On Internet, each conversation is a two way exchange of packets. Each packet is
labelied with the address number of its sender and receiver. Special purpose
computers called routers direct the packet on the next
leg of its journey. Each packet may take a different route and may arrive out of
order. A PAD (Portable Application Description) (Packet Assembler / Disassembler) puts them back in
the correct order. A routine can also be used to link two LANs (Local Area Networks)
together. It is smarter than a bridge. It looks at the destination of each message
and decides if it necessary to pass it on to the other net.