Just a couple of notes - I don't have the energy to check it all.
<backgroung in computer network> To me, this is a thing and not a field. I should think, "computer networking" or "computer networks."
I believe in the US we would say, "as
a systems administrator in
the Agency etc."
<managed security systems like Firewall,IDS etc.> If these are two different systems, use "Firewall
and IDS." If "IDS" is part of the Firewall brand name, I doubt it includes a comma. Also, I'd recommend replacing "like" with "such as."
Like could be taken as "similar to," meaning that you haven't actually had any Firewall experience. I'm not sure what it means to manage a system like Firewall. I thought proprietary systems had "admistrators." is that the same as "managers"?
I think someone in the business would say, "My experienc
es with Unix, Windows, networks, and security systems complement each other, and have allowed me to design a very large campus network, in which I was able to seamlessly integrate many servers and security systems within the network infrastructure.
<I hold MCSE etc.> [new paragraph]
Where are you pursuing your PhD?
<I am already done etc.> I've completed my coursework and have begun work on my dissertation.
Do you mean "qualities," or "qualifications"? you expect / you are looking for ??? (I'd suggest placing the "I am very interested etc." and the "opportunity" sentences at the beginning of this paragraph.)
<reach me at phone> What do you want to say here?
- A.