SNAX/XF and SNAX/APN Configuration and Management Manual

Configuring for Ethernet Support
SNAX/XF and SNAX/APN Configuration and Management Manual—425836-006
10-12
The HP Implementation on NonStop Systems

The unnumbered field is used for establishing and disconnecting the data link.
The LPDU is passed from the LLC layer down to the MAC layer. At this layer, the MAC
header and trailer is attached, as illustrated by the data frame in Figure 10-9.
Figure 10-9 on page 10-12 shows two types of frames that flow on the LAN:

A data frame contains the LPDU and is used to transfer information over the LAN.
The Ethernet header contains:

the start frame delimiter (SFD)

the destination and source MAC addresses (DA, SA)

the length field (LL) that gives the length of the LPDU or MAC data fields.
The Ethernet trailer is the frame check sequence (FCS)

A MAC frame provides control information between stations on the LAN. The MAC
frame has the same structure as the data frame, but instead of transporting SNA
data over the LAN, it transmits control information.
The HP Implementation on NonStop Systems
Configuration of resources for Ethernet support must be done using SCF or an SPI
application. To define SNAX Ethernet resources, you use the same SCF attributes that
define token-ring resources, but some of those attributes have been renamed and
some of the arguments of the attributes have different values. Additionally, some of the
functions of token-ring are not currently implemented in Ethernet. Table 10-2 on
page 10-13 gives the names of the token-ring attributes that are renamed and their
new names. The other Ethernet differences follow the table. For the details of all
Ethernet SCF attributes, see Section 14, Attributes for SNAX/XF and SNAX/APN
.
Figure 10-9. The MAC Frame Types
DA SA LPDU FCS
SFD DA SA LL MAC FCS
The Data Frame
The MAC Frame
SFD LL
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