questions asked during network engineer interview

Tue Jul 14 19:46:16 UTC 2020

On Tue, Jul 14, 2020 at 10:59 AM Ahmed elBorno <amaged at gmail.com> wrote:
>
> 15 years ago, I applied to a network admin role at Google, it was for their corporate office, not even the production network.
>
> I had less than two years experience.
>
> The interviewer asked me:
>
> 1) What is the difference between flow balancing techniques on Cisco IOS and Linux?
> 2) If we had a 1GB file that we need to transfer between America and Europe, how much time do we need, knowing that we start with a TCP size of X?

Hi Ahmed,

Those are terrible questions. I've been in the business for a quarter
century, a Linux and Cisco IOS user for most of that and I don't, off
hand, know the answer to #1. As for number #2, it's highly variable
depending on when you lose the first packet, ending fast window
growth. And you will. On a gigabyte transfer over any real-world
network, you will lose some packets both to congestion and bit errors.
And that's before you consider the long-fat-pipe problem. Trying to
treat it like a math train problem is bizarre.

My Google interviewers asked much better questions, along the lines of
"build me this" or "debug this problem." Even then they fell in to one
of the traps with that methodology: on the "debug this problem"
question, the interviewer wasn't familiar with one of the diagnostic
commands I went to, so he guessed at what the output would be. His
guess was just enough wrong to eliminate the cause he wanted me to
find. The command should have hung accessing a faulty NFS mount but in
his version of the story it didn't.

Regards,
Bill Herrin

-- 
William Herrin
bill at herrin.us
https://bill.herrin.us/