Links Redundancy which depends on STP or RSTP protocols to prevent
loops in Ethernet switched networks[ 76 ].
In Ethernet switched network links reliability can be achieved by
two ways or types;Dual Links and Redundant Paths, which serve for the
purpose of building highly available and morerobust network topology.
- 8 .1 Dual Links:
Dual links is the top choice for redundancy, providing two pre-
defined and diversified single links for twice the capacity. This choice is
used as a backup line, or a way to increase network reliability, and to
obviate the possibility of failure at a fiber, connector or port level [ 34 ].
3.8.2 Redundant Paths
There are many choices for the number and location of redundant
links ranging from zero redundancy to a full connectivity between
switches. A full mesh between switches is the best option from a failure
resiliency perspective. However, financial constraints prohibit
suchinfrastructure. There is an equilibrium point between minimizing costs
and satisfying resiliency requirements [ 76 ].
The most important and severe weakness of tree topology its
poorreliability, an analyzingof the capability of failure tolerance of both
ring-tree and ring-ring network and their reliability ofcommunication is
done, and an example to compare the tree, ring-tree, ring-ring network
respectivelyin two aspects above is used [ 77 ]. Based on these discussions, a
conclusionstate thatboth ring-tree and ring-ring networksare not only a type
of survivable network but also hold an underlying simple topology which
leads to their ease of network administration. This implies that they can
serve as a good candidate for an industrial computer or communication
network [ 77 ].