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Link Aggregation

The other aspect of bandwidth that a smart switch can help with is expanding it by combining switch ports to act as a single, higher-bandwidth port. This is particularly handy for removing the choke point that can be caused by a single uplink port on a busy switch. If multiple Gigabit-connected clients are trying to transfer large files to other Gigabit clients on an uplinked switch, you're going to have problems. It might take more clients than you'd expect because the hard drives on both systems will limit throughput far below that of the Gigabit link. But if you get enough clients going at once, things will eventually slow down.

Combining (aggregating) ports can help ease this pain. There are many ways to aggregate ports, but the GS108T supports only manual / static and Link Aggregation Control Protocol (LACP), which also known as 802.3ad.

If all you want to do is double (or triple) the bandwidth between two uplinked switches, you just go to the LAG Membership screen and select the ports you want in the LAG (Link Aggregation Group). Figure 5 shows ports 7 and 8 selected for a LAG 1.

Figure 5: Adding ports to a LAG

You then visit the LAG Configuration screen (Figure 6) to enable the LAG. If you set LACP to Disable, you get a static LAG. If you set it to Enable, 802.3ad handling is turned on. Again, for simply combining ports for switch-to-switch uplink, either static or LACP will work.

Figure 6: Configuring the LAG

If, on the other hand, you are aggregating ports to support higher bandwidth to teamed adapters in a device, you'll probably want to enable LACP, if the device supports it. Figure 7 shows the options presented by the driver(s) for two Intel Gigabit adapters in one of my systems, with 802.3ad selected. To set the GS108T to match, I'd just change the LACP setting for the LAG from Disable to Enable.

Figure 7: Intel NIC teaming options

I hope this series has provided some insight into how even a relatively inexpensive "smart" / managed switch can enhance the ability to control your LAN.