Signamax
™
065-7921PoE 12-Port 10/100/1000BaseT/TX Web Smart PoE Switch
46
3-6. Link Aggregation
Basically, Link Aggregation is to aggregate the bandwidth of more than one port to an
assigned logical link. This highly increases total bandwidth to the targeted device. There is
more than one Link Aggregation technology in many vendors’ switch products already, which
may cause the problem of interoperability. This is the reason why now we have 802.3ad Link
Aggregation Control Protocol (LACP).
Why 802.3ad (LACP)?
Network is varying. For example, if a port malfunctioned or unplugged accidentally in a
static trunk port, administrator has to reconfigure it, or the network will get trouble. Therefore,
offering a tool with automatic recovery capability is necessary for an administrator. LACP is a
protocol that allows a switch able to know whether its partner has the capability to co-setup a
trunk between them.
Usually, if administrator wishes to increase the bandwidth of a specific link, he may:
1.
Buy new network equipments with higher throughput, or
2. Aggregate the bandwidth of more than one port to a logical link.
If the item 1 is the case, you will pay much more cost beyond your budget, and the
solution caused by the limitation of hardware performance may not be scalable.
If the item 2 is the case, now you do not have to pay much more extra cost and can
keep flexible according to the demand of bandwidth because all equipments are there already.
And what’s more, you can avoid worrying about the interoperability issue. Applying LACP in
your network, you will not only gain benefits below to improve the performance of your network
but also have these investments usable to future new 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 mis-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 100Mbps or all 1000Mbps. You cannot aggregate a 1000Mbps
and two 100Mbps for a 1.2Gbps trunk port.
