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。横线处应选（ ）
(72)A message B. Packet
C.header D. package
