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Muggles have 3 models of network architecture:

enter image description here

How is the Floo Network built? It has the ability to:

  • disable fireplaces, e.g. Umbridge's Hogwarts lockout
  • add new fireplaces at will, e.g. Borgin and Burkes have an open fireplace during work hours, but require specific fireplaces (the Dursleys' fireplace didn't work).

  1. What are the requirements to be attached to the Network?
  2. How is it managed and who adds new fireplaces to the network and how?
  3. Can one simply join or disconnect at will or do you need to send a schedule to the Ministry or Floo Network Provider?
  • 43
    Does it even have a fixed architecture? Hogwarts doesn't. – Reinstate Monica Aug 17 '16 at 15:12
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    There's a fourth architecture you've forgotten: the completely connected one. It's not used by muggles much, due to the infrastructure costs but ... magic. – R.M. Aug 17 '16 at 15:28
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    Completely connected is special case of decentralized – janisz Aug 17 '16 at 16:58
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    Actually, the Dursleys' fireplace did work - it was just closed, so the Weasleys had to break their way in. Arthur did mention that he had to add the fireplace to the network, though, so it's somewhat flexible. – Luaan Aug 18 '16 at 7:39
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    "special case of decentralized" - perhaps you meant distributed? – Gallifreyan Feb 19 '17 at 15:12
64

Here's an insight into the possible structure of the network: In the Chamber of Secrets, Harry sees glimpses of other fireplaces as he is traveling through the Floo network:

It felt as though he was being sucked down a giant drain. He seemed to be spinning very fast — the roaring in his ears was deafening — he tried to keep his eyes open but the whirl of green flames made him feel sick —something hard knocked his elbow and he tucked it in tightly, still spinning and spinning — now it felt as though cold hands were slapping his face — squinting through his glasses he saw a blurred stream of fireplaces and snatched glimpses of the rooms beyond — his bacon sandwiches were churning inside him — he closed his eyes again wishing it would stop, and then… He fell, face forward, onto cold stone and felt the bridge of his glasses snap.

The detail of seeing multiple fireplaces before reaching the final destination would imply that the Floo network is not a centralized network model. That leaves us with a decentralized model, a distributed model, or something else (because magic).

As Zala pointed out, because of temporary connections and connections that can be easily disconnected, it would make a decentralized model quite an unattractive option. Thus I conclude that the Floo network most closely resembles the distributed model, unless there is a special network model that wizards and witches have knowledge of that Muggles do not.

EDIT: R.M. in the comments on the question suggested that a completely connected network would be feasible for wizards and witches. However, again with the evidence that a person traveling the Floo Network catches glimpses of multiple fireplaces, I doubt this is the case. Why stop at different nodes in the network if you can get to another fireplace in a single leap?

  • 14
    We don't have any indication that Harry's experience is normal - he screwed up his pronunciation. Maybe the other fireplaces were the network trying to settle on something, and normally you go direct. – Dan Smolinske Aug 17 '16 at 16:50
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    So maybe all fireplaces are connected to single bus like network bus and you need to pass bunch of them to get your destination. – janisz Aug 17 '16 at 17:06
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    I'm thinking this suggests ring. This is why you need training: wouldn't want to travel the wrong way round the ring. – Dewi Morgan Aug 17 '16 at 19:14
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    It sound like it's a lot like the internet with multiple nodes to your destination (traceroute) :') – Thomas Aug 18 '16 at 14:47
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    @DanSmolinske But Molly told him to make sure not to get off too early. That would make it seem like it's not direct. Note that they also went to check if he got off in the next fireplace. – Scimonster Aug 18 '16 at 20:18
38

From Pottermore's article on the Floo Network (written by JK Rowling):

Nearly every witch or wizard home is connected to the Floo Network. While a fireplace may be disconnected by the use of a simple spell, connection requires the permission of the Ministry of Magic, which regulates the Floo service and prevents Muggle fireplaces becoming inadvertently joined up (although temporary connection can be arranged in emergencies).

In addition to domestic fireplaces, there are around a thousand fireplaces across Britain connected to the Floo Network, including those at the Ministry of Magic, and various wizarding shops and inns. The fireplaces of Hogwarts are not generally connected, although there have been occasions when one or more has been tampered with, often without the staff’s knowledge.

This is pretty much all the information we have on the Floo Network other than what's in the books. JK Rowling never saw fit to go into sufficient detail as to explain, for instance, whether the graph-theoretic structure of the Floo Network is centralised, decentralised, or distributed as in your three diagrams.

  • 38
    Sometimes I have a felling like Magic world is Totalitarianism. Every aspect of your life if controlled by Ministry of Magic: apparition, floo, underage magic usage. – janisz Aug 17 '16 at 13:49
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    @janisz Many things are licensed or overseen by the government in real life too, not just in totalitarian states. – Rand al'Thor Aug 17 '16 at 13:54
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    @Neeshka "I had your fireplace connected to the Floo Network, you see - just for an afternoon, you know, so we could get Harry. Muggle fireplaces aren't supposed to be connected, strictly speaking - but I've got a useful contact at the Floo Regulation Panel and he fixed it for me." -- Arthur Weasley, GoF. – Rand al'Thor Aug 17 '16 at 14:28
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    When using the floo network in the second book, Mrs. Weasley tells Harry to be sure to get out at the right grate, and Harry actually experiences physically moving through space when he uses the floo network. These two things imply to me that like riding public transportation, you will pass by multiple different "stops" while using the network, which suggests that it is not a centralized network. However, when later it is shown people can simply stick their head in the fire, this seems to contradict the earlier description. – Kai Aug 17 '16 at 16:14
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    > Every aspect of your life if controlled by Ministry of Magic What you are allowed to remember is controlled by the Ministry too, and torture to death/insanity is not considered an exceptionally cruel and unusual punishment. – Daerdemandt Aug 18 '16 at 21:49
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Think of the Floo network as a set of roads, rather than an information network. On the internet you send a packet of information down a wire to a node, which then resends it to the next location, based on one of the topographies provided in the original post. In such a case, you have to worry about the integrity of the nodes and how they handle the information. But a road network is different, although it is similar to the "internet" graph. Rather than having nodes, you have intersections. There's nothing between you and your destination but the pathway. The downside, though, is that the traveller must be in control of its pathing, wether that's you, your driver, or the floo powder swirling around you. The intersections make no decisions, they simply exist.

Now in the floo network, it is described as Harry passing by several fireplaces and catching glimpses of what's through them. These glimpses can be confirmed as normal because, in The Cursed Child, Ron mentions seeing Albus and Scorpius with Delphini while he was going through the Floo. As such, these glimpses would be akin to seeing houses while driving down the street. Adding or removing a fireplace would have as much effect on the Floo network as building or demolishing a house along the road. It doesn't affect the path, only the availability of the end point.

As for ministry control over the Floo network, this would be analgous to your local government's control over public roads. They build and maintain whatever it is that you travel along. Finally, it seems likely that wizards would have built on the concepts of roads, since there is such a long and rich history of such pathways, rather than information networks which are a rather recent discovery.

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    That's actually a really interesting insight, similar to janisz's thought that the Floo Network could be like a network bus. – DBPriGuy Aug 17 '16 at 17:54
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    This is what makes more sense. Not sure why multiple answers are so afraid that disconnection a fireplace could isolate others. Like if unsubscribing my Internet line could disconnect other people! – Oriol Aug 18 '16 at 21:53
6

It would have to be Meshed/Distributed. Otherwise single Fireplaces couldn't be safely dissconnected without risking to dissconnect others. As temporary connections are possible as stated by JKR every other possibility would end in quite the mess.

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    Where does that "single fireplaces can be safely disconnected" bit of information come from? Maybe the Floo network is "quite the mess"? Maybe they disconnected the Dursleys' fireplace during a scheduled maintenance? Maybe there is a big Floo router at the Ministry of Magic and it is the only node that should always be up? There are tons of possibilities that match existing canon information about the Floo network. – neothoron Aug 17 '16 at 15:52
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    With centralized you can disconnect peers and this don't affect whole network. I wonder what happen when destination fireplace is disconnected when you're about to get there. – janisz Aug 17 '16 at 17:02
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    I can disconnect my computer from the Internet without breaking anyone else. The key is whether or not you have intermediaries (analogous to ISPs) who can't be so easily disconnected. Nothing in canon tells us much either way. – Kevin Aug 18 '16 at 5:33
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I have a feeling it's Decentralized, like the internet. Although a centralized network might make sense, given the Ministry's apparent power to regulate Floo network approved fireplaces, I think it is doubtful that Floo would have originated from a central point the way that telephone companies originally hooked each individual household up to a specific line and directed calls through a switchboard operator. Floo was probably in use from household to household and later became regulated by the ministry. Or, much like the modern internet, it was started as a government project and was expanded by other witches and wizards.

Zala brings up a good point, which is that disconnecting a fireplace without risking disconnecting others might make you think it's a completely distributed network, but I think you need to consider the fact that traveling through someone's fireplace is not the same as exiting it, and that, much like borgin and burke's, a fireplace owner might have the ability to disable the ability for others to exit through that chimney, without removing it from the network entirely.

My real reason for thinking it's decentralized though, is that, if you think about how Floo networks might have been first created, a large ministry down approach doesn't make sense, given what we know of witches and wizards. I can easily imagine small Floo networks being started up between relatives (imagine a witch in England using Floo powder to easily visit grandparents and cousins in India and America) or friends (imagine a group of Hufflepuffs starting up their own small network to keep in touch after they all leave Hogwarts and go their separate ways), and there got to be so many witches and wizards using it (and misuing it) that the ministry had to step in and regulate the thing so people stopped accidentally trespassing in other people's living rooms. So, small centralized networks which were later connected to each other makes the most sense to me.

2

Based on @DBPriGuy's answer, the structure could be something like this:

.----.-----.----------.-.-----.------.---.----.
1    2     3          4 5     6      7   8    9

similar to a large Muggle highway with periodic exits.

0

My thought would be a internet architecture or telecom this is because the user needs to address the exit location, (you would not need to do this with the high way idea), to have to have either architecture would also allow Mr Weasley to connect the dursleys fireplace to the floo network without alerting floo regulation panel, witch may also rule out the Telecom architecture, has increased pressure on the system would be noticed by the authorities.

Additionally a decentralised architecture would mean that it would be safer to travel along the floo network as any problems or disconnections would allow users to be safely redirected the caveat for this is the dursleys fire place where the fireplace was connected but there was a barrier, this would be consistent with the idea of users being able to see into other uses houses and uses not currently engage the system being able to see people currently in transit.

There is also a possibility users could have as a local network has demonstrated in the Prisoner of Azkaban. ( this opens the possibility of the flu network being more of a collection of different techniques of connection rather than having a single architecture)

  • In the world of HP fanfiction, most likely HPMOR, there is a common note of having "local" (isolated) Floo networks for all sorts of renegade/Death Eaters activities. On an unrelated note, one of those fanfics also had an idea of connecting the Sun aka the biggest fireplace around to Floo network, so they're pretty far from canon sometimes.. – kagali-san Aug 21 '16 at 1:14

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