624 research outputs found
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 ReRoute–Loop 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
IP Fast Reroute with Remote Loop-Free Alternates: the Unit Link Cost Case
Up to not so long ago, Loop-Free Alternates (LFA)
was the only viable option for providing fast protection in pure
IP and MPLS/LDP networks. Unfortunately, LFA cannot provide
protection for all possible failure cases in general. Recently, the
IETF has initiated the Remote Loop-Free Alternates (rLFA)
technique, as a simple extension to LFA, to boost the fraction
of failure cases covered by fast protection. Before further stan-
dardization and deployment, however, it is crucial to determine
to what extent rLFA can improve the level of protection in a
general IP network, as well as to find optimization methods to
tweak a network for 100% rLFA coverage. In this paper, we take
the first steps towards this goal by solving these problems in the
special, but practically relevant, case when each network link is
of unit cost. We also provide preliminary numerical evaluations
conducted on real IP network topologies, which suggest that rLFA
significantly improves the level of protection, and most networks
need only 2 − 3 new links to be added to attain 100% failure
case coverage
Efficient Algorithms to Enhance Recovery Schema in Link State Protocols
With the increasing demands for real-time applications traffic in net- works
such as video and voice a high convergence time for the existing routing
protocols when failure occurred is required. These applications can be very
sensitive to packet loss when link/node goes down. In this paper, we propose
two algorithms schemas for the link state protocol to reroute the traffic in
two states; first, pre-calculated an alternative and disjoint path with the
primary one from the source to the destination by re-routing traffic through
it, regardless of the locations of failure and the number of failed links.
Second, rerouting the traffic via an alternative path from a node whose local
link is down without the need to wait until the source node knows about the
failure. This is achieved by creating a new backup routing table based on the
original routing table which is computed by the dijkstra algorithm. The goal of
these algorithms is to reduce loss of packets, end-to-end delay time, improve
throughput and avoiding local loop when nodes re-converge the topology in case
of failure.Comment: 15 page
High Availability in the Future Internet
With the evolution of the Internet, a huge number of real-
time applications, like Voice over IP, has started to use IP as primary
transmission medium. These services require high availability, which is not
amongst the main features of today’s heterogeneous Internet where fail-
ures occur frequently. Unfortunately, the primary fast resilience scheme
implemented in IP routers, Loop-Free Alternates (LFA), usually does not
provide full protection against failures. Consequently, there has been a
growing interest in LFA-based network optimization methods, aimed at
tuning some aspect of the underlying IP topology to maximize the ratio
of failure cases covered by LFA. The main goal of this chapter is to give a
comprehensive overview of LFA and survey the related LFA network op-
timization methods, pointing out that these optimization tools can turn
LFA into an easy-to-deploy yet highly effective IP fast resilience scheme
Energy management in communication networks: a journey through modelling and optimization glasses
The widespread proliferation of Internet and wireless applications has
produced a significant increase of ICT energy footprint. As a response, in the
last five years, significant efforts have been undertaken to include
energy-awareness into network management. Several green networking frameworks
have been proposed by carefully managing the network routing and the power
state of network devices.
Even though approaches proposed differ based on network technologies and
sleep modes of nodes and interfaces, they all aim at tailoring the active
network resources to the varying traffic needs in order to minimize energy
consumption. From a modeling point of view, this has several commonalities with
classical network design and routing problems, even if with different
objectives and in a dynamic context.
With most researchers focused on addressing the complex and crucial
technological aspects of green networking schemes, there has been so far little
attention on understanding the modeling similarities and differences of
proposed solutions. This paper fills the gap surveying the literature with
optimization modeling glasses, following a tutorial approach that guides
through the different components of the models with a unified symbolism. A
detailed classification of the previous work based on the modeling issues
included is also proposed
- …