3Com CoreBuilder 3500, Implementation Manual, Page: 148 / 592

148 C
HAPTER
8: T
RUNKING
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3Com recommends that you use trunks to increase network
availability in the following scenarios:
■
Switch-to-switch connections in the data center and campus
interconnect areas
■
Switch-to-server connections in the data center and campus
interconnect areas
■
Downlinks from the data center to the campus interconnect
■
The trunking feature in 3Com switches is currently a proprietary
implementation. No
de facto standards currently exist.
Trunk Capacity
Guidelines
■
The device-to-device burst-transmission rate across a trunk is limited
to the speed of just
one of the port-to-port links within the trunk. For
example, the maximum burst rate over a 400 Mbps pipeline with four
trunked Fast Ethernet links is 100 Mbps. This limitation preserves
frame ordering between devices, usually by moving all traffic between
two specific MAC addresses across
only one port-to-port link .
Therefore, trunking provides no direct benefit for some one-way
applications, such as server-to-server backups. This limit exists for most
vendor implementations.
■
The total throughput of a trunk is typically less than the bandwidth
obtained by adding the theoretical capacity of its individual links. For
example, four 1000 Mbps links do not yield a 4000 Mbps trunk. This is
true with all vendor implementations.