1. ERCOT Wide Area Network Overview & EDS Communication Standard John Fisher ERCOT Network Manager

2. 2 ERCOT WAN The ERCOT WAN consists of 2 separate Wide Area Networks –IP WAN –Voice and RTU WAN (aka “Point-to-Point network) IP WAN (MPLS) –MPLS on Sprint network –Each MP is allocated 1.544Mbps bandwidth –ERCOT “core” is allocated 9Mbps per site (Austin and Taylor) –Majority of traffic is XML, HTTPS, and ICCP Voice and RTU WAN (Point-to-Point) –Dedicated T1s through AT&T DACS network –Provides connectivity for voice systems (turret, hotline, OPX) –Provides connectivity for RTUs –Provides redundant data connection for IP WAN

3. 3 IP Data WAN Overview

4. 4 Voice & RTU (Point-to-Point) WAN Overview

5. 5 ERCOT Internet Presence Highly secure –Encrypted data communications –Identity validation via digital certificates –Layered security architecture –Protected DMZ Highly reliable & highly redundant –Multiple layers of hardware redundancy –Adequate bandwidth –Multiple DNS servers –Redundant, diverse, carrier connections –Private IP space

6. 6 Internet Design Overview

7. 7 ICCP ICCP Stats (An example of a Market Participant) Currently runs at approx 128Kbps Nodal testing will increase their ICCP load by 100% Anticipate roughly 256Kbps of ICCP load. This is 25% of circuit capacity Capacity Calculation Total reliable* capacity is 1024Kbps –Equation as follows Point-to-Point T1 capacity = 24DS0 x 64Kbps each = 1,536Kbps Must reserve 8 DS0 (512Kbps) channels for voice 1,536 – 512 = 1024 * Reliable capacity is defined by amount of available bandwidth on Point-to-Point WAN. The MPLS network is capable of 1.544Mbps; however, we can only guarantee reliability of up to 1024Kbps due to requirement of dynamic failover to Point-to-Point network in the event of an MPLS network failure.

8. 8 Approach to EDS We do not want to impact Zonal production traffic with Nodal test traffic. All non-ICCP EDS traffic will transit the Internet. Once trending and analysis are complete, a determination will be made regarding availability of web services over the WAN. We hope to have statistical analysis complete by March 2008. The expected outcome of the analysis is that most, if not all, non-grid critical traffic will be moved to the Internet.