Madeline is the Network Manager for a local medical physician group named Med Corp. Madeline is trying to make a decision between adding traffic from a 64Kbps circuit onto an existing 256Kbps circuit (eliminating the slower circuit), or combining traffic from both onto a new 512Kbps circuit (eliminating both the 256K and 64K circuits). Given the following information, what is your recommendation to her? The organizations threshold to upgrade a circuit is a utilization rate of 75%. Hint: calculate the TRIB and utilization of both circuits. Add both TRIB values together and determine the estimated utilization if the existing circuits are combined. Use the organization's requirements to determine whether Med Corp retains the 256K circuit, or upgrades to the 512K circuit. circuit.

TRIB: K = # information bits per character M = frame length in characters R = data transmission rate in characters per second C = overhead characters (non-information characters) per frame P = probability a frame will require retransmission T = time between frames in seconds

Given that: 1. 256 Kbps Circuit 8 bit ASCII Total frame length 1500 bytes Data transmission rate 32 kilobytes per second Protocol administrative overhead 80 bits per frame Error rate is 15 frames in every 1000 frames Time between frames 37 milliseconds

2. 64 Kbps Circuit 8 bit ASCIITotal frame length 1500 bytes Data transmission rate 8500 characters per second Protocol administrative overhead 10 characters per frame Error rate is 10 frames in every 1000 frames Time between frames 25 milliseconds

Answer the following questions: 1. 256K Circuit TRIB: ___________ 2. 256K Circuit Utilization:__________________ 3. 64K Circuit TRIB: ________________ 4. 64K Circuit Utilization: _____________ 5. Estimated Utilization For Combining Both Circuits: ______________ 6. Should Madeline keep the existing 256K circuit or upgrade to 512k?

TRIB FORMULA FOR CALCULATING TRIB Number of information bits accepted TRIB = Total time required to get the bits accepted KM - C) (1 - P. TRIB = (MIR) T where K = information bits per character M = frame length in characters R = data transmission rate in characters per second C = average number of noninformation characters per frame (control characters) P = probability that a frame will require retransmission because of error T = time between frames in seconds, such as modem delay/tumaround time on half duplex and propogation delay on satellite transmission. This is the time required to reverse the direction of transmission from send to receive or receive to send on a half-duplex circuit. It can be obtained from the modem specification book and may be referred to as reclocking time