2020-03-02-types-of-networks.md (4992B) - raw
1 <!-- title: Centralized, decentralized and distributed networks --> 2 <!-- slug: types-of-networks --> 3 <!-- categories: Miscellany --> 4 <!-- date: 2020-03-02T00:00:00Z --> 5 6 When we are trying to understand a communications network, having an approximate 7 image of how the network operates can be very valuable. Do all communications go 8 through the same node? Is there a central authority? Can nodes communicate 9 directly with each other? Depending on how the network operates, we can classify 10 it as centralized, decentralized or distributed. 11 12 ### Centralized networks 13 14 When all the nodes on a network are connected to one unique node, we call it a 15 centralized network. All communications happen through that one "master" node. 16 An example of a centralized network is the one created by most instant 17 messengers, for example [Signal][s]. Every time we send a message, it goes to 18 Signal's servers and it is then sent to its destination. This creates a network 19 similar to the following, where everyone is connected to one server (or cluster 20 of servers). 21 22 <p style="text-align: center"><svg class="basic-svg" viewBox="0 0 633.9 523.77"><use xlink:href="/img/blog/2020/03/types-of-networks/centralized-network.svg#l"></use></svg></p> 23 24 Having everything go through the same computer has its pros and cons. On the one 25 hand, it makes deployment easier and faster, data consistency is easy to 26 maintain and it is an efficient network (if, for instance, you need to gather 27 data, it is all in one server). On the other hand, it creates a single point of 28 failure for the whole network (which also facilitates censorship) and it makes 29 it easier to abuse users (as the central server has a monopoly over the 30 network)[^common]. This type of network also makes escalation much harder, as 31 the resources are provided by one sole party. 32 33 [^common]: This is pretty usual. Whether it is services selling user's data, 34 censoring content, a sudden rise of prices, etc., when dealing with 35 centralized services, users don't have much choice but to leave the network 36 completely (which might not be affordable). 37 38 ### Decentralized networks 39 40 Decentralized networks don't have one central node, but multiple of them, which 41 are connected between themselves. When clients connect to the network, their 42 communications go through their "master" node, to the destination's "master" 43 node, and finally to the destination. An example of a decentralized network is 44 [e-mail][em]. When Alice (`email@example.com`) wants to send an e-mail to Bob 45 (`firstname.lastname@example.org`), Alice's computer sends the message to `example.com`'s 46 server. From there, it is sent to `example.org`, and finally `example.org` sends 47 it to Bob's computer. A decentralized network looks similar to the following 48 network. 49 50 <p style="text-align: center"><svg class="basic-svg" viewBox="0 0 633.9 523.77"><use xlink:href="/img/blog/2020/03/types-of-networks/decentralized-network.svg#l"></use></svg></p> 51 52 Decentralized networks solve some of the centralization problems: no entity has 53 control over the whole network anymore, allowing users to choose between 54 different providers and switch servers (or self-host) if one starts abusing its 55 power. If a server is down, others can still communicate ordinarily, which also 56 makes censorship more difficult. Decentralized networks are also easier to 57 escalate. Nonetheless, this type of network requires more infrastructure and can 58 become less efficient for certain operations (like global tasks). It is also 59 harder to deploy updates, as servers might update at different times, when each 60 administrator decides to do so. 61 62 ### Distributed networks 63 64 Distributed networks only have one type of node, and they are connected with 65 each other (although not necessarily all with all). This creates a very robust 66 network where all nodes are client and server at the same time. The [BitTorrent 67 protocol][bt] is an example of a protocol that works with a distributed network. 68 The following image shows what a distributed network looks like. 69 70 <p style="text-align: center"><svg class="basic-svg" viewBox="0 0 633.9 523.77"><use xlink:href="/img/blog/2020/03/types-of-networks/distributed-network.svg#l"></use></svg></p> 71 72 Because there are no central servers, distributed networks easily circumvent 73 censorship and are practically immune to denial-of-service attacks. Since every 74 user is client and server at the same time, these networks are highly scalable 75 without the need for additional central resources. However, distributed networks 76 make deployment a lot harder. 77 78 ## Final comments 79 80 I hope this post has clarified the main differences between centralized, 81 decentralized and distributed networks as well as showed some applications for 82 each of them. In the future, I might refer to this post when talking about 83 services and the type of network they rely on. 84 85 86 [s]: <https://signal.org/> "Signal" 87 [em]: <https://en.wikipedia.org/wiki/Email> "Email — Wikipedia" 88 [bt]: <https://en.wikipedia.org/wiki/BitTorrent> "BitTorrent — Wikipedia"