3 ms·
With their IPv4 /8 they had 2^24 IPv4 addresses to work with, or, from a network perspective, 2^16 /24 (65K) networks, each network containing no more than 254
by ghshephard 9y ago
With their IPv4 /8 they had 2^24 IPv4 addresses to work with, or, from a network perspective, 2^16 /24 (65K) networks, each network containing no more than 254 hosts.
If they had requested a boring /48 IPv6 allocation (that anybody can have just by asking) - they would have had 2^16 /64 networks, and each network could have had basically an infinite number of hosts.
But, this is the IPv6 world, so I would have expected MIT to claim they were a LIR (Local Internet Registry - equivalent of a small ISP or larger) - and asked for a /32 - which would have given them 2^32 networks - or 4 Billion networks to work with. They probably would have assigned the networks by segmenting them on a per site basis - so each site would have had a /48 assigned, so they could have up to 65K sites, each site having 65K networks, each network having (effectively) infinite number of hosts. That is, a /32 would have been far, far, far larger than their /8 was. Easier to manage as well (no VLSM - nothing ever smaller than a /64) And, keep in mind, with a single, no contest request, they could have gotten the /32 adjacent to theirs (another 4 Billion networks, or 65K /48s) so they could aggregate on a /31.
Instead, they've asked for a /24. And I'm just darn intrigued as to why they think they can make use of such an address space. If they weren't constrained with their /8, then a /32 would have been far more than they ever required. (And odds are a /48 would have been sufficient with even modest address management).
I mean, I work with really large mesh networks, millions of nodes, some of our subnets have 20K nodes each on them - we roll out /48s like they are nothing, and even after deploying a couple hundred customers over 10 years, and 25 million nodes, I think we've used up maybe 1500 /48s.
BTW - this doesn't even take into account that they can use RFC 4193 up the wazoo for all sorts of interesting non-globally routable experimental internal networks.
I"m just hoping someone from MIT is reading HN and will clue us in.
- xenadu02 9y agoI don't see what the problem is. The IPv6 address space is so large it doesn't matter at all.
- Terr_ 9y agoIsn't that what they once said about IPv4 when they were divvying it up?
- ghshephard 9y agoOrders of Magnitude are completely different, of course. When MIT got it's /8, (one of just 255 available), it gave them the ability to create 2^16 networks with just 254 hosts on each one. Now, anyone who wants to can ask for a /48, and they are automatically given it, and they are able to create 2^16 networks, each network with an effectively infinite number of hosts on it. And, there are so many /48s on the (current) Global Unicast space (prefixes starting with 001), that everyone on earth could be granted 4000 of them. And, in reality, ISPs started already conserving, and handing out /56s instead of /48s to most consumers/SoHo - further increasing that number by 255x. And that's just the 001 prefix. Based on what we learn about allocating space there, new policies can be device for the other 6 prefixes available. We aren't going to run out of IPv6 address space.
- ghshephard 9y agoThat's true when we are talking about /48s. There are enough /48s to hand out to everyone (and then everyone gets 65K networks to work with). In the current Global Unicast space (prefixes starting with 001) there are 2^45 /48s. Effectively unlimited number, as there are 2^33 people on earth - so everyone would get 2^12 /48s. There are 2^21 /24s in the existing Global Unicast Space. About 2 million. A large number, to be sure. But if every entity in the world MITs size asked for a /24, we'd start burning through them pretty quickly....
- koide 9y agoThey want it to sell it in a couple of centuries