December 10, 2019
By Tim Siglin Contributing Editor, Steve Nathans-Kelly
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SMW '19: id3as' Dom Robinson Talks SMAF and IP Multicast

Read the complete transcript of this interview:

Tim Siglin: Welcome back to Streaming Media West 2019. I'm Tim Siglin, Contributing Editor of Streaming Media Magazine, founding Executive Director of a not-for-profit Help Me Stream, and along with this gentleman here, a co-host of SM Advanced Forum, which is a monthly webcast or SMAF as we like to call it. So let's, since you were hats and I'm not gonna ask you to change hats, let's talk about SMAF quickly.

Dom Robinson: Cool.

Tim Siglin: So what is SMAF for those who might not know about it?

Dom Robinson: So for those of you who've been following streaming media for a long time, you might remember that there was a mailing list which predated social media by about a decade or something, which is a just an email list. The people who are interested in more advanced streaming techniques could subscribe to. And that mainly, it's really formed the heart in my mind, the core community of webcasters and early streaming engineers.

Tim Siglin: And your inbox, would get flooded with as people went back and forth on topics.

Dom Robinson: Dialogues, and it's actually really convenient. It was there, and the topics were always good. Also good pithy responses to

Tim Siglin: And as an aside to that, I signed up last week for the first time for an actual mailing list for open BSD.

Dom Robinson: Okay.

Tim Siglin: The Arm architecture, Arch 64, except I misread the thing, and instead of sending the subscribe arm to majordomo@openbsd.com, I sent it to orbit of bsd.com. So of course, everybody on the list got my subscription request, and a number of them were very gracious. And I said, "Is there any way to get rid of it?" One of the guys is like, "You know the internet never forgets." So anyways.

Dom Robinson: Yeah So the main industry's kind of the heart of it. And actually still within the streaming media community, there are tens if not hundreds of people who were on that list who form this sort of fabric of most of the global streaming infrastructure around the world these days. We've gone from being kind of bedroom fanatics to vice presidents of global organizations since the stream has exploded. So it's actually, it was a very interesting community. But for whatever reason it was wound down I don't know, maybe 2008, 2010. And I really missed it. Because that was my first social network, really, for a niche interest. And so we waited around three, four years to see if something would ever come off that. I had rather cheekily registered SM advanced forum.

Tim Siglin: Oh, very nice.

Dom Robinson: And then to make sure that it wasn't going to cause a rub the wrong way, I invited Eric to co-host it himself, and Mark East, and so it's about two-and-a-half years ago we started.

Tim Siglin: Right about, yeah.

Dom Robinson: Because I already do my Thursday night radio show, we just decided we'd do it on the first Thursday of the month, so from my wife's point of view, I'm tied up one day a month rather than,

Tim Siglin: Multiple days.

Dom Robinson: Rather than several days.

Tim Siglin: And we started with Google Hangouts and of course in the meantime Google Hangouts has been deprecated.

Dom Robinson: That's right.

Tim Siglin: So now we're on a system.

Dom Robinson: Which is a wonderful story in its own right. But yeah, so we didn't have a remote conferencing bridge, an MCU model if you like. And so over this summer, I rebuilt, or I built, I used a part of Open Source tools to build us a conference bridge, which means that we can carry on with pretty much the same technical delivery model. And we invite two guest on, every month, just to make sure people don't get bored of hearing from just you, me, Eric, and Mark.

Tim Siglin: Well oftentimes, not all four of us can be there.

Dom Robinson: Exactly, so we've got two guests. Well we started off with just having one guest to . And then we had Diane Strutner from Women In Streaming Media and Datazoom, but from Women in Streaming Media on. And we thought actually a bit of positive discrimination or whatever it's called these days. We thought actually give a second guest chair to the Women In Streaming Media to make sure that we

Tim Siglin: And that was right around the time Women In Streaming Media was actually starting up. So now for almost a year, where it's a male guest and a female guest.

Dom Robinson: Yeah and it's really good to say that. In fact, I'm really proud to honor International Women's Day, the edition in March, it falls on SMAF, first Thursday in March, so we decided we are going to handle the entire SMAF show over to the Women In Streaming Media and let them do an all-female transmission. Which I think is great. It's really added some variety and just some good valuable insight that sometimes gets crossed over in technical services.

Tim Siglin: And I think two other quick things to add on this, first of all, we're not beholding anybody because we try to do it all on Open Source solutions. Secondly, we don't actually take sponsors for that.

Dom Robinson: It is just a bit of fun.

Tim Siglin: The conversations are the types of conversations you would have had on a mailing list or that type of thing in the past. And we try to avoid it being fixed-topic and promotional. So we don't promote the guest companies. If they want to bring them up in conversation, that's fine, but it's not about Company X is promoting Product/Service Y, it's about, guys, you're experts in the industry. What's your opinion on this topic? And they flip through whatever topics come up, and it's always fun and a little bit of that was a video on demand and there's a podcast afterwards as well. So a slight segue, you did a presentation today. Was it on multicast?

Dom Robinson: IP multicast, yes.

Tim Siglin: It's something you've been interested in for longer probably than the SM Advanced Forum mailing list.

- [Dom] Oh yeah, my kink, if you like, is I just find IP multicast one of the most intriguing potential capabilities that the internet has had that we've never realized and taken advantage of.

Tim Siglin: So for somebody that might not know that streaming is unicast and multicast is this different thing, just briefly describe what multicast does and what the benefit is from a scalability standpoint.

Dom Robinson: So most people would be familiar with how unicast is delivered and it's always best to think first of all about live streaming when you think about multicast. It's just a little bit easier paradigm to look at. Basically what happens is today when you have multiple users watching a single stream, the center of the network or proxy service somewhere in the network, which would otherwise be called a CDN--

Tim Siglin: Right.

Dom Robinson: acts as the point of aggregation of all those connections, that set for thousand of users as connections to the stream. And as your audience grows, your network demand at that point of concentration of all traffic grows as well.

Tim Siglin: Because if it's a one-megabit stream and a hundred people watching, that's a hundred megabits of capacity that's consumed.

Dom Robinson: And so what IP multicast does is it works out that there's many people wanting the same piece of data. And it forwards that one pocket of data, one, if you like, one video or whatever you... It forwards that on all of the interfaces on the router to where there is a downstream subscriber. So you only send the chunk of data once over the network. It makes no difference if you have one or many users connected. You still only send one stream over the network, so it's incredibly efficient when it comes to scaling live. In common use, within private networks, for doing IPTV.

Tim Siglin: Sure.

Dom Robinson: It's been really successfully deployed for that purpose for a long time. But the problem is when you want to hand a multicast outside of that initial network into other networks, so over the public internet, coordinating the routing of that, it took maybe a decade after sort of the web had taken off to really nail the problems and the protocols. So it wasn't until about 2,000 that you start to see multicast protocols that didn't have adverse unintended consequences on the network really arrive. By then the internet was largely being built. And although the capability is latent, it's out there. It's not a new technology that needs to be rolled out. It's not generally turned on, or configured in the routers.

Tim Siglin: And there had been some real and potentially misinformed decisions around the fact that UDP and the way that works, verses TCP. That TCP was kinder, in terms of the way that it sent traffic across the internet.

Dom Robinson: Yeah, so TCP is, it's a great protocol for shared network infrastructure, because it backs off and it shares the capacity for some errors. UDP doesn't care, so it pushes the data through anyway.

Tim Siglin: And if you had a capacity problem, that would be a problem. These days we don't seem to really have capacity problems.

Dom Robinson: No, and actually outside of IP multicast, UDP has had a bit of a resurgence over the last couple of years with all the reliable UDP models that appeared from the likes of Qarva, Aspera, Motama, Zixi and so on because it allows you to use more bandwidth. The only problem with it is it's not very kind in a shared network.

Tim Siglin: Sure.

Dom Robinson: So it does flood the networks, so you have to make sure the IP link you're using isn't really being used by anyone else.

Tim Siglin: So you've talked about the history of that, what are the practical discussions the industry needs to have today about multicast? I mean, it's nice to talk about it sort of in a historic perspective.

Dom Robinson: Yeah, yeah.

Tim Siglin: We are still trying to figure out how to get to scale.

Dom Robinson: So there's a couple of things that have happened in multicast space in the last sort three to four years. Which have brought it back up and it was quite invigorating for me to go to many of the sessions here and actually multicast is popping up as a term much more. So some of the key values that it brings, in an encoding environment where you have a source video, being made available to a number of encoders to transcode and deliver onto the network. If you deliver that stream as a unicast to each of the encoders, you have to have a failure strategy if the connections lost from the source or there's a problem with the encoder. We build a lot of live streaming platforms and where we can we try to get our clients to deliver us a muticast transport stream, or at least a multicast source, because if an encoder fails, we can stand up a new one instantaneously, and pick multicast up and it gives you a much higher availability strategy.

Tim Siglin: The failover is in the encoders rather than in multiple streams.

Dom Robinson: Yeah, so you don't have to shut down a session and open a new one when one fails. You just tune into the multicast and pick it up. So it gives you much higher availability.

Tim Siglin: Does that also allow a stateless scenario? You know how obviously, in traditional media servers, you had to set up a state between the origins.

Dom Robinson: Yeah, absolutely it is.

Tim Siglin: Okay.

Dom Robinson: And that's what it is so good for. The multicast doesn't know who's listening.

Tim Siglin: And that was Jose intentionally photo bombing. Now, so what other benefits, just quickly, and then we will wrap this up.

Dom Robinson: For multicast?

Tim Siglin: For multicast, yeah.

Dom Robinson: So the other things that have emerged, there's a little talk in our group and together with ATSC 3 and LT Broadcast, so the new layer two technologies, which are being rolled out in ATSC 3's case for traditional broadcast and for LT Broadcast that's being deployed in the tail end of LT 4 and it's being spoken about as if it's going to be native to 5G, it's not quite at that stage yet. So that's reinvigorating discussion about the multicast.

Tim Siglin: And it makes perfect sense for mobile networks, which are closed networks, to do something like multicast.

Dom Robinson: Yeah, where you've got some degree of... And then the other thing that I think is really important is Bit-Indexed Explicit Replication, which is better known as BIER, and that's now being ratified by the ITF as a standard. And it's following a general trend in computing to move state from the network that's doing forwarding of the multicast, where you need some memory in each router, to remember who's subscribed to what. Now that state is being moved up into the packet header. So that the packet itself carries the forwarding map, if you like, and that means when a network receives an inbound via multicast stream, it knows which roots that should be forwarded out of, which means that you simplify the need to have multicast routing and multiple states in the network itself.

Tim Siglin: And replicators and the like.

Dom Robinson: So that's gonna make some degree of a change. But there's other--you need to hear the whole talk-- 'cause there's other economic complexities with making networks more efficient, that make them economically less lucrative. And it seeds an interesting, I think reasonably challenging perspective that I have, which is that, CDNs like to tell you they're congested, the bandwidth is scarce, because it puts a premium on the value that they can deliver. If they told you that they had abundant capacity and make it multicast, live streaming, and scale to new order, it would diminish the economic.

Tim Siglin: Well, the good news is the presentation will be up on Streaming Media sometime in the not too distant future. So we'll definitely point people toward that. Dom, as always, good to have you.

Dom Robinson: Hope to see you the first Thursday of the month, every month.

Tim Siglin: I was going to say, I won't shake the other hand.

Dom Robinson: No, no, don't do that. It was a production accident.

Tim Siglin: Right, it had nothing to do with Brexiteers.

Dom Robinson: No, it could have done. Let's just leave it at that.

Tim Siglin: Okay we will be right back with our next interview in just a moment.

Dom Robinson: Let's just time that right . There you go.