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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:
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.
Table 5.2 802 Specification Categories
|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.|
|802.14||Defines cable modem standards.|
|802.15||Defines wireless personal area networks (WPAN).|
|802.16||Defines broadband wireless standards.|
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:
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.
Figure 5.9 Project 802 LLC and MAC standards
|802.x||Standard Basis for standard|