GGE MS Protocol Stack (4)

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4. Overview of L123 and ACI/MMI
For one thing, Let us look back to the classical layering architecture, that is, 7-layer Open System Interconnection (OSI) Reference Model and to the TCP/IP, before starting to discuss the unitary framework of L123 and ACI/MMI, see Table 1 below.
                        Table 1. The comparison between OSI and TCP/IP


From the above comparison table between OSI and TCP/IP, the latter, namely TCP/IP, evolves from the former, namely OSI. Moreover, it is realized that both reference models still adapt the principle of functional modularity. Consequently, we shall lay a strong emphasis on the illustration of 7-layer OSI Reference Model.
Application Layer (Layer 7)
The Application Layer is the top layer of the reference model. It provides a set of interfaces for applications to obtain access to networked services as well ass access to the kinds of network services that support applications directly.
Presentation (Layer 6)
The Presentation Layer handles data format information for networked communications. This is done by converting data into a generic format that could be understood by both sides.
Session Layer (Layer 5)
The Session Layer permits two parties to hold ongoing communications called a session across a network.
Transport Layer (Layer 4)
The Transport Layer is responsible for creating and maintaining the basic end-to-end connection between communicating open systems, ensuring that the bits delivered to the receiver are the same as the bits transmitted by the sender; in the same order and without modification, loss or duplication
Network Layer (Layer 3)
The Network Layer is responsible for routing, to determine the quality of service (QoS) and flow control.
Data Link Layer (Layer 2)
The Data Link Layer transforms a stream of raw bits (0s and 1s) from the physical into a data frame and provides an error-free transfer from one node to another, allowing the layers above it to assume virtually error-free transmission.
Physical Layer (Layer 1)
The Physical Layer transforms raw bits into electromagnetic (or equivalent) signals for a particular transmission medium.
By the simple and quick review of 7-layer OSI Reference Model, we should be able to establish the layering concept in the area of communication, wire or wireless. Based on this background, we shall introduce this concept into GGE MS Protocol Stack. According to this layering technique, GGE MS Protocol Stack is viewed as being logically partitioned into an ordered set of layers represented in a vertical sequence, see Table 2 below. Note that the following Specs employed by GGE MS Protocol Stack are based on Release 99 Version.
                        Table 2. The layering structure in the GGE MS Protocol Stack


Under the layering structure of the GGE Protocol Stack, we shall expatiate on a set of key terms by the following diagram, as specified in Figure 6.
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