Editing OSI model (section)

==Cross-layer functions==
{{Further|Cross-layer optimization}}
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Cross-layer functions are services that are not tied to a given layer, but may affect more than one layer.<ref name="Mao 2009">{{cite book |last1=Mao |first1=Stephen |editor-first1=Alexander |chapter=Chapter 8: Fundamentals of communication networks |editor-last1=Wyglinski |editor-first2=Maziar |editor-last2=Nekovee |editor-first3=Thomas |editor-last3=Hou |title=Cognitive Radio Communications and Networks: Principles and Practice |year=2009 |publisher=Elsevier |page=[{{GBurl |id=d3HBCmFEmicC |pg=PA201}} 201] |isbn=978-0-08-087932-1 |id={{OCLC|635292718|528550718}}}} [{{GBurl |id=d3HBCmFEmicC}} Partial preview] at [[Google Books]].</ref> Some orthogonal aspects, such as management and [[Security service (telecommunication)|security]], involve all of the layers (See [[ITU-T]] X.800 Recommendation<ref name="x800"/>). These services are aimed at improving the [[Information security|CIA triad]]—[[confidentiality]], [[data integrity|integrity]], and [[availability]]—of the transmitted data.
Cross-layer functions are the norm, in practice, because the availability of a communication service is determined by the interaction between [[network design]] and [[network management]] protocols.

Specific examples of cross-layer functions include the following:
* [[Security service (telecommunication)]]<ref name=x800>{{cite web|url=http://www.itu.int/rec/T-REC-X.800-199103-I/e|title=ITU-T Recommendation X.800 (03/91), ''Security architecture for Open Systems Interconnection for CCITT applications''|publisher=ITU|access-date=14 August 2015}}</ref> as defined by [[ITU-T]] X.800 recommendation.
* Management functions, i.e. functions that permit to configure, instantiate, monitor, terminate the communications of two or more entities: there is a specific application-layer protocol, [[Common Management Information Protocol]] (CMIP) and its corresponding service, [[Common Management Information Service]] (CMIS), they need to interact with every layer in order to deal with their instances.
* [[Multiprotocol Label Switching]] (MPLS), ATM, and X.25 are 3a protocols. OSI subdivides the Network Layer into three sublayers: 3a) Subnetwork Access, 3b) Subnetwork Dependent Convergence and 3c) Subnetwork Independent Convergence.<ref name="Hegering, Abeck, & Neumair 1999">{{cite book |last1=Hegering |first1=Heinz-Gerd |last2=Abeck |first2=Sebastian |last3=Neumair |first3=Bernhard |chapter=Fundamental Structures of Networked Systems |chapter-url=https://archive.org/details/integratedmanage0000hege/page/12/mode/2up |chapter-url-access=registration |title=Integrated management of networked systems: concepts, architectures, and their operational application |url=https://archive.org/details/integratedmanage0000hege/page/12/mode/2up |url-access=registration |publisher=Morgan Kaufmann |publication-place=San Francisco, Calif. |year=1999 |isbn=978-1-55860-571-8 |oclc=1341886747 |page=[https://archive.org/details/integratedmanage0000hege/page/54/mode/2up 54] |via=Internet Archive}}</ref> It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a [[datagram]]-based service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames. Sometimes one sees reference to a Layer 2.5.
* Cross MAC and PHY Scheduling is essential in wireless networks because of the time-varying nature of wireless channels. By scheduling packet transmission only in favourable channel conditions, which requires the MAC layer to obtain channel state information from the PHY layer, network throughput can be significantly improved and energy waste can be avoided.<ref name="Miao & Song 2014">{{cite book |last1=Miao |first1=Guowang |author1-link=Guowang Miao |last2=Song |first2=Guocong |title=Energy and spectrum efficient wireless network design |url=https://archive.org/details/energyspectrumef0000mia |url-access=registration |publisher=Cambridge University Press |publication-place=New York |year=2014 |isbn=978-1-139-62677-4 |oclc=898138775 |page= |via=Internet Archive}}</ref>{{page needed |date=July 2024}}