PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
When a group is already started, IMA supports the addition of links to the group.
As illustrated by Figure 14, adding a link with a transport delay that is within the
range of the existing links does not present any problems. The DCB for the new
link must be aligned with the existing links and added to the round-robin for
playout.
Adding a link with a smaller transport delay increases the differential delay of the
group. This requires that the depth of the DCB buffer be larger than any of the
existing links. As long as the differential delay is within acceptable bounds, the
new link can be accepted. The DCB for the new link is aligned with the existing
links and added to the round-robin for playout.
Figure 15
- Snapshot of DCB Buffers after addition of Link with smaller
transport delay
DCB
DCB
DCB
DCB
Link 0
Link 1
Link 2
Link3
Write
Pointer 3
36
32
28
24
20
16
12
8
Write
Pointer 0
25
21
17
13
9
Write
Pointer 1
14
10
6
Write
Pointer 2
5
7
3
Group
Read
1
2
4
Pointer
Adding a link with a larger transport delay requires the DCB buffer depth to be
smaller than the DCB for the link with the largest delay. If the desired DCB depth
for the new link is less than 0, this means that the data for the other links has
been played out prior to the arrival of data for the new link. This is shown in
Figure 16. For the new link to be accepted, delay must be added to all other links
in the group. When delay is added to the other links in the group, the playout of
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
63
PMC [ PMC-SIERRA, INC ]
