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Configure LNM Support
Configuring Source-Route Bridging BC-127
Figure 51 LNM Linking to a Source-Route Bridge on Each Local Ring
If LNM requires information about a station somewhere on a Token Ring, it uses a proprietary IBM
protocol to query to one of the source-route bridges connected to that ring. If the bridge can provide
the requested information, it simply responds directly to LNM. If the bridge does not have the
necessary information, it queries the station using a protocol published in the IEEE 802.5
specification. In either case, the bridge uses the proprietary protocol to send a valid response back to
LNM, using the proprietary protocol.
As an analogy, consider a language translator who sits between a French-speaking diplomat and a
German-speaking diplomat. If the French diplomat asks the translator a question in French for the
German diplomat and the translator knows the answer, he or she simply responds without translating
the original question into German. If the French diplomat asks a question the translator does not
know how to answer, the translator must first translate the question to German, wait for the German
diplomat to answer, and then translate the answer back to French.
Similarly, if LNM queries a source-route bridge in the proprietary protocol and the bridge knows the
answer, it responds directly using the same protocol. If the bridge does not know the answer, it must
first translate the question to the IEEE 802.5 protocol, query the station on the ring, and then translate
the response back to the proprietary protocol to send to LNM.
Figure 52 illustrates requests from the LNM originating in an IBM proprietary protocol and then
translated into IEEE 802.5 MAC-level frames.
WAN
PC running
LNM
S1113a
Token
Ring
Token
Ring
Token
Ring
Token
Ring
Token
Ring
SRB B
SRB D
SRB C
SRB A