Contention-collision cancellation access control mode is an important access control mode in star networks.Due to the complexity of mathematical analysis for this mode in double-star networks

so far only the study on the condition of heavy load has been reported.Furthermore

the reliability of networking technology is dramatically improved

so that the instance of failed service is approximately ignored.Based on the above points

we formulate the general load double-star network combining light load and heavy load.Then we derive the expended waiting time

which is used to evaluate the performance of double-star network.Finally

we validate the mathematical result through simulation.The conclusion not only provides the the

oretical foundation for the application of reliable double-star network

but also firstly resolves non-classical queueing model

L\G\n

=2\RSS

and expands the theory of random service system.