User`s guide

Signamax 065-7931 16-Port 10/100/1000BaseT/TX WebSmart Switch
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3-6. Link Aggregation
The basic function of Link Aggregation is to aggregate the bandwidth of more
than one port to an assigned logical link. This highly increases the total available
bandwidth to the targeted device. There is more than one Link Aggregation
technology in many vendors’ switch products already, which may cause an
interoperability problem. This is the reason why the 802.3ad Link Aggregation
Control Protocol (LACP) standard was developed.
Why 802.3ad (LACP)?
Networks are constantly evolving and changing. For example, if a port
malfunctioned or was accidentally unplugged in a static trunk port, the administrator
has to reconfigure it, or the network will not operate properly. Therefore, offering a
tool with automatic recovery capability is necessary for an administrator. LACP is a
protocol that allows a switch to be able to know whether its partner has the
capability to co-setup a trunk between them.
Usually, if the administrator wishes to increase the bandwidth of a specific
link, he or she may:
1. Buy new network equipment with higher throughput, or
2. Aggregate the bandwidth of more than one port to a logical link.
If item 1 is the case, the solution’s cost may exceed the budget, and the
solution may not be scalable due to hardware limitations.
If item 2 is the case, costs are controlled and the existing equipment can
flexibly accommodate to the new bandwidth demands associated with changes in
the business. What’s more, the interoperability issue is no longer a concern. By
applying LACP in their network, a business reaps the benefits shown below of
improving the performance of their network and saving funds that can be used to
develop future products:
1. Public standardized specification
2. No interoperability issue
3. No change to IEEE 802.3 frame format, no change in software and
management.
4. Increased bandwidth and availability
5. Load sharing and redundancy
6. Automatic configuration
7. Rapid configuration and reconfiguration
8. Deterministic behavior
9. Low risk of duplication or incorrect ordering
10. Support existing IEEE 802.3 MAC Clients
11. Backwards compatibility with aggregation-unaware devices
There are also some constraints when applying LACP.
1. LACP does not support inter-switch bandwidth aggregation.
2. The ports aggregated must operate in full-duplex mode.
3. The ports in the same Link Aggregation Group must have the same
speed, for example, all with 100 Mbps or all 1000 Mbps. You cannot
aggregate a 1000 Mbps link and two 100 Mbps links to create a 1.2
Gbps trunk port.