
we obtain analytical bounds on the maximum relative error for a given value of
this parameter r. Although the BS algorithm is proposed in this paper as a tool to
sample nodes in a network, it can be used in any context in which sampling with
an arbitrary distribution is required, and only uniform sampling is available.
The BS algorithm has been used to choose long-range neighbors in complete and
incomplete tori, in order to build Kleinberg’s small-world networks. We observe
that using a very small number of iterations (1) BS has similar error as a simulation of the Kleinberg’s harmonic distribution and (2) the average number of hops
with greedy routing is no larger with BS than in a Kleinberg network. Furthermore, we have observed that before converging to the performance of a Kleinberg
network, the average number of hops with BS is significantly smaller (up to 14%
smaller in a 1000 x 1000 network).TRUEpu
Network-based Localized IP mobility Management: Proxy Mobile IPv6 and Current Trends in Standardization
Get PDFIP mobility support has been a hot topic over the last years, recently fostered by the role of IP in the evolution of the 3G mobile communication networks. Standardization bodies, namely IETF, IEEE and 3GPP are working on different aspects of the mobility aiming at improving the mobility
experience perceived by users. Traditional IP mobility support mechanisms, Mobile IPv4 or Mobile IPv6, are based on the operation of the terminal to keep ongoing sessions despite the movement. The current trend is towards network-based solutions where mobility support is based on network operation. Proxy Mobile IPv6 is a promising specification that allows network operators to provide
localized mobility support without relying on mobility functionality or configuration present in the mobile nodes, which greatly eases the deployment of the solution. This paper presents Proxy Mobile IPv6 and the different extensions that are been considered by the standardization bodies to enhance the basic protocol with interesting features needed to offer a richer mobility experience, namely, flow mobility, multicast and network mobility support.TRUEpu
Impact of Transient CSMA/CA Access Delays on Active Bandwidth Measurements
Get PDFWLAN devices based on CSMA/CA access schemes have become
a fundamental component of network deployments. In
such wireless scenarios, traditional networking applications, tools, and protocols, with their built-in measurement techniques, are usually run unchanged. However, their actual interaction with the dynamics of underlying wireless systems is not yet fully understood. A relevant example of such built-in techniques is bandwidth measurement. When considering WLAN environments, various preliminary studies have shown that the application of results obtained in wired setups is not straightforward. Indeed, the contention for medium sharing among multiple users inherent to CSMA/CA access schemes has remarkable consequences on the behavior of and results obtained by bandwidth measurement techniques.
In this paper, we focus on evaluating the effect of CSMA/CA-based contention on active bandwidth measurement
techniques. As a result, it presents the rate response
curve in steady state of a system with both FIFO and CSMA/CA-based contending cross-traffic. We also find
out that the distribution of access delay shows a transient
regime before reaching a stationary state. The duration of
such transient regime is characterized and bounded. We
also show how dispersion-based measurements that use a
short number of probing packets are biased measurements
of the achievable throughput, the origin of this bias lying on the transient detected in the access delay of probing packets.
Overall, the results presented in this paper have several
consequences that are expected to influence the design of bandwidth measurement tools as well as to better understand
the results obtained with them in CSMA/CA links.TRUEpu
Zero config residential gateway experiencies for next generation smart homes
Get PDFHome networks and home environments are developing so fast that a new generation of residential gateways is needed in order to allow emerging services and the huge amount
of available bandwidth to take advantage of this evolution. New protocols, applications, devices and services are appearing day after day and in order to properly cope with them, gateways must continuously be evolved. This article presents a novel architecture developed so as to allow the automatic update and configuration of residential gateways. While data flows are treated following a conventional procedure, it is for signaling messages that the architecture proposes an application layer processing. This allows for an easier deployment of new modules capable of understanding the different signaling protocols that are
needed to set up the corresponding services. These different modules (Configuration Agents) can be dynamically installed or uninstalled by Service Providers and can also interact with the rest of the layers of the architecture in order to configure the whole platform. This architecture has been validated by means of experiences within a SIP enabled environment to allow the automatic provisioning of QoS guaranteed services to next generation
smart homes.TRUEpu
One-ended multipath TCP
Get PDFThe IETF Multipath TCP (MPTCP) working group is tasked with developing an extension to TCP that allows TCP to work over multiple paths simultaneously. draft-van-beijnum-1e-mp-tcp was a proposal for the working group to work on a variant that only requires changes in the TCP sender. However, the working group adopted a variant where both the sender and the receiver are modified.Normal TCP/IP operation is for the routing system to select a best path that remains stable for some time, and for TCP to adjust to the properties of this path to optimize throughput. A multipath TCP would be able to either use capacity on multiple paths, or dynamically find the best performing path, and therefore reach higher throughput. By adapting to the properties of several paths through the usual congestion control algorithms, a multipath TCP shifts its traffic to less congested paths, leaving more capacity available for traffic that can't move to another path on more congested paths. And when a path fails, this can be detected and worked around by TCP much more quickly than by waiting for the routing system to repair the failure.
This memo specifies a multipath TCP that is implemented on the sending host only, without requiring modifications on the receiving host.IETFpu
H-P2PSIP: Interconnection of P2PSIP domains for global multimedia services based on a hierarchical DHT overlay network
Get PDFThe IETF P2PSIP WG is currently standardising a protocol for distributed multimedia services combining the media session functionality of SIP and the decentralised distribution and localisation of resources in peer-to-peer networks. The current P2PSIP scenarios only consider the infrastructure for the connectivity inside a single domain. This paper proposes an extension of the current work to a hierarchical multi-domain scenario: a two level hierarchical peer-to-peer overlay architecture for the interconnection of different P2PSIP domains. The purpose is the creation of a global decentralised multimedia services in enterprises, ISPs or community networks. We present a study of the routing performance and routing state in the particular case of a two-level distributed hash table hierarchy that uses Kademlia. The study is supported by an analytical model and its validation by a peer-to-peer simulator.TRUEpu
The Dynamic Community of Interest and Its Realization in ZODIAC
No full textThe ZODIAC project has been exploring a security first approach to networking based on a new idea, the dynamic community of interest, based on groups of users with a demonstrable need to know. ZODIAC uses the most challenging
network setting (the mobile ad hoc network) as a target, since each node must incorporate functions of both hosts and routers. The realization of the DCoI is a work in progress, but initial implementation results have shown that DCoI concepts can be translated into working systems.
The current system applies virtual machine containers, extensive use of cryptography and digital signatures, dispersity routing, DHT-based naming, and explicit rate control among other advanced techniques. Putting security to the forefront in the design has led to interesting
consequences for naming, authorization, and connection setup. In particular, it has demanded a hierarchical structure for DCoIs that may initially appear somewhat alien to Internet users. Nonetheless, our implementation has illustrated that a highly available network that provides confidentiality and integrity can be constructed
and made usable.TRUEpu