|By Marten Terpstra||
|January 16, 2014 12:45 PM EST||
There have been many articles describing overlay networks in the past few quarters. It's a relatively straightforward concept, not far removed from some of the older VPN technologies very popular a while ago. The actual transport of packets is probably the simplest, it is the control plane that is much harder to construct and therefore explain. It is therefore also that the control plane in overlay networks has seen the most innovation and change, and is likely to change some more in standard and proprietary ways in the next little while. A perfect example is the use of IP Multicast for unknown, multicast and broadcast traffic as defined in the latest IETF draft for VXLAN, but controller implementations try and avoid IP Multicast as part of the necessary data path. Which will continue to lead to changes in the control plane for learning, distribution of destinations, etc.
A Plexxi solution provides an optimized L1, L2 and L3 network. With the advent of overlay networks, the relationship and interaction between the physical, L2 and L3 network and the overlay infrastructure is important to understand. We strongly believe the control and data planes should be interconnected and coordinated/orchestrated. In this and next week’s blog, I will describe some key touch points of the two at the data plane: entropy as a mechanism to discern flow like information and the role and capabilities of a hardware gateway.
I looked at VXLAN, NVGRE and STT as the major overlay encapsulations. VXLAN and STT are very much driven by VMWare, with STT used as the tunnel encapsulation between vSwitch based VXLAN Tunnel End Points (VTEP), VXLAN used as the tunnel encapsulation to external entities like gateways. NVGRE of course is the tunnel protocol of choice for Microsoft’s overlay solution and very similar to to previous GRE based encapsulations. All encapsulations are IP based, allowing the tunnels to be transported across a basic IP infrastructure (with the above mentioned note for IP Multicast). VXLAN and NVGRE are packet based mechanisms, each original packet ends up being encapsulated into a new packet.
VXLAN is build on top of UDP. As shown below, an encapsulated ethernet packet has 54 bytes of new header information added (assuming it is being transported again over ethernet). The first 18 bytes contain the ethernet header containing the MAC address of the source VTEP and its next IP destination, most likely the next IP router/switch. This header changes at each IP hop. The next 20 bytes contain the IP header. The protocol is set to 17 for UDP. The source IP address is that of the originating VTEP, the destination IP address that of the destination VTEP. The IP header is followed by 8 bytes of UDP header containing source UDP port, destination UDP port (4789) and the usual UDP length and checksum fields. While formatted in a normal way, the UDP source port is used in a special way to create “entropy”, explained in more detail below.
A VXLAN Encapsulated Ethernet Packet
Following the UDP header is the actual 8 byte VXLAN header. Just about all fields except the 24 bit VXLAN Network Identifier (VNI) are reserved and set to zero. The VNI is key, it determines which VXLAN the original packet belongs to. When the destination VTEP receives this packet and decapsulates it, it will use this to find the right table to use for MAC address lookups of the original packet to get it to its destination. Only the original packets (shown with Ethernet headers above) follows the VXLAN header. For every packet sent out by a VM, VXLAN adds 54 bytes of new tunnel headers between the source and destination VTEP. Intermediate systems do all their forwarding based on this new header: ethernet switches will use the Outer Ethernet header, IP routers will use the Outer IPv4 header to route this packet towards its destination. Each IP router will replace the Outer Ethernet header with a new one representing itself as the source, and the next IP router as the destination.
NVGRE packets look very similar to VXLAN packets. The initial Outer Ethernet header is the same as VXLAN, representing the source tunnel endpoint and the first IP router as the source and destination. The next 20 bytes of IP header are also similar to VXLAN, except that the protocol is 47 for GRE. NVGRE encodes the Virtualized LAN (Virtual Subnet ID or VSID in NVGRE terms) inside the GRE header, using 24 bits of the original GRE Key field to represent the VSID, leaving 8 bits for a FlowID field, which serves a similar entropy function as the UDP source port for VXLAN, explain further below. The VSID in NVGRE and VNI in VXLAN represent the overlay virtual network ID for each of the technologies. Following the GRE header, the original (Ethernet) packet. NVGRE added 46 bytes of new header information to existing packets.
A NVGRE Encapsulated Ethernet Packet
As I mentioned in last week’s blog, a tunnel endpoint is an aggregation point and as a result, all of the individual flows that are put into a specific VTEP to VTEP tunnel go through the transport network based on the new headers that have been added. Many networks rely on some form of L2 or L3 ECMP to use all available bandwidth between any two points on the network, spine and leaf networks being the prime example of an absolute dependency on a very well functioning ECMP to perform at its best. Without discussing the virtues of ECMP again, tunneled packets need something in the new header that allows an hash calculation to make use of multiple ECMP paths. With pretty much all of the L2 and L3 header identical (except for the VNI or VSID) for all traffic between two tunnel endpoints, the creators of these encapsulations have been creative in encoding entropy in these new headers so that hash calculations for these headers can be used to place traffic onto multiple equal cost paths.
For VXLAN, this entropy is encoded in the UDP source port field. With only a single UDP VXLAN connection between any two endpoints allowed (and necessary), the source port is essentially irrelevant and can be used to mark a packet with a hash calculation result that in effect acts as a flow identifier for the inner packet. Except that it is not unique. The VXLAN spec does not specify exactly how to calculate this hash value, but its generally assumed that specific portions of the inner packet L2, L3 and/or L4 header are used to calculate this hash. The originating VTEP calculates this, puts it in the new UDP header as the source port, and it remains there unmodified until it arrives at the receiving VTEP. Intermediate systems that calculate hashes for L2 or L3 ECMP balancing typically use UDP ports as part of their calculation and as a result, different inner packet flows will result in different placement onto ECMP links. As mentioned, intermediate routers or switches that transport the VXLAN packet do not modify the UDP source port, they only use its value in their ECMP calculation.
NVGRE is fairly similar. GRE packets have no TCP or UDP header, and as a result network hardware typically has the ability to recognize these packets as GRE and use the 32-bit GRE key field as an information source in their ECMP calculations. GRE tunnel endpoints encode inner packet flows with individual (but not necessarily unique) key values, and as a result, intermediate network systems will calculate different hash results to place these inner packet flows onto multiple ECMP links. NVGRE has taken 24 of these bits to encode the VSID, but has left 8 bits to create this entropy at the tunnel endpoint, the field has been renamed FlowID. The VSID and FlowID combined will be used to calculate hashes for ECMP link placement. A possible challenge is that for networks that have many many flows inside a VSID between two specific NVGRE endpoints, the 8 bits worth of differentiation may not create a “normal” ECMP distribution.
While the packet formats have been constructed to ensure that the “normal” tools of entropy can be used for ECMP and LAG by existing switching hardware, the latest hardware platforms have the ability to look well beyond the outer headers. Many bits and pieces of the new headers can be examined and decisions can be made on them. While specific switching ASICs will have slightly different tools, the latest generations of them have he ability to look at VNI and VSID even when not acting as a gateway, and packet modification or forwarding decisions can be made on their value. Inner MAC and IP headers can also be examined and acted on, with a bit more complexity. Switching ASICs are built to have quick access to the most important fields to make decisions on, access to less common fields is there, but requires some manual construction by those that program the ASIC (the networking vendors).
When the switching platform is configured to be a gateway to provide bridging functions between regular VLANs and the tunneled VXLAN or NVGRE infrastructure, the ASIC has access to the entire original packet, since it actively encapsulates or decapsulates the original packet. That gives the switch decision choices very similar to a vSwitch, but at a smaller scale. More detail on the gateway function and STT next week.
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Architect for the Internet of Things and Intelligent Systems, described how to revolutionize your archit...
Jul. 28, 2015 06:30 PM EDT Reads: 1,370
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society-changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his session at @ThingsExpo, Jason Mondanaro, Director, Product Management at Metanga, discussed how you can plan to cooperate, partner, and form lasting all-star teams to change the world and it starts with business models and monetization strategies.
Jul. 28, 2015 04:30 PM EDT Reads: 1,751
The Internet of Everything (IoE) brings together people, process, data and things to make networked connections more relevant and valuable than ever before – transforming information into knowledge and knowledge into wisdom. IoE creates new capabilities, richer experiences, and unprecedented opportunities to improve business and government operations, decision making and mission support capabilities.
Jul. 28, 2015 04:00 PM EDT Reads: 217
The Internet of Things is not only adding billions of sensors and billions of terabytes to the Internet. It is also forcing a fundamental change in the way we envision Information Technology. For the first time, more data is being created by devices at the edge of the Internet rather than from centralized systems. What does this mean for today's IT professional? In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists addressed this very serious issue of profound change in the industry.
Jul. 28, 2015 03:00 PM EDT Reads: 1,247
Discussions about cloud computing are evolving into discussions about enterprise IT in general. As enterprises increasingly migrate toward their own unique clouds, new issues such as the use of containers and microservices emerge to keep things interesting. In this Power Panel at 16th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the state of cloud computing today, and what enterprise IT professionals need to know about how the latest topics and trends affect their organization.
Jul. 28, 2015 02:00 PM EDT Reads: 1,156
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
Jul. 28, 2015 11:45 AM EDT Reads: 407
For IoT to grow as quickly as analyst firms’ project, a lot is going to fall on developers to quickly bring applications to market. But the lack of a standard development platform threatens to slow growth and make application development more time consuming and costly, much like we’ve seen in the mobile space. In his session at @ThingsExpo, Mike Weiner, Product Manager of the Omega DevCloud with KORE Telematics Inc., discussed the evolving requirements for developers as IoT matures and conducted a live demonstration of how quickly application development can happen when the need to comply wit...
Jul. 28, 2015 11:15 AM EDT Reads: 221
Converging digital disruptions is creating a major sea change - Cisco calls this the Internet of Everything (IoE). IoE is the network connection of People, Process, Data and Things, fueled by Cloud, Mobile, Social, Analytics and Security, and it represents a $19Trillion value-at-stake over the next 10 years. In her keynote at @ThingsExpo, Manjula Talreja, VP of Cisco Consulting Services, discussed IoE and the enormous opportunities it provides to public and private firms alike. She will share what businesses must do to thrive in the IoE economy, citing examples from several industry sectors.
Jul. 28, 2015 11:00 AM EDT Reads: 2,026
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it! In her Opening Keynote at 16th Cloud Expo, Sandy Carter, IBM General Manager Cloud Ecosystem and Developers, and a Social Business Evangelist, d...
Jul. 27, 2015 09:00 PM EDT Reads: 2,037
There will be 150 billion connected devices by 2020. New digital businesses have already disrupted value chains across every industry. APIs are at the center of the digital business. You need to understand what assets you have that can be exposed digitally, what their digital value chain is, and how to create an effective business model around that value chain to compete in this economy. No enterprise can be complacent and not engage in the digital economy. Learn how to be the disruptor and not the disruptee.
Jul. 27, 2015 10:00 AM EDT Reads: 2,018
Akana has released Envision, an enhanced API analytics platform that helps enterprises mine critical insights across their digital eco-systems, understand their customers and partners and offer value-added personalized services. “In today’s digital economy, data-driven insights are proving to be a key differentiator for businesses. Understanding the data that is being tunneled through their APIs and how it can be used to optimize their business and operations is of paramount importance,” said Alistair Farquharson, CTO of Akana.
Jul. 27, 2015 09:00 AM EDT Reads: 307
Business as usual for IT is evolving into a "Make or Buy" decision on a service-by-service conversation with input from the LOBs. How does your organization move forward with cloud? In his general session at 16th Cloud Expo, Paul Maravei, Regional Sales Manager, Hybrid Cloud and Managed Services at Cisco, discusses how Cisco and its partners offer a market-leading portfolio and ecosystem of cloud infrastructure and application services that allow you to uniquely and securely combine cloud business applications and services across multiple cloud delivery models.
Jul. 27, 2015 08:00 AM EDT Reads: 1,890
The enterprise market will drive IoT device adoption over the next five years. In his session at @ThingsExpo, John Greenough, an analyst at BI Intelligence, division of Business Insider, analyzed how companies will adopt IoT products and the associated cost of adopting those products. John Greenough is the lead analyst covering the Internet of Things for BI Intelligence- Business Insider’s paid research service. Numerous IoT companies have cited his analysis of the IoT. Prior to joining BI Intelligence, he worked analyzing bank technology for Corporate Insight and The Clearing House Payment...
Jul. 26, 2015 09:00 PM EDT Reads: 1,556
In his keynote at 16th Cloud Expo, Rodney Rogers, CEO of Virtustream, discussed the evolution of the company from inception to its recent acquisition by EMC – including personal insights, lessons learned (and some WTF moments) along the way. Learn how Virtustream’s unique approach of combining the economics and elasticity of the consumer cloud model with proper performance, application automation and security into a platform became a breakout success with enterprise customers and a natural fit for the EMC Federation.
Jul. 26, 2015 08:00 AM EDT Reads: 2,139
"Optimal Design is a technology integration and product development firm that specializes in connecting devices to the cloud," stated Joe Wascow, Co-Founder & CMO of Optimal Design, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
Jul. 25, 2015 02:00 PM EDT Reads: 378
SYS-CON Events announced today that CommVault has been named “Bronze Sponsor” of SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. A singular vision – a belief in a better way to address current and future data management needs – guides CommVault in the development of Singular Information Management® solutions for high-performance data protection, universal availability and simplified management of data on complex storage networks. CommVault's exclusive single-platform architecture gives companies unp...
Jul. 25, 2015 01:00 PM EDT Reads: 1,938
Electric Cloud and Arynga have announced a product integration partnership that will bring Continuous Delivery solutions to the automotive Internet-of-Things (IoT) market. The joint solution will help automotive manufacturers, OEMs and system integrators adopt DevOps automation and Continuous Delivery practices that reduce software build and release cycle times within the complex and specific parameters of embedded and IoT software systems.
Jul. 25, 2015 12:15 PM EDT Reads: 442
"ciqada is a combined platform of hardware modules and server products that lets people take their existing devices or new devices and lets them be accessible over the Internet for their users," noted Geoff Engelstein of ciqada, a division of Mars International, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
Jul. 25, 2015 12:00 PM EDT Reads: 1,518
Internet of Things is moving from being a hype to a reality. Experts estimate that internet connected cars will grow to 152 million, while over 100 million internet connected wireless light bulbs and lamps will be operational by 2020. These and many other intriguing statistics highlight the importance of Internet powered devices and how market penetration is going to multiply many times over in the next few years.
Jul. 25, 2015 09:00 AM EDT Reads: 1,480
SYS-CON Events announced today that Dyn, the worldwide leader in Internet Performance, will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Dyn is a cloud-based Internet Performance company. Dyn helps companies monitor, control, and optimize online infrastructure for an exceptional end-user experience. Through a world-class network and unrivaled, objective intelligence into Internet conditions, Dyn ensures traffic gets delivered faster, safer, and more reliably than ever.
Jul. 24, 2015 11:00 PM EDT Reads: 2,043