Continuing our series of blog posts on the most representative technologies to consider when selecting switches, we will now address  port & link aggregation technologies.

Historical background on port & link aggregation

In the evolution of Ethernet standards, each new generation typically saw a tenfold increase in capacity compared to the previous one: 10 megabits/s, 100Mbits/s, 1000Mbits/s…

When applications required greater capacity, the usual recourse was to migrate to the latest Ethernet generation. However, the costs of infrastructure renewal could often be very high due to the novelty of these new generations. Moreover, this type of solution did not necessarily make the most out of previous investments.

As a result, some manufacturers began to introduce proprietary solutions to aggregate the capacity of various links. This way, significant improvements could be made while making use of existing infrastructure.

The adoption of proprietary solutions, however, brought compatibility issues. To address this, in March 2000, the IEEE developed the 802.3ad standard (LACP) for Ethernet channel port aggregation. It included the possibility of an automatic and negotiated configuration between peers at each end of a link.

How port or link aggregation works

Port and/or link aggregation offers a series of advantages:

Increased capacity: Thanks to link aggregation, the total connection capacity between two devices becomes that of the sum of their links.

Load balancing: Various load redistribution techniques can be applied among the links in a group. Some of these techniques try to minimize the effects of potential frame disarray.

Backup: If a link in a group fails, traffic is redistributed among the remaining operational links.

Manual vs. automatic configuration: Typically, switches allow you to statically and manually define a group of ports or links. However, the LACP protocol is almost always available to do this automatically and dynamically based on changes in different links. This negotiation occurs using LACPDU frames, establishing which ports of each switch are assigned to the same link.

The LACP protocol’s own packets are sent to a specific multicast group MAC address – 01:80:C2:00:00:02

During the initial discovery phase of LACP, these packets are transmitted every second. In the stable phase of LACP, it’s common to configure keep-alive mechanisms, which can be either slow (every 30 seconds) or fast (every second).

LACP – Link Aggregation load balancing mechanisms

In advanced LACP configurations, different load balancing mechanisms can be programmed:

• Load balancing based on source address, destination MAC address, or a combination of both
• Load balancing based on source address, destination IP address, or a combination of both
• Load balancing based on source and destination IP addresses, plus source and destination ports of the transport layer
• Advanced modes that incorporate combinations of the above criteria, along with other criteria based on VLANs, layer 2 protocols, etc.

These mechanisms seek to provide flexibility in load balancing control and minimize packet disarray for higher-level applications.

LACP – Link aggregation advantages

Unlike static port grouping, the use of LACP enables automatic fault detection. In some cases, a link between two switches may fail without one end detecting the port failure. Consequently, the switch carries on transmitting data through the faulty port until the whole network fails.

By utilizing LACP, each device makes sure that its counterpart at the other end supports link aggregation. In static aggregation, any configuration or cabling failure might slip by unnoticed and result in undesired connection behavior.

Conclusions on port or link aggregation

Link aggregation, in professional-grade switches, is a crucial tool for achieving an optimal and flexible network setup. It provides more capabilities than individual links without inflating deployment costs unnecessarily. It is also more reliable than using single links of higher standards.

This is particularly significant for network engineers managing LAN network planning and deployment, as well as the necessary device investments.

Windbit switches support link aggregation and LACP protocol, offering a powerful and flexible solution comparable to the most sophisticated models on the market.