Kleinrock's proposal was the first paper on the theory of packet-switching (PS), and in it he addressed issues such as message time lapse between communication nodes, channel capacity, usable link capacity to avoid jams, traffic changes, communication between different networks, and even spoke of routing techniques. Baran's study focused on packet switching networks where the nodes had multiple paths to each other, such that the destruction of one node would not hamper the transmission of message packets from the sending node to the receiving node. The key to this new system was a technique that Baran called "distributed communications." Like the telephone network, switching is concentrated and hierarchical. Calls go to a local office, then to a regional or national switching office if a connection beyond the local area is needed. Each user is connected to only one local office, and each local office serves a large number of users. Therefore, destroying a single local office would cut off many users from the network. A distributed system would have multiple switching nodes, and many links attached to each node. The redundancy would make it harder to cut off service to users, and the switching was distributed among all the nodes in the network so knocking out a few important centers would not disable the whole network. To move data through the network, Baran adapted a technique known as "message switching" or "store-and-forward switching." In a message switching system, each message is labeled with its origin and its destination and is then passed from node to node through the network. The message is temporarily stored at each node until it can be forwarded to the next node or the final destination. Each successive node uses the address information to determine the next step of the route. A common example of this is the postal system. This is still the main basis of network routing implemented in today's Internet, where packets of information are sent through routers to get them to the destination.