Cisco Cisco IOS Software Release 12.2 Release Notes
15
Cisco DSL Manager
OL-3177-01B
Limitations and Restrictions
Figure 2
SPVCs Dynamically Rerouted
Requirements
If you implement ring topology in a DSLAM subtend to achieve ATM trunk redundancy, the following
requirements apply:
requirements apply:
•
You must use SPVCs, PNNI, ATM signaling, and Interim Local Management Interface (ILMI) to
enable rerouting. PNNI, ATM signaling, and ILMI are enabled by default. Permanent connections
such as PVCs and shaped virtual paths (VPs) do not benefit from the redundant link.
enable rerouting. PNNI, ATM signaling, and ILMI are enabled by default. Permanent connections
such as PVCs and shaped virtual paths (VPs) do not benefit from the redundant link.
•
You must make the redundant link’s PNNI administrative weight higher than the PNNI weight of the
primary trunk. Once you change the weight of the redundant link, the subtend tree uses this link only
if a failure occurs.
primary trunk. Once you change the weight of the redundant link, the subtend tree uses this link only
if a failure occurs.
Limitations
When the redundant link is active, the following occurrences are problems:
•
Loss of subtending fairness.
•
Increase in latency as well as an increase in cell delay variation (CDV) between the cells.
Delay-sensitive traffic, such as voice and video, or traffic that is susceptible to jitter, such as constant
bit rate (CBR) voice, might be compromised. This technique is best realized for unspecified bit rate
(UBR) traffic, such as consumer internet access, where no strict quality of service (QoS) objectives
are required.
Delay-sensitive traffic, such as voice and video, or traffic that is susceptible to jitter, such as constant
bit rate (CBR) voice, might be compromised. This technique is best realized for unspecified bit rate
(UBR) traffic, such as consumer internet access, where no strict quality of service (QoS) objectives
are required.
Once the redundant link is active, the following occurrences are potential problems:
•
Greater possibility of increased congestion in the DSLAM ATM switch fabric, which might cause
loss of data.
loss of data.
•
When the main link is restored, there is downtime while the path is being rerouted. After the SPVCs
are rerouted to the redundant ATM trunk and the original trunk is repaired or brought back into
service, you must manually intervene. You must flap (shut/noshut) the subtend port. Because of
retries on the current path, you must keep the trunk down until the maximum retry interval expires.
are rerouted to the redundant ATM trunk and the original trunk is repaired or brought back into
service, you must manually intervene. You must flap (shut/noshut) the subtend port. Because of
retries on the current path, you must keep the trunk down until the maximum retry interval expires.
Cisco DSL Manager
If you are using versions of Cisco DSL Manager (CDM) earlier than CDM Release 3.4—from
CDM Release 1.0 to CDM Release 3.3(3)—do not upgrade the DSLAMs to this new Cisco IOS release.
CDM Release 1.0 to CDM Release 3.3(3)—do not upgrade the DSLAMs to this new Cisco IOS release.
If you use both the CDM network management application and the Cisco IOS command line interface to
manage your Cisco DSLAMs, you should be aware of certain configuration and procedural implications.
Refer to the Release Notes for the Cisco DSL Manager, Release 3.4, for this information.
manage your Cisco DSLAMs, you should be aware of certain configuration and procedural implications.
Refer to the Release Notes for the Cisco DSL Manager, Release 3.4, for this information.
DSLAM
CPE
DSLAM
CPE
DSLAM
CPE
ATM
X
Failure
Active
54057