(By Black Box) Although Ethernet is usually thought of as having a star topology, it’s also possible to build an Ethernet network as a ring. This configuration has the advantage of providing a redundant pathway if a link goes down. A ring topology is often used in application such as traffic signals and surveillance, where long distances may make it difficult to run fiber in a star formation from a central switch and where downtime must be minimized.

The key to the ring topology is spanning tree protocol. One switch-in this case, the switch in the central office-is the root of the spanning tree. A node on the opposite side of the ring blocks on of the ports leading back to the root switch, creating a topology that functions like a long line of Ethernet switches. If a link breaks, the network reorganizes itself to relink all the switches. Although this convergence isn’t instantaneous, it takes only a few seconds to bring the network back. In the diagram below, Hardened Managed Ethernet Switches create a ring topology that operates at Gigabit speed to support traffic cameras at the interaction. Industrial Ethernet Serial Servers make the connection from the switch to the serial interface on the traffic signals, enabling central management of the lights across the Ethernet network.

When most people think of counterfeit and substandard cable, they think of bulk cable and their backbone and horizontal runs. But don’t underestimate the importance of patch cables in your channel. Patch cables are the most overlooked component of the Permanent Link. Remember the saying, “A chain is only a strong as its weakest link?” The same principle applies to the permanent link. If a patch cable is non-compliant, it can ruin expensive electronics, invalidate warranties, cause poor network performance, and lead to a loss in productivity. Risky business.

The CCCA did large-scale performance testing of Category 6 copper patch cords. Test results showed an 85% failure rate in cables produced offshore by companies who are largely unknown in North America. 78% of the failing samples failed NEXT tests by a margin of 3 dB or more. A second sample set of Category 6 copper patch cords produced by multiple, well-recognized manufacturers was also tested and showed a 0% failure rate.

To further read this guide please click 'The importance of superior patch cables'

BlackBox: The PPP, EAP, and 802.1x protocols are often confused with each other, which is no wonder because they’re all interrelated and involve authentication.

Point-to-Point Protocol (PPP) was originally a protocol for connecting and authenticating dialup modems. Today’s PPP is usually encapsulated in Ethernet frames and operates over Ethernet as PPP over Ethernet (PPPoE). PPPoE is commonly used for cable modem or DSL connections to an ISP for Internet access. PPP includes two authentication mechanisms: Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP).

Extensible Authentication Protocol (EAP) is an authentication protocol framework that works inside PPP to provide support for authentication protocols beyond the original PAP and CHAP protocols. EAP supports a wide range of authentication mechanisms including Kerberos, passwords, certificates, and public key authentication, as well as hardware schemes such as authentication dongles, smart cards, and USB tokens.

802.11x simply takes the EAP framework out of PPP and puts it into Ethernet, packetizing it for transmission over a wired or wireless network. 802.11x has three parts:

• Supplicant: A user who wants to join the network.
• Authenticator: An access point, switch, or other device which acts as a proxy between the user and the authentication server.
• Authentication Server: A server, usually a RADIUS server, which decides whether to accept the user’s request for network access.

When a user tries to access a network through a wireless access point or by plugging into an Ethernet port, the authenticator—usually an access point or switch—consults with the authentication server before allowing the user onto the network.

OPC Foundation and PLCopen have combined their technologies to form one platform and manufacturer-independent information and communication architecture. The mix of OPC Unified Architecture (UA) and IEC 61131-3 is thus the future-safe basis for the realisation of automation tasks.

The objective is to increase the reusability of controller and visualisation modules and their communication and thus to considerably increase efficiency in the engineering process.

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