1. Set-top registration with the SDV Server (USRM) generally involves only the forward and reverse data paths (QPSK mod/demod), not QAMs....
2. …Except when a set-top has been rebooted, which causes it to lose the IP address of its SDV Server (USRM).
3. For example, a set-top code upgrade reboots the box and possibly causes the box to lose its state and forget that it was already registered with its SDV Server.
4. To find the IP address of its SDV Server, the box must find the Mini Carousel.
5. To find the Mini Carousel, a subset of all SDV frequencies is specified on the MAS server in a list called “Frequency/Modulation Pairs for SDV”. Some sites specify as few as 2 frequencies.
6. Care must be taken to ensure that the frequencies specified in the “Frequency/Modulation Pairs for SDV” list on the MAS server are not all on the same QAM chassis in any service group, or you’ll have a single point of failure in that service group.
7. With the density of modern QAM chassis, sites may need to double check point 6 above to make sure they don’t have a single point of failure in any service groups.
Set-top registration with an SDV Server (USRM) has next-to-nothing to do with QAMs… but not nothing.
Set-top registration is a 2-step handshake where an embedded SDV client running on a STB sends an InitReq to its SDV Server, and the SDV Server registers that STB by putting it in its database and sending an InitConf back to the STB. This only involves the out-of-band data path (QPSK mod/demod).
But what if the SDV client on the STB does not know the IP address of its SDV Server? That’s where the QAMs come in. Each service group has its own unique SDV Mini Carousel. The Mini Carousel, in addition to SDV tuning tables, also contains the IP address of the SDV Server for that service group. When a box boots up, it must locate the Mini Carousel in order to learn the IP address of its SDV Server. It knows that the Mini Carousel is on the well-known MPEG Program Number 62351, but what frequencies should it scan for that program number? This provisioning information is called a “scan list” by Cisco, but on the MAS server, it’s called “Frequency/Modulation Pairs for SDV”.
The “Frequency/Modulation Pairs for SDV” on the MAS server are a subset of their SDV frequencies with some sites specifying as few as 2 frequencies on the MAS server. If they have 16 SDV frequencies, but their “Frequency/Modulation Pairs for SDV” list on the MAS server only specifies 2 of these frequencies, then the STB had better be able to find at least 1 of those 2 frequencies, or it won’t be able to get SDV. So, to avoid a single point of failure, you should ensure that all the frequencies specified in the “Frequency/Modulation Pairs for SDV” list on the MAS server are not on the same QAM chassis. This scenario is one drawback to the density of modern QAM chassis.