IPTV - Behind the Glitz

Given mankind’s love affair with television and interest as of late in trendy packetized communications, it makes perfect sense that one of the most-talked about new technologies of the past few years has been IPTV. As broadcast TV takes its final bow in a few years, the world will enjoy thousands of high definition channels, quick channel changing, interactive programming. . . the list goes on and on.

But behind the glistening façade, there are some concerns over deploying such a revolutionary technology. A great number of technologies must be brought to bear “behind the scenes” to cajole IPTV into fulfilling its many tantalizing promises.

IP networks have always been best-effort in nature. Unlike the older, high-quality circuit-switched networks, there is normally no ‘maximum number of conversations’ in an IP network, which is what makes them so efficient. You can keep adding phone calls or video streams, but as you reach the maximum rated bandwidth of the ‘pipe’, every new media stream added causes an incremental degradation in most if not all of the other streams. That’s why things like overprovisioning and packet prioritization (in the form of Cisco’s MPLS) came about. Also, inherent design problems in networks or faulty network elements can cause packet congestion on networks and have a disastrous effect on IPTV service — indeed on a whole triple play infrastructure. Thus, network components need regular upgrading. Moreover, carriers must examine their IPTV network infrastructure with an eye toward provisioning, service availability and outage-recovery scenarios.

One often overlooked area of IPTV service delivery is IP naming and addressing. IPTV set-top devices (modems and converters) need IP addresses and network configuration information to operate on the IP network IPTV service may require multiple IP addresses, including different addresses for modems and TV converters, and real-time provision of new customers could entail complex rules using multiple IP-address assignments during the provisioning process, an . Such IP naming and address information is derived dynamically from Dynamic Host Configuration Protocol (DHCP) servers and then the Domain Name System (DNS) is used to locate services on the network. IP-address assignment also must be integrated with authentication and billing systems.

Problem is, DHCP servers were designed for a simpler Internet design, not a morass of triple or quad play technologies. DHCP servers are also vulnerable to Denial-of-Service (DoS) attacks, which can easily mess up IPTV service.

One company that has risen to the challenge of offering carrier-grade DHCP and DNS servers for next-gen networks is Nominum (www.nominum.com). Their IP address infrastructure products include the Nominum Foundation Dynamic Configuration Server (DCS) is a highly reliable DHCP server that can deal with strict IPTV service delivery requirements and provisioning environments. They also offer the Nominum Foundation Caching Name Server (CNS), a carrier-grade caching DNS server, which maps domain names to IP addresses for service delivery. As broadband carriers add IPTV service to their networks, they increase the overall DNS query load, which a Nominum CNS can handle with ease.

Nominum’s VP of Marketing, Albert Gouyet, says, “Nominum is very much working at the core of the IP network. We’ve focused on the carrier network — which includes cable operators, telcos and service providers — these past few years, all of which require very high performance DNS in their networks. We’ve mostly been involved with a DNS solution.”

“What’s new for us, which appeared last year, is our sales relating to IPTV,” says Goyet. “Most IPTV action these days is in Europe. Second place would be APAC, followed by the U.S. We’re all about getting devices online and allowing them to find the resources that they need. The absolute big new requirement in the IPTV context is the hardening of what it takes to get the devices online. By ‘hardening’, I mean a number of things. Obviously availability and reliability is very important. But also it’s the whole issue about how do you recognize a modem and a converter as they come on line for the first time? How do you provision them correctly? How do you capture any information that is required at the point of first connection? How do you assign them to the correct network? How do you do all of that in an environment that needs to be fairly flexible with business rules and subject to integration with authentication servers and billing systems, and how do you do that fairly quickly at the time when these devices show up on the network?”

“Technically, it is the DHCP server that’s responsible for all that,” says Goyet. “We’ve seen that many operators start with open source technology. Open source is reliable in a small environment, but when you start pushing it, it starts breaking up in various ways, and it’s not very flexible in terms of what you can do with it. In the context of IPTV, you might think of your data network has having some kind of quality expectation, and VoIP has higher expectations, and I’d say IPTV has even higher expectations, at least in terms of how long it takes to turn on the TV and get everything online.”

“It’s really all about the hardening and replacement of that layer for us right now,” says Goyet. “Of course, IPTV is just one of the catalysts that can spur operators to take another look at their networks. VoIP is the other one. And triple play, of course.”

I-Frame, You-Frame

Whether is exists alone or in a large triple play network, continual testing and monitoring is needed to ensure that IPTV sports an acceptable level of quality of service (or quality of experience) to the end user.

Keith Cobler, Marketing Manager at Tektronix, says, “There are two key areas as we see it. First is content verification, second is content delivery. Content verification ensures that the quality of the video is good before you put it into the system. The second part is about transporting that video across the network.”

“With IPTV, it’s all about the quality of experience for the end user,” says Cobler. “It’s much different than just voice or data systems. You’ve got to ensure that the quality of the video is good to the end user. That ties into three revenue streams now under triple play as opposed to one in the past. There’s a sort of pyramid of things that you need to look at to ensure that quality of experience. At the basic level, you’re looking at the various elements that make up the network. I’m talking about the DSLAM [Digital Subscriber Line Access Multiplexer], the ONTs [Optical Network Terminals] the routers, the switches the firewalls, the encoders. You’ve got to look at all that and make sure that the elements perform according to their specifications. Also, they must interoperate with one another in the network. That’s the first layer.”

“The second layer is when you look at things from the network level,” says Cobler, “examining things such as quality of service [QoS], Key Performance Indicators [KPIs] and Key Quality Indicators [KQIs], and other statistics at the network level. At the level above that, you’re looking at the services and applications. You’re scrutinizing the end user’s quality of experience. Is the end user’s quality of experience of IPTV good in his home? All the way to the monitor? To achieve this, you must have an underlying foundation at the element level, subsystem level and network level, and finally in the end user’s own living room. All of these must be functioning well to enable great user quality of experience.”

“At a high level, as I’ve said, there’s content verification,” says Cobler. “If you look at the video super head-end, how do you check for the quality and then how is it transported across the network? Before the transport, you’ve got your satellite farm. You’re basically taking in the video signal in. You must verify the content. Your video on demand [VoD] servers have a great deal of static content that needs to be verified. How is the quality impacted as you encode the content? How does it change after it has been packetized? Basically, throughout various points along the network, is the quality of the video changing at all as you transport it across the network?”

“For us at Tektronix, our technology can examine many variables,” says Cobler. “We have many solutions and tools that are used to verify the content, and we also have many tools that look at the network layer and look at the IP packets as they traverse the network. Again, it all has to do with those two areas: content verification and content delivery.”

“Think of an individual IPTV video packet and all of the transitions it makes across the network,” says Cobler. “Again, at the super head-end it’s encoded, packetized, transported, and then it goes to a central office. From there it also may go through some other encoders. It may be combined with local content, which is also encoded and then repacketized, and sent out to the local access networks. There, at the local level too, you could have some other things that may impact the network, just as they would any other IP network: latency, jitter and dropped packets.”

Cobler elaborates: “One of the key things about IPTV is that it is very sensitive to dropped packets — more so than VoIP service, which itself is very sensitive to latency issues. It all has to do which what kind of encoding you’re using in the network. In the MPEG transport stream, there are three different key frames: an B-Frame, P-Frame and I-Frame. [Editor’s Note: A B-frame, for bi-directional frame, or bi-directional predictive frame, depends upon frames before and after it and only contains data that has changed from the preceding frame or differs from the next frame’s data. P-frame designates a Predictive frame, or Predicted frame. P-frames follow I-frames and contain only data changed from the preceding I-frame. P-frames depend on I-frames to fill in most of its data. The I-frame, also known as a keyframe, is short for intraframe. An I-frame stores all the data required to display the frame. In common usage, I-frames are interspersed with P-frames and B-frames in a compressed video.] For example, if you’re going with MPEG-2 encoding, you may have an I-frame appearing every 12-15 frames. An I-frame contains all of the content from which you can reproduce the video frame, versus a P or B packet. If you drop an I-frame, you’ve got another I-frame coming along very soon.”

“But a trade-off can enter this scenario,” says Cobler. “Let’s say that a provider needs to conserve bandwidth, so it’s using a more efficient encoding scheme such as MPEG-4. With MPEG-4, an I-frame comes along every 120 or 150 frames. So if you drop an I-frame it takes a longer for another one to arrive. If an I-frame gets dropped, there’s a much bigger effect. An end user watching IPTV might have to wait one or two seconds before the video frame is updated. That, of course, impacts the user’s quality of experience.”

“Those are some of the issues,” says Cobler. “As I said, we focus on end user quality of experience. We also think about the network’s quality of service. We look at the network from a traditional telco perspective, ensuring quality.”

“We have two kinds of customers,” says Cobler. “First are the smaller regional IPTV players concerned about deploying IPTV and that’s it. Second are the larger telcos that are looking at IPTV as part of a triple play sent over a converged network on an IP core. The telcos’ issues are much more complicated. One of our strengths at Tektronix is that we focus on these converged services, where IPTV is the video portion of a triple play. Relative to data and voice, there are all sorts of issues with regard to prioritization of packets, dropped packets, and other things we can look at in an end-to-end network monitoring situation, where we can help ensure the network’s QoS, which lays the foundation for the end user’s quality of experience.”

“If you’re an end user, and suddenly you experience some degradation in service quality,” says Cobler, “how does a network operator figure out where the problem occurs? If the operator has a test and monitoring strategy that includes embedded probes in the network, we can then take a top-down look and we can say, ‘Okay, we experienced a QoS issue, we isolated it to this network element to this actual session, and we can drill down and see what the actual problem is with that.’ Our technology gives operators the ability to isolate and fix problems very rapidly. That’s important for large telcos, where IPTV is part of the triple play, since they’re talking about three revenue streams, not just one. A dissatisfied customer would probably cancel out all three services if one gives him problems.”

Back Office Blues

Aside from technical nuts-and-bolts concerns about IPTV quality, network operators soon discover that billing and operations support is another behind-the-scenes area of concern.

Beau Atwater, Executive Director of Portfolio Strategy at Telcordia (www.telcordia.com), says “Everyone’s talking about IPTV right now, and it’s very hyped up. Who knows, it could take off terrifically and be the best thing yet, or it may not, and we’ll be talking about something else in two years. But what I think is definitely true is that as service providers pursue these consumer-based services such as IPTV or even enterprise-based services, it’s not going to be easy to add services on top of existing networks. If you look at service providers in comparison to cable or satellite radio, or what have you, those guys have built networks specifically for one purpose, to deliver specific content. In the case of cable, it’s a specific network to deliver video transmission.”

“On the other hand, modern service providers operate a multi-use network,” says Atwater. “That leads to big challenges. We think the big way to solve big challenges is to make sure that your back office systems are in order, because if they aren’t then you’re going to be adding ‘silos’ of back office systems to support each individual service. But that just doesn’t scale; eventually the service provider runs out of money, or it competes with cable, or something like that. So, you need to have back office system capable of handling the whole breadth of services — IPTV is just one more added to these. It’s really that realm and service quality of management / customer experience that Telcordia sees as being critical to rolling out IPTV, digital services or content delivery or whatever you have. And it includes billing and operations support systems (OSS).”

So there you have it. IPTV may not be the easiest technology to deploy, but its huge potential audience has spurred carriers and other network operators to surmount any obstacle, resulting in an overhaul of everything from billing and OSS to network monitoring and traffic control. For end users, it should all be worth it.

Richard “Zippy” Grigonis is the Executive Editor of TMC’s IP Communications Group.