|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.
As enterprises work to take advantage of Big Data technologies, they frequently become distracted by product-level decisions. In most new Big Data builds this approach is completely counter-productive: it presupposes tools that may not be a fit for development teams, forces IT to take on the burden of evaluating and maintaining unfamiliar technology, and represents a major up-front expense. In his session at @BigDataExpo at @ThingsExpo, Andrew Warfield, CTO and Co-Founder of Coho Data, will dis...
Feb. 6, 2016 07:15 PM EST
SYS-CON Events announced today that Fusion, a leading provider of cloud services, will exhibit at 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. Fusion, a leading provider of integrated cloud solutions to small, medium and large businesses, is the industry's single source for the cloud. Fusion's advanced, proprietary cloud service platform enables the integration of leading edge solutions in the cloud, including clou...
Feb. 6, 2016 03:30 PM EST Reads: 703
With the Apple Watch making its way onto wrists all over the world, it’s only a matter of time before it becomes a staple in the workplace. In fact, Forrester reported that 68 percent of technology and business decision-makers characterize wearables as a top priority for 2015. Recognizing their business value early on, FinancialForce.com was the first to bring ERP to wearables, helping streamline communication across front and back office functions. In his session at @ThingsExpo, Kevin Roberts...
Feb. 6, 2016 03:15 PM EST Reads: 324
SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze 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. Commvault is a leading provider of data protection and information management...
Feb. 6, 2016 02:30 PM EST Reads: 350
SYS-CON Events announced today that Alert Logic, Inc., the leading provider of Security-as-a-Service solutions for the cloud, will exhibit at 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. Alert Logic, Inc., provides Security-as-a-Service for on-premises, cloud, and hybrid infrastructures, delivering deep security insight and continuous protection for customers at a lower cost than traditional security solutions. Ful...
Feb. 6, 2016 01:30 PM EST Reads: 339
SYS-CON Events announced today that VAI, a leading ERP software provider, will exhibit at 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. VAI (Vormittag Associates, Inc.) is a leading independent mid-market ERP software developer renowned for its flexible solutions and ability to automate critical business functions for the distribution, manufacturing, specialty retail and service sectors. An IBM Premier Business Part...
Feb. 6, 2016 01:00 PM EST Reads: 536
The cloud promises new levels of agility and cost-savings for Big Data, data warehousing and analytics. But it’s challenging to understand all the options – from IaaS and PaaS to newer services like HaaS (Hadoop as a Service) and BDaaS (Big Data as a Service). In her session at @BigDataExpo at @ThingsExpo, Hannah Smalltree, a director at Cazena, will provide an educational overview of emerging “as-a-service” options for Big Data in the cloud. This is critical background for IT and data profes...
Feb. 6, 2016 11:00 AM EST Reads: 115
With an estimated 50 billion devices connected to the Internet by 2020, several industries will begin to expand their capabilities for retaining end point data at the edge to better utilize the range of data types and sheer volume of M2M data generated by the Internet of Things. In his session at @ThingsExpo, Don DeLoach, CEO and President of Infobright, will discuss the infrastructures businesses will need to implement to handle this explosion of data by providing specific use cases for filte...
Feb. 6, 2016 11:00 AM EST
Fortunately, meaningful and tangible business cases for IoT are plentiful in a broad array of industries and vertical markets. These range from simple warranty cost reduction for capital intensive assets, to minimizing downtime for vital business tools, to creating feedback loops improving product design, to improving and enhancing enterprise customer experiences. All of these business cases, which will be briefly explored in this session, hinge on cost effectively extracting relevant data from ...
Feb. 6, 2016 09:00 AM EST
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2015 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 ad...
Feb. 6, 2016 05:00 AM EST Reads: 328
Most people haven’t heard the word, “gamification,” even though they probably, and perhaps unwittingly, participate in it every day. Gamification is “the process of adding games or game-like elements to something (as a task) so as to encourage participation.” Further, gamification is about bringing game mechanics – rules, constructs, processes, and methods – into the real world in an effort to engage people. In his session at @ThingsExpo, Robert Endo, owner and engagement manager of Intrepid D...
Feb. 5, 2016 09:00 PM EST Reads: 770
Eighty percent of a data scientist’s time is spent gathering and cleaning up data, and 80% of all data is unstructured and almost never analyzed. Cognitive computing, in combination with Big Data, is changing the equation by creating data reservoirs and using natural language processing to enable analysis of unstructured data sources. This is impacting every aspect of the analytics profession from how data is mined (and by whom) to how it is delivered. This is not some futuristic vision: it's ha...
Feb. 2, 2016 02:00 PM EST Reads: 401
WebRTC has had a real tough three or four years, and so have those working with it. Only a few short years ago, the development world were excited about WebRTC and proclaiming how awesome it was. You might have played with the technology a couple of years ago, only to find the extra infrastructure requirements were painful to implement and poorly documented. This probably left a bitter taste in your mouth, especially when things went wrong.
Feb. 2, 2016 04:30 AM EST Reads: 838
Learn how IoT, cloud, social networks and last but not least, humans, can be integrated into a seamless integration of cooperative organisms both cybernetic and biological. This has been enabled by recent advances in IoT device capabilities, messaging frameworks, presence and collaboration services, where devices can share information and make independent and human assisted decisions based upon social status from other entities. In his session at @ThingsExpo, Michael Heydt, founder of Seamless...
Feb. 1, 2016 05:00 AM EST Reads: 921
The IoT's basic concept of collecting data from as many sources possible to drive better decision making, create process innovation and realize additional revenue has been in use at large enterprises with deep pockets for decades. So what has changed? In his session at @ThingsExpo, Prasanna Sivaramakrishnan, Solutions Architect at Red Hat, discussed the impact commodity hardware, ubiquitous connectivity, and innovations in open source software are having on the connected universe of people, thi...
Jan. 31, 2016 09:00 PM EST Reads: 715
WebRTC: together these advances have created a perfect storm of technologies that are disrupting and transforming classic communications models and ecosystems. In his session at WebRTC Summit, Cary Bran, VP of Innovation and New Ventures at Plantronics and PLT Labs, provided an overview of this technological shift, including associated business and consumer communications impacts, and opportunities it may enable, complement or entirely transform.
Jan. 31, 2016 07:15 PM EST Reads: 1,135
There are so many tools and techniques for data analytics that even for a data scientist the choices, possible systems, and even the types of data can be daunting. In his session at @ThingsExpo, Chris Harrold, Global CTO for Big Data Solutions for EMC Corporation, showed how to perform a simple, but meaningful analysis of social sentiment data using freely available tools that take only minutes to download and install. Participants received the download information, scripts, and complete end-t...
Jan. 31, 2016 10:00 AM EST Reads: 1,195
For manufacturers, the Internet of Things (IoT) represents a jumping-off point for innovation, jobs, and revenue creation. But to adequately seize the opportunity, manufacturers must design devices that are interconnected, can continually sense their environment and process huge amounts of data. As a first step, manufacturers must embrace a new product development ecosystem in order to support these products.
Jan. 31, 2016 10:00 AM EST Reads: 797
Manufacturing connected IoT versions of traditional products requires more than multiple deep technology skills. It also requires a shift in mindset, to realize that connected, sensor-enabled “things” act more like services than what we usually think of as products. In his session at @ThingsExpo, David Friedman, CEO and co-founder of Ayla Networks, discussed how when sensors start generating detailed real-world data about products and how they’re being used, smart manufacturers can use the dat...
Jan. 30, 2016 07:45 PM EST Reads: 771
When it comes to IoT in the enterprise, namely the commercial building and hospitality markets, a benefit not getting the attention it deserves is energy efficiency, and IoT’s direct impact on a cleaner, greener environment when installed in smart buildings. Until now clean technology was offered piecemeal and led with point solutions that require significant systems integration to orchestrate and deploy. There didn't exist a 'top down' approach that can manage and monitor the way a Smart Buildi...
Jan. 30, 2016 03:45 PM EST Reads: 1,258