Remote - Winter 2012 - (Page 12)

Feature Article Utility Networks in Transition Kobi Gol, Solution Manager for Utilities, Transportation and Migration RAD Data Communications Power utility networks today are undergoing a revolutionary transformation. The SDH/SONET infrastructure and legacy substation devices are being phased out to make way for Ethernet transport and IP/packet-based networks. Driving the transition to next generation communications is the move towards Smart Grids, with functionalities like IP SCADA systems, the recently established IEC 61850 substation automation (SA) standard, as well as high-resolution, IP-based video surveillance. Packet transport’s high capacity and lower operational expense are wellsuited to handle the bursty traffic generated by the advanced grid applications envisioned in intelligent power networks. Accordingly, nearly every power utility is planning or has already begun the transformation of its T&D grid into an intelligent, packet-based network. The decision on which packet technology to use depends to a great extent on who is driving the transition within the utility organization. Those in charge of the distribution network, particularly the HAN (Home Area Network) and smart meters, tend to prefer routable IP/MPLS for its simpler addition of new devices to the network. Operations engineers find Layer 2 technology easier to manage in terms of bandwidth control, OAM (operations, administration and maintenance) and security. While the smart grid migration is inevitable, utilities remain cautious about IP transformation. They hold the deterministic behavior and high reliability of TDM (time division multiplexed) networks as the gold standard. In particular, certain utility applications such as SCADA and GOOSE (Generic Object-Oriented Substation Event) messaging require dependable service assurance tools to ensure low end-to-end delay, high availability and resiliency. Almost all applications require 99.99 or 99.999 percent availability. Packet technologies, and specifically Ethernet, have matured enough so that they now include mechanisms to guarantee this performance level. The coexistence of newly-introduced IP connections and next-generation equipment with legacy infrastructure and substation devices results in two types of communications traffic that must be transmitted over the utility network. These are Ethernet and IP-based data and signals from SA IEDs (intelligent electronic devices) and TDM-based traffic from existing equipment, e.g., analog voice, serial SCADA and Teleprotection signals. performance are required while it traverses the packet network. Along with native packet-based traffic, PWE requires a comprehensive set of carriergrade Ethernet tools to manage these performance dimensions. Carrier-Grade Ethernet Mechanisms Ethernet is no longer the LAN-oriented, connectionless-only technology it used to be, one that was associated with best effort performance. In recent years industry standards bodies have helped engineer Ethernet into a technology that features robust performance guarantees, reliability schemes and service management tools. These advancements have led to worldwide double-digit adoption rates of carrier-grade Ethernet. This shows the various steps that communications traffic undergoes as it moves through the network. Traffic Types and Transmission Scenarios This shows how legacy traffic is encapsulated as it moves through the packet network, emerging on the other side in its original form. Newly deployed Ethernet/IP/MPLS networks offer a native communications environment for that traffic. TDM-based traffic, however, requires special mechanisms for delivery, such as pseudowire emulation (PWE). This is an encapsulation method that allows a seamless connection by creating logical links, or virtual tunnels, between two elements across the packet network, while emulating the attributes of a TDM service. While other methods are anticipated in the future, PWE is currently the prevailing method for delivering traffic between legacy devices in a packet-based environment. There are several different standard protocols for PWE (among them SAToP, CESoPSN, and TDMoIP). Regardless of the specific standard used to carry the TDM traffic, control and monitoring of pseudowire 12 Ethernet advancements allow the use of mechanisms to provide missioncritical substation applications such as SCADA and IEC 61850 GOOSE messaging with the level of deterministic quality of service and priority they require. By managing bandwidth consumption and transmission priorities with CoS (Class of Service) granularity, multi-level hierarchical traffic management enables the desired performance, thanks to these tools: • Classification of incoming traffic into flows according to type and required CoS. Ethernet supports a wide variety of sorting criteria, such as VLAN-ID, Priority Code Point (PCP/P-bit) and MAC/IP address marking, to allow traffic identification in fine granularity. • Metering and policing for each flow to regulate traffic according to pre-defined bandwidth profiles. Rate limiting admits traffic into the network based on color: Green (admitted frames), yellow (“best-effort” transmission), or red (discarded frames). • Hierarchical scheduling defines the order in which the various flows are forwarded, using a two-step scheduling mechanism so that each flow receives the desired priority. In this manner, higher priority traffic is serviced first, while still preventing lower-priority queues from being “starved.” • Shaping to smooth out bursts and avoid buffer overruns in subsequent network elements. • Packet editing to signal proper handling instructions for subsequent network elements and ensure data integrity. Packet-based traffic management and hierarchical QoS tools. Carrier-grade Ethernet offers a wealth of tools to test, monitor and troubleshoot the operation of communications links. A comprehensive Ethernet OAM suite, along with delay, jitter and packet loss measurement schemes, diagnostic loopbacks and other means, are available remotely. They automatically perform the following procedures: • Connectivity verification • Stress testing • Performance monitoring • Fault detection • Fault propagation and isolation Performance Monitoring and Testing www.RemoteMagazine.com http://www.RemoteMagazine.com

Table of Contents for the Digital Edition of Remote - Winter 2012

Remote - Winter 2012
Editor's Choice
Automated Monitoring Out at the Network Edge
What’s in Your Radio Communication Tackle Box?
When Does Solar Make Sense for Remote Sites?
Utility Networks in Transition
TV White-Space Technology Makes Broadband Affordable for Remote Locations
Challenges of Remote Management over Satellite
SCADA Market: Charting Strong Growth Amidst Industry Speculation
SCADA
Networking
Security
Oniste Power
Environmental Monitoring
Industry News

Remote - Winter 2012