24 CHAPTER 2: OPTIMIZING BANDWIDTH
■ Before removing an entire aggregated link, you must disable all the
aggregated link ports or disconnect all the links, except one — if you
do not, a loop may be created.
■ When manually creating an aggregated link between two devices, the
ports in the aggregated link must not be physically connected
together until the aggregated link has been correctly configured at
both ends of the link. Failure to configure the aggregated link at both
ends before physically connecting the ports can result in a number of
serious network issues such as lost packets and network loops.
Traffic Distribution and Link Failure on Aggregated Links
To maximize throughput, all traffic is distributed across the individual links
that make up an aggregated link. Therefore, when a packet is made
available for transmission down an aggregated link, a hardware-based
traffic distribution mechanism determines which particular port in the link
should be used. The traffic is distributed among the member links as
efficiently as possible.
To avoid the potential problem of out-of-sequence packets (or “packet
re-ordering”), the Switch ensures that all the conversations between a
given pair of endstations will pass through the same port in the
aggregated link. Single-to-multiple endstation conversations, on the
other hand, may still take place over different ports.
If the link state on any of the ports in an aggregated link becomes
inactive due to link failure, then the Switch will automatically redirect the
aggregated link traffic to the remaining ports. Aggregated links therefore
provide built-in resilience for your network.
The Switch also has a mechanism to prevent the possible occurrence of
packet re-ordering when a link recovers too soon after a failure.
Aggregated Link —
Manual
Configuration
Example
The example shown in Figure 6
illustrates an 8 Gbps aggregated link
between two Switch units, (that is, each port is operating at 1000 Mbps,
full duplex).
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