This proposal does not have an indicated topic, but the topic itself must have some relationship with the networking security area. You can think of any topic as long as it is suitable. 

Basically, the project proposal consists the following components:

1. Project Description:  give a description of the major project 

2. Problem statement & Backgroud:  provide extensive background to the problem.  An extended background of the problem, the nature and complexity of the problem to be solved should be included.  

3. Complexity:  highlight the complexity of the problem to be solved 

4. Scope & Depth:  define the scope and the depth of the major project

5. Test Plan:   A detailed test plan may include the procedures, methodology, tools used, verification, pass/fail criteria, or examples of test cases 

6. Methodology:  describe the methodology, approach, and technologies to be used 

7. System/software Architecture diagram:  include a system/software architecture diagram.

8. Innovation(Most important part):  highlight the innovative components, as the major project should contain some elements, which are deemed to be innovative, experimental or exploratory in nature.

 it is strongly recommended that new leading edge technologies, even experimental, be considered. Even if these technologies are not required by the industry sponsor or client, or practically feasible, research on these areas should be included as part of the proposal. 

9. Technical Challenges(Most important part):  highlight expected technical challenges, which could include information regarding what will be learned above and beyond what is taught in the classroom while researching for the project 

10. Milestones:  provide details about estimated milestones in terms of time and effort.

I will also provide you with 3 sample proposals. These 3 samples are good examples of finished projects, you can take a look at it and start coming up some ideas of your own. The time limit is about a month.