SMW 17: id3as's Dom Robinson Talks Muxing, Multicasting, and Architecting CDNs

蒂姆Siglin: 欢迎回到流媒体西部2017. 我和id3as的Dom Robinson在一起. 多姆，快告诉我们什么是id3as.

Dom Robinson: Id3as是一家软件公司. 我们已经成立八年了. Very focused on micro-service architected delivery of video workflows. 关于 eight years ago we took what was then Reuters and is now Nasdaq's video workflow into the cloud, 这是相当大的一个, 这对他们来说是激进的举动. Big savings and we now deliver 35-40,000 live events a year for 那些家伙. 这一切都是完全自动化的，都是基于云的.

蒂姆Siglin: 这是一种公平披露类型的事件?

Dom Robinson: 公平披露，公司公告. It's a very cyclical, goodly business, as a case study in its own right.

蒂姆Siglin: 哦，我确定. 是的, because everybody wants to cram it into about two weeks of earnings

Dom Robinson: That's it, and then we have three months where there’s massive under-utilization. 他们找到我们，我们建议将其虚拟化. 这是在其他人以这种规模进行研究之前. 它给我们留下了一个非常有趣的堆栈. 我们使用一种不同寻常的电信语言, which will be familiar to the WhatsApp engineering team or the Twitter engineering team, 但大多数人都没听说过Erlang. 它确实是为开发电信级视频工作流而设计的. 它可以自我修复，这是最基本的. We don't have to spend a lot of time engineering for the failure cases. So that's where we as a very small company get a very strong competitive edge over much, 更大的公司.

蒂姆Siglin: Very interesting, and of course you’re a 流媒体 contributing editor.

Dom Robinson: 我要戴上作家的帽子.

蒂姆Siglin: 是的,完全. 你，我和埃里克已经成立了SMAF, 流媒体高级论坛, 我们不能在这里讨论这个吗, 但是人们可以来smadvanced论坛.来了解一下我们今天在展示厅做了什么.

你有一本书， 内容交付网络:基础、设计和演变. 我要用我最好的范娜·怀特表演来举起这本书, 我把它放在这里，这样它就成了特写的一部分, 但这是内容, 交付网络, 基本面, 设计和进化. 给我简单讲讲这本书.

Dom Robinson: 这是我为威利编辑第一本书的结果, 高级内容交付, 流媒体, 以及与穆卡迪姆·帕坦和拉梅什·西塔拉曼合作的云服务, I noticed that the academic books were always about current best practice. 人们之间的竞争非常激烈, “这是你能做到的最好的方法,这是完全正确的. 但有一种感觉是，人们进入了这个行业, 第一次进入这个领域, 或者从一个不同的角色转移过来, 真的很想了解流媒体内容交付网络. 他们没有上下文. 他们不了解行业的周期等等. The sections I'd written for that book were much more of a short concise history of the sector. 基本上, what I've done is I've done is I've elaborated on that and expanded that to this book, 这就更重要了, 在某种程度上, 我进入这个行业20多年.

It goes into technical detail about things like; I've got a real belief in service philosophies, as the fundamental driver between most technical decisions and how you should be architecting content delivery networks, 流工作流程, 也可能是你业务流程的其他方面.

蒂姆Siglin: 让我们稍微切线一下. We'll come back to the book at the very end, but cellular bonding, cellular muxing. This was something you got into early on and now I was just on a panel with Chris Knolton where we were talking about that as a nice redundancy to house ethernet. Where do you see that some of these technologies are going in terms of the ability to deliver live from almost anywhere? 过去是这样的, 如果你远程操作, 如果你进入“领域”,“你必须开一辆卫星卡车. Now most people are saying, "Oh yeah, we can do this with a couple of cellmuxes."

Dom Robinson: 是的, 如果你是清教徒式的, 这个功能在Linux内核中已经存在12年了, 甚至可能更久一点. Link aggregation control panel, LACP, was doing channel bonding a good decade ago.

蒂姆Siglin: 这是有道理的, 因为我们这些人, 比如我，刚开完视频会议, we would do ISDN bonding of B channels and then have the back-channel for control.

Dom Robinson: 当我开始为流媒体写作时, 六八年前没有人真正关注这个领域, 所以当埃里克让我多写一点关于它的东西时, I realized it wasn't good enough just to talk about link aggregation or channel bonded link aggregation. 我开始创建这些层.

You've got link aggregation, which you can just do with a standalone modem. 它是一个路由器. 你有5个不同的IP连接, 如果你正在处理像网络数据这样的小数据, 一个办公室可以感觉到他们都聚集在一起, 因为在所有办公室之间, 总是有可用性的. You can't treat it all as a single pipe if you're trying to stream over it. 你需要做什么, is you need something that will multiplex and demultiplex the signal at both ends. 然后你得到一个通道绑定链接聚合器, which actually bonds the different channels together with a counterpart system at the remote end, 这就产生了一点缓冲, 我会带着你, 如果你有三个1m的连接, 它会把它变成, 就其他方面而言, 一个3兆字节的管道.

蒂姆Siglin: This is similar in some ways to the home load balancers you can get if you have a DSL and a cable modem.

Dom Robinson: 是的，其中一些供应商是主要供应商. Vislink和Mushroom Networks, 那些家伙, 办公室之间有多个冗余管道吗, and actually being able to use them all as a single pipe to do high bandwidth file transfer, 诸如此类的事情.然后, 在他们之上还有另一代人, which is what you start seeing in backpacks and increasingly on camera top systems.

蒂姆Siglin: Teradek, LiveU等.

Dom Robinson: 完全, 这些家伙, what they've done is they've actually got the specific application of the encoding, 能否施加背压, 如果你喜欢的话, with the link aggregator You can understand whether you want to drop the bit rate of your video, 因为你的时间出了问题. 如果您的3mb下降到1mb, 你可以向编码器发送信号, 从3mb编码降为1mb编码. 我把这些叫做蜂窝复用，蜂窝复用.

蒂姆Siglin: That leads naturally into the very last topic I want to talk to you about, 哪个是可靠的UDP, 因为我们在这个小组讨论的一件事是, 细胞成键了. 就像你说的那样，你得到了你想要的, 但最终, if the network's not stable and if you can't aggregate together well from all these different service providers, 需要有前向纠错才能有可靠的UDP, 你觉得未来会怎样?

Dom Robinson: Reliable UDP, I certainly was using it 18 years ago within global mix, within multicast. We were interested in scaling multicasts in the public consumer networks, 疯狂的项目, 不同的故事, 书里有, 但基本上, when you're pushing a packet out with a connection in this environment, 也就是UDP, 但别忘了, TCP是带反向通道的UDP协议, TCP就像UDP的一个特定用例. 这是一个非常非常好的网站，而且非常成熟. 问题是, 它被设计成一个好的网络公民, so it shares the session over the network and if two people doing separate things are trying to use the same link, 这对双方都公平. What's happened with a lot of the more recent entrants to the space, 他们是说, “嗯, if this is your IP network and you don't want to be a good net citizen to other people, 然后强制UDP关闭. 使链接饱和，并且没有TCP来支持您的网络.

蒂姆Siglin: 我想到TCP和卡通术语, 奇普和戴尔, 那两只花栗鼠——“你先来。, no after you; no, after you”--where UDP is sort of Hulk coming in and just blasting through.

Dom Robinson: 不顾一切地开过去. 那么问题是, 当你开始丢失数据包时, 你需要一些智慧来管理它. Where we went, we built our own link aggregation and contribution stack. 我想是类似SRT的东西, 但也, 我们的结果更像是快速的, 作为一种进化, 斯皮迪. 我们试图把TCP变成类似UDP的东西, 而不是将所有的TCP连接转换为UDP. What we're interested in is very, very, very small fragments of data over many paths.

蒂姆Siglin: Doesn't that increase the chattiness though, or are you decreasing the chattiness?

Dom Robinson: It also allows the back-off processes to happen in lots of different managed ways, and you don't have to implement a reliability protocol over the top. 这是一个可靠性协议. 它就是有效的. 尤其是对纳斯达克的人来说, they use that extensively and the field encoders we develop for them just because it's quick and easy and they don't have to think about firewalls. 它还带来了链接聚合，细胞结合作为副产品.

蒂姆Siglin: 它做遍历之类的事情?

Dom Robinson: 这是TCP.

蒂姆Siglin: 因为这是TCP，你说得对，说得对. 好的，人们在哪里可以买到这本书?

Dom Robinson: 去 亚马逊. 这是最快把副本送到的方法. 你可以去 威利.com网站, and if you message me directly during November, I can give you a little 20% off token as well.

蒂姆Siglin: 流媒体2017折扣. 太棒了. 谢谢你，唐，一如既往，我喜欢这顶帽子.

Dom Robinson: 是啊，这是我写作时用的. 回到id3as.