I was looking at a Raspberry Pi board and was struck with how large the ethernet
connector is in comparison to the board as a whole. It strikes me: ethernet
connectors haven't changed that I'm aware in pretty much 25 years. Every other
cable has changed several times in that time frame. I imaging that if anybody
cared, ethernet cables could be many times smaller. Looking at wiring closets,
etc, it seems like it might be a big win for density too.
So why, oh why, nanog the omniscient do we still use rj45's?
It's not all about density. You *Must* have positive retention and
alignment. None of the USB nor firewire standards provide for positive
retention. eSATA does sort of in some variants but the connectors for USB
are especially delicate and easy to break off and destroy. There's the
size of the Cat5/5e/6 cable to be considered too.
Then you must consider that the standard must allow for local termination,
the RJ45 (And it's relatives) are pretty good at this. Fast, reliable,
repeatable termination with a single simple tool that requires only a
little bit of mechanical input from the user of the tool.
The primary reason that pops to mind is backwards compatibility... Ubiquitous availablity of the
parts for RJ45 connectors (end connectors, wall plates, panels, etc.) also means that it is more
economical to continue using the well established connector. A new connector would
drive up costs initially, whereas continuing to use RJ45 is cheap and already works.
I'm going to go by the "Necessity is the mother of invention" theory
here and say that it's basically because the need for a subcompact
ethernet connector hasn't shown up in masse yet. It was probably just
adopted because it's inexpensive, easy to install using tools already
out there in the telecom world, and it works well enough at the
required feedline impedance of 100 ohms. That being said, any
connector that works for balanced line signalling with a feedline
impedance of 100 ohms and a favorable frequency response up to 100mc
(100base-T / cat5) or 250mc (1000baseT / cat6) should work just fine.
For obvious reasons, standardization of the submini ethernet connector
should be present industrywide, so you don't have to start carrying
around adapters.
Boy would I ever love an ethernet connector that works like Apple's
MagSafe... or at least just kinda friction fits like USB... THOSE
TABS...
If you've ever dealt with connections like micro-usb on a day-in-day out
plugging and unplugging at not quite head on connections, you know how bad
this can be on a hardwired connection. With very few exceptions, its very
difficult to have an rj45 go in any way but the way its designed to (well
you can, but you have to try reeeeeeeally hard).
Add onto it that any replacement would be caught in enough intellectual
property rights junk to price it into oblivion and would either require tons
of adapters to make it work with legacy hardware (defeat the purpose), or
would require replacing all of that legacy hardware entirely.
Seen an AUI or vampire tap recently? Vampires made a certain amount of sense, but the AUI connector seemed to have little purpose other than recycling weak metal from Coors beer cans. IIRC, the inventor apologized.
There is also the factor that cat5 is the principle desktop to network
connection. That being the case, there's very strong motivation for
ensuring that construction of that cable can be done very easily by
barely trained folks. Otherwise, laying out an office or cube farm
becomes considerably more difficult and expensive. RJ45 is and always
has been a very easy termination as long as you can tell one color
from another.
How many people here have gotten good enough that they can cut a
cable and pop connectors on each end in under 3 minutes? How many have
gotten good enough that the failure rate for *hand made* cables is sub
1:1000? Show me another connector type where that will be true.
Really, it will remain that way until the bandwidth needs from the
desktop begin to push the GE threshold. Until then, why bother
changing anything? When that does happen, it'll pretty well deal with
itself.
If you look at the Raspberry Pi though, it takes a substantial piece of real estate
though. Not everything needs to be industrial strength connectors as witnessed
by USB and HDMI -- if they fail I'm just as unhappy as if ethernet fails. Surely we
want keep shrinking these cute little purpose built controller-like things and not
*have* to rely on wireless as the only other space-saving means?
Do note that the 8P8C on the Raspberry Pi has integrated magnetics
that you can't see without an x-ray imager. The space is not as wasted
as some might think.
Nothing stops a mfr from using whatever they want and providing a
dongle, but now they need board space for the transformers.
Sort of like saying why haven't we changed from RJ-48's for phones...old habits die hard I guess! For the most part the RJ-45 connector is pretty sturdy...remember those silly dongle cables that were used for pc-card Ethernet adapters in laptops...those things would last about a month before dying!
As for the Raspiberry PI (I own one) it was silly to even put Ethernet on that instead of wi-fi, especially for the educational market that the PI was initially developed for; what classroom has Ethernet running to every desk especially in poor nations where copper theft is rampart!