7 Types of Circuits Suitable for SIP Trunking

This is our 5th of 12 blogs on the subject of SIP Trunks. Subscribe in the box to the right to receive an email notification for each one in the series.

Looking for circuit options for SIP Trunking in the San Francisco Bay area? See what options await you, as we break down the 6 options that are at your disposal in our area.


Fiber has been around for a while, but what’s new is that it is now being widely installed in business offices. AT&T alone is spending $6B by 2015 on fiber. Fiber circuits can handle vast amounts of bandwidth. However, fiber is not everywhere, and it’s expensive to lay new fiber cable. If you are lucky, your building is already “lit”. 

Bandwidth: 10MB to over 1GB

Type: Synchronous, bandwidth guaranteed

Price*: $599 for 5MB, $1,799 for 100MB

Lead Time: 3 weeks to one year

Ethernet over Copper (EoC)

This again is a newer technology. It uses old copper wires and “bonds” them (up to 24 pairs) to increase speed. It is the least expensive business-class synchronous data circuit. This service is not available to businesses located far from a Central Office. 

Bandwidth: 1.5MB to 50MB

Type: Synchronous, bandwidth guaranteed

Price*: $249 to $1,799

Lead Time: Three weeks to three months


Cable companies provide cheap and plentiful bandwidth, so their circuits provide plenty capacity for voice and data for smaller offices. However, cable companies offer their basic business service on a “best efforts” basis, meaning that they don’t guarantee quality or reliability. For smaller companies, this “best efforts” approach has been adequate, but expectations need to be managed. It has been our experience that “your mileage may vary” but, in general, it’s good enough for voice for smaller offices (less than 15 users). It is recommended to establish QoS on any cable circuit to prioritize voice.

There is a caveat when working with Comcast in the Bay Area. They will sign contracts for locations for which they do not have service. They then attempt to get the landlord to pay the construction costs and try to sell other customers within the building. If they are not successful, they will refuse to deliver service or present the customer with the construction bill. The highest construction bill that we’ve seen was over $100,000.  The customer promptly ripped up the contract.

Bandwidth:  3MB upload/20MB download – 20MB upload/150MB download.

Type: Asynchronous, bandwidth – best efforts

Price*:  $39 – $199

Lead Time:  One month to infinity


A single T1 has 1.5MB of bandwidth. T1’s are old technology, but they are reliable. They can be bonded together to increase bandwidth to 6MB. T1’s are rapidly being replaced by newer technology that is less expensive and provides much greater bandwidth. If you have a contract, you’ll have to keep your T1 until the contract expires. Until then, you’ll have a high quality/low bandwidth reliable connection for your SIP Trunking

Bandwidth: 1.5MB – 6MB (four T1’s bonded)

Type: Synchronous, guaranteed bandwidth

Price: $240 – $970

Lead Time: 3-4 weeks


The bandwidth required for one uncompressed phone call is 80K. The slowest DSL connection provides 384K upload speed. Simple math would indicate that the circuit would support four simultaneous calls. However, that leaves no room for any data that is impractical. So, if your company has an older slow speed DSL circuit, VoIP will not work.  

Bandwidth:  384K/1.5MB – 1.5MB/6MB.

Type: Asynchronous, bandwidth – best efforts

Price*: $29 to $99.

Lead Time: 2-3 weeks


There is a relatively new type of DSL called ADSL2+, and it is an improvement over traditional DSL. AT&T (UVerse Max product), Sonic.net and TelePacific are San Francisco Bay Area Internet providers who utilize this technology. ADSL2+ allows for several calls while leaving suitable bandwidth for Internet access. Our experience is that it works well in very small environments. Having said that, DSL is the least suitable choice for VoIP and a hardware QoS device is highly recommended.

Bandwidth:  1MB/12MB – 3MB/40MB

Type: Asynchronous, bandwidth – best efforts

Price*: $29 to $99.

Lead Time: 2-3 weeks


Wireless Internet circuits are typically not recommended for SIP Trunking applications. There are many different types of technologies and frequencies used for wireless data, and each produces different results with VoIP. Some of them are susceptible to transmission failures due to inclement weather. With so many variables, it’s hard to speak generically to the suitability of wireless Internet for SIP trunking. However, it is possible in some areas to find a wireless provider who has VoIP technology down.

      * PRICING:  All pricing is based upon averages in the SF Bay area on July 2014.

Best Efforts Vs. Guaranteed Business Circuits

DSL and cable are both services that are provided on a “best efforts” basis by the carrier. This means that the carrier will not guarantee the speed or uptime. Very rarely do these circuits deliver the speed they promised. 

While both DSL and cable are improving every day, putting VoIP on a best-efforts circuit in turn gives you “best efforts phone quality.” For some businesses that do not heavily rely on their phones to conduct business, DSL or cable is adequate. For critical telephone users, best-efforts probably isn’t enough.

In my next blog in this SIP Trunking series, I will share with you how to dramatically increase voice & data reliability by adding redundant internet connections. You’ll want to read this!

We offer business-class communication solutions with responsive local support

To learn more, call us today at (510) 785-2480