Figure 29 Translation Between Ethernet Ii And Fddi Rfc 1042 Frame Formats - Plaintree WaveSwitch 100 User Manual

Coexistence of Ethernet II and RFC 1042 frames
The Ethernet and FDDI LANs are joined by a translating switch or bridge
(WaveSwitch 100, for example) which, in this case, performs only RFC
1042 frame translations. Ethernet II frames must be translated to FDDI
RFC 1042 frames when transferred to the FDDI network. All RFC 1042
frames are, by default, translated to Ethernet II frames when bridged from
the FDDI network to the Ethernet network.
This means that RFC 1042 frames sent by the fileserver (that is, all frames
FS1 sends) will be seen on the Ethernet network as Ethernet II frames. If an
Ethernet station which sends RFC 1042 frames cannot recognize Ethernet II
frames in response, it will not be able to communicate with the FDDI
stations.
A reasonable provision to deal with this problem is to expect that any station
which sends an RFC 1042 frame must recognize responses encoded as
either Ethernet II frames or as RFC 1042 frames. Unfortunately, few
implementations support this reasonable expectation (Figure 29). Two
famous and ubiquitous examples are AppleTalk and the Novell ODI driver
architecture used in NetWare 3.1x and 4.xx.
Figure 29
Translation between Ethernet II and FDDI RFC 1042 frame formats
Destination Address
Source Address
Ether Type
Ether Type
> 1500 decimal
FCS/CRC
104 WaveSwitch 100 Ethernet Switch User Manual
Ethernet II
Frame Control
Destination Address
Source Address
DSAP AA
AA
SSAP
03
Control
00 00 00
RFC 1042 OUI
Ether Type
FCS/CRC
FDDI SNAP RFC 1042
12195