●The network layer provides services to the transport layer.It can be based on either（71）.In both cases,its main job is（72）packets from the source to the destination.In network layer,subnets can easily become congested，increasing the delay and（73）for packets.Network designers attempt to avoid congestion by proper design.Techniques include（74）policy,caching,flow control,and more.The next step beyond just dealing with congestion is to actually try to achieve a promised quality of service.The methods that can be used for this include buffering at the client,traffic shaping,resource（请作答此空），and admission control.Approaches that have been designed for good quality of service include integrated services（including RSVP）,differentiated services，and MPLS.

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th the network layer,the transport layer is the heart of the protocol ( ).The network layer provides end-to-end () delivery using datagrams or virtual circuits.The transport layer builds on the network layer to provide data transport from a process on a () machine to a process on a destination machine with a desired level of reliability that is independent of the physical (请作答此空) currently in use.It provides the abstractions that applications nedd to use the network..Without the () layer,the wh

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n the physical layer networks can be connected by（ ）_or hubs.which just move the bits from one network to an identical network.One layer up we find bridges and switches which operate at data link layer.They can accept（请作答此空）examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process in me network layer,we have routers that can connect two networks,If two networks have（ ）network layer,the router may be able to translate between the p

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n network such as the Internet. In science, cloud computing is a （ ）for distributed computing over a network, and means the （ ）to run a program or application on many connected computers at the same time.The architecture of a cloud is developed at three layers: infrastructure, platform, and application. The infrastucture layer is built with virtualized computestorageand network resources. The platform lay-er is for general-purpose and repeated usage of the collection of software resources. The a

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