Optimizing SCADA Network Communications: An Overview of Metropolitan Wide SCADA Communications Options by John McCain and Russ Straayer

The Legacy Approach 2 and 4 wire phones lines, 1200 bps VHF and UHF radios Point-to-Point Microwave These Were Typically… –Homogeneous –Well Understood –User-Controlled

Today’s World Open Standards Many Possible Solutions Simple to Complex Economical to Expensive Wired, Wireless, Public, Private

Wire Line Methods Analog Point to Point Modems Analog Multipoint Modems DDS Frame Relay Point-to-Point and Mesh Networks ATM T1 and Higher

Fiber SONET or Fiber Ring Fiber Ethernet New! Fiber Modem

Wireless Wireless Common Carrier Networks VHF and UHF Point-to-Point and Multi- Point ISM Band License Free –900 MHz, 2.4 GHz, 5 GHz Point-to-Point Licensed Microwave

Analog Modems Point-to-Point to 19.2 Kbps (Private Wire) Multi-Point to 9.6 Kbps Hard to purchase, not always available The base line for comparison

DDS 56/64 Kbps Point-to-Point or Multi-Point (56) Digital May be used with T-1 access line at host Not always available

Frame Relay Packet Switched Network Bandwidth available in small increments Not always available ECONOMICAL for longer distances “Automatic” Redundancy

ATM High Speed Expensive Not usually appropriate for SCADA

T1 and Higher T1, T3, OC-3, etc. More bandwidth than normally needed Minimum speed for “useful” Ethernet May be expensive

Fiber & SONET High cost High bandwidth Expertise Complexity

Fiber Modem Economical addition when adding fiber for other uses Low cost termination for RS-232 equipment Lower speed option for fiber

Fiber Ethernet Uses standard Ethernet equipment for small networks Lower cost than SONET 10/100 Mbps

VHF and UHF Radio Privately Owned and Maintained Lower speeds (19.2 Kbps or less) New frequencies hard to obtain ISM band equipment often has higher bandwidth and easier implementation

Wireless Common-Carrier Networks CDPD pay-per-byte Satellite delivery Wireless Internet Missing Coverage Areas Cost May be used to fill in “holes”

ISM Band Radio 9.6 Kbps to 100 Mbps (claimed:-) 900 Mhz, 2.4 Ghz, 5.8 Ghz Serial or Ethernet interfaces Insecure frequencies Range from several to 100 Miles+ Too Many Unrealistic Vendor Claims!!

Point-to-Point Microwave Licensed, secure May be expensive Always Point-to-Point High Bandwidth

The Organization Office WAN Lay the cost on someone else! Being forced upon SCADA users Not Deterministic Not SCADA-Reliable, No Accountability Be Careful Here

What to Do…. Start with a Needs Analysis –Analyze for total life cycle cost –Determine actual bandwidth requirements –Examine in-house expertise –Get to know your vendors….well –What growth requirements are there –Physical and geographic criteria? Consider a “MIXED” system!

Conclusion A successful SCADA WAN network is usually a compromise between reliability, cost, bandwidth, and flexibility. Today, more than ever, SCADA operators must economize while still providing the necessary control and data acquisition functions with increased reliability. Most SCADA networks contain a technology mixture that grew in complexity over the years. Insure that your analysis allows for even more growth in the future as well as flexibility and reliability.

For More Information Our Booth at PowerGen

Point to Point Example Frame Relay

Point to Multipoint Example Frame Relay

Multiple Redundant Hosts Frame Relay

Scada F/R with Ethernet Access, Remote Management 56 kbps T-1 Frame Relay-1 DCB SR DATA MULTIPLEXER SR-BPF-01/DSU SR-BPF-04 DCB SR DATA MULTIPLEXER SR-BPF-01/DSU DigiCHANNEL AC DigiCHANNEL AC Athena Frame Switch Host Computer SR-BPF-04 Host Computer RTU Remote RTUs Primary Host Site Backup Host Site DCB T1 DSU DCB T1 DSU LAN Etherpath DCB ACCESS SWITCH Access Switch DCB ACCESS SWITCH Access Switch LAN To Management Ports I/O Device Multiple Units I/O Device

SCADA with F/R, Voice, Ethernet, Backup Links

SCADA Via Ethernet

SCADA Via Frame Relay

Scada via Frame Relay with Redundant Host Site

Legacy (Conitel) Protocol Via Frame Relay

SCADA Via Routed Ethernet

Scada Via F/R with Modem or Radio Backup using ASU-BU 6/21/01 Russ Straayer

BPF Frame Relay Solution 1 or 4 ports Async ports 300 bps to bps Composite speeds to 128 kbps Async protocol transparent Fast data propagation Easy to configure

1 and 4 Ports Units Multiple polling systems, one line 40 DLCI’s per port Support multiple or redundant RTU’s

Multiple Speeds Not all systems run the same speed Different speeds at each end of the line Mix systems over the same phone lines Mix polling and non-polling applications

Fast Composite Faster data propagation Matches vendor offerings

Protocol Transparent Setup is much more simple More general purpose More future proof

Fast Propagation Times 50 to 100 ms Comparable to modems Less than host timeouts

Easy Configuration AT YOUR COMMAND >> SM SHOW MAP PORT DLCI ASSIGNMENTS [Total 1:3, 2:3, 3:3, 4:3]

Other DCB SCADA Solutions EtherPoll 202T Modems Fast Poll Modems SCADA Point to Point Multiplexer SCADA Point to Multipoint Multiplexer