Routers
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Routers

Information Security Professiona
When I send an email from, say, my work PC to a friend at his corporate email address, my message is broken into packets and passed to my company’s border (or perimeter) router.  Not just a clever name, the border router, as the name implies, sits on the border between my company’s intranet and the Internet.  It knows the static IP address range of our corporate network.  And, through “experience,” it comes to know the addresses of the external devices around it.  It puts this map into a routing table which it then references to determine where to send various kinds of information.  This map can change, so the process happens, to some extent, continuously.  Routes also can be hard-coded.  

When I hit “send,” my email message can traverse a number of different paths on its journey to my friend.  The algorithms used to determine the best route all have cool acronyms like RIP, OSPF, and BGP.  The bottom line is that the router uses its most current knowledge of the “information superhighway” to determine to which router it should forward the little chunks.

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.

 

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