Networking

Video: Intro into IPv6

Posted on by Russell Trafford-Jones

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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Speaker

Alex Latzko Alex Latzko
Lead Network Architect
ServerCentral Turing Group

Video: IP Fundamentals For Broadcast Seminar IV

Posted on by Russell Trafford-Jones

“When networking gets real”, perhaps, could have been the title of this last of 4 talks about IP for broadcast. This session wraps up a number of topics from the classic ‘TCP Vs. UDP’ discussion to IPv6 and examines the switches and networks that make up a network as well as the architecture options. Not only that, but we also look at VPNs and firewalls finishing by discussing some aspects of network security. When viewed with the previous three talks, this discusses many of the nuances from the topics already covered bringing in the relevance of ‘real world’ situations.

Wayne Pecena, President of SBE, starts by discussing subnets and collision domains. The issue with any NIC (Network Interface Controller) is that it’s not to know when someone else is talking on the wire (i.e. when another NIC is sending a message by changing the voltage of the wire). It’s important that NICs detect when other NICs are sending messages and seek to avoid sending while this is happening. If this does’t work out well, then two messages on the same wire are seen as a ‘collision’. It’s no surprise that collisions are to be avoided which is the starting point of Wayne’s discussion.

Moving from Layer 2 to Layer 4, Wayne pits TCP against UDP looking at the pros and cons of each protocol. Whilst this is no secret, as part of the previous talks this is just what’s needed to round the topic off ahead of talking about network architecture.

“Building and Securing a Segmented IP Network Infrastructure” is the title of the next talk which starts to deal with real-world problems when an engineer gets back from a training session and starts to actually specify a network herself. How should the routers and switches be interconnected to deliver the functionality required by the business and, as we shall see, which routers/switches are actually needed? Wayne discusses some of the considerations of purchasing switches (layer 2) and routers (layer 3 & 2) including the differing terms used by HP and Cisco before talking about how to assign IP addresses, also called an IP space. Wayne takes us through IP addressing plans, examples of what they would look like in excel along with a lot of the real-world thinking behind it.

Security is next on the list, not just in terms of ‘cybersecurity’ in the general sense but in terms of best practice, firewalls and VPNs. Wayne takes a good segment of time out to discus the different aspects of firewalls – how they work, ACLs (Access-control Lists), and port security amongst other topics before doing the same for VPNs (Virtual Private Networks) before making the point that a VPN and a firewall are not the same. A VPN allows you to extend a network out from a building to be in another – the typical example being from your work’s address into your home. Whilst a VPN is secured so that only certain people can extend the network, a firewall more generally acts to prevent anything coming into a network.

As an addendum to this talk, Wayne explains IPV4 depletion and how IPv6 addressing works. In practice, for broadcasters deploying within their company in the year 2020, IPv6 is unlikely to be a topic needed. However, for people who are distributing to homes and working closer with CDNs and ISPs, there is a chance that this information is more relevant on a day-to-day basis. Whilst IP address depletion is a real thing, since every company has a 10.x.x.x address space to play with, most companies use internal equipment with an IPv4 address plan.
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Speaker

Wayne Pecena Wayne Pecena
Director of Engineering, KAMU TV/FM at Texas A&M University
President, Society of Broadcast Engineers AKA SBE

Video: Buffer Sizing and Video QoE Measurements at Netflix

Posted on by Russell Trafford-Jones

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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Speakers

Bruce Spang Bruce Spang
PhD Student, Stanford

Video: ABA IP Fundamentals For Broadcast

Posted on by Russell Trafford-Jones

IP explained from the fundamentals here in this in this talk from Wayne Pecena building up a picture of networking from the basics. This talk discusses not just the essentials for uncompressed video over IP, SMPTE ST 2110 for instance, but for any use of IP within broadcast even if just for management traffic. Networking is a fundamental skill, so even if you know what an IP address is, it’s worth diving down and shoring up the foundations by listening to this talk from the President of SBE and long-standing Director of Engineering at Texas A&M University.

This talk covers what a Network is, what elements make up a network and an insight into how the internet developed out of a small number of these elements. Wayne then looks at the different standards organisations that specify protocols for use in networking and IP. He explains what they do and highlights the IETF’s famous RFCs as well as the IEEE’s 802-series of ethernet standards including 802.11 for Wi-Fi.

The OSI model is next, which is an important piece of the puzzle for understanding networking. Once you understand, as the OSI model lays out, that different aspects of networking are built on top of, but operate separately from other parts, fault-finding, desiring networks and understanding the individual technologies becomes much easier. The OSI model explains how the standards that define the physical cables work underneath those for Ethernet as separate layers. There are layers all the way up to how your software works but much of broadcasting that takes place in studios and MCRs can be handled within the first 4, out of 7 layers.

The last section of the talk deals with how packets are formed by adding information from each layer to the data payload. Wayne then finishes off with a look at fibre interfaces, different types of SFP and the fibres themselves.

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Speaker

Wayne Pecena Wayne Pecena
Director of Engineering, KAMU TV/FM at Texas A&M University
President, Society of Broadcast Engineers AKA SBE