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MAC-PHY! When to MAC-PHY vs R-PHY

Happy Friday Everyone. Today is May 11th and this is episode 38 of Get Your Tech On, our show on All Things DOCSIS. I’m Brady Volpe, Founder of The Volpe Firm and Nimble This a technology fan in cable. With us is, John Downey, “the prognosticator”. John is also CMTS Technical Leader at Cisco Systems, welcome John. And Jeff Finkelstein Executive Director of Advanced Technology at Cox Communication. Today’s topic is MAC-PHY. CableLabs has had a spec on remote Mac-PHY since 2015 but recently has been in the process of updating it and Jeff is one of the folks involved in the process, so we can get the latest updates.

First a Question from a Listener:
“Before we get on this topic let’s cover a question from one of our listeners also from Cox communications.

The questions is “In reference to DOCSIS 3.1, what are the average speeds you are seeing out of the modem Ethernet port?

Using the Viavi one expert meter, RF on coax at modem is reading 1.05-1.10 Gbps. It doesn’t make sense that for one, the average Speedtest on our network is averaging 500-714 Mbps max. The Viavi meter Ethernet ports will only run around 400-690Mbps max.

In my onecheck, all correct profiles for d3.1 are present and active. LDPC is working like a charm, and there seems to be no other physical layer impairments present causing the bottleneck.

Any ideas? Hope y’all are doing well, keep the YouTube videos coming!”

Topics to Be Covered Today:

• The benefits of MAC-PHY
• CableLabs working group on MAC-PHY
• When to MAC-PHY

A short introduction to PHY and MAC layers

PHY is the short form of Physical Layer or medium. It is the layer-1 in OSI stack. It interfaces physical medium with MAC and upper layers. Physical medium can be copper wire, fiber optic cable, twisted pair or even wireless channel.

What is MAC Layer
MAC is the short form of Medium Access Control Layer. It is the layer-2 in OSI stack. It interfaces PHY layer and Upper layers (i.e. network and above).

End Podcast
John, and Jeff thank you for your time today. This was a great episode. Our next Episode May 18th. Our topic will be 10GIG Over Coax and DOCSIS 3.1 with Daniel Etman of Enrest.

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