思科认证考试（Cisco）CCNA考试七十九题-8-
71. which layer is responsible for providing mechanisms for multiplexing
upper-layer application, session establishment, and tear-down of virtual circuits?
a. application b. presentation c. session d. transport
answer d.
72. which layer is responsible for coordinating communication between systems?
a. application b. presentation c. session d. physical
answer c.
73. which layer is responsible for negotiating data transfer syntax?
a. application b. presentation c. session d. transport
answer b.
74. which of the following is a characteristic of a switch, but not of a repeater?
a. switches forward packets based on the ipx or ip address in the frame.
b. switches forward packets based only on the ip address in the packet.
c. switches forward packets based on the ip address in the frame
d. switches forward packets based on the mac address in the frame
answer d. switches are network device that filters, forwards, and floods frames
based on the destination address of each frame. the switch operates at the data
link layer of the osi model. switches use layer 2 addresses to filter the network
75. how does the cut-through switching technique work?
a. the lan switch copies the entire frame into its buffers and then looks up the
destination address in its forwarding, table and determines the outgoing interface
b. the switch waits only for the header to be received before it checks the
destination address and starts forwarding the packets
c. by using broadcast addresses as source addresses
d. by using a class ii repeater in a collision domain
answer b. packet switching approach that streams data through a switch so that the
leading edge of a packet exits the switch at the output port before the packet
finishes entering the input port. a device using cut-through packet switching
reads, processes, and forwards packets as soon as the destination address is looked
up, and the outgoing port determined. also known as on-the-fly packet switching.
76. how do switches use store and forward?
a. the switch waits only for the header to be received before it checks the
destination address and starts forwarding the packets
b. the lan switch copies the entire frame into its buffers and then looks up the