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