802.3ad - Link Aggregation

Link Aggregation allows for multiple 10, 100, or 1000Mbps Ethernet ports to be combined to form one high speed, logical link to another network device. Think about each Ethernet port as a tube in varying widths depending on it’s speed (10Mbps would be a straw, 100Mbps would be a paper roll..etc). Link aggregation essentially combines all 3 tubes to create, say, a large pipe. Any combination of the three supported port speeds can be used to create the logical link because the switch handles the distribution of traffic to each port dynamically.

The difference between physical links and logical links is that physical links are referring to the actual physical cabling (CAT5 Ethernet) versus the logical links that refers to the virtual combining of all three links to form a large pipe.

Along with distributing traffic among ports evenly, the switch will also be able to redistribute traffic to the ports that are still active if one of the physical links goes down. In order to utilize this technology, both the switch and the device connecting to the switch need to support the 802.3ad standard.

Prior to this standard, many vendors created proprietary methods of combining ports, which was referred to as “Port Trunking”. Because each vendor had their own method of implementing port trunking, compatibility across vendors was an issue. 802.3ad should eliminate this problem by standardizing the method by which every vendor implements the same technology based on the 802.3ad standard.

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