Choosing a Transport

CSIs are made up of network transports (lines or channels) and  the carrier’s equipment used to terminate these lines.  Each CSI has  multiple carrier trans- ports to offer any customer.

A transport is a physical or wireless channel (or aggregate of contiguous channels) that supports the  transmission of electrical, optical data, telemet- ric data, voice,  or video  signals.

Wow! That’s  a mouthful. It really is easier to just  think  of a transport as a physical line. In the  case of wireless communications, the  transport is a chan- nel that corresponds to a unique frequency assigned to your  cell phone or PDA. Currently, more  than fifteen transport types are available.

With so many  transports to choose from, how is anyone supposed to
decide which to use? Cost and  bandwidth become large factors in any CSI or transport-related decision. This is true whether you’re  a large company with offices all across the country, a single location with a large campus-like setting

of many  buildings, a single  location with one or more  floors, or just  a residen- tial customer looking to reduce your monthly telephone bill and improve your  Internet access. Ultimately, deciding what  transport to use becomes the  key decision point for any network, including VoIP.

To better understand transports, consider the  T1 transport, easily  the most popular dedicated transport in the  corporate sector. It’s not  unusual for com- panies to have  many  T1 lines  throughout their private network. One reason that T1 lines  are popular is because the  bandwidth they provide can be opti- mized  using  dynamic channel allocation. This means a T1 line can be subdi-  vided into twenty-four smaller bandwidth channels. These channels may be assigned to a bandwidth pool  that supports computer data, VoIP, and  video  traffic. The terminating equipment for the  T1 line can assign, at the  moment needed, a specific channel or group of channels to bring  up a VoIP telephone call or a videoconference call. When the  need is over, the  channels are returned to the  bandwidth pool.

Dynamic  bandwidth allocation is not  available on all network transports. This is one of the  reasons why it is important to know what  type  of transport or transports you’re  planning to use.  Your carrier may or may not make these points of distinction in a transport leasing deal.  Dedicated (private) trans- ports are not  owned by the  customer; they’re leased and there is a monthly access charge based on the  distance from point A to point B. But the  higher cost of dedicated transports is well worth it.

An important rule to follow when selecting network transports is to start with the  question “What will we be using  the  network for?” This leads to a discus- sion  of uses for network transports. These applications (uses) are called transport services.

Any transport can be used for one or more  transport services. A POTS line, for example, is used for telephone services. Many customers use a POTS line at home for computer modem dialup services or to support broadband DSL services. As a result, a POTS line running DSL can support VoIP telephony in the  home.

A T1 transport is often  called private line  service because it’s dedicated to the  customer’s use.  None of the  carrier’s other customers or customers of other carriers can share the  line. The customer may run all sorts of applica- tions (transport services) on the  T1 line. These applications may include computer data, VoIP telephony, and videoconferencing.

VoIP is considered first and  foremost a transport service. VoIP runs on many  of the  same transports that support computer data and  video.  It uses packet- switching protocols to support telephony services, so it has the  potential to eliminate or replace older transports and  services that can’t integrate data, voice,  and  video  on the  same transport.

The carriers of the  future need to incorporate VoIP and  related products and services into their business offerings. The most successful carriers are those that not  only include VoIP but  can lease VoIP services out  of two or more  of the  five CSIs.