Echelon OpenLDV User Manual download pdf (Page 19)

OpenLDV Programmer’s Guide 11

the seven layers of the OSI Model and which OSI layers a Layer 2 or Layer 5

network interface handles.

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

Application Layer

Layer 5

Network

Interface

Layer 2

Network

Interface

Figure 3. Network Interfaces and the Seven Layers of the OSI Model

A Layer 2 network interface handles only the first two layers of the OSI Model,

and thus only sends and receives network packets; an application must

implement the rest of the ISO/IEC 14908-1 protocol to communicate with the

network.

A LonScanner Protocol Analyzer uses a Layer 2 network interface. The

LonScanner Protocol Analyzer implements the rest of the ISO/IEC 14908-1

protocol to communicate with and analyze the network.

A Layer 5 network interface handles the first five layers of the OSI Model, and

thus not only sends and receives network packets, but also implements layers 1

through 5 of the ISO/IEC 14908-1 protocol to communicate with the network.

Most OpenLDV applications use Layer 5 network interfaces so that they need not

implement Layers 3 to 5 of the ISO/IEC 14908-1 protocol.

OpenLDV Application Architecture

The OpenLDV application architecture also uses the OSI Model, and provides a

programming framework for communicating with the network, as shown in

Figure 4 on page 12.

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Echelon OpenLDV User Manual Page 19