Information Technology Reference
In-Depth Information
When a connection request arrives, the working path should first be computed. For
this purpose, the cost of each link is tuned based on Eq.(7) and then through the
Dijkstra's algorithm, the minimal cost path is considered as working path from the
source node to the destination node. The cost function cwp i for finding the working
path with the requested bandwidth ( RB ) on i -th link is defined as:
cwp c f RB
∞ f
(7)
where ci is the basic cost of i-th link and can be a constant or a variable number.
Moreover, fi is the free capacity.
After finding the working path, the first working and backup segments should be
calculated. Therefore, the beginning node is considered as the first node and also any
node among source and destination is considered as an end node. Then, for every
candidate working segment, the cost of each link in the network is tuned according to
Eq.(8). The cost function cbsi for computing the backup segment with the requested
bandwidth (RB) on i-th link is computed as
ε RBsh
cbs εα. RB
f sh sh f
(8)
∞ sh f
where ε is a sufficient small positive constant say 0.01 or 0.001, and α is a positive
constant parameter. The parameter shi is shareable capacity, which is the capacity
reserved by some working segments and is shared by this working segment, where
the “some working segments” should be link-disjoint with this working segment
[28].
The minimal cost path from the first node and each end node is found and denoted as
the corresponding candidate backup segment if its hop count is lower or equal to Hc.
The candidate backup segment with the highest priority is considered as the first
backup segment. If the first backup segment cannot be found, the connection request
is blocked.
If the selected end node of the first backup segment equals destination, the first
backup segment can cover the whole working path and then the bandwidth resources
are assigned to the first pair of working and backup segments. Therefore, the
algorithm is over.
The algorithm should continue if the first backup segment cannot protect the whole
working path and another required working and backup segment has to be
determined.
3.9. Network Coding [29]
This refers to performing linear coding operations on traffic carried by the network at
intermediate network nodes. In network coding, a node receives information from all or some
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