3Com 4500G Series, Configuration Manual

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Table 1-2 Basic and extended LACP functions
Category Description
Basic LACP functions
Implemented through the basic LACPDU fields including the system LACP
priority, system MAC address, port LACP priority, port number, and
operational key.
Each member port in a LACP-enabled aggregation group exchanges the
above information with its peer. When a member port receives an LACPDU,
it compares the received information with the information received on the
other member ports. In this way the two systems reach an agreement on
which ports should be placed in the selected state.
Extended LACP
functions
Implemented by extending the LACPDU with new Type/Length/Value (TLV)
fields.
This is how the LACP multi-active detection (MAD) mechanism of the
Intelligent Resilient Framework (IRF) feature is implemented.
Switches of the 4500G series that support extended LACP functions can
function as intermediate devices in LACP MAD implementation
For details about IRF, member devices, intermediate devices, and the LACP MAD mechanism, see the
operation manuals of IRF-supported devices.
2) LACP priorities
There are two types of LACP priorities: system LACP priority and port LACP priority, as described in
Table 1-3 .
Table 1-3 LACP priorities
Type Description Remarks
System LACP
priority
Used by two peer devices (or systems) to determine which one is
superior in link aggregation.
In dynamic link aggregation, the system that has higher system
LACP priority sets the selected state of member ports on its side first
and then the system that has lower priority sets port state
accordingly.
Port LACP
priority Determines the likelihood of a member port to be selected on a
system. The higher port LACP priority, the higher likelihood.
The
higher the
priority
value, the
higher the
priority.
Marker protocol
During a session, if member ports are added to or removed from a dynamic link aggregation group,,
service traffic will need to be redistributed among all the new member ports of the link aggregation
group. The Marker protocol can be employed to quickly redistribute service traffic within link
aggregation groups and ensure the orderly transmission of data frames. The process is as follows:
z
The device stops transmitting service traffic and starts a timer during which no data frames will be
transmitted on the links.
z
The local end uses the Marker protocol to send a Marker Protocol Data Unit (PDU).