To LAG, or not to LAG...or MCABC?

Products PTP
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It's a question that comes up a lot...I have a multicore radio (PTP820C, PTP820C-HP, PTP820F....) and in the configuration - and even earlier than that in Link Planner - I am faced with a choice.  What to I chose, and why should I chose it?  Let's start with the Link Planning.  Let's say you selected a PTP820C radio at 11 Ghz for a seven mile clear LOS link.  You have selected the radio.  If you are in the US, you might have selected PTP820C (Wide) for the hardware.  Maybe if you are in Canada or other parts of the world, you didn't get the "Wide" choice.  That all has bearing on what is offered next in the configuraiton.  In Link Planner there is a field called "Ethernet Configuration", and in my US based link, it offers the following choices:

1.  Single Ethernet (MCABC)

2.  Multiple Ethernet with LAG

3. Multiple Ethernet without LAG.

"What the heck do those mean?" you might ask.  Well, lets start with the the Acronyms, we network types love our acronyms.

1.  MCABC - that one stands for "Multi Core Automatic Bonded Channel".  You'll see you don't get that option if you put two PTP820S (single core) radios onto the same antenna, only with a true multi-core radio like the PTP820C and PTP820C-HP (and any future multi core radios we might invent).  In my fictional PTP820C link, I chose the wide radios (that means they occupy nearly 80 MHz of spectrum per core, per direction) and if I have good enough signal into the far end, I could see as much as 650 Mbps per carrier - that works out to 1.3 Gbps of capacity in each direction.  If my aim is to squeeze every bit of throughput out of that link, I have to consider a few things.

1.  MCABC is really good and really efficient - nearly lossless - in bonding thos carriers, but...and this is a big but.  My PTP820C or PTP820C-HP radios can only support 1 Gbps full duplex to any one interface.  If I chose to bond them with MCABC, I'd lose access to 150 Mbps in each direction or 300 Mbps aggregate.  MCABC makes a lot of sense if I'm either in an area that does not support 80 MHz channles, or in a band like 23 Ghz or 6 GHz that only allows up to 60 Mhz wide channles.  So there is my first decision point, if channels are 60 MHz or smaller, strongly consider MCABC.  There is a license key for MCABC, link planner will add it to the Bill of Materials if you chose it.

2.   Multiple Ethernet with LAG.  This choice implies that each of the two radio cores will send data on a seperate ethernet cable (you'll need an extra port activation license - Link Planner should add that to the BOM along with any additional cabling needed).  The assumption is that the links will be bonded by switches they are connected to.  Chose the switches wisely, the best are able to keep about 92% of the capacity while the worst could drop that number to 72%.

3.  Multiple Ethernet without LAG.  In this scenario the two paths are kept seperate.  Maybe used by different users.  In one case I worked with, a service provider was able to get access to a desirable city owend tower if they gave the 911 emergency system a seperate path at the same time.  That's a scenario where this makes sense, although I'm sure there are more but you get the idea.  Each radio path is it's own thing and the two will likely never meet.   In this scenario you'll also need a licese and cabling to enable that second data path, and once again Link Planner should take care if it for you if you make the right choices.

I hope this adds a bit of clarity to what can be a confusing decision.

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Thanks for sharing and helping to clarify, Alan. I wanted to add that typically multiple ethernet with and without LAG can both be aggregated in a switch or be treated as separate connections.

Multiple ethernet with LAG requires the operator to create a LAG group of the two radio cores within the PTP820C and establish a Multipoint (MP) service with three service points - the LAG group of both radios being one service point and the two user data ports (ethernet and/or SFP) as two additional service points. Because this is being set up as an MP service and not a typical P2P pipe service this requires the LAG group to be configured as an SNP service point and the user ports as SAP service points and a specific V-LAN ID each or bundled V-LAN ID's each. This is one of the more complex options for running multiple data runs. 

Multuple ethernet without LAG is the simpler of the two non-MC-ABC options and involves the operator configuring two separate P2P pipes. One P2P pipe would be a service of one radio core and an ethernet port and the second P2P pipe would be a service of the other radio core and the other ethernet port. 

In both cases you can either LAG the runs in a switch or just treat them as separate runs for segregated traffic in a switch. 

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Thanks for the information. I was just going through this choice last month for a new link I needed. Because of frequency constraints we went with a PTP820c 6GHz at 60mhz with MCABC. I've always found it cleaner and easier for management doing MCABC instead of lag.

I thought I read somewhere that MCABC isn't support at 80mhz? Is that not the case anymore?

-Chris

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Chris,

Good point - thanks for pointing that out. MC-ABC is not supported on 80MHz channels any more so multiple ethernet with/without LAG would be the two remaining options. The other thing to point out is that for 80MHz channels the max throughput is 1.2Gbps over the RF link and the ethernet ports are gigabit so it would usually be best to run multiple ethernet. In your case with the 6GHz frequency band  60MHz is the largest channel size so the gigabit port would be sufficient to pass the maximum achievable throuhput across the RF link of about a gig with the MC-ABC setup.