CoS - Class of Service - an Ethernet field used when 802.1q tagging is implemented to allow prioritisation of frames.
DF bit - "Do Not Fragment" bit - flag in IP header 'flags' field used to define whether or not the packet should be fragmented. Can be 'set' in a route map for policy routing.
DS field - Field in the IP header used to define the packet's traffic classification - aka DiffServ, Differentiated Services - in the past [RFC791 / RFC1349] was called the ToS (Type of Service) field. Now contains DSCP and ECN [RFC2474]. Used in QoS.
IP precedence - Fist three bits in the DS field used to classify IP traffic. Aligns with Ethernet CoS field values. Used in QoS. Can be 'set' in a route map for policy routing.
ToS - Type of Service