What Is A Cross-layer Function?

Cross-layer functions are services that are not tied to a given layer but may affect more than one layer. Some orthogonal aspects, such as management and security, involve all of the layers.

These services are aimed at improving the CIA triad—confidentiality, 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) as defined by ITU-T X.800 recommendation.
Management functions, i.e. functions that permit to configure, instantiation, monitoring, and termination of 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. It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provides 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.

Why cross-layer design is useful?

• It is used in cutting off the congestion in various internet applications.
• It is used in various Routing Schemes and for reservation mechanisms.
• It is used for inefficient transfer of multimedia resources in wireless networks.
• This strategy supports information exchange and optimization across layers.

What is cross-layer protocol?

Cross-layer protocol allows protocols of the OSI model to cooperate and share network status information; this will ensure that the best route is chosen by taking into consideration energy consumption and performance requirements.