Alcatel-Lucent 7705 Interface Configuration Manual page 63

Once a path becomes part of an IMA group logical link, the path ceases to exist as a physical
ATM path interface. This means that:
After the primary member has been added, each additional member added to the group will
only be accepted if it matches the configuration of the IMA group. ATM interface
characteristics are not part of this verification as they are overwritten or reset to defaults
when a link is added to or removed from an IMA group.
When a member is assigned to an IMA group, it is automatically assigned an IMA link ID.
IMA link IDs are in range from 0 to 7 and stay constant as long as the router does not reboot.
When configuring IMA groups, consider the following guidelines.
7705 SAR OS Interface Configuration Guide
• ATM interface characteristics enforced over the link are those of a group. When a
link is removed from an IMA group, the link's ATM characteristics are reset to ATM
interface defaults.
• no services can be configured on the member link itself
• IMA groups should contain at least two members.
• A maximum of eight members can be included in an IMA group.
• A maximum of eight IMA groups can be configured on a single adapter card.
• IMA bundles can only be aggregated on a single adapter card.
• IMA group maximum bandwidth and minimum link settings allow, by default, for
oversubscription of shaped services. When that occurs, however, scheduling of
traffic over an IMA group ATM interface degrades to round-robin between shaped
services. To preserve full ATM traffic management even during a member link
failure, it is recommended that maximum bandwidth be set to minimum links.
• When configuring the red differential delay for IMA groups on the 16-port T1/E1
ASAP Adapter card, the value configured is converted into an acceptable frame
sequence number delay on a link since delay is granular to IMA frame sequence
number difference. For E1 channels (receiving frame time 27 ms), configured values
map to the enforced values as follows: 0 ms maps to 0 frame sequence number
difference (27 ms delay), 1 to 27 ms maps to 1 frame sequence number difference
(54 ms delay), 28 to 50 ms maps to 2 frame sequence number difference (81 ms
delay). Similarly, for DS1 channels (receiving frame time 35 ms), configured values
map to enforced values as follows: 0 ms maps to 0 frame sequence number
difference (35 ms delay), 1 to 27 ms maps to 1 frame sequence number difference
(70 ms delay), 28 to 50 ms maps to 2 frame sequence number difference (105 ms
delay).
7705 SAR Interfaces
Page 63