Cisco Model 6109 6 MHz Off-Air Reference (NTSC) Guide De Montage
Min Mode vs. Max Mode and Available Bandwidth
78-4021139-01 Rev D
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Min Mode vs. Max Mode and Available Bandwidth
When a USRM Server operating in supervised mode first comes online, it sends a
trap to the DNCS to request provisioning. The DNCS responds by sending
provisioning information for the server, which includes (among other things) a value
for the maximum bandwidth for the service group(s).
In the "old" SDV Server world, this value determined how much bandwidth (in the
In the "old" SDV Server world, this value determined how much bandwidth (in the
form of shell sessions) the DNCS would allocate to the SDV Server, and was the
maximum available bandwidth in the service group. In the "new" USRM world,
however, the DNCS no longer allocates QAM/Service Group bandwidth, so the
term "maximum bandwidth" takes on a slightly different meaning.
For SDV Service Groups on a USRM, the maximum available bandwidth for a
For SDV Service Groups on a USRM, the maximum available bandwidth for a
service group is equal to the maximum bandwidth of a QAM carrier times the
number of QAM carriers in the service group. For a 256-QAM carrier, the USRM
uses a value of 38.814 Mbps
as the maximum available bandwidth on a QAM
carrier. So for a service group made up of four 256-QAM carriers, the maximum
available bandwidth in the service group is equal to 38.814 * 4 = 155.256 Mbps.
Regardless of max mode or min mode settings, the USRM attempts to use all 155.256
Mbps of available QAM bandwidth, if it can, for programs requested by a user.
The USRM interprets the terms "maximum bandwidth" and "minimum bandwidth"
The USRM interprets the terms "maximum bandwidth" and "minimum bandwidth"
as measures of how much programming the USRM should keep created on the
QAM. Take, for example, a service group that is comprised of 16 256-QAM carriers
where the USRM is designated to operate in max mode, and the operator sets a value
of 600 Mbps as the maximum bandwidth for the service group. The USRM attempts
to always keep 600 Mbps of programming created on the service group. However,
the USRM will satisfy requests for up to 620 Mbps of services if enough bandwidth
exists for a particular service on any one carrier.
As another example, consider a service group set up initially with 12 256-QAM
As another example, consider a service group set up initially with 12 256-QAM
carriers and a max bandwidth value of 450 Mbps. If four additional 256-QAM
carriers are added to the service group but this max bandwidth setting is not
changed, the USRM will fill 450 Mbps of bandwidth with programming (max mode),
but will use all 620 Mbps of bandwidth to satisfy customer requests.
1
For non-Cisco QAMs, this value may not be 38.814. We recommend verifying the maximum
allowable bandwidth on a 256-QAM carrier with each QAM vendor. This setting can be
changed on a USRM-wide basis by a Cisco service-level user.