Video: Intro into IPv6

It’s certainly taken its time to get here, but IPv6 is increasingly used on the internet. Google now report that just under 30% of the traffic to Google is IPv6 and both Akamai and APNIC show UK IPv6 readiness at around 30% with the US around 50%. Deployment within most enterprise environments, however, is often non existant with many products in the broadcast sector not supporting it at all.

Alex Latzko is an IPv6 evangelist and stands before us to introduce those who are IPv4 savvy to IPv6. For those of us who learnt it once, this is an accessible refresher. Those new to the topic will be able to follow, too, if they have a decent grasp of IPv4. Depending on where you are in the broadcast chain, the impetus to understand IPv6 may be strong, so grab your copy of the slides and let’s watch.

There are no broadcast addresses in IPv6

Alex Latzko
Alex, from ServerCentral Turing Group starts by explaining IPv6 addresses. Familiar to some as a far-too-long mix of hexadecimal numbers and colons, Alex says this is a benefit given the vast range of numbers possible allowing much more flexibility in the way we use the IPv6 address space over IPv4. He takes us through the meanings of the addresses starting with well-known tricks like abbreviating runs of zeros with a double colon, but less well-known ones too, like how to embed IPv4 addresses within an IPv6 address as well as the prefixes for multicast traffic. Alex goes on to show the importance of MAC addresses in IPv6. EUI-64 is a building block used for IPv6 functions which creates a 64-bit string from the 48-bit MAC address. This then allows us to create the important ‘link local’ address.

The last half of the presentation starts with a look at the CIDR prefix lengths that are in use and, is some cases, agreed as standards on the internet at large and in customer networks. For instance, internet routing works on blocks of /48 or larger. Within customer networks, blocks are often /64.

In IPv6, ARP is no longer. ARP can’t work because it uses broadcast addresses which don’t exist within the IPV6 world. This gives rise to the Neighbour Discovery Protocol which allows you to do something very similar. Specifically, it allows you to find your neighbours, routers, detect duplicate addresses and more.

Alex covers whether ‘NAT’ is possible in IPv6 and then looks at how routing works. Starting by imploring us to use ‘proper hierarchy’, he explains that there is no need to conserve IPv6 space. In terms of routing, the landscape is varied in terms of protocols to use. RIP is out of the window, as v1 and v2 have no knowledge of IPv6, OPSFv3 is a beacon of hope, though deployment is often in parallel with the IPv6-ignorant OSPFv2. The good news is that IS-IS, as well as BGP, are perfectly happy with either.

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Download the presentation


Alex Latzko Alex Latzko
Lead Network Architect
ServerCentral Turing Group

Video: Buffer Sizing and Video QoE Measurements at Netflix

At a time when Netflix is cutting streaming quality to reduce bandwidth, we take a look at the work that’s gone into optimising latency within the switch at ISPs which was surprisingly high.

Bruce Spang interned at Netflix and studied the phenomenon of unexpected latency variation within the netflix caches they deploy at ISPs to reduce latency and bandwidth usage. He starts by introducing us to the TCP buffering models looking at how they work and what they are trying to achieve with the aim of identifying how big it is supposed to be. The reason this is important is that if it’s a big buffer, you may find that data takes a long time to leave the buffer when it gets full, thus adding latency to the packets as they travel through. Too small, of course, and packets have to be dropped. This creates more rebuffing which impacts the ABR choice leading to lower quality.

Bruce was part of an experiment that studied whether the buffer model in use behaved as expected and whist he found that it did most of the time, he did find that video performance varied which was undesirable. To explain this, he details the testing they did and the finding that congestion, as you would expect, increases latency more during a congested time. Moreover, he showed that a 500MB had more latency than 50MB.

To explain the unexplained behaviour such as long-tail content having lower latency than popular content, Bruce explains how he looked under the hood of the router to see how VOQs are used to create queues of traffic and how they work. Seeing the relatively simply logic behind the system, Bruce talks about the results they’ve achieved working with the vendor to improve the buffering logic.

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Bruce Spang Bruce Spang
PhD Student, Stanford

Video: SNMP is Dead

SNMP has long been widely used in the broadcast industry and is a great example of the industry using a technology which is there but has never quite satisfied all the needs not least security. Here, Rob Shakir and Carl Lebsack from Google explain their dissatisfaction with SNMP and tell of the system, gRPC, Google has written and implemented in response to stream telemetry at a high frequency. As larger facilities move to uncompressed essences over IP, this should solve a number of issues for the broadcast industry.

This talk given at NANOG 73 covers:

  • SNMP inefficiencies
  • The requirement for time-accurate data collection
  • The need for finer granularity
  • Inability of SNMP to contain large amounts of data
  • Reasons streaming the telemetry works better
  • Discussion around deployment of gRPC


Rob Shakir, Rob Shakir
Network Management & IP Architect,
Carl Lebsack Carl Lebsack
Technical Lead for Network Streaming,

Video: Everything You Always Wanted to Know About Optical Networking

From the NANOG conference (North American Network Operators’ Group), Richard A Steenbergen tells us everything we need to know about fibre optics; essential knowledge in today’s network-centric world – though fibre has been in frequent use in broadcast for a long time.

Whether this is new to you, or you’ve been using fibre for ages, you’re sure to get something out this detailed look at optics covering:

  • How fibre works (the basics, fibre types and limitations, etc)
  • Optical power (understanding dBm, loss, using light meters, etc)
  • Working with optics (choosing the right type, designing optical networks, etc)
  • DWDM (how it works, muxes, OADMs and ROADMs, amps, etc)
  • Dispersion and other impairments (what is it, why do we care, how do we fix it)
  • Optical Myths (can I hurt myself looking into fibre, can I overload my optic, etc)
  • An update on the latest state-of-the-art optical technologies and trends.

You may also want to check out this page on the different types of fibre connectors


Richard A Steenbergen Richard A Steenbergen
Former CTO, PacketFabric,
Current CEO, Petabit Scale