Side_1_360

In the first step the physical network is dimen-
sioned without considering LSPs. Each traffic
flow connection will be treated at the IP-packet
level in every router it crosses. The iteration is
carried out until changes for all the main vari-
ables attached to the traffic flows (e.g. mean
traffic, capacities needed) are below specified
thresholds (convergence criteria). The resulting
network from the first step has one LSP per
physical link with the capacity of the physical
link. It should be noted that an LSP would not be
needed and this notion is introduced for simplifi-
cation.

In the second step we are looking for cost-effec-
tive solutions by separating and cross-connect-
ing LSPs. Here, cross-connecting means to
extend an LSP through a router (corresponding
packets not examined on IP level) and on the
subsequent hop (or hops). This is accomplished
by looking at one router at the time. The cost
model as described above and the relevant segre-
gation schemes are used when deciding whether
or not to cross-connect traffic flows by using an
LSP. The saving or additional cost related to
transmission, switching and control before and
after the cross-connection are calculated and
compared. If the net saving is above a specified
threshold, the bundle of traffic flows will be
assigned to an LSP and cross-connected in the
router. The segregation scheme is applied when

LSPs are considered for cross-connection. Each

traffic flow type is characterised by a CoS

parameter, and the CoS parameter is used for the

segregation. The segregation scheme for LSPs

can be defined for any other combination of CoS

parameters.

The dimensioning algorithm implemented has

a fixed routing scheme and segregates traffic

flows according to their CoS parameter. Other

schemes for routing and service priority may be

considered as well.

The dimensioning procedure results in a cost-

effective network solution considering the cost

factors and weight factors chosen. The solution

has the set of LSPs in the logical network that

should be close to the obtainable minimal net-

work cost. The characteristics of the network

elements are given as the bandwidth on the

physical links of each LSP and the capacity of

the routers for switching and control functional-

ity. Variables for the resulting service quality

and network utilisation can also be calculated.

The procedure may be used to study the sensitiv-

ity for changes in cost factors, weight factors,

traffic demand, topology, and so forth. The

dimensioning procedure presented is modular.

Therefore, several of the steps can be replaced

by corresponding expressions such that alterna-

Read input

initialise

First part - LSP level not considered Second part - Separating and

cross-connecting LSPs

Sort routers according to

number of incoming LSPs

Select next router, n

Consider routers according

to decreasing number of

incoming LSPs (select n)

Calculate characteristics of

offered traffic on outgoing

transmission link (n)

For every incoming LSP to n

evaluate crossconnecting gain

for portions of the traffic flow

For every transmission link (n,m)

calculate capacities, blocking and

characteristics of served traffic

More routers More routers

yes yes

no no

yes yes

no no

Convergence Convergence

Network solution,

Physical network dimensioned physical and logical

Figure 12 Flow chart showing

main outline of program