SOI QUESTION: 5.1.2 Agreement of IPsec SA cryptographic algorithms

["Theodore Ts'o" <tytso@mit.edu>]

Please discuss and answer this question: 

5.1.2 Agreement of IPsec SA cryptographic algorithms

JFK's SA negotiation uses pre-defined suites, and Bob presents a single 
suite to Alice. In IKEv2 SA negotiation allows the two parties to agree on 
the most preferred parameters, the same as it does for key negotiation.

5.1.2.A) Is it important to allow negotiation of the SA algorithms?

Implications from the scenarios:

[none]