| 词条 | Physical layer |
| 释义 |
{{refimprove|date=October 2009}} {{lead extra info|date=August 2018}}}}{{OSI model}} In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer.[1] This layer may be implemented by a PHY chip. 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] The physical layer defines the means of transmitting raw bits[4] rather than logical data packets 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 here. 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 signals.[5][6] Physical signaling sublayerIn a local area network (LAN) or a metropolitan area network (MAN) using Open Systems Interconnection (OSI) architecture, the physical signaling sublayer is the portion of the physical layer that[7][8]
Relation to the Internet ProtocolThe 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 an equivalent layer that deals exclusively with hardware-level specifications and interfaces, as this model does not concern itself directly with physical interfaces. Several RFCs mention a physical layer and data link layer, but that is in the context of IEEE protocols. RFC 1122 and 1123 do not mention any physical layer functionality or physical layer standards. List of services{{Prose|section|date=October 2017}}{{Unreferenced section|date=October 2018}}The major functions and services performed by the physical layer are:
The physical layer is also concerned with:[13]
TechnologiesThe following technologies provide physical layer services:
Network equipmentThe following network equipment provides physical layer services:[14][15]
See also
References1. ^{{cite book | last = Banzal | first = Shashi | title = Data and Computer Network Communication | publisher = Firewall Media | year = 2007 | location = | pages = 41 | url = https://books.google.com/books?id=UD0h_GqgbHgC&printsec=frontcover&dq=network%2B+guide+to+networks&src=bmrr#v=onepage&q&f=false}} 2. ^{{cite book | last = Iyengar | first = Shisharama | title = Fundamentals of Sensor Network Programming | publisher = Wiley | year = 2010 | location = | pages = 136 | url = https://books.google.com/books?id=UD0h_GqgbHgC&printsec=frontcover&dq=network%2B+guide+to+networks&src=bmrr#v=onepage&q&f=false}} 3. ^{{Cite news|url=https://interworks.com/blog/bfair/2011/07/30/physical-layer/|title=The Physical Layer {{!}} InterWorks|date=2011-07-30|work=InterWorks|access-date=2018-08-14|language=en-US}} 4. ^{{cite web |url=http://www.erg.abdn.ac.uk/users/gorry/course/phy-pages/phy.html |archiveurl=https://web.archive.org/web/20090618154921/http://www.erg.abdn.ac.uk/users/gorry/course/phy-pages/phy.html |archivedate=2009-06-18 |title=Physical Layer |author=Gorry Fairhurst |date=2001-01-01}} 5. ^{{Cite web|url=https://www.networkworld.com/article/3239677/lan-wan/the-osi-model-explained-how-to-understand-and-remember-the-7-layer-network-model.html|title=The OSI model explained: How to understand (and remember) the 7 layer network model|last=Shaw|first=Keith|date=2018-10-22|website=Network World|language=en|access-date=2019-02-15}} 6. ^{{Cite web|url=https://www.researchgate.net/publication/288180515_DATA_COMMUNICATION_NETWORKING|title=(PDF) DATA COMMUNICATION & NETWORKING|website=ResearchGate|language=en|access-date=2019-02-15}} 7. ^{{FS1037C}} 8. ^{{cite web |url=http://www.tiaonline.org/market_intelligence/glossary/index.cfm?term=%26%23TC%5DSR%3FN%0A |title=physical signaling sublayer (PLS) |access-date=2011-07-29}} 9. ^{{Cite web|url=https://fossbytes.com/physical-layer/|title=Physical Layer Of OSI Model: Working Functionalities and Protocols|last=Shekhar|first=Amar|date=2016-04-07|website=Fossbytes|language=en-US|access-date=2019-02-15}} 10. ^{{Cite book|url=https://books.google.es/books?id=cLwO-Hh6_VEC&printsec=frontcover&dq=The+physical+layer+Providing+a+standardized+interface+to+a+physical+transmission+medium,+including++Mechanical+specification+of+electrical+connectors+and+cables,+for+example+maximum+cable+length+Electrical+specification+of+transmission+line+signal+level+and+impedance+Radio+interface,+including+electromagnetic+spectrum+frequency+allocation+and+specification+of+signal+strength,+analog+bandwidth,+etc.+Specifications+for+IR+over+optical+fiber+or+a+wireless+IR+communication+link&hl=en&sa=X&ved=0ahUKEwjx3fKs6b3gAhUq6KYKHQ0gCXAQ6AEIKDAA#v=onepage&q&f=false|title=Transmission and Distribution Electrical Engineering|last=Bayliss|first=Colin R.|last2=Bayliss|first2=Colin|last3=Hardy|first3=Brian|date=2012-02-14|publisher=Elsevier|isbn=9780080969121|language=en}} 11. ^{{Cite web|url=https://en.wikibooks.org/wiki/CCNA_Certification/Physical_Layer|title=CCNA Certification/Physical Layer - Wikibooks, open books for an open world|website=en.wikibooks.org|access-date=2019-02-15}} 12. ^{{cite book|last1= Bertsekas|first1= Dimitri |last2=Gallager |first2= Robert |title= Data Networks |publisher= Prentice Hall |year= 1992|isbn= 0-13-200916-1|page=61}} 13. ^{{Cite book|url=https://books.google.es/books?id=bwUNZvJbEeQC&printsec=frontcover&dq=The+physical+layer+is+also+concerned+with:++Bit+rate+Point-to-point,+multipoint+or+point-to-multipoint+line+configuration+Physical+network+topology,+for+example+bus,+ring,+mesh+or+star+network+Serial+or+parallel+communication+Simplex,+half+duplex+or+full+duplex+transmission+mode+Autonegotiation&hl=en&sa=X&ved=0ahUKEwishIeD6b3gAhUB06YKHRP4CfAQ6AEIMDAB#v=onepage&q&f=false|title=Data Communications and Networking|last=Forouzan|first=Behrouz A.|last2=Fegan|first2=Sophia Chung|date=2007|publisher=Huga Media|isbn=9780072967753|language=en}} 14. ^{{Cite book|url=https://books.google.es/books?id=JxEEAAAAMBAJ&pg=PA60&lpg=PA60&dq=The+following+network+equipment+provides+physical+layer+services:++Network+interface+controller+Repeater+Ethernet+hub+Modem+Fiber+media+converter&source=bl&ots=F4jbiPAnq8&sig=ACfU3U3_wCL4AJgZ8ekvhBPV0VOk3RP4wA&hl=en&sa=X&ved=2ahUKEwjcg-X06b3gAhXHyKYKHWCPD8Q4ChDoATADegQIBxAB#v=onepage&q=The%20following%20network%20equipment%20provides%20physical%20layer%20services:%20%20Network%20interface%20controller%20Repeater%20Ethernet%20hub%20Modem%20Fiber%20media%20converter&f=false|title=Network World|last=Inc|first=IDG Network World|date=1991-02-11|publisher=IDG Network World Inc|language=en}} 15. ^{{Cite web|url=https://www.business.com/articles/local-area-network-hardware-assembly/|title=Hardware Elements Of Your Network|website=business.com|access-date=2019-02-15}} External links
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