Solution to Homework 6:
When the information (data) is broken up into small groups and each is transmitted over the network independently (maybe through dirrerent routes) it is called packet switching. It differs from circuit switching because there is no dedicated path between the sender and receiver. Packet switching is better suited for data communications is bacuase data can be broken up into packets and recombined without worrying about sequencing and delay of individula packets. Whereas in voice and video the packets need to arrive in sequence with minimal delays.
Connection Oriented service has a dedicated path established for the duration of the call and it is torn down after the call (thisis a data call) whereas in connectionless service there is no dedicated path and each packet travels independently over different routes.
Leased lines are distances sensitive. PDN's are volume sensitive (by number of packets) and dial-up circuits are priced by the regulators as a fixed monthly rate. Regulators may allow pricing based on residential or business rates and occasionally more if the business is located in a remote area.
Initially, the transfers from the suburban office were handled at the end of each business day., averaging 65 claims of 500 characters apiece from each of the 10 offices per city. The total daily traffic from each agent site was 140,000 bits. At these levels, each suburban site transmitted for one to two hours per day, and each downtown area transmitted for about four hours daily.
Over time, the volume of claims to be processed grew. Although no additional agents or sites were added, the volume grew to five times the previous amount.
With the growth in business, the company recognized the competitive value of interactive claims processing, allowing agents to immediately access and update records in the regional and corporate centers. The new service was installed and averaged 500 to 1000 daily 1000-character queries from each agent site. All queries were directed primarily to databases at the downtown offices. Unresolved queries were redirected to Hartford headquarters. This type of traffic load required an average of two terminals at each agents' site to be able to access either the downtown or the corporate center on demand. Transmission was sporadic with total daily traffic under 1 million characters.
The company then embarked on a major expansion. Suburban offices increased to an average of 25-30 per downtown site. Downtown locations increased to 50 and regional centers were established in New York, Chicago, and San Franscisco. Traffic volumes for both end-of-day processing and interactive queries experienced a 10-20 fold growth.
At each stage of the health insurer's growth, sketch the topology of the network (i.e., what are the sites that need to be linked?). What is the appropriate communications approach for supporting data transmission requirements for each stage? A qualitative analysis of the problem statement will suffice. You should provide a rationale for your recommendation.
The initial volumes of traffic are relatively modest, and so the insurance company would not be advised to invest in special equipment or services. Simple dial up service using the PSTN with modems would suffice. As the traffic volume grows, a dedicated-circuit service would be more cost effective. The company can lease lines between each suburban office and its downtoiwn office and between each downtown office office and headquarters.
With the introduction of interactive traffic, the organization may want to make use of public packet switched network. The combination of both interactive low-volume queries from many agent offices and multiple destinations (downtown and Hartford centers) warrants a volume-sensitive pricing approach.
With the expansion of the number of offices, a private packet switching network appears to the most cost effective approach. It eliminates the time duration (or connect time) sensitive tariffs of the PSTN and the volume sensitive pricing of the PDN. Also, although traffic volumes are high, the large interactive component favors this solution over the leased line solution.