Information finds its way around the Internet with the help of something called a router.  A router directs information where it needs to go based on IP addresses.  

When a chunk of my message arrives at the first router outside of our intranet, that router looks at the destination information and asks, “Which way should it go?”  If that router just so happens to be the border router of my friend’s corporate network, the packet is sent to the network-facing interface of the router.  If not, that router uses its ever-evolving knowledge of the network to determine where to send it.  Bam!  Faster than you can say spam, my message is speeding towards my unsuspecting friend.

The process continues until my packet is received at my friend’s corporate network, where it is welcomed with open arms.  That is, assuming I or my network have not been blacklisted as a source of meaningless drivel or messages of malicious intent.  (Screening out content from blacklisted sources is a task that can be assigned to a router, but more commonly is handled by a firewall.)  Once my message is safely inside, it is sent to my friend’s PC based on his IP address which, as mentioned, can be static or dynamically assigned.

Next time: bridges.