9,864 research outputs found
Engineering a new loop-free shortest paths routing algorithm
International audienceWe present LFR (Loop Free Routing), a new loop-free distance vector routing algorithm, which is able to update the shortest paths of a distributed network with n nodes in fully dynamic scenarios. If Phi is the total number of nodes affected by a set of updates to the network, and phi is the maximum number of destinations for which a node is affected, then LFR requires O(Phi*Delta) messages and O(n + phi*Delta) space per node, where Delta is the maximum degree of the nodes of the network. We experimentally compare LFR with DUAL, one of the most popular loop-free distance vector algorithms, which is part of CISCO's EIGRP protocol and requires O(Phi*Delta) messages and Î(n*Delta) space per node. The experiments are based on both real-world and artificial instances and show that LFR is always the best choice in terms of memory require- ments, while in terms of messages LFR outperforms DUAL on real-world instances, whereas DUAL is the best choice on artificial instances
Fast network configuration in Software Defined Networking
Software Defined Networking (SDN) provides a framework to dynamically adjust and re-program the data plane with the use of flow rules. The realization of highly adaptive SDNs with the ability to respond to changing demands or recover after a network failure in a short period of time, hinges on efficient updates of flow rules. We model the time to deploy a set of flow rules by the update time at the bottleneck switch, and formulate the problem of selecting paths to minimize the deployment time under feasibility constraints as a mixed integer linear program (MILP). To reduce the computation time of determining flow rules, we propose efficient heuristics designed to approximate the minimum-deployment-time solution by relaxing the MILP or selecting the paths sequentially. Through extensive simulations we show that our algorithms outperform current, shortest path based solutions by reducing the total network configuration time up to 55% while having similar packet loss, in the considered scenarios. We also demonstrate that in a networked environment with a certain fraction of failed links, our algorithms are able to reduce the average time to reestablish disrupted flows by 40%
Making Name-Based Content Routing More Efficient than Link-State Routing
The Diffusive Name-based Routing Protocol (DNRP) is introduced for efficient
name-based routing in information-centric networks (ICN). DNRP establishes and
maintains multiple loop-free routes to the nearest instances of a name prefix
using only distance information. DNRP eliminates the need for periodic updates,
maintaining topology information, storing complete paths to content replicas,
or knowing about all the sites storing replicas of named content. DNRP is
suitable for large ICNs with large numbers of prefixes stored at multiple
sites. It is shown that DNRP provides loop-free routes to content independently
of the state of the topology and that it converges within a finite time to
correct routes to name prefixes after arbitrary changes in the network topology
or the placement of prefix instances. The result of simulation experiments
illustrates that DNRP is more efficient than link-state routing approaches
Optimizing IGP Link Costs for Improving IP-level Resilience
Recently, major vendors have introduced new router
platforms to the market that support fast IP-level failure pro-
tection out of the box. The implementations are based on the
IP Fast ReRouteâLoop Free Alternates (LFA) standard. LFA
is simple, unobtrusive, and easily deployable. This simplicity,
however, comes at a severe price, in that LFA usually cannot
protect all possible failure scenarios. In this paper, we give new
graph theoretical tools for analyzing LFA failure case coverage
and we seek ways for improvement. In particular, we investigate
how to optimize IGP link costs to maximize the number of
protected failure scenarios, we show that this problem is NP-
complete even in a very restricted formulation, and we give exact
and approximate algorithms to solve it. Our simulation studies
show that a deliberate selection of IGP costs can bring many
networks close to complete LFA-based protection
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
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