[154581] in North American Network Operators' Group
Re: job screening question
daemon@ATHENA.MIT.EDU (William Herrin)
Thu Jul 5 23:06:16 2012
In-Reply-To: <87A5E4C5-2AC5-461B-8A50-98DDCF57A8BA@delong.com>
From: William Herrin <bill@herrin.us>
Date: Thu, 5 Jul 2012 23:05:21 -0400
To: Owen DeLong <owen@delong.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Thu, Jul 5, 2012 at 10:25 PM, Owen DeLong <owen@delong.com> wrote:
> On Jul 5, 2012, at 5:50 PM, Scott Weeks wrote:
>> --- bill@herrin.us wrote:
>> From: William Herrin <bill@herrin.us>
>>
>>> 5. What is the reason for the 100m distance limit within an ethernet collision domain?
>>
>> What's an ethernet collision domain? Seriously, when was the last time
>> you dealt with a half duplex ethernet?
>> -----------------------------------------
>>
>>
>> Now if someone answered it that way, I'd definitely be
>> interested while the HR person would just hang up...
>
> +1 -- That would be a perfectly valid answer and one of the list of answers I would actually give to HR.
Incidentally, 100m was the segment limit. IIRC the collision domain
comprising the longest wire distance between any two hosts was larger,
something around 200m for fast ethernet. Essentially, the collision
signal caused by receiving the first bit of the overlapping packet had
to get back to the sender before the sender finished the 64-byte
minimum-size packet. Allow for the speed of light and variances in the
electronics and that was the width of the collision domain.
Carrier sensing multiple access with collision detection. CSMA/CD. I
haven't thought about that in a long time.
-Bill
--
William D. Herrin ................ herrin@dirtside.com bill@herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004
