The “P” in EPN stands for “Programmable,” as in “Evolved Programmable Network” and Cisco has just made the “P” easier to achieve to help drive services to the cloud. We’ve now contributed Basic ConfD, a free version of our powerful ConfD by Tail-f management agent software to the networking industry. Tail-f joined Cisco last summer and this announcement demonstrates Cisco’s commitment to not only embrace but also drive open standards in the best interest of the entire ecosystem. Read More »
Written by Igor Dayen, SP Product and Solutions Marketing
If you had a chance to join us at Cisco Live Milan last month, thank you very much for making this another exciting event for all of us. If you missed out being there in person, let me give you a brief summary of the highlights. Milan is the main industrial, commercial, and financial center of Italy and a leading global city where the EXPO 2015 will take place. What could be better than such a city to host the Cisco Live 2015 event! It proved to be fertile grounds for driving innovations with our service provider customers and partners. Our exhibition was structured to tell the story of the Open Network Strategy by presenting over 15 technology and business demos. We also brought the newest routers and switches with us to showcase the latest innovations that service providers can start deploying today. Last but not least we have teamed up with the DevNet area where attendees could get their hands on developing applications and learning on virtualization, orchestration, and automation. Our service provider booth of the Cisco Campus in the World of Solutions was very busy: “standing room only” and so many insightful conversations were conversations around the NFV (Network Functions Virtualization) and the SDN (Software Defined Networks), as pillars for delivering cloud services and an automated networking handling respectively, have matured significantly and are ready for prime time. Read More »
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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
- draft-sd-l2vpn-evpn-overlay – A Network Virtualization Overlay Solution using EVPN
- draft-sajassi-l2vpn-evpn-inter-subnet-forwarding-03 – IP Inter-Subnet Forwarding in EVPN
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.
- BRKDCT-2404 -VXLAN deployment models – A practical perspective (by Victor Moreno)
- BRKDCT-3378 – Building Simplified, Automated and Scalable Data Center Networks with Overlays (VXLAN/FabricPath) (by Lukas Krattiger)
Do you have appetite for more? Post a comment, tweet about it and have the conversation going … Thanks for reading and Happy Networking!
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.
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.
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.