Welcome!

@CloudExpo Authors: Liz McMillan, Yeshim Deniz, Pat Romanski, Elizabeth White, Kevin Sparenberg

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.

@CloudExpo Stories
DX World EXPO, LLC., a Lighthouse Point, Florida-based startup trade show producer and the creator of "DXWorldEXPO® - Digital Transformation Conference & Expo" has announced its executive management team. The team is headed by Levent Selamoglu, who has been named CEO. "Now is the time for a truly global DX event, to bring together the leading minds from the technology world in a conversation about Digital Transformation," he said in making the announcement.
"We are focused on SAP running in the clouds, to make this super easy because we believe in the tremendous value of those powerful worlds - SAP and the cloud," explained Frank Stienhans, CTO of Ocean9, Inc., in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
"Peak 10 is a hybrid infrastructure provider across the nation. We are in the thick of things when it comes to hybrid IT," explained , Chief Technology Officer at Peak 10, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
"DX encompasses the continuing technology revolution, and is addressing society's most important issues throughout the entire $78 trillion 21st-century global economy," said Roger Strukhoff, Conference Chair. "DX World Expo has organized these issues along 10 tracks with more than 150 of the world's top speakers coming to Istanbul to help change the world."
"We are still a relatively small software house and we are focusing on certain industries like FinTech, med tech, energy and utilities. We help our customers with their digital transformation," noted Piotr Stawinski, Founder and CEO of EARP Integration, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
"I think DevOps is now a rambunctious teenager – it’s starting to get a mind of its own, wanting to get its own things but it still needs some adult supervision," explained Thomas Hooker, VP of marketing at CollabNet, in this SYS-CON.tv interview at DevOps Summit at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
"We've been engaging with a lot of customers including Panasonic, we've been involved with Cisco and now we're working with the U.S. government - the Department of Homeland Security," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held June 6-8, 2017, at the Javits Center in New York City, NY.
"We're here to tell the world about our cloud-scale infrastructure that we have at Juniper combined with the world-class security that we put into the cloud," explained Lisa Guess, VP of Systems Engineering at Juniper Networks, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
"I will be talking about ChatOps and ChatOps as a way to solve some problems in the DevOps space," explained Himanshu Chhetri, CTO of Addteq, in this SYS-CON.tv interview at @DevOpsSummit at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
Your homes and cars can be automated and self-serviced. Why can't your storage? From simply asking questions to analyze and troubleshoot your infrastructure, to provisioning storage with snapshots, recovery and replication, your wildest sci-fi dream has come true. In his session at @DevOpsSummit at 20th Cloud Expo, Dan Florea, Director of Product Management at Tintri, provided a ChatOps demo where you can talk to your storage and manage it from anywhere, through Slack and similar services with...
The financial services market is one of the most data-driven industries in the world, yet it’s bogged down by legacy CPU technologies that simply can’t keep up with the task of querying and visualizing billions of records. In his session at 20th Cloud Expo, Karthik Lalithraj, a Principal Solutions Architect at Kinetica, discussed how the advent of advanced in-database analytics on the GPU makes it possible to run sophisticated data science workloads on the same database that is housing the rich...
SYS-CON Events announced today that Massive Networks will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Massive Networks mission is simple. To help your business operate seamlessly with fast, reliable, and secure internet and network solutions. Improve your customer's experience with outstanding connections to your cloud.
"We are an IT services solution provider and we sell software to support those solutions. Our focus and key areas are around security, enterprise monitoring, and continuous delivery optimization," noted John Balsavage, President of A&I Solutions, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
Everything run by electricity will eventually be connected to the Internet. Get ahead of the Internet of Things revolution and join Akvelon expert and IoT industry leader, Sergey Grebnov, in his session at @ThingsExpo, for an educational dive into the world of managing your home, workplace and all the devices they contain with the power of machine-based AI and intelligent Bot services for a completely streamlined experience.
"We want to show that our solution is far less expensive with a much better total cost of ownership so we announced several key features. One is called geo-distributed erasure coding, another is support for KVM and we introduced a new capability called Multi-Part," explained Tim Desai, Senior Product Marketing Manager at Hitachi Data Systems, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
There is a huge demand for responsive, real-time mobile and web experiences, but current architectural patterns do not easily accommodate applications that respond to events in real time. Common solutions using message queues or HTTP long-polling quickly lead to resiliency, scalability and development velocity challenges. In his session at 21st Cloud Expo, Ryland Degnan, a Senior Software Engineer on the Netflix Edge Platform team, will discuss how by leveraging a reactive stream-based protocol,...
DevOps at Cloud Expo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to w...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
"The Striim platform is a full end-to-end streaming integration and analytics platform that is middleware that covers a lot of different use cases," explained Steve Wilkes, Founder and CTO at Striim, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
SYS-CON Events announced today that Calligo, an innovative cloud service provider offering mid-sized companies the highest levels of data privacy and security, has been named "Bronze Sponsor" of SYS-CON's 21st International Cloud Expo ®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Calligo offers unparalleled application performance guarantees, commercial flexibility and a personalised support service from its globally located cloud plat...