What Does “Five Nines” Mean to You?

By: John Shepler

Five nines reliability. It's the standard often quoted for traditional telephone service and top network equipment vendors. But what does it really mean? Just how close to perfect is five nines anyway? Let’s take a look.


Reliability or Availability
The spoken term five-nines refers to the number 99.999%. This number is generally referred to as a reliability figure. Actually, what people call reliability is more correctly called "availability." It's not just how often a piece of equipment has a software crash or a power supply bursts into flames that is really important. It's how much of the time you actually get to use it. In other words, how much of the time is this particular device available. Availability includes how often it breaks and then how fast it gets put back into service. You also have to include how often it is out of service or unavailable due to routine maintenance.

An Example
Say your softswitch has a software glitch that only shows up under obscure combinations of events. When the glitch occurs once every six months, the software crashes and automatically reboots. That takes a minute. Does this switch have five nines uptime? Yes. Now if a power supply smokes once a year and it takes 20 minutes to fix it, that's not good enough for five nines even though the power supply failure occurs less frequently.

By the Numbers
Here are some handy numbers to give you perspective on the whole nines issue:

Five nines or 99.999% availability means 5 minutes, 15 seconds or less of downtime in a year.

Or, if you are really ambitious, shoot for six nines or 99.9999% availability, which allows 32 seconds or less downtime per year.

Otherwise, four nines or 99.99% availability allows 52 minutes, 36 seconds downtime per year.

Three nines or 99.9% availability allows 8 hours, 46 minutes downtime per year. This is often acceptable for many non-critical applications.

Two nines or 99% availability allows 3 days, 15 hours and 40 minutes downtime per year. That’s somewhat marginal for business.

One nine or 9% availability allows over 332 days of downtime per year. That's right. You're only up and running about a month out of the year on average.

Zero nines, of course, is totally useless. It's 100% downtime per year.

How do you get more nines?
Buy the best equipment that's the easiest to repair. Then add redundancy. Highly reliable systems often include multiple power supplies & processors, plus battery backup, diesel or natural gas generators for longer power outages than batteries can handle, multiple diverse communication lines and extras of whatever else is likely to fail. Buggy software that crashes all the time is going to hurt your reliability. If it goes down a lot and takes a long time to get back online your availability also be hurt.

Include Everything
One thing to be aware of is that the five nines criteria tends to apply to whatever the person quoting it says it applies to. PBX systems that meet five nines availability may only do so for the core system and might not include individual line cards and certainly not the phones themselves and their wiring. If it's REALLY important that you minimize downtime, you need to consider EVERYTHING that can fail and make sure it is backed up and/or very easy to fix.

On Cloud 9’s
Another option to consider seriously is to move all those hardware availability issues to the cloud. Cloud services aren’t perfect, either, but they often can provide higher service availability than you can afford locally. That’s because the cloud architecture is designed for considerable redundancy and fast failover when problems occur. If you do opt for the cloud, though, be sure you have highly reliable bandwidth connections to your provider. A 5 nines hosted PBX system isn’t all that available if you have a flakey internet connection from your facility to the cloud. A dedicated SIP Trunk or a set of redundant trunks is a much better solution.

Nines for Your Needs
How many nines do you need and what’s the cost for WAN or cloud availability? Get the best price vs performance options for your particular requirements now.

100 Mbps Business Ethernet vs OC3 SONET Bandwidth

By: John Shepler

Many high tech companies and large corporations got into fiber optic bandwidth service years ago. The service they chose was the one available: OC3 SONET. Since then, many have upgraded to higher speeds, also in the SONET family of service, or simply stuck with the OC3 that has been performing reliably over the years.

The entrance of 100 Mbps and higher Ethernet MAN and WAN bandwidth is challenging the dominance of SONET fiber service. Long time users are taking a closer look at the competition. Companies upgrading or ordering bandwidth the for first time are doing their homework before choosing one technology over the other.

SONET (Synchronous Optical NETwork) in the SDH (Synchronous Digital Hierarchy) became the core of most metropolitan, wide area and international networks over the last decades. It was originally developed as a massive telephone trunking technology designed to bundle hundreds and thousands of simultaneous phone calls for long distance transport. With the rise of computer to computer communications and the Internet, SONET services were the logical choice to carry data packets as well as voice channels.

What does SONET have going for it? It is a very mature and well supported technology understood by all of the telephone companies and most network carriers. It is highly reliable and can survive certain fiber cuts and equipment failures. There are a number of service levels available between 155 Mbps and 100 Gbps. Costs have also come down over the years to the point where even smaller companies can consider the entry level OC3 SONET service.

Why throw over a winning service for a newer technology like Carrier Ethernet? It comes down to cost, service features and scalability.

In case you haven’t noticed, just about everything that can communicate uses Ethernet. This includes nearly every corporate LAN, all PCs, printers, scanners, routers, network switches and wireless access points. That’s expanding now to telephones, televisions and any other equipment that is joining the “Internet of Things.” Why not an all-Ethernet world?

The brand of Ethernet that leaves your property is called Carrier Ethernet. It has been standardized by and industry group, the Metro Ethernet Forum (MEF), so that it works over long distances, has the operations and maintenance features needed for carrier operations and is compatible from provider to provider.

Let’s compare two very common bandwidth services: 100 Mbps Ethernet vs OC3 SONET. Both are provided over fiber optic strands and delivered to your organization at a specified demarcation point. For Ethernet you use a simple Ethernet copper or fiber patch cord to connect your equipment to the carrier’s demarc. OC3 requires a special interface module that plugs into a router to convert between the Ethernet on your LAN and the SONET that runs on the carrier lines.

This is one reason why SONET is losing ground to Ethernet. If your network and everything on it is running Ethernet, why do a protocol conversion from Ethernet to SONET and back again at the far end just to send Ethernet packets from point to point over to the Internet? There are inefficiencies associated with that conversion process. Plus, you need a specific interface module for each SONET level. An OC3 module won’t work for OC12 or OC48.

SONET has specific service levels, although you can sometimes get fractional or rate limited services below the maximum line speed. Ethernet is scalable by design. The carrier provides an Ethernet port with a maximum speed, typically 100, 1,000 or 10,000 Mbps. Your actual service level can be any speed up to the capacity of the port. You pretty much pay for the bandwidth you are actually using rather than the capability of the circuit.

Scalability can also save you money. A 100 Mbps or Fast Ethernet connection on a 1,000 Mbps Gigabit Ethernet port can be scaled up or down easily. With SONET you start out at 155 Mbps for the entry level OC3. That sounds like 50% more bandwidth and it is. However, many companies really need 50 or 100 Mbps but had to buy 155 Mbps because it was that or nothing. If your 100 Mbps Ethernet connection bogs down, you can call the service provider and ask for an upgrade to 150 or 200 Mbps and have it in a matter of hours or days. If you tap out an OC3 connection, you have to wait days or weeks for an upgrade to the next generally available SONET level of OC12 at 622 Mbps.

Besides being able to order just the bandwidth you need now while knowing that you can easily upgrade when the need arises, Ethernet service tends to be less expensive than SONET on a per Mbps basis. But how about the quality of service? Both can deliver your packets with high reliability, low latency, and rock solid bandwidth. SONET tends to have fewer “flavors” available. It’s usually a protected ring arrangement with symmetrical dedicated bandwidth and five-nines (99.999%) reliability.

With business Ethernet, you need to be aware of what you are ordering. You can now get Carrier Ethernet with the same redundant path protection as SONET to ensure that if one circuit fails, the system will automatically switch to the other path in under 50 mSec. You can also get the same 99.999% reliability, low latency & jitter, and symmetrical dedicated bandwidth that you’ve come to expect with SONET services. However, if your applications aren’t so critical and you are more interested in saving money than in having the ultimate in performance, be aware that you can also order Ethernet services with asymmetrical bandwidth, shared bandwidth and unprotected circuits. These flavors of Ethernet work well for general Internet usage and casual PC backup to the cloud and are considerably cheaper.

Is SONET or Ethernet the best choice for your business bandwidth needs? Get free consulting help from a bandwidth expert who can also get you the best pricing from multiple carriers who offer services for your location. Also get instant online quotes for many bandwidth services up to 1 Gbps.