Commonly regulators and Internet service providers (ISPs) monitor and publish the offeredrnquality of service (QoS) to improve broadband Internet QoS focusing on transparency andrncustomer empowerment. This is aimed mainly to create competition between ISPs and providernfreedom of choice on best operators for customers which is mainly crucial in multi-operatorsrnenvironment. Some of the researches done on differentiated customer traffic to improve QoSrnmainly used metrics throughput, delay & packet loss only. While others use hardware QoSrnmeasurement approach which is expensive than the software and challenging. Moreover otherrnresearches on operators and regulators tried to improve QoS based only on performancernmeasurement which does not show the E2E QoS. Whereas in ET, the sole operator of Ethiopia,rnfixed wireless broadband Internet (FWBBI) is provided in traditional or similar/ equitablernmanners that is based on best efforts. Despite various customer traffics require variable QoSrnrequirements, some traffics require guaranteed bandwidth such as business critical datarnapplications and others like real time interactive application services such as Voice over Internetrn(VoIP) and video conferencing are highly sensitive to delay, jitter and packet loss. Hence bestrneffort service offering does not guarantee business critical data applications and user satisfaction. rnThis research identifies important QoS metrics to apply in service level agreement (SLA). It alsornprovides QoS assessment result on FWBBI service from end-user perspective. The QoSrnmeasurement is done by ICMP ping and testmy.net tools to get the actual quality the customersrnare offered. Additionally MATLAB analysis is mainly done by probability distribution to show thernnetwork capability in the design of QoS-SLA. The QoS result in FWBBI service showed that therernis fair quality on average throughput (52% of subscription speed) and packet loss (12%), whilerndelay (>400 ms) and jitter (>50 ms) values showed poor quality. The design of appropriate QoSSLArnrnis also delivered by this research. The FWBBI service QoS-SLA comprises three customerrntraffic classes - gold (A), silver (B) and bronze (C). This classification is done by defining thresholdrnvalues for the metrics throughput, delay, jitter, and packet loss. Where this guaranteed level ofrnQoS allow ET to enhance QoS and support the current works to provide BB Internet SLA, improvernefficiency in resource utilization and creates transparency for enhancing customer satisfaction.