Branch offices are the life blood for a wide range of businesses. Financial service companies, insurance, retail, education and government vertical markets depend heavily on having a physical presence in the neighborhood of their customers. However, having a physical office means you need a reliable means to communicate with both customers serviced by the office and the employees in the branch office. To date, most branch offices have low-cost stand-alone TDM telephone systems (aka Key Systems) and use the expensive legacy PSTN to make and receive telephone calls between offices and to their customers.
- Reduction of trunk lines to branch offices
- Elimination of toll charges for inter-office calling
- Consolidation of trunking facilities
- Centralized applications (voice mail, IVR and ACD systems)
- Easier remote management and elimination of "truck rolls"
- Improved productivity with Unified Communications capabilities
- Survivability - what happens at the branch if the wide-area network goes down or accidentally cut? An extreme example of this is the outage in San Jose, CA on April 8th, 2009 where a major fiber optic line was cut by vandals.
- Local Numbers - will you still have the same local numbers that long-established customers have on their prescription bottles or refrigerator magnets?
- E911 - if there is an emergency, will the first responders be directed to the right facility?
- Broadband Availability? - while quite common in urban and suburban areas, wireline broadband is either very difficult to get or very expensive in most of rural America. Common wireless technologies including EVDO, WiMax and satellite are not conducive to voice traffic and may insert significant latency or jitter.
A Fully Distributed architecture with separate stand-alone equipment at each site pushes all the intelligence to the branch offices, but doesn't consolidate resources or save enough money to make it viable over the long haul. Many of the smaller IP-PBX or communications appliance vendors are touting this architecture, mostly because customers are used to this from the key system days.
A Fully Centralized architecture moves all the intelligence to the core with a large IP-PBX or Softswitch at the headquarters or hosting site and just network equipment and IP phones at the branches. This architecture dramatically reduces costs of the equipment at the branches, but is highly dependent on the quality and stability of the WAN. Local number portability and E911 questions create other problems.
It seems that a hybrid architecture that combines the the best attributes of the fully distributed and fully centralized is much more realistic and is becoming the reference for most network designs going forward. This architecture puts some intelligence at the branch offices, which could include either a small IP-PBX or SIP Proxy to handle intra-office calls or emergency calling. The large centralized IP-PBX or Softswitch would manage inter-office traffic. Other application components including voice mail, local IVR and ACD at the branch offices off-load these services from the central site and allow them to operate with less expensive WAN services or in cases of a WAN failure.