Fiber optic leased lines have been employed for decades by major corporations and businesses, like video production and distribution, that can’t function without the bandwidth fiber affords. Nearly all of this bandwidth has been supplied by a telephone industry standard called SONET for Synchronous Optical NETworking.SONET picks up where T-carrier stops. T1 is good for 1.5 Mbps and up to 12 Mbps when multiple T1 lines are bonded. T3, often called DS3, is a 45 Mbps service, although it can be rate limited to 10 or 20 Mbps to lower costs. DS3 stands at the crossroads between copper and fiber. DS3 bandwidth is most often carried on a multiplexed SONET service for most of the transport distance and then converted to coaxial copper connections at the customer site.
SONET fiber optic lines start with OC-3 at 155 Mbps. Like DS3, OC-3 can be rate limited to offer fractional OC-3 bandwidth at 50 or 100 Mbps. Most often it is leased as a full rate OC-3 service.
Other SONET service levels offer increasing bandwidth. OC-12 runs at 622 Mbps. OC-24 is a Gigabit service running at 1.2 Gbps. It is not widely offered. The next popular SONET service is OC-48 at 2.5 Gbps. OC-192 steps this up to 10 Gbps. OC-768 is a 40 Gbps line service that has been popular as a carrier backbone but now offered to businesses in some areas.
Note the big gaps in bandwidth between the SONET optical carrier levels. If you need a Gigabit connection, you may have to order an OC-48 service even though it has twice the bandwidth you require. We’ll take a look at how Carrier Ethernet is far more scalable and can give you fine degree of granularity for selecting just the right bandwidth for your applications.
Another thing about SONET is that it is a TDM or Time Division Multiplexed technology. This means that the signal is a string of bits divided into small channels and carefully synchronized to communicate with other SONET lines. Why this arrangement? It is the telephony legacy of SONET. It was designed to be compatible with Bell’s T-Carrier standards that are also TDM-based. Each channel in a T1 line or OC-768 is 64 Kbps to support one telephone call. Of course, these channels can now be combined so that you can use the entire line capacity less overhead to transport your data packets.
Since SONET is not a packet switched protocol, you need a protocol converter to translate between TDM and Ethernet in order to get your network data from place to place. That is generally a plug-in module for your router. Each SONET level has a specifically designed module that is unique to that optical carrier level.
What SONET has going for it is a long history and extensive deployment worldwide. You don’t have to worry about the intricacies of protocol conversion or signal interfacing, as they problems were solved long ago. SONET is most popular when deployed in rings of two redundant fibers that can switch in under 50 Msec to keep the data flowing even when faults in the system occur. Most metropolitan and long haul fiber optic networks are set up in the SONET ring topology for reliability.
What now competes with SONET is Ethernet over Fiber (EoF). Yes, this is the familiar Ethernet protocol that runs on your LAN but extended for long haul transport. The extended protocol is called Carrier Ethernet.
The advantages of Carrier Ethernet include easy and rapid scalability, a packet oriented protocol directly compatible with nearly all company networks and edge routers, and a considerable cost savings compared with SONET. Typical service levels start at 10 Mbps, the standard Ethernet service level. Other popular options are 100 Mbps Fast Ethernet, 1000 Mbps Gigabit Ethernet (GigE) and 10,000 Mbps or 10 Gigabit Ethernet (10 GigE).
You aren’t limited to these particular service levels. You can pretty much pick any bandwidth you like as long as the Ethernet Port installed at your facility can support the maximum speed you require. Easy scalability also means that you can often simply call your service provider and request an increase in bandwidth. It’s likely to be available in a matter of days if not hours.
Ethernet over FIber was almost unknown even a few years ago but now widely deployed. If available at your location, you’ll find that the cost per Mbps is much lower than SONET, perhaps half the cost for the same bandwidth. This is why Carrier Ethernet is rapidly taking over the fiber optic transport market, although SONET prices have also been plunging in response to the new competition.
Does your company require higher bandwidths that you can get from copper wireline services? Are you using fiber now but wondering if you can get a better price? Do you have a new application and want to get the best deal on bandwidth? If any of these apply, get competitive quotes on SONET and Ethernet fiber optic leased lines available for your business location.
