Additive length dependent asymmetry
Ethernet Cables have maximum physical length that it can run reliably while keeping its promised speed for its category. This is 100 m (328ft). For Cat 6, this is up to 5 Gbps based on Multi-gig NBASE-T standard. However, it is well known Cat 6 can support 10G up to 55m distance.
The maximum allowed length of a Cat 6 cable is 100 meters (328 ft). This consists of 90 meters (295 ft) of solid “horizontal” cabling between the patch panel and the wall jack, plus 5 meters (16 ft) of stranded patch cable between each jack and the attached device.
Category 6 Cable (Wikipedia)
One thing I did not realize based on the statement above is cables length are additive. Now I am fairly certain switches reset the length as it can supply power/data at full strength through it, but Ethernet jacks, patch panels cannot.
Therefore, between the Netgear switch and MacBook Pro, there are 4 ethernet cables in my case. What’s tricky here is as a individual component, perhaps 1.5 or 3ft Ultra Clarity cable may provide Cat 6 quality but when it becomes a part of long run cable path, it could cause a problem. This actually makes scientifically a sense.
Ethernet Cables are no different from electric wires where the cable itself has intrinsic resistance. The higher the resistance, the more signal attenuates going through the medium i.e. less total distance it can travel. When resisters are added in serial manner i.e. ethernet cable to ethernet cable, total resistance are simply additive.
Here analogy is imagine you are doing a bowing. The variable here is a floor material i.e. how much friction (= resistance) there is. Otherwise, amount of the force one puts to the ball is consider equal.
So in the case above, the bowling ball will arrive to the pin with full speed due to lack of friction between the ball and smooth floor.
Now the difference case is at the beginning and end, there is some bumpy, perhaps ground with gravels. Now the ball won’t even to the pin.
The two analogies represent, a matching, perfect quality Ethernet Cables connected together will have full distance as the first case while poor quality patch cables at the both ends reduces travel distance even though middle, the longest part of the cable still remains to be in high quality.
Basically, this is proving/showing that even if each of the 3 pieces of the ethernet cables between two computers (main horizontal run and patch cables at both ends) pass 10Gbps speed, that does not gurantee putting three together will work even if the total distance are under the category specification.
3 Ethernet Cables pass 10Gbps speed, that does not gurantee putting three together will work even if the total distance are under the category specification.
There are even claims that cat 5e can do 10G in short distance (up to 45m) (ref).
I believe this is exactly what has happened at least in part of my case. After this hypothesis, I’ve done the last attempt of the fix for this round.
Change
- Changed Dining room cables on network rack side i.e. two from keystone to switch.
What’s next?
I have just received replacement cable, merely 3 days after my first email to TrueCABLE. The installer is scheduled to be back next Friday i.e. 6 days from the time of this writing. In the mean time, I have ordered following three items:
As of now, I am still suspicious TrueCABLE I got for this time has some defect that is resulting in not full performance as I am pushing to its extreme since my goal is 10G at some distance, any suboptimal quality can manifest itself.
Fluke tester will hopefully confirm this as well as tells me exact distance/run of my Ethernet Cables. If they are over 55m, I would have to go Cat 6A.
Patch cable issues were real. Although CableMatter and TrueCable are better than the Ultra Clarity, they may not necessary be the best. I always wanted to have UniFi’s flexible patch cables for their form factor so this would be a good test.
I’ve got CableMatter’s Keystone, which worked at least for shorter range cable runs I have at full 10G but for that I had used left over cable from the original work rather than the most recent add-on. Therefore, it is uncertain the difference/issue currently is keystone vs. cable itself. However, TrueCABLE tech support said if they determine cable isn’t the issue, the next step will be using a different keystone. So I went ahead and asked which keystones they’d recommend.
there are three keystone brands that I have tested and know work. First up is Shaxon. Second is Platinum Tools. Third is 10GTek. They all passed on Permanent Link testing with a Fluke DSX-8000 with our Cat6 cable. You can elect to grab Cat6A jacks if you like…they are backward compatible and don’t cost that much more. Just a little extra security!
Email from TrueCABLE
For others that I have tested, well…
1. VCE just barely passes. I suspect their Cat6 jacks are re-marked Cat5e.2. LINKOMM jacks don’t pass at all.
The idea here is simple. For just $11, I can potentially avoid bringing back installer as I know these keystones should work.
All these are in effort to minimize unknown variables by the time the installer comes back. So if there is an issue, I can truly blame on the cable run and have installer redo his work right at the spot.