Table 1

c _ij

The cost of request transmission from nodes i to node j

\( {a}_i^t \)

The consultation fee of node i for responding to each request of type t

\( {h}_i^t \)

The maximum number of consultation requests of type t that node i can respond

\( {l}_i^t \)

The minimum number of consultation requests of type t that node i should respond

\( {r}_i^t \)

The number of consultation requests of type t that node i has per day

u _ij

The maximum capacity of the link between node i and node j in both directions

\( {x}_{ik}^t \)

\( \left\{\begin{array}{c}1\ \mathrm{if}\ \mathrm{node}\ i\ \mathrm{is}\ \mathrm{allowed}\ \mathrm{to}\ \mathrm{respond}\ \mathrm{to}\ \mathrm{the}\ \mathrm{requests}\ \mathrm{of}\ \mathrm{type}\ t\ \mathrm{from}\ \mathrm{node}\ k\ \\ {}\\ {}0\ \mathrm{Otherwise}\ \end{array}\ \right. \)

m ^t

The number of consultations needed per request for the requests of type t