3Com Network Connections and Topologies, PLM Series Network Cabling, Daisy-chained devices

5 Network Connections and Topologies

5.1PLM Series Network Cabling

The common cable categories used for high band- width network connectivity are Cat-5e and Cat-6; these are preferred choices for PLM Series network use. However, Cat-5 may be used in limited applica- tions, as explained below.

Cat-6, as the designation implies, is the newer standard, and it is designed to accommodate high- speed networks up to 250 MHz. The 10000BASE-TX standard (using 2 pairs) requires Cat-6 cabling. Cat-6 is fully compatible with all PLM Series network applica- tions (including use with Dante) as it accommodates all current Ethernet protocols.

Cat-5e (using 4 pairs) supports 1000BASE-T ap- plications, and is also fully suited to all PLM Series applications, including Dante.

Cat-5 cabling meets the requirements for the PLM Ethernet control network. However, the higher ratings of Cat-5e and Cat-6 are recommended for use as the backbone between switches, particularly if Dante is being used.

Cat-3 or Cat-4 cables may still be in use in some installations. Neither of these satisfies the bandwidth requirements of 100BASE-TX or 1000BASE-T net- working, and should not be used with PLM Series networks.

Table 5.1 can be used as a guide when specifying maximum recommended lengths for Ethernet cables within a PLM network:

	Spectral
	Bandwidth	Max Length	LAN
	100 MHz	100 m	100BASE-TX
Cat-5
			100BASE-TX
Cat-5e	100 MHz	100 m	1000BASE-T
	250 MHz	100 m	1000BASE-TX
Cat-6

Table 5.1: Recommended PLM network cable lengths

5.2PLM Series Topology Overview

Thanks to the auto-sense and auto-uplink features of the PLM Series’ Ethernet ports, connecting multiple units is a simple task. A free-topology network can be implemented easily, including external switches or hubs as required.

Following are some examples of various network configurations that can be used when setting up a PLM network.

5.2.1 Daisy-chained devices

If a daisy chain network system (see figure 3) is implemented, the secondary Ethernet connectors on PLM Series devices can be used as “loop-thru outputs” to send the audio and/or control signal to the next unit in the chain (i.e. in the same rack). As an example, a system utilizing a Dolby Lake Processor as a “break in point” would find the DLP typically connected to the Primary Ethernet port of the first PLM in the rack. The signal would then travel from the Secondary Ethernet connector of this PLM Series unit to the Primary Ethernet connector of the next unit in the system, and so on.

Care must be exercised in implementing a chain topology network, as the number of PLM Series devices being connected in this way will have a critical bearing on network

performance parameters such as overall latency. Also, the use of single layer cabling to connect the network will introduce the possibility of Single Point of Failure issues, which should be avoided at all costs when operating critical systems Therefore, this top- ology is NOT recommended at all for applications using Dante and it is NOT recommended for applica- tions with more than 10 PLMs, even when not using Dante.

100
	100		100
		100
	100		100

Figure 5.2.1: Daisy chain network topology

8PLM Series Network Configuration Guide