BRKCRS-3900: NBase-T and the Evolution of Ethernet

Presenters: Dave Zacks, Distinguished Engineer; Peter Zones, Principle Engineer

History has been: 10x performnce increase at 3x the cost. 40Gb broke that model –> 100Gb PHYs were very expensive; industry needed/wanted an intermediate step.

Ethernet has a really strong roadmap and will continue to evolve for a very long time. Roadmap:

  • 25Gb – direct server connect (Twinax)
  • 40GBase-T (Cat 8 cable!)
  • 2.5/5G – N-BaseT
  • 400Gb
  • More


  • Serializer/deserializer
  • Turns bits on the wire into bytes and vise-versa
  • 40Gb Ethernet based on 4x10Gb SERDES

100m is the sweet spot for copper cable lengths. Why? CSMA/CD and also electrical wiring, placement of wiring closets just make 100m the right fit.

Cisco Mgig

  • PoE/PoE+/UPoE
  • Standards compliant
  • Investment protection (existing cable plant)
  • Supports 100M but not 10M; (had to drop something as far as standards and nobody uses 10M anymore really)

802.11ac Wave 2

  • Max PHY rate: 6.8Gbps (in absolute best conditions)
  • More likely 3-ish Gb/s
  • Point: it’s more than 1Gbs

Cisco Mgig products:

  • 4500E line card
  • New 3850 models with Mgig ports
  • New compact 3560CX with 2x Mgig ports

Between 2003 and 2014, approx 70 billion meters of Cat 5e and Cat 6 cabling were sold

NBase-T must support existing cabling plants. 90% of the install base is Cat 5e and Cat6. Cat 6a is 8%. Cat 7 is 1%.

Cat 5e and Cat6 installed outlets are still growing (!)

The growth in wireless cannot be overstated as the driver for Nbase-T.

  • More users connect via wireless now than wired
  • Google processes more searches via mobile devices (wirelessly conected) than non-mobile
  • 11ac Wave  2 coming; industry expects Wave 2 to start outselling Wave 1 very quickly after products become available
  • Side note: CLUS NOC is showing the majority of connected devices at the conference are 11ac, far exceeding 11n
  • Beyond Wave 2, there’s Wave 3
  • Beyond 11ac there’s 11ax
  • Wireless is a monster and will keep growing like this

The standards (1000Base-T at 100m) covers the worst case channel; the channel in the middle of the bundle (the victim channel). Your actual realized performance and lenth is subject to which channel is being used, quality of the cable, number of connectors and much more.

IEEE 802.3bz – 2.5G/5GBASE-T standard

Is there a competing standard? There was, but they voted in support of NBase-T. 

My goal is not to split the industry. If we do that, we’ve done you [customers] a disservice. –Peter

Cisco Canada’s new headquarters in Toronto is one of the most technologically advanced buildings in the world.

  • All lights powered by PoE from the wiring closet
  • 140x 3560CX switches up in the ceiling
  • Full building automation


  • 802.3bt 4PPoE targets 100W at the PSE
  • Sends power down all 4 pairs
  • Backwards compat with PoE/PoE+


  • Power over Data Line
  • Power for one-pair ethernet
  • Use cases: vehicles, IoT, new areas where Ethernet hasn’t gone before

Plastic Optical Fiber (POF) – Fiber cable that’s so easy to use it’s perfect for the house where you can cut and splice it without special tools

Deterministic Ethernet

  • Use cases: precise time sync; guaranteed end-to-end latency; extremly low packet loss ratios
  • Who needs it: industrial (process control, machine control, vehicles); audio/video transport
  • How? Zero congestion loss; redundancy (1+1, like SONET)
  • Slides list many standards related to this area from IEEE
  • To get this right, IEEE and IETF need to work together (networks are both Layer 2 (IEEE) and Layer 3 (IETF))
  • New IETF working group “detnet”
  • 802.3br / 802.1Qbu  – Preemption – a new standard that will allow a port to stop sending a less important frame in mid-send, send a high priority frame, and then resume sending the other frame.

6 thoughts on “BRKCRS-3900: NBase-T and the Evolution of Ethernet”

  1. I just want to ask, the current 40Gbps uses 4 x 10Gb SerDes.

    Will the NBase-T be bases on 2.5Gb SerDes ?
    Or will it be 10 Gb SerDes that some how can negotiate for 2.5/5 Gb speed?

      1. Thx, That is what I thought as well but so far no one could confirm. It will be great then since i could expect basically 10Gbps Ethernet connection, but down clocked to 5G /2.5 should cable fair to meet requirement.

        But that also brings me concern, I don’t see how we could get the 10Gbps Ethernet prices down by a significant margin….

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