Link Aggregation Control Protocol

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What Does Link Aggregation Control Protocol Mean?

Link Aggregation Control Protocol or LACP is one element of an IEEE specification (802.3ad) that provides guidance on the practice of link aggregation for data connections.


Importantly, LACP typically applies to strategies that bundle individual links of Ethernet connections, and not wireless transfers.

Techopedia Explains Link Aggregation Control Protocol

To understand Link Aggregation Control Protocol, it’s important to first know what link aggregation is and what it means for networks.

What is Link Aggregation?

Link aggregation is the practice of bundling individual links on a network to promote better performance outcomes.

The semantics here can vary: insiders might talk about similar practices like port trunking or link bundling in ways that can cloud the particular definition: again, LACP is built on specific protocol revealed in IEEE 802.3ad and elsewhere.

Experts may refer to groups of ports as “link aggregation groups” or label the parts and pieces, including physical ports, in more nuanced ways, which might require some clarification.

What Are Some of the Major Things That Link Aggravation Does?

First, it provides redundant network activity. Suppose you have a single link, and that link fails. All of a sudden, you have a 100% lack of data connectivity. Your system just cuts off, it “goes dark.”

With link aggregation, on the other hand, you get multiple delivery paths, and the ability to do load-balancing across all of the available links. Now, using the same link for each related packet is still a best practice.

Making sure that all related data packets go through the same individual link solves potential problems with out-of-order packets, and link aggregation has to address this reality.

However, as you might imagine, the bundling of individual links leads to much more durable signal interfaces.

There’s also the promise of “graceful degradation” — in other words, failure occurs slowly, and gradually, not all at once.

Instead of “cutting off,” a signal might only initially suffer a small but of degradation, giving the end user or other stakeholders time to react and diagnose the problem and address it.

Various link aggregation configuration guidelines help to optimize how link aggregation protects network data and performance.

With that in mind, LACP promotes the formation of better logical virtual links or bundles that can be handled as one unified whole by an MAC client.

Generally, the bundling offers system designers and administrators new ways of addressing points of failure and recovery capabilities without going to greater extremes.

As part of Link Aggregation Control Protocol practices, engineers identify the aggregated interface, and confirm link status. The identifier value for the virtual local area network will also be included.

As noted by experts, it’s important that devices on both ends of the connection support link aggregation in the same ways, so “termination” may also be important.

Systems inherent in the LACP process can also help to handle the out-of-order packet problem: tools referred to as “scheduling algorithms” define packet-to-packet activity to keep things working well.

Although vendor systems provide for this protocol, some open source providers also accommodate the implementation of link aggregation with resources to help support this type of approach.

In general, LACP helps to standardize how link aggregation happens, for more durable Ethernet transmissions.


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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.