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SUMMARYConnecting workstations and servers using different drivers can cause problems when using Source Level Routing across bridges using IBM PC- NET/TOKEN RING Bridge Program 1.01.
MORE INFORMATIONNOT Supported by Microsoft
Supported by Microsoft
DefinitionIBM PC-NET refers to a complete network involving PC NET drivers over PC-NET cards. Using LAN Manager on PC-NET cards is an Ethernet 802.3 network.ExplanationThe LAN Manager PC-NET (802.3) mac layer does not understand the IBM PC-NET mac frame format, which includes a 2-byte field of all zeroes before the routing field. The IBM implementation of PC-NET uses this field, and adds a source routing information field, as shown below. Following the IEEE 802.3 implementation, Microsoft uses this field to indicate the length of the info field or type (dix), so a string of zeros is meaningless and the frame is disregarded. Also, the Microsoft 802.3 implementation does not include the Route Information field.However, the token ring frames see the source routing field on both sides, IBM PC-NET and LAN Manager, because of the 802.5 frame definition:
To enable collision detection, the frame must contain at least 64 bytes,
not including the Start Delimiter(SD) field. The combination of data and
pad fields must be at least 46 bytes.
The Frame Check Sequence(FCS) field stores the CRC check from the sending side. When the receiving station performs its CRC, the results do not match, because of the zeros in the IBM ZERO field. Additional query words: source routing PC-NET 2.20 2.2 pcnet pc net
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