Need to Know - Fast Switched Ethernet

Orna Berry, co-founder of Ornet Data Communications, an Israeliswitching manufacturer, discusses the benefits of deploying 100Mbps fastEthernet.

The Fast Ethernet market has taken off. Where are people deploying 100 Mbps Ethernet technology today?

The most common use of Fast Ethernet is as a Lan backbone, often interconnecting Ethernet switches which are being used as edge devices. One such network is at Carnegie Mellon University in Pittsburgh, Pennsylvania. This network is famous for its size - it has 9,000 end-stations - and for early adoption of simple network management protocol (SNMP), home SNMP and SNMP applications. It is also notable for its original use of the Cisco AGS+ as a collapsed backbone, or a backbone in a box in the very early 90s, and its continuous evolution of multistage switched networks. Networks that are called 'switched' use industry known, Ethernet-categorised switches and multiport Ethernet routers (used in bridged mode) which serve as scalable Ethernet switches.

What is the second most common reason for deploying Fast Ethernet?

Fast Ethernet can be used effectively in high speed interfaces to connect servers in a client server environment. One reason why the common availability of 10/100 Mbps Network Interface Cards (NICs) has not promoted a greater use of Fast Ethernet technology is that it requires changing the infrastructure from CAT 3, used by Ethernet, to CAT 5. The wiring cost far exceeds the cost of the devices (switches and NICs combined), and while switches can bring 10 Mbps to the desktop with the current infrastructure, this is not the case for the 100 Mbps connections. This is why 100 Mbps Fast Ethernet is seen today in the Lan backbone and in server connectivity but not in general use, even if 10/100 NICs are available.

Will the emergence of ATM reduce the popularity of Fast Ethernet?

I believe the contrary is true. Ethernet Lans with an ATM backbone require the changing of the Ethernet frames into ATM cells and the transformation of ATM cells back into Ethernet frames. Moving frames between Ethernet and Fast Ethernet requires no transformation, so it is simple and cost effective. This is why we see the emergence of Gigabit Ethernet as a candidate as a Lan backbone for Fast Ethernet. We therefore see that the emergence of Fast Ethernet products defers the use of ATM for some time to come.

What influence are applications having on the deployment of Fast Ethernet?

Applications such as multimedia, Internet and Internet telephony are encouraging the deployment of Fast Ethernet to the desktop. The need to improve real time services for Ethernet is motivating the IEEE 802.1 standardisation body to promote additional standards such as Virtual Networking (VLAN) with priorities. This will enable real time traffic on the Lan to become more feasible. Wan high performance applications will also require ATM's capacity and services.

Is there much difference between the cost of Ethernet and Fast Ethernet cards and switches?

I have already mentioned that Fast Ethernet wiring is more expensive than wiring required for Ethernet. NICs cost about the same and are sold as serving both Ethernet and Fast Ethernet. Ethernet switches are still significantly more expensive for Fast Ethernet. With Ethernet switching becoming more and more common, Fast Ethernet will soon become a commodity, and Gigabit Ethernet will allow further migration serving as a Fast Ethernet backbone and server applications. According to recent figures (source: Infonetics Research, 1996), Fast Ethernet ports remain twice as costly as Ethernet ports. That price difference is likely to become smaller over time.

What is the emerging architecture of those Lans that are cost conscious and performance hungry?

Multi-stage switched architecture is beginning to establish its presence on the market. Which is to say that Switched Ethernet to the desktop with Fast Ethernet Switching in the backbone, and Fast Ethernet connectivity to high performance servers and stations. Gigabit Ethernet is emerging as a follow up to Lan switching and high speed linking technology. This migration uses the current infrastructure while exploiting parallelism and providing higher aggregate bandwidth. By multistage switched Lans, I mean that front end connections are switched and interconnected via backbone switches.

In the future, we anticipate a new tier of Lan switching to serve as a backbone for today's backbones (i.e., Gigabit switching). We see this trend in today's large networks such as the Carnegie Mellon University network.