试题出自试卷《2016年下半年网络规划设计师考试上午真题（专业解析+参考答案）》

The diffserv approach to providing QoS in networks employs a small， well-defined set of building blocks from which you can build a variety of（ ）. Its aim is to define the differentiated services （DS） byte， the Type of Service （ToS） byte from the Internet Protocol Version 4 （ ）and the Traffic Class byte from IP Version 6， and mark the standardized DS byte of the packet such that it receives a particular forwarding treatment， or per-hop behavior （PHB）， at each network node. The diffserv architecture provides a（ ）within which service providers can offer customers a range of network services， each differentiated based on performance. A customer can choose the （ ）level needed on a packet-by-packet basis by simply marking the packet’s Differentiated Services Code Point （DSCP） field to a specific value.This （ ）specifies the PHB given to the packet within the service provider network.