In mobile computing world, migration is important for survival. Mobility originated from the desire to move either toward resources or away from scarcity. Mobile computing is about both physical and logical computing entities that move all system data from one source location to another destination. Mobile computing provides some physical entities that are computers which change locations as and when required. Here, logical entities are instances of a running user application or a mobile agent that automatically configures device. Therefore, mobile agents can migrate any where over internet. Nomadic computing refers to limited migration. Migration is within a building at a pedestrian speed. Interleaved pattern of user relocation and in door connections is also refer to nomadic access. For example, in the same vein, users carrying laptop with DIAL UP modems are engaged in nomadic computing. If the user needs access to a network such as the internet on the go, they must resort to slow wireless WAN systems primarily intended for telephone use. Higher speed wirelesses LANs are only available in specific sites. However, there are some constraints, technical and some other limitations while doing mobile computing. For Example, when working mobile, one is dependent on public networks, requiring careful use of VPNs. Therefore, there are some leaks to security standards in this case. Also, there is some power consumption in the process. Since the grid cannot be used, mobile computers must rely entirely on battery power. Combined with compact size, this means unusually expensive batteries must be used. Hence battery power should be properly maintained for better utilization of this technology. Sometime, weather and terrain problems as well as distance limited connection exist with some technologies. Reception in tunnels and some buildings is poor. Potential health damage from cellular radio frequency emission is not known yet. However, more car accidents are related to drivers who were talking through a mobile device. Also, cell phones may interfere with sensitive medical devices. We can say that human interface has been increased with mobile devices. So, there can be some health problem regarding to electromagnetic interferences. Yet these problems are not proven. But precaution is the first step to cure. As HMDs are still uncommon, screens are often too small. Keyboards are impractical, especially one handed, and alternate methods such as speech or handwriting recognition require training. Mobile computing is a generic term describing ones ability to use technology while moving, as opposed to portable computers. Distributed computing as we know, works on static wired network. Hence it is more secured as compared to any other computing mechanisms here before.