|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.
Small teams are more effective. The general agreement is that anything from 5 to 12 is the 'right' small. But of course small teams will also have 'small' throughput - relatively speaking. So if your demand is X and the throughput of a small team is X/10, you probably need 10 teams to meet that demand. But more teams also mean more effort to coordinate and align their efforts in the same direction. So, the challenge is how to harness the power of small teams and yet orchestrate multiples of them...
May. 24, 2016 09:15 AM EDT Reads: 1,772
SYS-CON Events announced today the Docker Meets Kubernetes – Intro into the Kubernetes World, being held June 9, 2016, in conjunction with 18th Cloud Expo | @ThingsExpo, at the Javits Center in New York, NY. Register for 'Docker Meets Kubernetes Workshop' Here! This workshop led by Sebastian Scheele, co-founder of Loodse, introduces participants to Kubernetes (container orchestration). Through a combination of instructor-led presentations, demonstrations, and hands-on labs, participants learn ...
May. 24, 2016 09:00 AM EDT Reads: 1,773
The initial debate is over: Any enterprise with a serious commitment to IT is migrating to the cloud. But things are not so simple. There is a complex mix of on-premises, colocated, and public-cloud deployments. In this power panel at 18th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists will look at the present state of cloud from the C-level view, and how great companies and rock star executives can use cloud computing to meet their most ambitious and disruptive business ...
May. 24, 2016 09:00 AM EDT Reads: 1,965
The demand for organizations to expand their infrastructure to multiple IT environments like the cloud, on-premise, mobile, bring your own device (BYOD) and the Internet of Things (IoT) continues to grow. As this hybrid infrastructure increases, the challenge to monitor the security of these systems increases in volume and complexity. In his session at 18th Cloud Expo, Stephen Coty, Chief Security Evangelist at Alert Logic, will show how properly configured and managed security architecture can...
May. 24, 2016 09:00 AM EDT Reads: 1,920
Last week I had the pleasure of speaking on a panel at Sapphire Ventures Next-Gen Tech Stack Forum in San Francisco. Obviously, I was excited to join the discussion, but as a participant the event crystallized not only where the larger software development market is relative to microservices, container technologies (like Docker), continuous integration and deployment; but also provided insight into where DevOps is heading in the coming years.
May. 24, 2016 07:15 AM EDT Reads: 1,380
Admittedly, two years ago I was a bulk contributor to the DevOps noise with conversations rooted in the movement around culture, principles, and goals. And while all of these elements of DevOps environments are important, I’ve found that the biggest challenge now is a lack of understanding as to why DevOps is beneficial. It’s getting the wheels going, or just taking the next step. The best way to start on the road to change is to take a look at the companies that have already made great headway ...
May. 24, 2016 07:15 AM EDT Reads: 1,587
Agile teams report the lowest rate of measuring non-functional requirements. What does this mean for the evolution of quality in this era of Continuous Everything? To explore how the rise of SDLC acceleration trends such as Agile, DevOps, and Continuous Delivery are impacting software quality, Parasoft conducted a survey about measuring and monitoring non-functional requirements (NFRs). Here's a glimpse at what we discovered and what it means for the evolution of quality in this era of Continuo...
May. 24, 2016 06:45 AM EDT Reads: 1,372
You might already know them from theagileadmin.com, but let me introduce you to two of the leading minds in the Rugged DevOps movement: James Wickett and Ernest Mueller. Both James and Ernest are active leaders in the DevOps space, in addition to helping organize events such as DevOpsDays Austinand LASCON. Our conversation covered a lot of bases from the founding of Rugged DevOps to aligning organizational silos to lessons learned from W. Edwards Demings.
May. 24, 2016 06:45 AM EDT Reads: 1,293
SYS-CON Events announced today BZ Media LLC has been named “Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. BZ Media LLC is a high-tech media company that produces technical conferences and expositions, and publishes a magazine, newsletters and websites in the software development, SharePoint, mobile development and Commercial Drone markets.
May. 24, 2016 06:00 AM EDT Reads: 3,362
When I talk about driving innovation with self-organizing teams, I emphasize that such self-organization includes expecting the participants to organize their own teams, give themselves their own goals, and determine for themselves how to measure their success. In contrast, the definition of skunkworks points out that members of such teams are “usually specially selected.” Good thing he added the word usually – because specially selecting such teams throws a wrench in the entire works, limiting...
May. 24, 2016 05:15 AM EDT Reads: 1,415
SYS-CON Events announced today TechTarget has been named “Media Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. TechTarget is the Web’s leading destination for serious technology buyers researching and making enterprise technology decisions. Its extensive global networ...
May. 24, 2016 04:00 AM EDT Reads: 2,992
Application development and delivery methods have undergone radical changes in recent years to improve scalability and resiliency. Container images are the new build and deployment artifacts that are used to ship and run software. While startups have long been comfortable experimenting with and embracing new technologies, even large enterprises are now re-architecting their software systems so that they can benefit from container-enabled micro services architectures. With the launch of DC/OS, w...
May. 24, 2016 04:00 AM EDT Reads: 1,282
Earlier this week, we hosted a Continuous Discussion (#c9d9) on Continuous Delivery (CD) automation and orchestration, featuring expert panelists Dondee Tan, Test Architect at Alaska Air, Taco Bakker, a LEAN Six Sigma black belt focusing on CD, and our own Sam Fell and Anders Wallgren. During this episode, we discussed the differences between CD automation and orchestration, their challenges with setting up CD pipelines and some of the common chokepoints, as well as some best practices and tips...
May. 24, 2016 03:45 AM EDT Reads: 1,201
As AT&Ts VP of Domain 2.0 architecture writes one aspect of their Domain 2.0 strategy is a goal to embrace a Microservices Application Architecture. One page 9 they describe how these envisage them fitting into the ECOMP architecture: "The initial steps of the recipes include a homing and placement task using constraints specified in the requests. ‘Homing and Placement' are micro-services involving orchestration, inventory, and controllers responsible for infrastructure, network, and applicati...
May. 24, 2016 02:45 AM EDT Reads: 1,550
Automation is a critical component of DevOps and Continuous Delivery. This morning on #c9d9 we discussed CD Automation and how you can apply Automation to accelerate release cycles, improve quality, safety and governance? What is the difference between Automation and Orchestration? Where should you begin your journey to introduce both?
May. 24, 2016 01:30 AM EDT Reads: 1,218
While there has been much ado about interoperability, there are still no real solutions, same as last year and the year before that. The large EHR vendors who continue to dominate the market still maintain that interoperability is all but solved, still can't connect EHRs across the continuum causing frustration by providers and a disservice to patients. The ONC pays lip service to the problem, but that is about it. It is time for the healthcare industry to consider alternatives like middleware w...
May. 23, 2016 10:00 PM EDT Reads: 1,400
The pace of innovation, vendor lock-in, production sustainability, cost-effectiveness, and managing risk… In his session at 18th Cloud Expo, Dan Choquette, Founder of RackN, will discuss how CIOs are challenged finding the balance of finding the right tools, technology and operational model that serves the business the best. He will discuss how clouds, open source software and infrastructure solutions have benefits but also drawbacks and how workload and operational portability between vendors...
May. 23, 2016 07:00 PM EDT Reads: 1,716
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York and Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty ...
May. 23, 2016 05:00 PM EDT Reads: 4,606
Our CTO, Anders Wallgren, recently sat down to take part in the “B2B Nation: IT” podcast — the series dedicated to serving the IT professional community with expert opinions and advice on the world of information technology. Listen to the great conversation, where Anders shares his thoughts on DevOps lessons from large enterprises, the growth of microservices and containers, and more.
May. 23, 2016 04:00 PM EDT Reads: 1,414
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Containers, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit y...
May. 23, 2016 04:00 PM EDT Reads: 1,813