Summing up the CSIs

A CSI is like a highway system that lays out  all the  many  roads that enable people to drive  to their destinations. Within our highway system, we could characterize some roads as being large or wide, some roads as small or narrow, and  some roads as being  between these two extremes. Roads may be further broken  down  by type  of surface, that is, asphalt, concrete, gravel, or dirt.

Similarly, we could characterize a CSI as having  great  amounts of bandwidth capacity or limited bandwidth capacity; as single  channel or multichannel; as switched or dedicated; or as circuit-switched or packet-switched.
VoIP runs best in a dedicated, packet-switched carrier services network. For a company with multiple locations, this  means primarily using transports coming out  of the  DS and  OC CSIs. Wireless transports may be used to aug- ment or support the  routine need for remote telephony services.

Carrier service companies are constantly adding and  upgrading network transport lines  and  equipment in all five of the  CSIs. They  also  grow by merg- ing with carriers that are more  heavily vested in another CSI than they  are. This is important to understand if you’re  running VoIP in a multilocation net- work. If you have  private, dedicated transports, you’re not  so much con- cerned with how much of the  dedicated line is owned by one or more  carrier providers as you are with the  underlying requirement that it be dedicated to your  VoIP network 24 hours a day, 365 days  a year. At the  same time,  if you



can acquire dedicated lines  that are owned from point A to point B by one carrier company, chances are that the  single  owner may be more apt to resolve maintenance problems than a dedicated line owned by several car- rier  companies.

Just  like the  highway system, CSIs are not  owned by any one carrier because all carriers own a portion of each CSI. What they  do not  own they must lease from other carriers at wholesale and  resell to the customer. Most carrier ser- vice companies can lease network transports from all five CSIs.

Carrier companies have  countless miles of copper and  fiber-optic cable run- ning through underground conduits across the  country and  the world. In addition, the  carriers strategically locate their facilities throughout the  coun- try to terminate and  switch out  all their network transport lines  and  wireless channels to best support their customer base. Taken  in total, all these net- works  constitute the  five CSIs described in this  chapter.