1,728 research outputs found
Avoiding Loops and Packet Losses in ISP Networks
Even in well managed Large ISP networks failures of links and routers are common Due to these failures the routers update their routing tables Transient loops can occur in the networks when the routers adapt their forwarding tables In this paper a new approach is proposed that lets the network converge to its optimal state without loops and the related packet lossless The mechanism OUTFC-Ordered Updating Technique with Fast Convergence is based on an ordering of the updates of the forwarding tables of the routers and fast convergence Typically we have chosen a Network consisting of routers and Link costs for simulation Link failures are simulated Avoiding transient loops in each case is demonstrated by constructing a Reverse Shortest PathTree RSP
Fast emergency paths schema to overcome transient link failures in ospf routing
A reliable network infrastructure must be able to sustain traffic flows, even
when a failure occurs and changes the network topology. During the occurrence
of a failure, routing protocols, like OSPF, take from hundreds of milliseconds
to various seconds in order to converge. During this convergence period,
packets might traverse a longer path or even a loop. An even worse transient
behaviour is that packets are dropped even though destinations are reachable.
In this context, this paper describes a proactive fast rerouting approach,
named Fast Emergency Paths Schema (FEP-S), to overcome problems originating
from transient link failures in OSPF routing. Extensive experiments were done
using several network topologies with different dimensionality degrees. Results
show that the recovery paths, obtained by FEPS, are shorter than those from
other rerouting approaches and can improve the network reliability by reducing
the packet loss rate during the routing protocols convergence caused by a
failure.Comment: 18 page
Identifying Design Requirements for Wireless Routing Link Metrics
In this paper, we identify and analyze the requirements to design a new
routing link metric for wireless multihop networks. Considering these
requirements, when a link metric is proposed, then both the design and
implementation of the link metric with a routing protocol become easy.
Secondly, the underlying network issues can easily be tackled. Thirdly, an
appreciable performance of the network is guaranteed. Along with the existing
implementation of three link metrics Expected Transmission Count (ETX), Minimum
Delay (MD), and Minimum Loss (ML), we implement inverse ETX; invETX with
Optimized Link State Routing (OLSR) using NS-2.34. The simulation results show
that how the computational burden of a metric degrades the performance of the
respective protocol and how a metric has to trade-off between different
performance parameters
Survey of Consistent Network Updates
Computer networks have become a critical infrastructure. Designing dependable computer networks however is challenging, as such networks should not only meet strict requirements in terms of correctness, availability, and performance, but they should also be flexible enough to support fast updates, e.g., due to a change in the security policy, an increasing traffic demand, or a failure. The advent of Software-Defined Networks (SDNs) promises to provide such flexiblities, allowing to update networks in a fine-grained manner, also enabling a more online traffic engineering. In this paper, we present a structured survey of mechanisms and protocols to update computer networks in a fast and consistent manner. In particular, we identify and discuss the different desirable update consistency properties a network should provide, the algorithmic techniques which are needed to meet these consistency properties, their implications on the speed and costs at which updates can be performed. We also discuss the relationship of consistent network update problems to classic algorithmic optimization problems. While our survey is mainly motivated by the advent of Software-Defined Networks (SDNs), the fundamental underlying problems are not new, and we also provide a historical perspective of the subject
Multipath inter-domain policy routing
Dissertação submetida para a obtenção do grau de Doutor em Engenharia Electrotécnica e de ComputadoresRouting can be abstracted to be a path nding problem in a graph that models the
network. The problem can be modelled using an algebraic approach that describes the
way routes are calculated and ranked. The shortest path problem is the most common
form and consists in nding the path with the smallest cost.
The inter-domain scenario introduces some new challenges to the routing problem:
the routing is performed between independently con gured and managed networks; the ranking of the paths is not based on measurable metrics but on policies; and the forwarding is destination based hop-by-hop.
In this thesis we departed from the Border gateway Protocol (BGP) identifying its main
problems and elaborating on some ideal characteristics for a routing protocol suited for the inter-domain reality. The main areas and contributions of this work are the following:
The current state of the art in algebraic modeling of routing problems is used to
provide a list of possible alternative conditions for the correct operation of such
protocols. For each condition the consequences in terms of optimality and network restrictions are presented.
A routing architecture for the inter-domain scenario is presented. It is proven that
it achieves a multipath routing solution in nite time without causing forwarding
loops. We discuss its advantages and weaknesses.
A tra c-engineering scheme is designed to take advantage of the proposed architecture.
It works using only local information and cooperation of remote ASes to minimize congestion in the network with minimal signalling.
Finally a general model of a routing protocol based on hierarchical policies is used to study how e cient is the protocol operation when the correctness conditions are
met. This results in some conclusions on how the policies should be chosen and applied in order to achieve speci c goals.Portuguese Science and Technology Foundation -(FCT/MCTES)grant SFRH/BD/44476/2008; CTS multi-annual funding project PEst OE/EEI/UI0066/2011; MPSat project PTDC/EEA TEL/099074/2008; OPPORTUNISTICCR project PTDC/EEA-TEL/115981/2009; Fentocells project PTDC/EEA TEL/120666/201
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