4 ms·

Computers on the internet are pointed to by special numbers. Usually the special numbers look like 4 numbers with '.' like 123.45.67.89 Each of those 4 numbers

by pilom 9y ago

Computers on the internet are pointed to by special numbers. Usually the special numbers look like 4 numbers with '.' like 123.45.67.89 Each of those 4 numbers can be between 0 and 255 so (to be more simple) the lowest special number would be 0.0.0.0 and the highest would be 255.255.255.255. Back when the internet was still young, you would go to ARIN (the American Registry of Internet Numbers) and say "I think I need 256 special numbers" and they would give you a block of 256 of them. Something like 1.2.3.0 - 1.2.3.255. If you asked for about 65,000 special they might give you 231.45.0.0 through 231.45.255.255. MIT (the Massachusettes Institute of Technology in Boston, MA, USA) was one of the first people to ask for special numbers and so asked for over 16,000,000 of them (this was 1/256 of all of them) and so MIT was given 18.0.0.0-18.255.255.255. Now today, all of the special numbers have given to people and companies. This makes each special number extra special and large groups of special numbers very extra special. Since MIT had 16,000,000 of the special numbers all next to each other, they decided to sell half of their special numbers for a lot of money. Edit: Simple English: https://xkcd.com/simplewriter/ https://xkcd.com/simplewriter/

ghaff 9y ago
One of your words is wrong though. Cambridge, not Boston :-) OK, we're picky about that sort of thing. I think it's also more like the special big blocks of special numbers were given away without thinking much when the internet was young.
VLM 9y ago
I'm so old that I predate CIDR and in the old days before netmasks the netmask was essentially implied by the first couple bits of an ip address so all msb zero ip addrs were class A aka /8 allocations. All MSB 00 or whatever it was were class B implying a netmask of 255.255.0.0 aka a /16 allocation. Before CIDR you couldn't route or advertise rando netmasks like a /9 or a /20. There were no steps between a /16 and a /8 so if you convinced (someone, forget who) that you "need" more than 65K ip addresses (and MIT is big enough to need more, theoretically) then you got a /8. A lot of noobs think ipv4 rolled out with CIDR; not so. For "a long time" people had to make due with classful routing. From memory, isn't RIP v1 only classful routing compatible? Been awhile since I used something that old.
- tbyehl 9y ago
  One of my friends took a CCNA class and had her mind blown by Class C != /24. I was shocked they're still teaching anything about classful networking in 2017. I think the last time I saw RIPv1 was 1998.
Someone 9y ago
"MIT [...] asked for over 16,000,000 of them" I don't think they specifically asked for 16 million of them. Back at the time, that was the unit in which they were doled out. https://en.wikipedia.org/wiki/Classful_network#Background https://en.wikipedia.org/wiki/Classful_network#Background: "Originally, a 32-bit IPv4 address was logically subdivided into the network number field, the most significant 8 bits of an address, which specified the particular network a host was attached to, and the local address, also called rest field (the rest of the address), which uniquely identifies a host connected to that network. This format was sufficient at a time when only a few large networks existed, such as the ARPANET, which was assigned the network number 10, and before the wide proliferation of local area networks (LANs). As a consequence of this architecture, the address space supported only a low number (254) of independent networks, and it became clear very early on that this would not be enough."

by pilom 9y ago

ghaff 9y ago

One of your words is wrong though. Cambridge, not Boston :-) OK, we're picky about that sort of thing. I think it's also more like the special big blocks of special numbers were given away without thinking much when the internet was young.

VLM 9y ago

I'm so old that I predate CIDR and in the old days before netmasks the netmask was essentially implied by the first couple bits of an ip address so all msb zero ip addrs were class A aka /8 allocations. All MSB 00 or whatever it was were class B implying a netmask of 255.255.0.0 aka a /16 allocation. Before CIDR you couldn't route or advertise rando netmasks like a /9 or a /20. There were no steps between a /16 and a /8 so if you convinced (someone, forget who) that you "need" more than 65K ip addresses (and MIT is big enough to need more, theoretically) then you got a /8. A lot of noobs think ipv4 rolled out with CIDR; not so. For "a long time" people had to make due with classful routing. From memory, isn't RIP v1 only classful routing compatible? Been awhile since I used something that old.

tbyehl 9y ago
One of my friends took a CCNA class and had her mind blown by Class C != /24. I was shocked they're still teaching anything about classful networking in 2017. I think the last time I saw RIPv1 was 1998.

Someone 9y ago

"MIT [...] asked for over 16,000,000 of them" I don't think they specifically asked for 16 million of them. Back at the time, that was the unit in which they were doled out. https://en.wikipedia.org/wiki/Classful_network#Background https://en.wikipedia.org/wiki/Classful_network#Background: "Originally, a 32-bit IPv4 address was logically subdivided into the network number field, the most significant 8 bits of an address, which specified the particular network a host was attached to, and the local address, also called rest field (the rest of the address), which uniquely identifies a host connected to that network. This format was sufficient at a time when only a few large networks existed, such as the ARPANET, which was assigned the network number 10, and before the wide proliferation of local area networks (LANs). As a consequence of this architecture, the address space supported only a low number (254) of independent networks, and it became clear very early on that this would not be enough."