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SNAX/XF and SNAX/APN Configuration and Management Manual

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Configuring for Ethernet Support
SNAX/XF and SNAX/APN Configuration and Management Manual—425836-006
10-5
The IEEE Specifications
802.5—a ring topology using a token-passing access method
The IEEE also defined an internetworking and network management standard (802.1),
and a logical link control standard (802.2). NonStop support for Ethernet is concerned
with LLC (802.2) and CSMA/CD (802.3) standards.
The (802.2) LLC Services
The LLC layer concerns links between network entities; in the case of Ethernet, these
are links between stations in the network. There are three key LLC services:
The LLC layer allows different types of conversation to take place on the LAN.
These conversation types are related to the amount of error detection, frame
sequencing, and flow control required by the user application. For details, see
Types of Conversation on page 10-10.
The LLC layer organizes the physical network node into multiple logical network
entities (service access points, or SAPs) for program communication—essentially
providing an entry point on the LAN to any number of different higher-level protocol
stacks—for example, SNA, Internet, or NetBIOS stacks. For details, see SAPs and
Link-station Addresses on page 10-8.
The LLC layer provides a single frame type, the Link Protocol Data Unit (LPDU),
that is encapsulated in the MAC data frame. For details, see Description of Frames
on page 10-11 and Figure 10-9 on page 10-12.
The (802.3) CSMA/CD MAC Services
The MAC services defined by IEEE 802.3 govern the management of the network that
use MAC frames. These services are provided by the Ethernet adapters and are not
discussed in this manual. For more information, see the Ethernet Adapter Installation
and Support Guide for the E4SA adapter, the Gigabit Ethernet Adapter Installation and
Support Guide for the GESA adapter, the Fast Ethernet Adapter Installation and
Support Guide for the FESA adapter, or the Gigabit 4-Port ServerNet Adapter
Installation and Support Guide for the G4SA adapter.