What's the best way to transport SCADA traffic?

Should we use T1 or Ethernet as our data-transport protocol? That's the question most power utilities struggle with when they're planning a data communications network to carry SCADA* traffic. 

Many utilities see T1 as the better security solution. But they also believe Ethernet is the more cost-effective solution.

Actually, you can use both.

Because of T1's long history of security and reliability, you're probably using copper T1 links to pick up SCADA traffic from your remote terminal units (RTUs).  However, if you plan to support other types of traffic as well, you'll definitely want to migrate your network to Ethernet.

 Yet even if you look only at your SCADA traffic, a lot of new equipment features Ethernet interfaces. With IP-based data coming off these interfaces, you have to decide whether to transport it over your existing TDM/SONET network.

If you have embedded equipment that can support Ethernet over SONET (EoS), you can probably put off that decision for a while. You can make incremental upgrades as needed. Still, it's important to take a longer-term look at the issue.

For one thing, as more RTUs support Ethernet interfaces, it's going to become increasingly difficult to get T1 links—most of these connections eventually will be fiber- and Ethernet-based. Plus, the SONET multiplexers are going to become obsolete or, at least, more expensive.  Manufacturers likely will not sell it at a discount as they will the newer Ethernet- or MPLS-based equipment.

The point is, depending on your specific business model and SCADA requirements, Ethernet can be a good choice. By using secure protocols such as MPLS, you can classify your services according to priority to ensure delivery of critical communications.

Networking solutions are available that offer you the best of both the T1 and Ethernet worlds. They provide T1-type characteristics, including time division multiplexing for alarm protocols, DS0 grooming to groom and fill onto Ethernet and maintaining the SCADA circuits over TDM and T1 termination and transport. They also provide Ethernet-type features, including Ethernet switching for 10/100/1000 Mbps interfaces and Ethernet reliability, including traffic quality-of-service and performance-monitoring and fault management.

*SCADA: supervisory control and data acquisition