Couple of things from watching these vendor videos on making Cat8A cable in the field:
- Cat 8 cable is very thick and not going to bend much inside the rack.
- The typical bend radius for a shielded category cable is 8 times the cables outside diameter. This is to ensure the shield and the relationship between the shield and the conductors is not compromised during installation. – Source
- They don’t mention spectrum testing to ensure that cable can operate at 2000Mhz which I would consider mandatory at this level of performance. Can you trust a hand assembled cable ? Can you trust BaseT cable ?
- Cat 8 Field terminations require vendor specific tools depending on connector brand chosen.
- This process strikes me a much less reliable than a premanufactured DAC using TwinAx or Fibre. And SFP modules using DAC have chips that monitor the cable and provide feedback to the switch about cable degradation. Do 25/40GbaseT SFP modules do that ? Do switches support that ?
- I’m open to changing my mind. Send me data.
- Why is EXR brand of cable using a single shield wrap while Leviton is foil wrapped per pair plus a full wired braid ?
- Some research shows that the standard does not specify braid and shield. Caveat Emptor since there are plenty of dodgy cable makers and installers out there.
- Did I mention how important spectrum testing would be for this type of cabling ?
- Still not sure where the earth for the shield is managed ? Inside the NIC or at the network device ? Idle speculation really.
Some other thoughts:
- Max Speed of Cat8 is 40GBase-T which is already obsolete. There is a 25Gbase-T standard that I could be convinced about …. but still would use DAC by choice. Mature technology and all that.
- Cabling distance up to 30 meters (NOT 100 meters like Cat 5/6 for 10GBaseT. Limited to Server to Top of Rack.
- Single patch/horizontal run for Cat 8 is 3 +24 + 3 = 30 metres.
- Cat8 cable operates at a frequency of 2 GHz (2000 MHz), which enables higher bandwidth and requires shielding.
The EtherealMind View
I will continue to recommend using Coax (TwinAx, Copper DAC) or Active Fibre optic cables as more predictable solutions. There is so much to go wrong with copper cables as these termination videos demonstrate.
- the detection of BaseT cabling failures is impractical and unreliable. Twin or Fibre DAC cables can provide feedback to the switch via the onboard interface.
- mechanical reliability of these cables seems lower than DAC
- 30 metres is quite short some uses.