IP Convergence: Beyond VoIP, Beyond Cost Savings

Don't get me wrong, Bob Metcalfe invented a good thing in Ethernet, but I wonder if people aren't just a little too in love with it. I've been a happy user of Ethernet ever since I first got into networking. I never really had to deal with token ring, although I did work with FDDI a bit in the early nineties. I even had the joy of working with 10base2 (thinnet) and 10base5 (anyone remember vampire tap transceivers?) when I was an assistant network manager at the UofA, which was a royal pain in the neck troubleshoot when it broke, and I'm very happy for everyone that 10baseT is now the standard for everyday ethernet use (100mbit and lower).

But I'm not talking about any of that. What I'm talking about is everyoine asking for their network service as ethernet. It's not a problem in and of itself, but what I have personally found (and would love to be validated in this, so please leave comments) is every customer that asks for it wants it for a different reason, and many of those reasons are false, based on misconstrued data and market propaganda.

When I ask customers why they want ethernet, here are some the answers I've heard (all of which stem from some sort of misconception):

• I want you, my VPN provider, to have a demark at my premise
  
• It's simpler, because it's layer 2
  
• I can use cheaper hardware because I don't need routers any more
  
• VPLS is a superior way to build VPN's

Part of the problem is that there are so many ways to utilize ethernet as part of a network design, but I emphasize that it is part of a network design, not usually the network design itself.

Let's take each of the misconceptions one at a time. Ethernet does not necessarily mean the provider has a demark at your premise. It depends on how it's delivered. Unless a customer specifies that they are looking for a managed service where we put a router at your prem and manage it for you, we'll assume that you want to get a quote for an ethernet local loop from your local provider, and we'll use that to deliver access to your location instead of a traditional T1/E1/DS3/OC-n local loop.

The next one is one of my favorites, because using a protocol designed for LANs and putting it in the WAN is anything but simple. Some of you IT managers probably still have to deal with those nasty things called broadcast storms because you've got too many PC's on your network trying to talk at the same time. The problem is solved by breaking the network up into multiple collision domains by adding routers. Now, imagine that your LAN now has as much as 200ms of latency between nodes, and imagine the effect of a broadcast storm. Disasterous! Don't plan on connecting your switches right to an all ethernet WAN, not only is it a recipe for disaster but with many implementations of ethernet VPNs it doesn't work because each path to each site is mapped into a different Virtual LAN (VLAN), and recombining these VLAN's into one LAN requires a router, even if you're using VPLS.

So, all that said, there are still good reasons to use ethernet. For one thing, the cost of a router interface is cheaper than that of a SONET interface on a per-meg basis, especially if you use one of those hybrid switch/routers like you'll find from vendors such as Foundry and Cisco (their 7600 OSR). Also, some local carriers to have an ethernet product that offers a better price/meg on Ethernet than for traditional pricing. Availability of such access can really help you stretch your IT budget dollar to provide more for your internal customers.

If this proves to be a topic of interest for our readers, I'll be sure and post many followup blogs on this subject.