Layers in Data Communication System Architecture
- Physical passive infrastructure: right of way, ducts, fibre cables, fibre core terminated in an optical distribution frame with patch panels. Actors on this level includes real estate owners, both public and private, other infrastructure actors, such as power utility companies, railway companies, pipeline companies (water, gas, oil, etc.). Several fibre owners lease dark fibre to operators or end-users.
- Optical transmission including wavelength division multiplexing (WDM) providing several communication channels in the same fibre core. Fibre owners sometimes provide wavelengths rather than dark fibre, sometimes both.
- Link level: includes a variety of link level services for Local Area Network LAN, Metropolitan Area Network MAN and Wide Area Network WAN implemented by switches, etc. Operators on this level include "service operator-neutral" network operators.
- Network level (IP), including unicast, multicast, anycast. Operators on this level include Internet Service Providers (ISPs)
- End-to-end transport level, including connection-oriented Transfer Control Protocol (TCP) and datagram (UDP). Commercial services on this level are rare.
- Services including session, presentation and application functionality, such as email (SMTP, POP, IMAP), web services (HTTP), File Transfer Protocol (FTP), terminal access (TELNET), etc. Typical commercial actors on this level include Internet Cafes.
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