Two packets A and B are sent in the order A-B and will traverse a connectionless communication network. They will arrive at the destination ().
A. in any order, after having traversed the same route
B. in the order A-B, after possibly having traversed different routes
C. in any order, after possibly having traversed different routes
D. in the order A-B, after having traversed the same route
查看答案
The service of TCP is（ ）.
A. connectionless transmission
B. unreliable data transmission
C. datagram
D. reliable data transmission
The UDP segment includes （ ）.
A. checksum
B. receive window
C. sequence number
D. acknowledgement number
The application of ( ) is loss-tolerant.
A. stored audio/video
B. file transfer
C. Web documents
D. text messaging
Which of the following is the default port number of TCP control connection in FTP?
A. 20
B. 21
C. 25
D. 80
微信支付 
支付宝支付