From 612e99161f4faf415eeeaf70908f416debfa291e Mon Sep 17 00:00:00 2001 From: Dimitri Staessens Date: Sat, 11 Jan 2020 15:12:15 +0100 Subject: content: Split OSI overview to different section --- content/en/docs/Concepts/problem_osi.md | 80 +++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 content/en/docs/Concepts/problem_osi.md diff --git a/content/en/docs/Concepts/problem_osi.md b/content/en/docs/Concepts/problem_osi.md new file mode 100644 index 0000000..845de5e --- /dev/null +++ b/content/en/docs/Concepts/problem_osi.md @@ -0,0 +1,80 @@ +--- +title: "The problem with the current layered model of the Internet" +author: "Dimitri Staessens" + +date: 2019-07-06 +weight: 1 +description: > + The current networking paradigm +--- + +{{
}} + +Every computer science class that deals with networks explains the +[7-layer OSI model](https://www.bmc.com/blogs/osi-model-7-layers/). +Open Systems Interconnect (OSI) defines 7 layers, each providing an +abstraction for a certain *function* that a network application may +need. + +From top to bottom, the layers provide (roughly) the following +functions: + +The __application layer__ implements the details of the application +protocol (such as HTTP), which specifies the operations and data that +the application understands (requesting a web page). + +The __presentation layer__ provides independence of data representation, +and may also perform encryption. + +The __session layer__ sets up and manages sessions (think of a session +as a conversation or dialogue) between the applications. + +The __transport layer__ handles individual chunks of data (think of them +as words in the conversation), and can ensure that there is end-to-end +reliability (no words or phrases get lost). + +The __network layer__ forwards the packets across the network, it +provides such things as addressing and congestion control. + +The __datalink layer__ encodes data into bits and moves them between +hosts. It handles errors in the physical layer. It has two sub-layers: +Media access control layer (MAC), which says when hosts can transmit +on the medium, and logical link control (LLC) that deals with error +handling and control of transmission rates. + +Finally, the __physical layer__ is responsible for translating the +bits into a signal (e.g. laser pulses in a fibre) that is carried +between endpoints. + +This functional layering provides a logical order for the steps that +data passes through between applications. Indeed, existing (packet) +networks go through these steps in roughly this order (however, some +may be skipped). + +However, when looking at current networking solutions in more depth, +things are not as simple as these 7 layers seem to indicate. Consider +a realistic scenario for a software developer working +remotely. Usually it goes something like this: he connects over the +Internet to the company __Virtual Private Network__ (VPN) and then +establishes an SSH __tunnel__ over the development server to a virtual +machine and then establishes another SSH connection into that virtual +machine. + +We are all familiar enough with this kind of technologies to take them +for granted. But what is really happnening here? Let's assume that the +Internet layers between the home of the developer and his office +aren't too complicated. The home network is IP over Wi-Fi, the office +network IP over Ethernet, and the telecom operater has a simple IP +over xDSL copper network (because in reality operator networks are +nothing like L3 over L2 over L1). Now, the VPN, such as openVPN, +creates a new network on top of IP, for instance a layer 2 network +over TAP interfaces supported by a TLS connection to the VPN server. + +Technologies such as VPNs, tunnels and some others (VLANs, +Multi-Protocol Label switching) seriously jumble around the layers in +this layered model. Now, by my book these counter-examples prove that +the 7-layered model is, to put it bluntly, wrong. That doesn't mean +it's useless, but from a purely scientific view, there has to be a +better model, one that actually fits implementations. + +Ouroboros is our answer towards a more complete model for computer networks. \ No newline at end of file -- cgit v1.2.3