Cisco Systems BC-109 manual LNM Linking to a Source-Route Bridge on Each Local Ring

Configure LNM Support

Figure 51 LNM Linking to a Source-Route Bridge on Each Local Ring

Token

Ring

PC running

LNM

SRB B

Token	SRB A	Token	SRB C	WAN	SRB D
Ring		Ring

Token

Ring

Token

Ring

S1113a

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.

Configuring Source-Route Bridging BC-127