PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
If sufficient links are not accepted, the group will not become operational. Note
that within any collection of links that are targeted to form an IMA group the group
may not become operational even though there are combinations of Prx links that
meet the programmed maximum DCB threshold. This would occur in situations
where the internal algorithm used to determine link order may not select the
combination or “tightest” grouping of links that would otherwise meet the
programmed maximum DCB threshold. In this case, the relative delays of the
links are available to the plane management (.i.e. microprocessor) using the
read_delay command. The microprocessor can then analyze this information,
remove the offending link or links and restart the group.
10.2.5.2
Link Addition and Differential Delay
Once a group is started, the delay profile for the group is determined. In order to
add links, the delay on the new links must be compatible with the existing links in
the group and be able to be synchronized with the existing links within the DCB
constraints.
There are two mechanisms regarding delay that can be used.
The first method uses the guardband capability. At group start-up, a guardband is
added to the link with the longest transport delay. This guardband results in
additional delay to be queued in the DCBs for each link in the group. The
guardband allows for links with a longer transport delay to be added in the future
without introducing any additional CDV.
The second method allows the delay accumulated per link to be increased
dynamically. This method will introduce additional delay to all of the links within
the group when a link with a larger transport delay is added to the group. The
process of adding additional delay to the links within a group will cause additional
CDV to be introduced when the playout of data is stopped while the delay is
accumulated.
The RIPP determines the delay of the links that are being added and performs
the appropriate action to either include the link in the group or to reject the link if
the link cannot be synchronized within the DCB constraints If a link is rejected
due to delay, a LODS defect will be reported on the link.
When links are deleted from the group, the delay of the remaining links is not
adjusted.
See 10.2.4.2 for more details on the management of the DCB buffers.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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PMC [ PMC-SIERRA, INC ]
