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Lesson 2: The IEEE 802.x Standard

The bottom two layers of the OSI reference model pertain to hardware: the NIC and the network cabling. To further refine the requirements for hardware that operate within these layers, the Institute of Electrical and Electronics Engineers (IEEE) has developed enhancements specific to different NICs and cabling. Collectively, these refinements are known as the 802 project. This lesson describes these enhancements and how they relate to OSI.

The 802 Project Model

When local area networks (LANs) first began to emerge as potential business tools in the late 1970s, the IEEE realized that there was a need to define certain LAN standards. To accomplish this task, the IEEE launched what became known as Project 802, named for the year and month it began (1980, February).

Although the published IEEE 802 standards actually predated the ISO standards, both were in development at roughly the same time, and both shared information that resulted in the creation of two compatible models.

Project 802 defined network standards for the physical components of a network (the interface card and the cabling) that are accounted for in the physical and data-link layers of the OSI reference model.

The 802 specifications set standards for:

The 802 specifications define the ways NICs access and transfer data over physical media. These include connecting, maintaining, and disconnecting network devices.
Choosing which protocol to run at the data-link layer is the single most important decision you make when designing a LAN. This protocol defines the speed of the network, the method used to access the physical network, the types of cables you can use, and the NICs and drivers you install.

IEEE 802 Categories

The LAN standards defined by the 802 committees are classified into 16 categories that can be identified by their 802 number as shown in Table 5.2:

Table 5.2 802 Specification Categories
Specification Description
802.1 Sets Internetworking standards related to network management.
802.2 Defines the general standard for the data-link layer. The IEEE divides this layer into two sublayers: the LLC and MAC layers (discussed in the previous lesson). The MAC layer varies with different network types and is defined by standard IEEE 802.3.
802.3 Defines the MAC layer for bus networks that use Carrier-Sense Multiple Access with Collision Detection (CSMA/CD). This is the Ethernet Standard.
802.4 Defines the MAC layer for bus networks that use a token-passing mechanism (Token Bus LAN).
802.5 Defines the MAC layer for token ring networks (Token Ring LAN).
802.6 Sets standards for metropolitan area networks (MANs), which are data networks designed for towns or cities. In terms of geographic breadth, MANs are larger than LANs, but smaller than WANs. MANs are usually characterized by very-high-speed connections using fiber-optic cables or other digital media.
802.7 Used by the Broadband Technical Advisory Group.
802.8 Used by the Fiber-Optic Technical Advisory Group.
802.9 Defines integrated voice/data networks.
802.10 Defines network security.
802.11 Defines wireless network standards.
802.12 Defines Demand Priority Access LAN, 100BaseVG-AnyLAN.
802.13 Unused.
802.14 Defines cable modem standards.
802.15 Defines wireless personal area networks (WPAN).
802.16 Defines broadband wireless standards.

Enhancements to the OSI Reference Model

The bottom two OSI layers, the physical layer and the data-link layer, define how multiple computers can use the network simultaneously without interfering with each other.

The IEEE 802 project incorporated the specifications in those two layers to create standards that have defined the dominant LAN environments. Figure 5.8 shows the data-link layer and its two sublayers.

After deciding that more detail was needed at the data-link layer, the 802 standards committee divided the data-link layer into two sublayers:

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Figure 5.8 Project 802 LLC and MAC sublayers

Logical Link Control (LLC) Sublayer

The LLC sublayer manages data-link communication and defines the use of logical interface points called service access points (SAP). Other computers can refer to and use SAPs to transfer information from the LLC sublayer to the upper OSI layers. Category 802.2 defines these standards.

Media Access Control (MAC) Sublayer

As Figure 5.9 indicates, the MAC sublayer is the lower of the two sublayers, providing shared access to the physical layer for the computers' NICs. The MAC layer communicates directly with the NIC and is responsible for delivering error-free data between two computers on the network.

Categories 802.3, 802.4, 802.5, and 802.12 define standards for both this sublayer and OSI layer 1, the physical layer.

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Figure 5.9 Project 802 LLC and MAC standards

Exercise 5.2: Describing IEEE 802.x Standards Categories

In this exercise, IEEE 802 standards categories are listed in the left column. In the right column, enter a description of what each category represents.
802.x Standard Basis for standard


Lesson Summary

The following points summarize the main elements of this lesson: