Network planning
Oct 30, 2009 1:58 PM
To keep on-air networks safe from the Internet, some broadcasters just disconnect their network from the Internet when it’s not in use. This is the most assured way to protect your network. Whenever remote access is required by the manufacturer to do an upgrade or diagnose a problem, the engineer just plugs in a network patch cord connecting that system to the Internet and disconnects it when done, but this may be impractical in some situations. A telephone-controlled power switch can overcome this problem by remotely turning on or off the power to the firewall or network router. These are also used to remotely reboot important computers without having to physically be in the studio.
Many of the industrial computers supplied today come with at least two Ethernet ports. One port is used for the computer to communicate with the rest of the system it’s a part of, but the second one can have a completely different network setup (e.g. IP address, subnet mask, gateway). This can be the maintenance port that does not interfere with the dataflow of its normal operations.
Using subnets
At one TV station, when the automation system was installed, all four computers plugged into a network switch, and the default network settings from the supplier were used. When the video server showed up, it used several computers all plugged into a GigE switch, and, again, the network setup that came with the system was used. Finally, when the encoding system arrived, the default network settings were used as well.
Fig 4.
All of these systems worked fine alone, but when operators wanted to use the master control workstation to access both the automation and video servers, they had to install a second network interface card (NIC) in the workstation so it could access two unrelated networks. And when they wanted the new GPS master clock to feed network time protocol (NTP) to all of the on-air systems, they found that it was difficult to do. These separate, unrelated networks were now causing a problem in that they could not communicate between each other or share a common address where a single workstation could monitor and control them all.
This is what subnets are for: They allow a larger network to be broken up into smaller subnetworks or allow a common addressing scheme to share needed data. They can also isolate data common to just that subnet. The automation system, video server and master control would be on their own subnets. Whenever a message was sent from one subnet to another, it would pass through a network router. In a subnet configuration, a workstation with just one NIC could communicate with all the subnets, and the installation of the NTP could be easily accomplished. (See Figure 4.)
Next time
The next tutorial is cover subnets and how they work.
Continue reading part two of Network planning.
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