Physical layer

In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer. This layer may be implemented by a PHY chip.

OSI model
by layer

The physical layer defines the means of transmitting raw bits[1] over a physical data link connecting network nodes. The bitstream may be grouped into code words or symbols and converted to a physical signal that is transmitted over a transmission medium. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to broadcast on, the line code to use and similar low-level parameters, are specified by the physical layer.

Role

The physical layer consists of the electronic circuit transmission technologies of a network.[2] It is a fundamental layer underlying the higher level functions in a network, and can be implemented through a great number of different hardware technologies with widely varying characteristics.[3]

Within the semantics of the OSI model, the physical layer translates logical communications requests from the data link layer into hardware-specific operations to cause transmission or reception of electronic (or other) signals.[4][5] The physical layer supports higher layers responsible for generation of logical data packets.

Physical signaling sublayer

In a network using Open Systems Interconnection (OSI) architecture, the physical signaling sublayer is the portion of the physical layer that[6][7]

Relation to the Internet Protocol

The Internet protocol suite, as defined in RFC 1122 and RFC 1123, is a high-level networking description used for the Internet and similar networks. It does not define a layer that deals exclusively with hardware-level specifications and interfaces, as this model does not concern itself directly with physical interfaces. Request for Comments (RFCs) that address topics of the physical layer and the data link layer, usually have the context of IEEE protocols. RFC 1122 and 1123 do not mention any physical layer functionality or standards.

List of services

The major functions and services performed by the physical layer are:

The physical layer is also concerned with:[12]

Technologies

The following technologies provide physical layer services:

gollark: Hmm, what if 10x esolang based around... decimal number manipulation?
gollark: Sadly, no, that doesn't seem to exist.
gollark: It's for enterprise developers. I'm an enterprise *and* rockstar developer.
gollark: https://github.com/joaomilho/Enterprise
gollark: There's one cool programming* language which uses `.E™` extensions.

See also

References
  1. Gorry Fairhurst (2001-01-01). "Physical Layer". Archived from the original on 2009-06-18.
  2. Iyengar, Shisharama (2010). Fundamentals of Sensor Network Programming. Wiley. p. 136.
  3. "The Physical Layer | InterWorks". InterWorks. 2011-07-30. Retrieved 2018-08-14.
  4. Shaw, Keith (2018-10-22). "The OSI model explained: How to understand (and remember) the 7 layer network model". Network World. Retrieved 2019-02-15.
  5. "(PDF) DATA COMMUNICATION & NETWORKING". ResearchGate. Retrieved 2019-02-15.
  6.  This article incorporates public domain material from the General Services Administration document: "Federal Standard 1037C".
  7. "physical signaling sublayer (PLS)". Archived from the original on 2010-12-27. Retrieved 2011-07-29.
  8. Shekhar, Amar (2016-04-07). "Physical Layer Of OSI Model: Working Functionalities and Protocols". Fossbytes. Retrieved 2019-02-15.
  9. Bayliss, Colin R.; Bayliss, Colin; Hardy, Brian (2012-02-14). Transmission and Distribution Electrical Engineering. Elsevier. ISBN 9780080969121.
  10. "CCNA Certification/Physical Layer - Wikibooks, open books for an open world". en.wikibooks.org. Retrieved 2019-02-15.
  11. Bertsekas, Dimitri; Gallager, Robert (1992). Data Networks. Prentice Hall. p. 61. ISBN 0-13-200916-1.
  12. Forouzan, Behrouz A.; Fegan, Sophia Chung (2007). Data Communications and Networking. Huga Media. ISBN 9780072967753.
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