Mobile Tutorials, Satellite And IPTV tutorials, PC And Automotive Tips

What is Link Aggregation As a Networking Technique?

Home » Technology » What is Link Aggregation As a Networking Technique?

Published on at > Last Updated by .- Leave a Comment

What is Link Aggregation?

Link aggregation refers to ‘bundling’ physical link segments with the same transmission media type and rate. Logically, it resembles a single link. Link aggregation, also known as trunking, allows for the simultaneous utilization of multiple physical links between switches or between switches and servers, exponentially increasing bandwidth.

Types And Classifications of Link Aggregation

Link aggregation modes are divided into static aggregation and dynamic aggregation.

1. Static Aggregation

static link aggregation

Static aggregation is also called static Trunk (on mode). Users need to configure the aggregation group number manually and port members and directly add multiple physical ports to the aggregation group to form a logical port.
Don’t Miss:

Static aggregation does not run the LACP protocol. Since the status of the link’s peer port cannot be detected if it is down, as long as the local port is up, traffic will still be forwarded to the peer port, which may cause some service interruptions.

2. Dynamic Aggregation

dynamic link aggregation

Dynamic aggregation runs the LACP protocol based on the IEEE802.3 ad. LACP (Link Aggregation Control Protocol) is a standard protocol described by IEEE 802.3 ad.

LACP is a protocol that implements dynamic link aggregation. Simply put, it is a protocol that dynamically aggregates multiple physical ports into a Trunk group to improve bandwidth and redundancy.

LACP allows switches to negotiate through messages to determine which physical links can be bundled together and set corresponding parameters, such as priority, activity status, etc. When multiple physical links are bundled into a logical link, they share the same IP address and MAC address, thus forming a logical high-speed channel.

How does LACP(Link Aggregation Control Protocol) Work?

1. LACP dynamic mode aggregation group establishment process

LACP exchanges information with the peer through LACPDU (Link Aggregation Control Protocol Data Unit).
 After the LACP protocol is enabled on a certain port, the LACPDU message contains information such as the device’s system priority, MAC address, interface priority, interface number, and operation key. After the peer receives this information, it is combined with the information saved by other ports.
The information is compared to select a port that can be aggregated. Both parties agree on whether the port joins or exits a dynamic aggregation group and determine the link responsible for business traffic.
  • Both ends send LACPDU messages to each other.
     Create a link aggregation group on devices at both ends, configure LACP mode, and configure member interfaces. Currently, the LACP protocol is enabled on the member interface, and both ends send LACPDU messages to each other. The LACPDU message contains information such as the device’s system priority, MAC address, interface priority, interface number, and operation key.
  • Member interface joins link aggregation group. Both devices at both ends will receive LACPDU packets sent from the opposite end. Both ends view and record the peer information, compare this information with the information saved by other member interfaces of the aggregation group, and select a link aggregation group to join.
  • Determine the aggregation group active interface.
     Active interfaces in the link aggregation group are selected based on the interface priority, and data is forwarded from these active links in a load-balancing manner.

2. LACP Working Mode

LACP working modes can be divided into active mode and passive mode:
  • In active mode, the network device actively sends LACPDU and waits for a response from the peer device. If the peer device also supports LACP and is configured in passive mode, it will respond with LACPDU to establish link aggregation.
  • In passive mode, the network device only receives LACPDU and responds accordingly according to the request. Devices in passive mode are usually not active.
If the LACP working mode of the dynamic aggregation group member port is passive mode and the peer end is also the same, neither end will send LACPDU. If the working mode of LACP on either end is active mode, LACPDUs can be exchanged between member ports.

3. LACP Time Out Mode

LACP timeout modes include long timeout and short timeout.
  • The long timeout mode is to send LACPDU slowly (30-second cycle), and the long timeout is a 90-second timeout.
  • The short timeout mode is to send LACPDU quickly (1-second period), and the short timeout is 3 3-second timeout.
The default LACP timeout mode is long timeout. That is, the sending cycle is 30 seconds to send an LACP protocol message, and if no LACP protocol message from the peer is received for more than 90 seconds, the negotiation fails.

What are the benefits of link aggregation?

  • Increase link bandwidth

    Link aggregation can increase network bandwidth. It forms a logical interface by aggregating multiple physical ports together. The maximum bandwidth of the link aggregation interface can reach the sum of the bandwidths of all member interfaces, thereby achieving a peer-to-peer physical link and doubling the bandwidth simultaneously.

  • Improve Network Reliability

    Link aggregation realizes link redundancy backup. When link aggregation is configured, when an active link fails, traffic can be switched to other available member links, thereby improving the reliability of the link aggregation interface and achieving link redundancy. For example, in the case of cross-slot link aggregation, service interruption caused by a single-slot failure can be well avoided.

  • Implement traffic load sharing.

    Within a link aggregation group, traffic can be shared to all member links based on certain rules. For example, the five-tuple includes source IP, destination IP, etc., thereby achieving load sharing of inbound/outbound loads on each member link. Reduce pressure on a single link.

What Are The “Use Scenarios” for Link Aggregation?

1. Fixed home broadband & campus network access scenarios

what is link aggregation?
With the increase in fixed network services, including home broadband, IPTV, and other traffic, the access bandwidth pressure of OLT is gradually increasing. Fast and convenient broadband can be doubled through link aggregation. In addition, the increase in campus network access traffic is also experiencing rapid growth, and link aggregation is also widely used in campus network switch connections.

2. Mobile bearer access scenario

Mobile bearer access scenario

With the rapid growth of 5G services such as data and high-definition video services, the requirements for large bandwidth and high reliability of mobile bearer networks have also increased significantly. Link aggregation technology is widely deployed in mobile backhaul IPRAN networks to achieve 10GE/ The 100GE link bandwidth is expanded, and link redundancy is ensured to achieve a high-reliability business guarantee.

3. BRAS network scenario

BRAS network scenarioBRAS is the core equipment for fixed network business authentication and authentication. It has very high requirements, whether it is the increase in access user traffic or link security and reliability. The deployment of link aggregation in the BRAS network has the flexibility of bandwidth expansion. As access user traffic increases, link aggregation group members can be added to adjust the bandwidth of the link aggregation link dynamically; at the same time, link aggregation cross-board Bundling ensures the reliability of each board for tens of thousands of users.

4. Data center scenario

Link aggregation in Data center scenario

Data centers such as 5G telecom cloud networks are the most core and critical networks for mobile services. The large number of applications of link aggregation ensures the bandwidth expansion and link reliability of mobile services in the data center while also reducing the load of link aggregation. Balancing can effectively utilize each member link of the link group to ensure efficiency.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.