Cisco Blogs


Cisco Blog > Data Center

VXLAN/EVPN: Standards based Overlay with Control-Plane

Given the tremendous interest in VXLAN with MP-BGP based EVPN Control-Plane (short EVPN) at Cisco Live in Milan, I decided to write a “short” technology brief blog post on this topic.

VXLAN (IETF RFC7348) has been designed to solve specific problems faced with Classical Ethernet for a few decades now. By introducing an abstraction through encapsulation, VXLAN has become the de-facto standard overlay of choice in the industry. Chief among the advantages provided by VXLAN; extension of the todays limited VLAN space and the increase in the scalability provided for Layer-2 Domains.

Extended Namespace – The available VLAN space from the IEEE 802.1Q encapsulation perspective is limited to a 12-bit field, which provides 4096 VLANs or segments. By encapsulating the original Ethernet frame with a VXLAN header, the newly introduced addressing field offers 24-bits, thereby providing a much larger namespace with up to 16 Million Virtual Network Identifiers (VNIs) or segments.

 

 

 

While the VXLAN VNI allows unique identification of a large number of tenant segments which is especially useful in high-scale multi-tenant deployments, the problems and requirements of large Layer-2 Domains are not sufficiently addressed. However, significant improvements in the following areas have been achieved:

  • No dependency on Spanning-Tree protocol by leveraging Layer-3 routing protocols
  • Layer-3 routing with Equal Cost Multi-Path (ECMP) allows all available links to be used
  • Scalability, convergence, and resiliency of a Layer-3 network
  • Isolation of Broadcast and Failure Domains

IETF RFC7348 – VXLAN: A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks

Scalable Layer-2 Domains

The abstraction by using a VXLAN-like overlay does not inherently change the Flood & Learn behavior introduced by Ethernet. In typical deployments of VXLAN, BUM (Broadcast, Unicast, Multicast) traffic is forwarded via layer-3 multicast in the underlay that in turn aids in the learning process so that subsequent traffic need not be subjected to this “flood” semantic. A control-plane is required to minimize the flood behavior and proactively distribute End-Host information to participating entities (typically called Virtual Tunnel End Points aka VTEPs) in the same segment – learning.

Control-plane protocols are mostly employed in the layer-3 routing space where predominantly IP prefix information is exchanged. Over the past years, some of the well-known routing protocols have been extended to also learn and exchange Layer-2 MAC addresses. An early technology adoption with MAC addresses in a routing-protocol was Cisco’s OTV (Overlay Transport Virtualization), which employed IS-IS to significantly reduce flooding across Data Center Interconnects (DCI).

Multi-Protocol BGP (MP-BGP) introduced a new Network Layer Reachability Information (NLRI) to carry both, Layer-2 MAC and Layer-3 IP information at the same time. By having the combined set of MAC and IP information available for forwarding decisions, optimized routing and switching within a network becomes feasible and the need for flood to do learning get minimized or even eliminated. This extension that allows BGP to transport Layer-2 MAC and Layer-3 IP information is called EVPN – Ethernet Virtual Private Network.

EVPN is documented in the following IETF drafts

Integrated Route and Bridge (IRB) – VXLAN-EVPN offers significant advantages in Overlay networking by optimizing forwarding decision within the network based on Layer-2 MAC as well as Layer-3 IP information. The decision on forwarding via routing or switching can be done as close as possible to the End-Host, on any given Leaf/ToR (Top-of-Rack) Switch. The Leaf Switch provides the Distributed Anycast Gateway for routing, which acts completely stateless and does not require the exchange of protocol signalization for election or failover decision. All the reachability information available within the BGP control-plane is sufficient to provide the gateway service. The Distributed Anycast Gateway also provides integrated routing and bridging (IRB) decision at the Leaf Switch, which can be extended across a significant number of nodes. All the Leaf Switches host active default gateways for their respective configured subnets; the well known semantic of First Hop Routing Protocols (FHRP) with active/standby does not apply anymore.

Summary – The advantages provided by a VXLAN-EVPN solution are briefly summarized as follows:

  • Standards based Overlay (VXLAN) with Standards based Control-Plane (BGP)
  • Layer-2 MAC and Layer-3 IP information distribution by Control-Plane (BGP)
  • Forwarding decision based on Control-Plane (minimizes flooding)
  • Integrated Routing/Bridging (IRB) for Optimized Forwarding in the Overlay
  • Leverages Layer-3 ECMP – all links forwarding – in the Underlay
  • Significantly larger Name-Space in the Overlay (16M segments)
  • Integration of Physical and Virtual Networks with Hybrid Overlays
  • It facilitates Software-Defined-Networking (SDN)

Simply formulated, VXLAN-EVPN provides a standards-based Overlay that supports Segmentation, Host Mobility, and High Scale.

VXLAN-EVPN is available on Nexus 9300 (NX-OS 7.0) with  Nexus 7000/7700 (F3 linecards) to follow in the upcoming major release. Additional Data Center Switching platforms, like the Nexus 5600, will follow shortly after.

A detailed whitepaper on this topic is available on Cisco.com. In addition, VXLAN-EVPN was featured during the following Cisco Live! Sessions.

Do you have appetite for more? Post a comment, tweet about it and have the conversation going … Thanks for reading and Happy Networking!

Tags: , , , , , , , , , , , ,

Your Design Engineers Need Support and ‘Expertise on Tap’ Too!

If you are involved in designing, supporting or managing a data center, you will undoubtedly rely on technical support services from one or more vendors.  Running your data center, there is always the risk of a hardware failure or being impacted by a software defect.  While relatively rare, hardware does occasionally fail unfortunately.  However you undoubtedly have technical support in place to deal with such problems.  You may have invested in a few extra switches as backup, you may also have failover mechanisms in place.  Almost certainly you will have a support contract in place with your Cisco partner or with Cisco, so you have break/fix expertise on tap for when something goes wrong.   This is critical support for your business, no debate from me.

Engineer Under Stress!

Engineer Under Stress!

Now, arguably the most important resource you have in your data center is not so much individual switches, routers or servers.  It’s your engineers, those who design and support your data center.  If they have a problem, where and how do they get help?  Who helps them when they are stretched?  When business pressures are telling?  Of course, their colleagues and managers can and will help.  Where, however, can they tap into additional sources of expertise so that they can become even more productive for you?  This is where Cisco Optimization Services come in – including our award-winning Cisco Network Optimization Service (or “NOS” for short), Collaboration Optimization Service, and the one I’m involved with, Cisco Data Center Optimization Services.

 

Read More »

Tags: , , , , , , , ,

Evolving Your Organization with Software Defined Networking

Software Defined Networking (SDN) is an exciting evolution in IT.  Today, connections throughout a network are made by directly connecting to routers to control them.  This is a process that can be time-consuming and prone to error, depending upon the size of the network being managed.  Furthermore, the effort involved in making changes across large networks can slow the pace of innovation within an organization.

SDN moves control to the application layer.  This provides numerous benefits to IT:

  • Unified point of automation and management
  • Consistent deployment of policies throughout the network
  • Improved operational efficiency
  • Rapid deployment of new features like security and QoS
  • Simplified network management overall

Many people think SDN is the future of data center networking.  Cloud provider OneNeck, for example, is investing in developing the expertise to lead the market in transitioning its customers to SDN.  In their blog, Leading the Market with Software Defined Networking (SDN), OneNeck describes how they are working with Cisco to bring SDN to market.

OneNeck’s SDN lab, for example, is a great example of how our partners add value to Cisco technology.  SDN introduces a whole new management framework for networking.  By working with real-world SDN applications in their lab, OneNeck is developing the skill sets and expertise required to enables its customers to evolve with confidence.

Learn more about Cisco’s SDN solutions, including the Cisco Nexus 9000 series switches, Application Centric Infrastructure (ACI) and Cisco Intercloud Fabric.

Tags: , ,

OpenStack Podcast #16: Interview with Pere Monclus

At Cisco we’re passionate about networking, and we have a ton of respect for those who are pushing the boundaries in this realm—even when they don’t work for our company.

Case in point: Co-founder and CTO of PLUMgrid, Pere Monclus. He’s actually a former Cisco employee, and his depth of knowledge when it comes to networking–particularly networking as it applies to OpenStack–is formidable. What’s more, he’s got a talent for taking difficult-to-understand concepts and making them easily digestible. In our interview last week he provided a great explanation of how SDN came about and what problems it is trying to solve. He also explained why network virtualization is so complicated compared to server virtualization, why—contrary to popular opinion–OpenStack Neutron is not broken, and why the cloud has forced the rise of global IT infrastructure companies.

Want to take your networking knowledge to the next level? Settle back and listen in. You’re in for a treat.

To see who we’re interviewing next, or to sign-up for the OpenStack Podcast, check out the show schedule! Interested in participating? Tweet us at @nextcast and @nikiacosta.

For a full transcript of the  interview, click read more below.

Read More »

Tags: , , , ,

Getting Value from Professional Organizations

As a Cisco team member, I’m convinced that the value of professional organizations cannot be understated. It’s understood that employees across various industries have a lot on their plate these days. Data centers, SDN’s or large solutions that help a manufacturing plant to become more “connected” are more than enough projects to keep us busy. However, employees often forget the value of professional organizations that are relevant within each industry. Whether an employee belongs to a professional organization or not, employees must realize the value that these organizations have: professional credibility, influence messaging on a ground level and increasing visibility for Cisco are some of the most important aspects that being involved with professional organizations can bring about.

Professional Credibility

Professional organizations are a place where I can network, learn and help deliver Cisco messaging as well as educate, engage and contact customers through community involvement.  When I first joined Cisco 15 years ago, I regularly attended and presented at monthly users group meetings, but over the years, Cisco’s participation at these meetings has waned and appears to be trending down. Often, I think we take for granted the value of professional organizations, but they provide a standard for professional credibility and give Cisco a broader visibility. As a member of an industry professional organization, specifically the Institute of Electrical and Electronic Engineers (IEEE), I get tremendous value through education and networking.  I know my colleague Rick Geiger, who is on the Gridwise Alliance Board of Directors, would agree. At the local and state level, large impacts are possible as professional association members are able to drive professional credibility, influence agendas and position topics to society members who work or interact with our customer base.

For example, several months ago I received a monthly newsletter promoting a seminar on Software Defined Networking (SDN). One line stated “Software Defined Networking has got Cisco shaking in their boots because it just might completely transform what types of equipment are needed to build a network.  Do I have your attention now?”  Needless to say, I registered and attended – member discount to boot.

Education of members was the primary purpose of the seminar, meaning attendees expected the delivery of neutral, fair and technically accurate presentation on the future of software defined networks.  As I saw it, the presentation on SDN was focused on a Google approach to SDN architecture for data centers, and included a good amount of Cisco bashing. Nonetheless, the seminar provided an opportunity to influence the messaging at ground level and the topics discussed seemed to be informative and beneficial for all those in attendance.

Influence Messaging and Topics at Ground Level

Understanding the messaging and positioning of the local technical mavens presents a golden opportunity to counter and influence at street level. The bottom line, secure all forums to get Cisco’s messaging to our end users.  The IEEE meeting provided a good opportunity to secure a date and timeslot to present Cisco’s SDN and Application-Centric Infrastructure strategies as well as an opportunity to counter any negative perception the audience picked.  As Mike Robinson, Practice Architect states:

“As a member of UTC’s Smart Network Council, I get to collaborate with leading utilities in the United States who are dealing with the industry’s pressing issues. This is hugely valuable. It offers a direct path to decision makers, a seat at the table as they develop their strategies, and it builds trust as a colleague (as opposed to coming across just as a vendor). Also, through UTC I get the opportunity to speak at conventions, periodic forums, and regional meetings.”

Broader Visibility for Cisco

Cisco will also have an opportunity to drive thought leadership to influencers – Mavens and Sales specialists who will attend the upcoming session I secured. Account managers, engineers and other members of the sales team should make it a priority to get engaged with professional organizations, user groups and other community influencers.

Read More »

Tags: , , ,