  Many systems require frequent and regular updates of a certain information.
These updates have to be transferred regularly from the source to the
destination. We consider scenarios in which an old packet becomes completely
obsolete, in the presence of a new packet. In this context, if a new packet
arrives at the source while it is transferring a packet, one needs to decide
the packet to be dropped. New packet has recent information, but might require
more time to transfer. Thus it is not clear as to which packet to be dis-
carded, and this is the main focus of the paper. Recently introduced
performance metrics, called average age of information (AAoI) and peak age of
information (PAoI) of the information available at the destination, are the
relevant performance measures. These type of systems do not require storage
buffers, of size more than one, at the source queue. We consider single source
/ multiple sources regularly updating information to a single destination
possibly over wireless channels to derive optimal drop policies that optimize
the AAoI. We showed that the state independent (static) policies like dropping
always the old packets or dropping always the new packets is optimal in many
scenarios, among an appropriate set of stationary Markov policies. We consider
relevant games when multiple sources compete. In many scenarios, the
non-cooperative solution almost minimizes the social objective, the sum of
AAoIs of all the sources.
