3Com PLM Series, NCG-PLM manual Ethernet Cabling Limitations, Dual daisy-chained switches

5 Network Connections and Topologies

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Figure 5.2.3: Daisy chained switches

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Figure 5.2.5: Dual daisy chain switch topology

5.2.5 Dual daisy-chained switches

This is a hybrid that combines the ease of wiring of the daisy chain topology with the 100% avoid- ance of SPF issues in the dual redundant star/spoke configuration (figure 5.2.5). It is simply two “daisy chained switch” networks in parallel: the primary and secondary networks are connected independently using the dual redundant mode in the PLMs.

If the control computer only has one network card, it can be connected to only one of the network layers. The solution to this situation can be as follows:

•Manually disconnect from the “blue“ network layer and connect to the “red” network layer instead if one or more PLMs are inaccessible via the blue network (see figure 5.2.5). This can be done easily by using a simple hardware switch box.

•A more advanced solution would be to equip the PC with two identical network cards and appropriate drivers so that it can be connected to both networks simultaneously.

5.2.6 Other combination networks

In larger system network topologies, a good solution

may be to place a group of local switches in each “zone”, which are first interconnected to form a “local area network” (e.g. Stage Left). These area networks are then interconnected with a main backbone. A different topology for the main backbone than that of the local area network may be chosen, depending on your specific application and resources.

Figure 5.2.6 shows an example of a combined net- work utilizing both Star and Daisy Chained switch ring topologies.

5.3 Ethernet Cabling Limitations

The maximum cable length allowed between any two devices on a network is defined by the Ethernet protocol and is limited to 100 meters (330 feet) for copper connections. The term “devices” includes:

•The host PC running the Dolby Lake Controller PLM Edition software

•Any switch on the network

•Any access point

•Any PLM

Optical fiber can be used if longer distances are needed. Multi-mode fiber supports up to 550 meters (1800 feet) and single mode supports even longer

10PLM Series Network Configuration Guide