Link Aggregation is a technology that will allow us to "join" several physical links, into a single logical link, to have speeds of 2Gbps or more. Link aggregation , or IEEE 802.3ad , is a data networking term that describes how to use multiple full-duplex Ethernet links to communicate between two computers, spreading the traffic between them.
Trunking or link aggregation is an inexpensive way to install a high-speed network faster than a single port or device of the technology available. It basically consists of grouping several devices that work simultaneously at their maximum speed as if it were a single link with greater capacity.
LACP
The LACP protocol (Link Aggregation Control Protocol–IEEE 802.3ad) allows us to unite several physical connections of a network device forming a single virtual one with the aim of achieving higher speed access as well as improving the availability and redundancy of the link. This link aggregation or port trunk will be responsible, in case of failure of one of the physical connections that form it, of redistributing the load among the remaining links, thus achieving continuous operation without interruptions.
What is Link Aggregation and what is it used for?
Link Aggregation is a very interesting function included in network cards with two ports, and also in NAS servers that have two or more Gigabit Ethernet ports. Link Aggregation allows us to combine two or more physical links (either Fast-Ethernet, Gigabit Ethernet and even 10Gigabit) so that we can expand the bandwidth of the connection. If, for example, we join two cables at 1Gbps , we will have a performance of up to 2Gbps.
This technique can be useful to join a router with a switch, or two switches, so that the connection, at least locally, is as fast as possible, something very important if we usually share files and resources on the local network. Thanks to this technology, we can also have the different network equipment, such as a NAS, connected with higher bandwidth.
Regardless of our Internet connection, if we have a NAS connected to the local network through a single Gigabit Ethernet cable, the maximum speed at which we can copy files, or download them to our computer, will be 1 Gbps, approximately 110 MB/s approximately . This can mean that, if several users access the NAS at the same time, the bandwidth of the Gigabit Ethernet connection will be shared among them, and they will not be able to take full advantage of the modern NAS hardware. The same can happen with a very powerful computer connected to a local network that shares files with other users on the LAN. If our computer is limited by the Gigabit Ethernet port of the network card, it is most likely that if other computers on the network try to access our shared resources, we will easily run out of bandwidth and they will have to share the speed between them.
Link Aggregation is a standard that is currently available in all managed switches and in most operating systems and NAS servers, however, for this function to work correctly, it is necessary to meet certain requirements regarding the configuration of both, three or more links that we are going to “join” into a single logical link:
- All links that are part of the Link Aggregation must always be Full-Duplex.
- The synchronization speed of all the links must be exactly the same, if one link synchronizes at 1Gbps, all of them must synchronize at this speed.
- If we are configuring the Link Aggregation in a managed switch, it is necessary that the VLANs configuration in the links be the same (either trunk, access mode or trunk with certain VLANs).
If any of these requirements are not met, the Link Aggregation cannot be negotiated correctly. A very important detail is that, when we configure a Link Aggregation and one of the links fails, the link that is still active will work without problems, in this way, we will not be left without a wired connection. Another important aspect is the Link Aggregation algorithms for load balancing, when we configure this in a high-end manageable switch, we can choose the load balancing management algorithm, these algorithms can be the following:
- src-ip: Check the source IP by balancing the traffic depending on the source.
- src-mac: Check the source MAC by balancing the traffic depending on the source.
- dst-ip: Check the destination IP by balancing the traffic depending on the destination of the traffic.
- dst-mac: checks the destination MAC by balancing the traffic depending on the destination of the traffic.
- src-dst-ip: checks both source and destination IPs, and allows greater granularity so that traffic is better balanced between physical links.
- src-dst-mac: Checks both source and destination MACs, and allows greater granularity so that traffic is better balanced between physical links.
- src-dst-ip-port: checks both source and destination IP as well as the port (TCP or UDP) used, this algorithm is the one with the greatest granularity.
As you have seen, Link Aggregation is a really interesting standard protocol, which will allow us to increase bandwidth and provide us with failover of the wired connection.
Requirements
This protocol can be implemented in our switches from both the Smart and Managed ranges of D-Link . With it we can form up to 32 port trunk groups where, in turn, each one can have up to 8 ports (except that each port can only belong to one group). The ports chosen to form the port trunk must have the same speed and identical configuration (full duplex, members of the same VLANs, the same STP status, ...). Once the link aggregation is formed , load balancing will be applied automatically based on an algorithm that we can determine. The options on which you can base your decision on which port to send the information through are:
• Source MAC >> is the option that is marked by default
• Destination MAC
• source/destination MAC
• source IP
• destination IP
• source/destination IP
Buy technology with Link Aggregation
The first thing we are going to need is that the network equipment is compatible with this technology. Not all routers support Link Aggregation, just as not all switches do. Most high-end routers will support this technology, having two Gigabit Ethernet ports dedicated to Link Aggregation .
Manageable switches are the same, a good switch will allow us to perfectly manage our Link Aggregation connections , either to connect a PC or a NAS or to connect to the router and have a higher speed router-switch link.
Today's mid-high range NAS come with multiple Gigabit Ethernet ports. In the case of a PC, the best we can do is buy a network card that supports this feature.
Link Aggregation on Synology NAS
Synology NAS supports multiple LANs, allowing you to combine those LAN interfaces with the help of Link Aggregation technology. Link Aggregation increases the bandwidth of Synology NAS by aggregating multiple network interfaces and provides failover function for traffic so that the network connection is maintained in case of connection failure.
After the LAN interfaces are bonded, you will see a new interface called Bond in Control Panel > Network > Network Interface , which can be configured in the same way as other interfaces (such as LAN or PPPoE).
- Link Aggregation is only available on models with at least two LAN ports.
- By enabling Link Aggregation, network traffic will automatically adjust and balance for each connected device.
- If the network interfaces are connected to multiple switches, make sure the switch ports are in the same LAN or VLAN.
Mode descriptions:
- Adaptive Load Balancing : This mode optimizes the network traffic received and sent by Synology NAS regardless of whether the switch supports Link Aggregation or not. To avoid unexpected errors, do not enable Link Aggregation on the switch even if it is supported.
- IEEE 802.3ad Dynamic Link Aggregation : This mode optimizes the network traffic received and sent by the Synology NAS and requires IEEE 802.3ad (Dynamic) Link Aggregation (LACP, 802.1AX) to be enabled on the switches. If multiple switches are used, they must be stackable and properly configured.
- Balance XOR : This mode balances the network traffic received and sent by the Synology NAS and requires Static Link Aggregation to be enabled on the switches. If multiple switches are used, they must be stackable and properly configured. Even if the switch does not support Link Aggregation, it is still possible to balance the Synology NAS. This mode can detect lost links, but not the cause (for example, when Ethernet cables are unplugged or the switch is not configured correctly).
- Active/ Sleep : This mode provides the network fault tolerance feature to the Synology NAS. That is, when the active network interface goes offline, one of the other LAN ports will take over to maintain the network connection. You can choose this mode without configuring the switch or with a switch that supports IEEE 802.3ad Link Aggregation.
If you have enabled Open vSwitch, you can select one of the following modes:
- SLB Balance - This mode balances network traffic without requiring support for specific network switches and enables the connection between two switches.
- TCP Balance – This mode enables connection to switches configured as Dynamic Link Aggregation (IEEE 802.3ad LACP). If multiple switches are used, they must be stackable and properly configured.
- Active/Backup Mode : This mode provides your Synology NAS with network fault tolerance via two network interfaces. When the active network interface malfunctions, the other will take over to maintain network connectivity. You can choose this mode without setting the switch.
Some gaming motherboards usually have two 1Gbps network cards with Link Aggregation support. If we have a link of more than 1 Gbps, such as 2.5G or 5G, and even if we have network connections at 10Gbps, or through Link Aggregation, we can get a little more bandwidth in our wired connection.
Alternatives if I don't want to use Link Aggregation
Although Link Aggregation has its own approved standard, IEEE 802.3ad , for many it is the "cheap option" to go beyond Gigabit Ethernet. However, if we want a network that is as professional as possible, there are other much better options to take the bandwidth of our connection to a new level.
If we don't mind making a significant investment, the best alternative to Link Aggregation is to set up a 10 Gbps network made up of a router compatible with this protocol, 10G switches, 10G network cards, and of course, category 6 cable or higher.
Sources:
https://www.redeszone.net/tutoriales/redes-cable/link-aggregation-que-es-como-pulsa/
https://eu.dlink.com/es/es/resource-centre/articles/configurar-link-aggregation
https://kb.synology.com/en-us/DSM/help/DSM/AdminCenter/connection_network_linkaggr?version=6
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