[ih] capacity v bandwidth

[Jack Haverty]

Getting back to the original capacity<->bandwidth topic...

I don't think "capacity" is the right terminology either.  Capacity 
usually means how much "stuff" can be held, i.e.:


            noun

 1. The ability to receive, hold, or absorb something.
    the storage capacity of a car's trunk.
 2. The maximum amount that can be contained.
    a bin filled to capacity.

So it's appropriate to talk about the capacity of a 5TB drive, or 64GB 
of memory in a computer.  But "capacity" says nothing about rate of flow 
of the "stuff" involved, whether it's bits on a wire or gallons of oil 
in a tank car.

As an industry or science or engineering discipline, it seems to me that 
"networking" has avoided defining and adopting its own terminology for 
important constructs.   Terms like "bits" are generic.  Terms like 
"packets" are borrowed from earlier disciplines.   Pony Express riders 
carried "packets" via horseback:

"In the context of thePony Express, the mail packet was called 
a*mochila*(Spanish for "backpack" or "pouch"). It was a specialized 
leather saddlebag designed to hold approximately*20 pounds*of mail, with 
the horse carrying an additional*20 pounds*of material."

Back in the 1980s, I remember discussions using terms such as something 
like "kilobytes per minute per mile".   That reflected the reality of 
transmitting data over distances.  The further you had to move data, the 
harder it was to do and the more it cost to do it.  As far as I 
remember, no one created a term for such metrics.

Other disciplines have created terminology.  Medical of course has been 
quite prolific.  Same with Law.  Even disciplines such as Electricity 
has unique terminology.  For example, "ampacity" is a term in electrical 
codes, used to define how much current a particular wire can carry.  
That dictates how much power can be moved through the wire.  A wire has 
lots of relevant parameters that factor into its ampacity.

Why hasn't our networking industry developed its own terminology...?

So, I don't know when or why "bandwidth" became common.

But I do remember the history of another networking term.  In the early 
Internet, the boxes interconnecting networks were called "gateways".  
  Today they're called "routers".  But why the change...?

In the early/mid 1980s, BBN was selling X.25 networks to all sorts of 
corporations and government users.  Our small sales force would find 
prospects.  Sometimes they asked about this new "Internet" thing, and I 
got called in to explain what it was.  All users were struggling with 
how to integrate their suddenly affordable PCs and workstations.   The 
Internet seemed like a possible solution.

Our sales force reported back that prospects liked the Internet story, 
but hated the thought of having "gateways" in their IT world.  Other 
companies (e.g., IBM) had products called "gateways", and the users had 
apparently experienced lots of problems with such systems.  The term 
"gateway" was a potent killer of sales.

So we started callig them "routers".  Other companies (cisco, proteon, 
...) probably had similar experiences in their sales activities.  
Gateways faded into historical oblivion, to be replaced by routers - 
same products, but much more palatable to customers.

What's in a Name?  A lot.

/Jack Haverty



On 5/31/26 13:57, Brian E Carpenter via Internet-history wrote:
> Unfortunately we failed to correct that terminological error in RFC 6214
> (the IPv6 version of RFC 1149), and worse we discussed 
> "bandwidth-delay product".
>
> Regards/Ngā mihi
>    Brian Carpenter
>
> On 01-Jun-26 07:53, D Waitzman via Internet-history wrote:
>> In RFC-1149, I wrote "The bandwidth is limited to the leg length."
>>
>> I stand corrected that I should have used "capacity", but then the 
>> pun would not work.
>> What's more important, the pun or technically accuracy? :-)
>>
>> -- 
>> David Waitzman
>>

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