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Technical Security: MAC Addresses
Before diving into the details of the Internet and networks in general, I wanted to cover a few bona fide propeller-head concepts. I already spoke of packets, headers, and ports. Today, it is MAC addresses.
Everything that talks on a network has a unique address. Everything. Every network card, every router, every wireless adapter, everything! This unique identifier is called a MAC address.
MAC is an abbreviation for media access control. A MAC address is a 48-bit number, which literally is etched onto the device. This address is permanent. The first 24 bits are unique to the manufacturer of the device. The next 24 bits uniquely identify the specific individual device. Considering how many computer-related devices are out there in the world, at first blush, it may seem as though a 48-bit number would not allow for one distinct number per device. But consider that 24 bits, translated into decimal, is 16,777,215. That means that almost 17 million different widgets could be shipped from each of almost 17 million manufacturers and still each have their own unique address. That’s a lot of network cards! And since there probably are not 16,777,215 manufacturers of network cards, it would not surprise me if some of the big guys had more than one number from that pool of the first 24 bits.
The good news is, since everything has a unique address, it can be found as long as it is hanging out on the Internet.
Consider this parallel ...
Everyone who has a cell phone has a unique phone number.
Admittedly, no number is assigned to the phone at the factory, and once a number is assigned to a phone, it is not permanent since I can move the number when I upgrade. But you could say the phone number uniquely identifies me, so long as I keep that number. In effect I have a unique MAC address in the form of my mobile phone. So when someone places a call to my mobile phone number, the system finds me—whether I'm in Cleveland, San Francisco, Sydney or Mumbai—and connects me to the caller. And even though the phone may be sitting on the kitchen table where any nosy person in the house could answer it, theoretically any call which comes in is intended for me and me alone.
SCRAPPY TIP: Remember MACs. MACs play an important role in securing wireless networks. The topic will be revisited in a future section on wireless.
Next time, I will start talking about intranets.
Everything that talks on a network has a unique address. Everything. Every network card, every router, every wireless adapter, everything! This unique identifier is called a MAC address.
MAC is an abbreviation for media access control. A MAC address is a 48-bit number, which literally is etched onto the device. This address is permanent. The first 24 bits are unique to the manufacturer of the device. The next 24 bits uniquely identify the specific individual device. Considering how many computer-related devices are out there in the world, at first blush, it may seem as though a 48-bit number would not allow for one distinct number per device. But consider that 24 bits, translated into decimal, is 16,777,215. That means that almost 17 million different widgets could be shipped from each of almost 17 million manufacturers and still each have their own unique address. That’s a lot of network cards! And since there probably are not 16,777,215 manufacturers of network cards, it would not surprise me if some of the big guys had more than one number from that pool of the first 24 bits.
The good news is, since everything has a unique address, it can be found as long as it is hanging out on the Internet.
Consider this parallel ...
Everyone who has a cell phone has a unique phone number.
Admittedly, no number is assigned to the phone at the factory, and once a number is assigned to a phone, it is not permanent since I can move the number when I upgrade. But you could say the phone number uniquely identifies me, so long as I keep that number. In effect I have a unique MAC address in the form of my mobile phone. So when someone places a call to my mobile phone number, the system finds me—whether I'm in Cleveland, San Francisco, Sydney or Mumbai—and connects me to the caller. And even though the phone may be sitting on the kitchen table where any nosy person in the house could answer it, theoretically any call which comes in is intended for me and me alone.
SCRAPPY TIP: Remember MACs. MACs play an important role in securing wireless networks. The topic will be revisited in a future section on wireless.
Next time, I will start talking about intranets.
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