Internet Key Exchange (IKE) is the default automated key management protocol selected for use with Internet Protocol Security protocol. The IKE has been implemented a lot but it has been critized whole the time. The scalability of the IKE is a question to be analyzed more seriously and that is the main issue of this paper. This paper presents estimations on the effort of the IKE negotiation using two different cases. The estimation is done theoretically but there are also concrete packet sizes and transmission times counted. The estimation introduces a scenario where a user needs a secure connection to some application server.