Welcome!

Containers Expo Blog Authors: Elizabeth White, Stackify Blog, John Rauser, Liz McMillan, Don MacVittie

Related Topics: Containers Expo Blog, Microservices Expo, Microsoft Cloud, Open Source Cloud, @CloudExpo, SDN Journal

Containers Expo Blog: Blog Post

Managing Tables in Our New Virtual Reality

Networking really comes down to the art of managing tables and rules.

In traditional networks, MAC addresses are inserted into tables using standard learning techniques.  When packets arrive, if the source MAC address is not known, it is added to the MAC forwarding table for that VLAN with the ingress interface as its destination. If the destination is unknown, the packet is flooded through the VLAN, with the side effect that each switch along the way inserts the source MAC address in its own forwarding table for that VLAN. Assuming the destination actually exists, one of the flooded copies will reach its destination. The device at the destination MAC address receives the packet, and (hopefully) responds. The response is destined for the device that sent the original packet, for which each switch has learned how to get to from the flooded packet. The packet makes it way back to the original source with the side effect of the source of this response packet being learned and inserted into the forwarding table along the switch path back to the original sender. Sounds complicated, but its basic MAC learning and this is how ethernet networks have found sources and destinations for a long long time.

phonebook

IP addresses are learning slightly differently. ARP is used to create a mapping between a MAC address and an IP address. When a device wants to send an IP packet to a device on the same subnet, it will send out an ARP request for the destination device, and that device (or someone else on its behalf in the case of proxy ARP) will respond with an response that provides the mapping between MAC address and IP address. When the IP packet is destined for another subnet, the source will pass the packet to gateway for the destination subnet, using ARP the exact same way to get the MAC to IP address mapping. That gateway is determined by yet another table, the IP routing table, containing IP subnets and a pointer to the IP address of the device that can get you there. The latter is built using static entries configured by the administrator, or routing protocols like OSPF, ISIS or BGP.

So far so good. We have 3 tables to maintain: the MAC table (also known as the L2 forwarding table), the ARP table (also know as the IP host table) and the IP routing table.

When a network is divided into multiple virtual networks, each of these tables could be split into multiple versions, one for each virtual network. As an example I may have 10 separate L2 forwarding tables, each containing many MAC addresses in many VLANs. This immediately brings us to the first challenge in managing these tables. If I receive an ethernet packet, which of multiple tables do I use to lookup the destination, or similarly, in which table do I insert the source MAC address I just learned? It is clear that a switch must know to which virtual network this packet belongs before it attempts to use its L2 forwarding table. Similarly, by learning then source of this packet, I need to know which of multiple tables to insert its address into.

There are several ways by which to associate a packet with a forwarding table, or really with a Virtual Network. The most basic and probably most used is a static mapping of the combination of ingress port (on the switch) and VLAN. The administrator has created a table that simply says "any packet coming in on this port on this VLAN belongs to Virtual Network X". Virtual Network X is now associated with one of the forwarding tables and we have found the table we are dealing with. We can learn source and put them in the right table and we can lookup the destination. When the destination is not present in that table, we have our next challenge: how do we flood in a Virtualized Network? We would normally send the packet out every port that this VLAN configured (along an STP or otherwise managed loop free path), but we want to reach only those switches that have this Virtual Network configured (statically or dynamically).

This is where different solutions take different approaches. In Shortest Path Bridging for instance, the set of switches that have member ports in a specific Virtual Network (I-SID in SPB terms) are discovered using ISIS. As part of that discovery, a SPF calculated tree is created covering all these switches, and the packet is flooded along this tree, very similar to normal VLAN flooding. Because SPB traffic is encapsulated, only the edge switches decapsulate this packet and learn the original source.

Overlay networks like VXLAN solve the problem in a very similar way in the pure definition of the protocol. When a packet is destined for an unknown destination, it is "flooded" to all other VXLAN endpoints that have members for that Virtual Network (VNI in the case of VXLAN). Because VXLAN runs on top of IP, its version of flooding needs an IP based mechanism, and the mechanism of choice is IP Multicast. Each VNI is represented by an IP multicast group, and all VXLAN endpoints (VTEPs) join this group. When a packet needs to be flooded, it is multicast on that specific group, the receiving VTEPs decapsulate the packet, learn the source and all is good.

There have been many articles and opinions on the use of IP Multicast for flooding (which is essentially the same as multicasting or broadcasting) in VXLAN. One of VXLANs strengths is that it can travel across any IP infrastructure, including the largest of them all, the Internet. However, ubiquitous IP connectivity is nowhere near the same as ubiquitous IP Multicast connectivity. And this is why most controller (distributed or central) overlay solutions have attacked that problem. And this is also where it gets complicated.

A first benefit of having a controller that manages the overlay network is simple: you have a complete inventory of all overlay endpoints that exist in the network. You probably even have an inventory of which Virtual Networks each serves, because all of this is provisioned data. This means I don't have to discover all the endpoints a packet needs to be flooded to, I know them all, I can simply replicate the packet to each and every end point as a unicast packet. Current implementations of the controller based virtualization solutions use this. The advantage is that it is really simple. The disadvantage, its a lot of overhead when you have many endpoints.

When you think through the creation of overlay networks and how VMs are created and attached to Virtual Switches and attached to Virtual Networks, you quickly realize that all of this is provisioned information through the overlay and VM orchestration system. Which raises the question, why attempt to dynamically learn at all? If I know exactly where a VM is (using VM as a equivalent of a MAC and IP address here), which VTEP it is hiding behind, and which Virtual Network it is part of, why can I not simply tell all the other VTEPs about this from the controller? All provisioned information could be exchanged outside of the normal inline learning mechanisms, so mechanisms like flooding and even ARP are greatly reduced or even completely removed in such networks. All information is known and the controller pro-actively pushes this information to those that need to know.

It is a different way of solving some of the more challenging (but basic and fundamental) network behaviors, but one that makes complete sense. It does raise many scaling questions, we have taken methods that have traditionally been distributed and turned it into centralized table management. And whether the controller runs distributed, clustered or as a single entity, it is still a centrally managed entity. The next little while will tell us whether the scale and performance are sufficient for the networks we intend to build.

This however does not mean that there is no need for dynamic learning in an overlay network. Any network will have devices that are outside of the control of the overlay controller. These devices need to be discovered and learned somehow. That is the work of VXLan gateways and Service Nodes in NSX. And those create a completely new challenge. Less so of functionality and far more of control. The ultimate challenge is less how they are managed, that is "just" engineering work. The real challenge is who manages the tables.

[Today's fun fact: The plastic things on the end of shoelaces are called "aglets". And I guarantee you won't remember that by tomorrow]

The post Managing Tables in our new Virtual Reality 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
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...
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
SYS-CON Events announced today that Evatronix 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. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things’). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing? IoT is not about the devices, it’s about the data consumed and generated. The devices are tools, mechanisms, conduits. In his session at Internet of Things at Cloud Expo | DXWor...
Everything run by electricity will eventually be connected to the Internet. Get ahead of the Internet of Things revolution. In his session at @ThingsExpo, Akvelon expert and IoT industry leader Sergey Grebnov provided 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.
SYS-CON Events announced today that Synametrics Technologies will exhibit at SYS-CON's 22nd International Cloud Expo®, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Synametrics Technologies is a privately held company based in Plainsboro, New Jersey that has been providing solutions for the developer community since 1997. Based on the success of its initial product offerings such as WinSQL, Xeams, SynaMan and Syncrify, Synametrics continues to create and hone inn...