PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
10.2.5.3
Removing accumulated delay
In some situations, removal of accumulated delay may be desired. This usually
occurs after a group has been operational for a period of time and the link
characteristics in terms of transport delay have changed. The adjust_delay
command is provided to remove delay from the group. The execution of this
command will effect the CDV of the group while the delay is reduced. Any delay
adjustment to the group will also effect the CDV of a connection carried on that
group. This is additive, if 20 ms of delay is removed from the group, a particular
connection within the group will experience an additional 20 ms of CDV. This will
generally only be a concern to CBR or VBR-rt traffic flows. This increase in CDV
may cause traffic to be policed out or real time applications to experience slips.
To minimize the effect on the group traffic rate, while the delay is being reduced,
the ATM cells from the group will be transferred to the ATM layer at a rate of
(1+1/16)*IDCR versus IDCR. In other words, the group will playout data 6.25%
faster to the ATM layer during the process of delay reduction.
The amount of time the delay removal takes depends upon the amount of delay
to be removed. For example, a group where 200 ms of delay is to be removed
takes approximately 3 seconds for the process to complete.
While delay adjustments are being made to a group, new links can not be added
and links can not be recovered from an error state. The S/UNI-IMA-8 will reject
any requests to start a LASR procedure. However, while delay adjustments are
in progress, links can be deleted or made unusable.
10.2.5.4
Group Start-up Procedure
When the Add_Group Command is issued, the Group state machine will enter
the start-up state and start to send IMA frames on the configured Tx links.
10.2.5.4.1
Start-up State
While in the start-up state, the configured tx link state machines will be reporting
the Unusable state and the rx-link state machines will be reporting Not_In_Group.
At this point, the S/UNI-IMA-8 will start to monitor the incoming ICP cells. When
ICP cells are received with the FE indicating that the Group is in Start-up, the
S/UNI-IMA-8 will transition to the Start-up-Ack state if the M value, the Group
Symmetry, the OAM Label and IMA_ID (optional) values are acceptable.
Otherwise, the S/UNI-IMA-8 will transition into the Config-Aborted State.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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PMC [ PMC-SIERRA, INC ]
