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Jun 7th, 2010
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Welcome to the Cisco Networking Professionals Ask the Expert conversation. This is an opportunity to learn how SDV allows operators to add video services without requiring additional bandwidth in the network with Cisco expert Gary Springer.  Gary is a distinguished engineer in Cisco's Access and Transport Technology Group in Atlanta, Ga. He is a control system architect specializing in video system control and one of the lead architects of the Cisco Switched Digital Video (SDV) solution. His team developed the SDV Server. Springer joined Cisco with the acquisition of Scientific-Atlanta, where he had worked since 1984. Springer holds a bachelor's degree in electrical engineering from North Carolina State University.

In addition, join Ask the Experts' second TweetChat with Gary Springer on June 15, 2010 at 10 am PT.

Gary might not be able to answer each question due to the volume expected during this event.

Our moderators will post many of the unanswered questions in other discussion forums shortly after the event. This event lasts through June 18, 2010. Visit this forum often to view responses to your questions and the questions of other community members.

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j.miller_32 Tue, 06/08/2010 - 11:57
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What is the typical bandwidth savings when using SDV?

springg Tue, 06/08/2010 - 12:21
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The initial deployments were operated with approximately 2x bandwidth savings, i.e. the available network bandwidth for switched programs was half of the total switched programs bandwidth. As our customers operated their systems and monitored performance, they were able to increase the bandwidth efficiency even further. I have heard of systems operating with 3x bandwidth savings.


astinus Wed, 06/09/2010 - 06:37
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Hi Gary,

I'm a Tivo fan, and I live in a market served by SDV.  We have an adapter and it seems to work pretty well, but my question is, are there plans to convert the "adapter" functionality to a simple IP based interface whereby the end device could send a simple message to the provider via IP when its time to to "switch" to a different signal?



springg Wed, 06/09/2010 - 08:08
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Hi Jim,

Since tuning adaptors are generally available from cable operators to enable devices like the Tivo to access the switched channels and, as you said, work well, we are not currently planning development of another solution.


steve_vanburen Fri, 06/11/2010 - 11:47
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Gary, how many QAM channels are typically used for SDV?


springg Fri, 06/11/2010 - 11:59
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Hi Steve,

The early deployments started small in the range of 4- to 8-channels per service group. With the success of SDV in saving bandwidth, and the growth in the demand and availability of HD content, many systems have now expanded to 16- to 20-channels per service group. I think this will grow even more to probably on the order of 24-channels per service group. The demand for HD is driving this. HD requires typically 4x the bandwidth as standard definition programs. SDV is an ideal technology to enable many HD programs.


l.canales77 Mon, 06/14/2010 - 09:09
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What edge devices are compatible with the Cisco SDV system?

springg Mon, 06/14/2010 - 09:33
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Edge QAM devices that implement one of the standard edge QAM session setup protocols are compatible with the Cisco SDV solution. The Generic Qam Interface (GQI) protocol is the most widely deployed session setup protocol in SDV networks. This protocol enables the Cisco SDV server to create and teardown sessions on the QAM edge device in response to requests for switched services from users.

ciscomoderator Tue, 06/15/2010 - 11:32
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Answers and tips on Switched Digital Video from our expert, Gary  Springer.  This is a transcript of the TweetChat session held on June  15, 2010.

Q: What do you do when switch digital video exceeds the network  capacity?
A: Add more QAM channels to the service group. Our solution supports up  to 48 QAM channels per service group.

Q: How much bandwidth is consumed for switching digital video while T1  is not available?
A:  Typical digital video rates are 3.75-Mbps for standard definition  and 15-Mbps for high definition programs. Non-broadcast digital video is  typically clamped to not exceed a bandwidth value. The number  represents the clamped (i.e. upper limit) bandwidth.

Q: When does a edge device report an interface alarm?
A: When (1) the device fails to accept a setup or teardown command or  (2) the device fails to respond to a status query.

TIP: If the log files are too large to use with tools, set MaxFileSize  under LogManager>Configuration to limit size of files.

Q: How do I inhibit alarms for an edge device that is being repaired?
A: Set the AdminState for the device to the Maintenance state. This will  inhibit alarms from the device and also prevent its attempted use.

Q: Can the SDV sources be prioritized?
A: Yes.The SdvSm->Source Priority page allows configuration of the  priority of SDV sources. The software will prioritize the list of  sources using this configuration.

TIP: To force a program to always be active, set the program OfferState  to Static.

Q: Can you connect switched digital video with teleconferencing?
A: It hasn't been done yet but our SDV solution exposes interfaces to  allow external systems to request resources. So it is possible.

Q: What algorithm or configuration selects how many programs are active  and the set of active programs? 
A: The operator configures the minimum active bandwidth. The active  programs are selected by first, the number of users viewing the program  and then the provisioned priority.

Q:What do the log levels (Min,Normal,Max,Capture) represent?
A: Normal corresponds to normal recording keeping. Min selects only  error messages. Max selects all transactions. Capture selects binary  messages.


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