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（71）. Its aim is to define the differentiated services (DS) byte, the Type of Service (ToS) byte from the Internet Protocol Version 4 （72） 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 （73） within which service providers can offer customers a range of network services, each differentiated based on performance. A customer can choose the （74） 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 （75） specifies the PHB given to the packet within the service provider network.