Meanwhile the use of WLAN grows in accelerate pass, a large number of problems related to the security issues in the IEEE 802.11b have been discussed in technical papers, pointing vulnerabilities and deficiencies, from where a non authorized access to the informations passing on the network could be possible. The lack of strong solutions in authentication, confidentiality, and integrity of the data in the internal mechanisms of the protocol IEEE 802.11b, demands to operate in conjunction with the protocol IEEE 802.1x. Therefore it is possible to get authentication and cryptography in a efficient and trustful manner. The amount of extra packets, inserted for authentication and cryptography of the messages, could have a negative impact in the performance of the network. A experimental measurements of the degradation of the network throughput, when the mechanisms of IEEE 802.1x are used, were done and presented here.