[单项选择]The network layer provides services to the______layer. It can be based on either virtual circuits or datagrams. In both cases, its main job is routing packets from the source to the destination.
A. transport
B. application
C. presentation
D. data link

[单项选择]

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，flowcontrol，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 (75) ，and admission control．Approaches that have been designed for good quality of service include integrated services(including RSVP) ，differentiated services， and MPLS．

（71）处填（）。
A. virtual circuits or datagrams
B. TCP or UDP
C. TCP or IP
D. IP or ARP

[单项选择]

Traditional network layer packet forwarding relies on the information provided by network layer （） protocols, or static routing, to make an independent （）decisions at each hop within the network. The forwarding （） is based solely on the destination （） IP address. All packets for the same destination follow the same path across the network if no other equal-cost paths exist. Whenever a router has two equal-cost （） toward a destination, the packets toward the destination might take one or both of them, resulting in some degree of load sharing.

Traditional network layer packet forwarding relies on the information provided by network layer （） protocols, or static routing
A. rotating
B. routing
C. transmission
D. management

[单项选择]（）is a network layer device that supports multiple LAN interfaces and segments LANs into smaller collision and broadcast domains。
A. Repeater
B. Bridge
C. Router
D. Galway

[单项选择] (74) is a network layer device that supports multiple LAN interfaces and segments LANs into smaller collision and broadcast domains.
A. Repeater
B. Router
C. Bridge
D. Switch

[单项选择] (74) is a network layer device that supports multiple LAN interfaces and segments LANs into smaller collision and broadcast domains。
A. Repeater
B. Bridge
C. Router
D. Galway

[单项选择]Factoring provides the following services except _____________.
A. maintenance of the sales ledger
B. collection of accounts receivable
C. 100% non-recourse finance to the seller despite commercial disputes between the seller and the buyer
D. credit risk protection on the buyer

[单项选择]

TCP/IP (71) layer protocols provide services to the application (72) running on a computer. The application layer does not define the application itself, but rather it defines (73) that applications need — like the ability to transfer a file in the case of HTTP. In short, the application layer provides an (74) between software running on a computer and the network itself. The TCP/IP application layer includes a relatively large number of protocols, with HTTP being only one of those. The TCP/IP (75) layer consists of two main protocol options — the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

（71）处应填（）。
A. application
B. transport
C. link
D. network