Link Aggregation

Question

Link Aggregation

Trying to setup and test Link Aggregation on a local network using a Mac Mini (2012) with built-in ethernet and a Thunderbolt to Ethernet Adapter. I'm also using a Netgear GS108T switch that supports Link Aggregation.

Link Aggregation setup pages from the netgear switch:

According to System Preferences, the Link Aggregation is setup correctly.

My understanding of Link Aggregation is that when multiple clients send or request data, it will split across the multiple connections (in my test case, sending a 4GB file from two separate machines). But this simply is not happening. Each client is uploading at roughly 55MB/s vs the theoretical 125MB/s. When one of the clients uploads by itself, it reaches ~112MB/s. Without the ethernet bond set up and using individual IPs (for the ethernet and TB->Ethernet adapter) on another switch with both clients uploading at the same time, it reaches combined speeds of 230MB/s since they are each using their own IP address.

Is my thought process on how link aggregation completely wrong, or am I just not setting things up correctly?

Posted on Dec 30, 2016 4:43 PM

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Answer 1

BDAqua

Level 10

250,259 points

Dec 30, 2016 11:02 PM in response to Josh Schaefer

I'm far from expert on this, but I never heard of it splitting requests, only combining ports for a single request.

To be able to use link aggregation, the following prerequisites must be fulfilled. All of the aggregated links must:

be in full duplex mode

use the same data transmission rates (at least 1 Gbit/s)

use parallel point-to-point connections

connect to precisely one endpoint on a switch or server

https://www.thomas-krenn.com/en/wiki/Link_Aggregation_and_LACP_basics

https://en.wikipedia.org/wiki/Link_aggregation

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Answer 2

Dec 31, 2016 1:31 AM in response to BDAqua

Thanks for bolding that section, but what it means is that the ethernet connections go to the same switch/computer.

I ended up partially figuring it out after taking a break from bashing my head into the wall... it turns out that simply removing the setup in System Preferences->Networking for the ethernet bond and letting the two ports (Ethernet and TB->Ethernet adapter) stay as they are configured on the GS108T switch and as individual components in System Preferences, I was able to achieve around 190MB/s sustained write speed to the server from two separate clients. Toss a download from the server on each one of the clients at the same time and I saw a max throughput of ~300MB/s combined read/write speed.

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Answer 3

BDAqua

Level 10

250,259 points

Dec 31, 2016 8:56 AM in response to Josh Schaefer

Ah, great work, thanks for the report! 🙂

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