Fiber ring topology provides both distance and resilience

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.

PPP, EAP, 802.1x…what’s the difference?

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:

5 ways to get more mileage from your existing infrastructure

#1. Repurpose unused phone wires for Ethernet.

Campus phone systems are usually built around 25- and 50-pair trunk cable. Most of these wire pairs are redundant and not used as phone lines. These spare pairs can be commandeered for Ethernet through the use of Ethernet extenders, which not only transparently establish a network connection on phone cable, but can also extend links farther than the usual 100-meter limit for Ethernet on copper. Ethernet extenders are an ideal solution for linking isolated workstations without laying new cable.

#2. Upgrade to fiber on your existing copper ports.
Fiber optic cable has many advantages, including speed, distance, and resistance to EMI/RFI, plus it’s now usually less expensive to install than the equivalent copper infrastructure. What usually stops the installation of fiber is the prospect of having to replace expensive network switches with fiber switches and having to install fiber NICs in PCs.

Media converters are a simple way to convert the RJ-45 ports on existing equipment to fiber. Because media converters are transparent to data, they’re “invisible” to the network—literally plug-and-play. In the data center, modular media converter systems feature powered chassis that house and power multiple media converters—a whole switch’s worth of copper ports can be converted to fiber without cluttering the rack. On the desktop side, tiny USB-powered media converters bring fiber to the desktop without the driver issues and incompatibilities created by fiber NICs.

Going where your network doesn’t want to go

One of the most aggravating infrastructure challenges occurs when you get asked to put a workstation in some inconvenient, too far, difficult-to-wire spot. If there’s a room at the far end of some unused hallway, or a shack at the edge of campus, chances are you’re going to get a request for an Ethernet port there.

Whenever you need to put a connection in one of these types of places, your first move should be to check to see if there’s any existing cable that can be adapted for Ethernet by using Ethernet extenders. Most modern buildings have unused voice-grade wires or unused coax. Additionally, many campuses have installed 25- or 50-pair telephone trunk cables between buildings. You can hijack these unused wires for Ethernet use.

A simple option for expanding your corporate or service-provider LANs!

Ethernet extenders are easy to set up—all you need to do is to plug in one at each end of the twisted-pair wire or coax. Sometimes you’ll also need to set a DIP switch for local or remote operation. Once the Ethernet extenders are installed, there’s nothing to configure, and the extenders are transparent to network operation.