Load Balancing Using Link Aggregation - Huawei AR530 series Configuration Manual

Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching

2.2.5 Load Balancing Using Link Aggregation

A data flow is a group of data packets with one or more identical attributes. The attributes include
the source MAC address, destination MAC address, source IP address, destination IP address,
source TCP/UDP port number, and destination TCP/UDP port number.
Because there are multiple physical links between devices of the Eth-Trunk, the first data frame
of the same data flow is transmitted on one physical link, and the second data frame may be
transmitted on another physical link. In this case, the second data frame may arrive at the remote
device earlier than the first data frame. As a result, packet mis-sequencing occurs.
To prevent packet mis-sequencing, Eth-Trunk uses the load balancing mechanism. This
mechanism uses the hash algorithm to calculate the address in a data frame and generates a
HASH-KEY. Then the system searches for the outbound interface in the Eth-Trunk forwarding
table based on the generated HASH-KEY value. Each MAC or IP address corresponds to a
HASH-KEY, so the system uses different outbound interfaces to forward data. This mechanism
ensures that frames of the same data flow are forwarded on the same physical link and
implements flow-based load balancing. Flow-based load balancing ensures the sequence of data
transmission, but reduces the bandwidth usage.
2.3 Application Environment
This section describes application environments of Ethernet link aggregation.
2.3.1 Application of Eth-Trunk
As shown in
through the UPE and PE-AGG. To ensure the bandwidth and reliability of the link between the
UPE and PE-AGG, an LAG, Eth-Trunk 1, is established.
Issue 01 (2014-11-30)
2. Select the backup link with the highest priority among N backup links to replace the
faulty active link.
The highest priority backup link becomes the active link and begins forwarding data.
Figure 2-9, traffic of services with different priorities is sent to the core network
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