Explain the basic idea about IPsec protocol

 you have been introduced to a set of concepts, protocols and threats to network security. Using your own words, write a summary about network security explaining the following factors: 

a. Explain the basic idea about IPsec protocol, its aim and disadvantages

 b. Do a comparison between Caesar cipher using diagraph coding and Vigenère Cipher in terms of their operation and level of security .

 c. Explain the Message Digest Algorithm 5 (MD5) and describe briefly its operation.

 Note: In answering the above question, you should adhere to the following: • Your word count should not exceed 500 words. • You should refer to reliable resources (books, papers, conferences, and AOU e-library). Include at least two references. • Use cross-referencing and citation. • All the references must be cited in proper format.