Welcome!

Linux Containers Authors: Liz McMillan, Yeshim Deniz, Elizabeth White, Pat Romanski, Jyoti Bansal

Related Topics: SDN Journal, Java IoT, Linux Containers, Containers Expo Blog, @CloudExpo, Cloud Security

SDN Journal: Blog Post

What SDN Can Do for Multicast Topologies

IP Multicast is one of those technologies that most everyone loves to hate

IP Multicast is one of those technologies that most everyone loves to hate. It’s almost the perfect example of how complicated we have made networking. Getting IP Multicast to run depends on several protocols that are all somewhat intertwined or dependent on each, their relationship sometimes explicit, sometimes implicit.

Even trying to describe the basic operation is complicated.

When an application or service provides information using IP multicast, it simply starts sending it onto a specific multicast group. The multicast router for the subnet of the sender sees the incoming multicast packet and will initially have no forwarding information for that stream in its forwarding hardware. The packet is passed onto the CPU of that router, which will encapsulate this packet and send it towards a special multicast router designated the Rendez-vous Point (RP). When the RP has installed the multicast routes for this group, it will tell the multicast router on the sender’s segment to stop sending. When it does, this router installs its own multicast routes for the source tree (the tree specific to this sender) and the shared tree (the one towards the RP) without any outgoing interfaces, and the traffic is dropped at this first router. But, the network (well at least the part between the sender and the RP) is now aware of this multicast stream. And who is sending.

Now when we want to join this IP Multicast group, the first action is send an IGMP join out on the subnet you are attached to. The IP Multicast router that serves this subnet sees the join and determines where RP can be found. It takes the client join, and sends it towards the RP, using the unicast routing table as its guide. Every multicast router along the way registers that there is a listener on the interface this join came in on and passes it along towards the IP. All along this path, the unicast routing entry for the RP is used to create the tree towards the listener.

Once received by the RP, the shared tree and the source tree towards the sender have been joined. We have an end to end path between sender and receiver, with the RP in the middle of it all. All that is left is to send a join from the RP towards the router on the sender’s subnet to essentially tell it to start passing the actual multicast along the path towards the RP (the source tree), where the RP will then push it out onto the shared tree towards the destination. Voila, it’s as simple as that.

But wait, we are not done. Once the packets start to flow from source to destination, the multicast router closest to the destination will send another join message for this group, but this time towards the sender. It is only now that it can do this because those first few data packets actually indicate who the sender is. That join is passed router to router to router towards the router on the sender’s subnet, and once arrived, that router will now also start sending the multicast data along that path towards the receiver. The receiving subnet router sees that stream appearing and will now send a prune message onto the shared tree towards the RP, indicating it no longer needs the multicast stream through the RP.

If you are not familiar with IP Multicast and after reading the above are not confused, congratulations, your brain is very well wired for complex networking.

If you step away from how IGMP and PIM implement this today as above, the most fundamental of IP multicast topologies is that you need to build a forwarding tree that is rooted in the source, with the destinations as its leaves. At each intermediate node in the tree, the packets are replicated to its branches, therefore creating the least amount of duplication. And by using a tree, it is loop free, packets won’t swirl around the network bringing it to its knees.

The challenging part though is that the tree is based on the unicast forwarding topology. From a leaf on this tree towards the sender, each step is identical to how a unicast IP packet would be forwarded. The forwarding topologies are connected and dependent on each other. IP Multicast is built on top of a unicast routed infrastructure, and unicast routing changes can have dramatic impacts to the multicast forwarding topologies.

I mentioned here before that I once spent a wonderful 2 weeks in Delhi working on a network where surveillance cameras created an aggregate 8Gbit/sec worth of multicast data, with a requirement that any unicast change would have limited impact to these streams. Believe me, it is extremely hard to engineer and tune, and we had the luxury of hijacking a really large network night after night to simulate failures.

SDN based architectures have the opportunity to change all this. Multicast forwarding was designed the way it was designed to work on arbitrary network topologies, with random senders and receivers coming and going. It builds trees on the fly and on demand. For many networks, topologies are not arbitrary, and those applications that consume/produce lots of multicast do not have randomly placed senders and receivers that come and go as they please.  Many of them are well known or placed in fairly static and fixed topologies.

A controller with a global view of the network can create multicast topologies ahead of time. It knows all possible replication points and can create distribution trees among them. It can create different distribution trees for different multicast groups. It can create them independent of the unicast forwarding. It can calculate backup topologies in case portions of the tree fail. And it can do all of that guaranteeing there are no loops and optimal replication. When applications indicate their participation in specific multicast streams as senders or listeners to this controller, it can optimize very specifically based on those participants. The possibilities are endless.

We had a customer visit us yesterday that has very significant multicast needs and we walked him through some of these possibilities. He left with a huge smile on his face. And that smile on his face was not because he really liked what we built (even though he did), but it was because we showed him that if you remove legacy network thinking and constraints, networking can yet again be extremely exciting and creates solutions that he did not think were possible, in a fairly simple and straightforward way. And that, in turn, is truly exciting to us.

The post What SDN can do for Multicast Topologies appeared first on Plexxi.

Read the original blog entry...

More Stories By Marten Terpstra

Marten Terpstra is a Product Management Director at Plexxi Inc. Marten has extensive knowledge of the architecture, design, deployment and management of enterprise and carrier networks.

@ThingsExpo Stories
SYS-CON Events announced today that Carbonite will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Carbonite protects your entire IT footprint with the right level of protection for each workload, ensuring lower costs and dependable solutions with DoubleTake and Evault.
SYS-CON Events announced today that Tappest will exhibit MooseFS at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. MooseFS is a breakthrough concept in the storage industry. It allows you to secure stored data with either duplication or erasure coding using any server. The newest – 4.0 version of the software enables users to maintain the redundancy level with even 50% less hard drive space required. The software func...
SYS-CON Events announced today that delaPlex will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. delaPlex pioneered Software Development as a Service (SDaaS), which provides scalable resources to build, test, and deploy software. It’s a fast and more reliable way to develop a new product or expand your in-house team.
SYS-CON Events announced today that Technologic Systems Inc., an embedded systems solutions company, will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Technologic Systems is an embedded systems company with headquarters in Fountain Hills, Arizona. They have been in business for 32 years, helping more than 8,000 OEM customers and building over a hundred COTS products that have never been discontinued. Technologic Systems’ pr...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
SYS-CON Events announced today that Cloudistics, an on-premises cloud computing company, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Cloudistics delivers a complete public cloud experience with composable on-premises infrastructures to medium and large enterprises. Its software-defined technology natively converges network, storage, compute, virtualization, and management into a ...
SYS-CON Events announced today that EARP will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. "We are a software house, so we perfectly understand challenges that other software houses face in their projects. We can augment a team, that will work with the same standards and processes as our partners' internal teams. Our teams will deliver the same quality within the required time and budget just as our partn...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend @CloudExpo | @ThingsExpo, June 6-8, 2017, at the Javits Center in New York City, NY and October 31 - November 2, 2017, Santa Clara Convention Center, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
DevOps at Cloud Expo – being held October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA – announces that its Call for Papers is open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's largest enterprises – and delivering real r...
New competitors, disruptive technologies, and growing expectations are pushing every business to both adopt and deliver new digital services. This ‘Digital Transformation’ demands rapid delivery and continuous iteration of new competitive services via multiple channels, which in turn demands new service delivery techniques – including DevOps. In this power panel at @DevOpsSummit 20th Cloud Expo, moderated by DevOps Conference Co-Chair Andi Mann, panelists will examine how DevOps helps to meet th...
Most technology leaders, contemporary and from the hardware era, are reshaping their businesses to do software in the hope of capturing value in IoT. Although IoT is relatively new in the market, it has already gone through many promotional terms such as IoE, IoX, SDX, Edge/Fog, Mist Compute, etc. Ultimately, irrespective of the name, it is about deriving value from independent software assets participating in an ecosystem as one comprehensive solution.
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
SYS-CON Events announced today that A&I Solutions has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 1999, A&I Solutions is a leading information technology (IT) software and services provider focusing on best-in-class enterprise solutions. By partnering with industry leaders in technology, A&I assures customers high performance levels across all IT environments including: mai...
SYS-CON Events announced today that Systena America will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Systena Group has been in business for various software development and verification in Japan, US, ASEAN, and China by utilizing the knowledge we gained from all types of device development for various industries including smartphones (Android/iOS), wireless communication, security technology and IoT serv...
Every successful software product evolves from an idea to an enterprise system. Notably, the same way is passed by the product owner's company. In his session at 20th Cloud Expo, Oleg Lola, CEO of MobiDev, will provide a generalized overview of the evolution of a software product, the product owner, the needs that arise at various stages of this process, and the value brought by a software development partner to the product owner as a response to these needs.
Five years ago development was seen as a dead-end career, now it’s anything but – with an explosion in mobile and IoT initiatives increasing the demand for skilled engineers. But apart from having a ready supply of great coders, what constitutes true ‘DevOps Royalty’? It’ll be the ability to craft resilient architectures, supportability, security everywhere across the software lifecycle. In his keynote at @DevOpsSummit at 20th Cloud Expo, Jeffrey Scheaffer, GM and SVP, Continuous Delivery Busine...
SYS-CON Events announced today that Progress, a global leader in application development, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Enterprises today are rapidly adopting the cloud, while continuing to retain business-critical/sensitive data inside the firewall. This is creating two separate data silos – one inside the firewall and the other outside the firewall. Cloud ISVs ofte...
SYS-CON Events announced today that Outscale will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Outscale's technology makes an automated and adaptable Cloud available to businesses, supporting them in the most complex IT projects while controlling their operational aspects. You boost your IT infrastructure's reactivity, with request responses that only take a few seconds.
SYS-CON Events announced today that Interoute has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Interoute is the owner operator of Europe's largest network and a global cloud services platform, which encompasses over 70,000 km of lit fiber, 15 data centers, 17 virtual data centers and 33 colocation centers, with connections to 195 additional partner data centers. Our full-service Unifie...
SYS-CON Events announced today that CollabNet, a global leader in enterprise software development, release automation and DevOps solutions, will be a Bronze Sponsor of SYS-CON's 20th International Cloud Expo®, taking place from June 6-8, 2017, at the Javits Center in New York City, NY. CollabNet offers a broad range of solutions with the mission of helping modern organizations deliver quality software at speed. The company’s latest innovation, the DevOps Lifecycle Manager (DLM), supports Value S...