Generally speaking, symmetrical type bandwidth is considered "commercial grade" and tends to be used by the SMB/Enterprise market VS. consumer/residential end users. All because of the reasons I listed above, plus it lends itself to work better in a LAN environment- as the circuit is robust, efficient, and quite reliable, etc. You really get what you pay for. Finally, if you have applications that require real time traffic, such as: VoIP, SIP, and video conferencing + Citrix, VPN, heavy file transfer- commercial bandwidth (T1, DS3, Metro Fiber Ethernet) is essential.
Optical carrier services such as SONET and Gigabit Ethernet are becoming more available and less expensive as the need for bandwidth increases to support such applications as enterprise VoIP, tele-radiology, off site data backup for disaster recovery and video transport.
SONET, the Classic Optical Carrier
SONET is an acronym for Synchronous Optical Network. SONET was developed as a set of standards for telephone carriers in the mid-1980's. SONET picks up where lower speed trunk lines leave off but still maintains compatibility at the digital signal level.
For instance, the basic signal level for SONET circuits is STS-1 for synchronous transport signal. It's speed is 51.84 Mbps which is capable of carrying 1 DS3. A DS3 is the same digital signal level used by a 45 Mbps T3 line in the copper type carrier world. It is also the capacity of 28 DS-1 signals, the same as 28 T1 lines. When carried on fiber optic cable, a STS-1 signal is called an OC-1. An OC3 line would be the equivalent of 3 T3 lines and an OC48 would have the same capacity of 48 T3 lines.
SONET was designed to carry telephone conversations, so it handles the TDM (time division multiplexing) digital voice channels from PBX and telephone carrier switches easily. Because it is synchronized like the T-carriers, you can add or remove channels at will with an add-drop multiplexer. This makes it easy to interconnect a group of locations in a regional or even nationwide network.
SONET can be provisioned as a point to point circuit or hub and spoke star network, but the protocol really shines when it is set up as a ring of two independent loops. The system is designed to automatically switch from the main to the backup loop in 50 milliseconds or less if a fault occurs. This is called automatic protection switching.
Data over SONET
Like T1, SONET was originally designed to handle high capacity telephone traffic in digital format. It has since been used to carry high speed digital traffic, including backbone service for Internet Service Providers. ATM, Frame Relay, and Ethernet protocol signals can all be encapsulated and sent over SONET ring networks. If you are using a T1 or T3 data line now, it may well be carried by an optical network and dropped off and converted to the copper signal format at your location.
IP Services
Internet Protocol has become the defacto standard for data communications. Switched Ethernet networks running at 10 Mbps, Fast Ethernet at 100 Mbps, Gigabit Ethernet at 1 Gbps and 10 Gig Ethernet at 10 Gbps are the basic network speeds for large and small enterprises alike. The beauty of IP based services is that a corporate network in one city can connect via an Ethernet service provisioned on fiber optic cable to a similar network in another city and they'll work like one big network. The fiber optic circuit is simply a long, very long, network cable.
The current trend is to convert everything into IP format so that telephone calls, file transfers, Internet service and video conferencing can share the same network. That process is called convergence. Converging all those proprietary networks into one big one often has cost savings benefits especially at the enterprise level. You'll just have to be sure to have enough network bandwidth to handle all the extra data packets and quality of service management tools to ensure that voice and video signals get the priority they need to run as well as they did on their own networks.
