The network layer provides services to the transport layer.It can be based on either（   ）.  In both cases,  its main job is （  ）packets from the source to the destination.
In network layer, subnets can easily become congested, increasing the delay and （  ）for packets.Network designers attempt to avoid congestion by proper design.Techniques include （  ） policy, caching, flow control, and more.
The next step beyond just dealing with congestion is to actually try to achieve a promisedquality of service.The methods that can be used for this include buffering at the client, trafficshaping, resource （  ）, and admission control.Approaches that have been designed forgood quality of service include integrated services （including RSVP）, differentiated services, and MPLS.