I've heard blockchain is built on top of the ISO/OSI stack. Does it means blockchain belongs to the layer 7 (Application layer) of the Osi architecture?


Bitcoin uses TCP which would put it at layer 7 of that description, but there's nothing particular that requires it. The transport layer for data is orthogonal to the system, it could alternatively use raw frames, carrier pigeons, or have the packets inked onto the heads of slaves. Systems exist which allow for data to be transfered through a TV satellite relay for example, which skips the networking layers entirely.



This isn't really true in any meaningful sense.

Before the Internet became really ubiquitous with the invention of the World-wide-web (HTTP etc), there were two major competing global-scale inter-networking protocol suites. The Internet is based on a four-layer network model. The competing X25 networks were based on the ISO/OSI 7-layer model. However X25 lost out to the Internet Protocol Suite (often referred to as the TCP/IP protocol suite)

It is inappropriate to map any Internet application to the ISO/OSI model although people often do this.

The Internet model's 4 layers are typically described as:

  • Application
  • Transport
  • Inter-Networking
  • Datalink or Network-Access.

The Bitcoin/Blockchain protocols are an application-layer protocol.

Transport layer protocols are typically TCP or UDP although other, rarely used, protocols exist.

Internetworking is mostly IP (IPV4 and IPV6) and ICMP

Datalink layer protocols vary considerably and are usually some form of Ethernet at the edges of the Internet (i.e. the LANs) but a variety of different protocols are used as you progress towards the core.



     Protocol Layering
                    |     higher-level    |
                    |        TCP          |
                    |  internet protocol  |
                    |communication network|
                            Figure 1


    |Telnet| | FTP | |Voice|   ...  |     |  Application Level    
          |   |         |             |
         | TCP |     | RTP |  ...  |     |  Host Level
            |           |             |
         |    Internet Protocol & ICMP   |  Gateway Level
           |   Local Network Protocol  |    Network Level
                      Protocol Relationships
                            Figure 2.

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