第3套
(1)is used to ensure the confidentiality,integrity and authenticity  of the two end points in the private network .the(2),an application  layer protocol,authenticates each peer in an IPsec transaction ,IKE  negotiates security policy,determining which algorithm may be used  to set up theRunnel .It also handles the exchang of session keys  used for that one transaction.Networks that use (3)to secure data  traffic can automatically authenticate devices by using (4)whichVerify the identities of the two users who are sending  information back and forth .IPsec can be ideal way to secure data in  large networks that require (5) connections among many devices。 
(1) A.Encryption B.Code C.Certificate D. Tunnel 
(2) A.associated links B.Internet Key Exchange C IPsec D. encryption 
(3) A authenticity  B.password C.IPsec D. Internet Key Exchange 
(4) A.protocols  B.keywords C.IKE D. digital certificates 
(5) A.free B.strict C.secure D.remote 
答案:1:A,2:B,3:C,4:D,5:C