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SDN | Rick Mur

Rick Mur

Limitless Networking

Category: SDN

What is P4?

Recently I attended a workshop organised by the Open NFP organisation about Data Plane acceleration. The primary goal of the workshop was to get students and researchers (why was I there you may think) familiar with the P4 programming language.

P4 is a programming language created to simplify writing data planes for networking use cases.  Recently the P4-16 spec was released and could be considered a mature version of the language.

Now I’m not a hardcore developer. I know my way around in Python, GoLang and C#, but I never wrote anything more low level like C. P4 is created a little bit like GoLang, where I do not mean it as comparison, but as an architecture. P4 is designed so you only need to focus on the actual networking features that you want to make available on the hardware you are programming it for. Then when you compile it, it will generate runtime code for your hardware. Or as the creators explain it:

At one level, P4 is just a simple language for declaring how packets are to be processed. At another level, P4 turns network system design on its head.

There is no need to worry on low level memory management or other things that would slow down your development for that specific feature that nobody has in their platforms.

Now this is a major advantage. Full freedom in writing anything you’d like right? The downside is that very little (basic) functionality is not present when you start pushing code to a piece of hardware. You really have to do everything yourself. Which I think is  underestimated. P4 does help you in giving you some standard functionality in their spec that vendors should implement when they offer P4 capabilities, like basic switching or load balancing (ECMP) functionality.

Who supports it?

P4 is relatively new and therefore hardware support is not very common. I was able to find 2 products to support the full P4 spec at this moment.

Barefoot Tofino chip

Barefoot is the inventor of the P4 language and they have created a very fast ASIC like chipset. The chipset does not use a proprietary SDK like Broadcom, Cavium or silicon from large network vendors, but is fully open due to the support of P4.

They are partnering with white box vendors to create switches (32 port 100GBE) that are currently shipping.

Netronome Agilio SmartNIC

Netronome was one of the organizers of the workshop I attended and they have a shipping product. Their SmartNIC products are standard PCIe NIC’s with various connections that support offloading data plane functionality to the NIC rather than letting applications or the kernel spend a lot of CPU on it.

These products are not your typical switch or NIC, they basically do not have a default feature set available to use. The Barefoot switch for example, does not come with an operating system (NOS) and the NIC always needs to be programmed before any functionality works.

What about OpenFlow?

The most typically asked question would be: Is P4 the successor of OpenFlow? The answer to that is really simple: No! In some cases P4 may even use OpenFlow to program it’s forwarding table(s). Diagram courtesy of P4.org:

The P4 language is designed to program your networking hardware (or even software components). P4 does not contain a control-plane protocol to learn about forwarding table entries (that could be learned through a traditional or home grown routing protocol).  In other words: you have to write your own forwarding table programming protocol/application or use an existing one (like OpenFlow).

What about existing vendors?

There are rumours that major networking vendors (Cisco, Juniper, Nokia, etc.) could start supporting (parts of) P4 on their own silicon or implement the Barefoot Tofino chip in products, but no announcements have been made at time of this writing. Vendors are starting to open up their operating systems via programmability features (see Juniper’s Extension Toolkit JET for example), but this does not allow to directly program new features into the hardware (which is programmable in some cases like Juniper MX).

Summary

P4 will open up a lot of features that are currently unknown or don’t exist. It allows for a fully open and programmable data-plane. The use case for this technology would, as always, be the web-scale companies, who want to free up as much CPU resources to perform other tasks and leave the networking hardware to perform all networking functions.

For lower scale deployments, my opinion would be that, tools like DPDK, XDP or eBPF would already free up sufficient CPU resources and optimise user space or kernel networking enough for most people.

For more information on all the mentioned acronyms and tools, click the links in this blog.

One noticeable fun fact was that during the workshop I attended, I was able to spot one person on a Mac, two corporate Windows machines and all others running Linux 🙂

VMware NSX 101 – Components

Today I want to explain the basic components and the set-up of VMware NSX. In this case I’m referring to NSX for vSphere or NSX-V for short. I want to explain what components are involved, how you set them up for an initial deployment and what the requirements are.

Versioning

At time of this writing the latest release is NSX 6.1.4. This version added support for vSphere 6, although you cannot use any vSphere 6 feature in this release, there is support for the platform itself only.

vSphere

The first step is of course deploy your ESXi vSphere cluster with ESXi 5.5 or 6.0 with vCenter 5.5 or 6.0. I recommend using the vCenter Server Appliance (VCSA) instead of the Windows version. You will also need a Windows VM where the vSphere Update Manager is installed, this is not available as virtual appliance, only as Windows application. I also highly recommend installing an Active Directory server to manage all of your passwords. You will be installing a large amount of machines with all different usernames and possibly passwords. I recommend picking a very long and difficult one, as all VMware appliances seem to require a different password complexity.

 

After deploying the initial cluster it’s also essential to deploy a Distributed vSwitch across the nodes where you will be deploying virtual networks. For this feature you will need the Enterprise license (or the trial will suffice) when running ESXi 5.5 Update 3 and NSX (before that Enterprise Plus was required).

NSX Manager

The only component you download is the NSX Manager. This OVA file contains everything you will need for deploying NSX. After deploying the OVA through vCenter you are able to log-in to the Web GUI of the NSX Manager. The only setting available is connecting to the vSphere Single Sign-On server and to vCenter. When deploying all components make sure you set NTP servers for everything in the lab. There are many integrations and they all rely on authentication that also takes time into consideration.

 

After connecting the NSX Manager you will no longer need it that GUI. Within the vSphere Web Client a “Networking & Security” tab is now available.

NSX Controller

The next step is to deploy at least 3 NSX Controllers in the cluster. This is automatically done by the Manager after filling in required information. You need 3 for redundancy as the cluster will select a master controller, which is done by using a majority number (quorum). With only 2 nodes, there is no majority and therefore at least 3 are required for redundancy (think of RAID with Parity disks). The controller is the critical piece of the software. Here all ARP requests are handled and all information is shared with the ESXi hosts. The Controller will also take care of multicast replication when the unicast mode is chosen for transport.

Prepare hosts

The following step is to install 3 kernel modules in all hosts. This is done using the VMware Update Manager (the Windows application) and just a single click in the GUI. It will install the NSX module to communicate with the controllers, the Distributed Logical Router (DLR) and the Distributed Firewall. No configuration is necessary as all changes are pushed by the controllers.

NSX Edge

To get traffic to and from the virtual environment you will require an NSX Edge today, as soon as OVSDB is available this could be your MX router as well! The NSX Edge has 2 forms, the first is the Distributed Logical Router that offers basic routing, bridging and firewall features. The second version is a VM that traffic is hair pinned through, like a software router. The second version also offers VPN and Load Balancing features.

Pools

To support the VXLAN transport, the hosts need to get an IP address to use as source address. This can be assigned using DHCP or an IP Pool, more on this in a next blog! Next a Segment ID pool needs to be created to allocate VNI’s for the virtual networks (called logical switches). Today it’s not supported to have more than 4000 segments on NSX, which combines the regular port groups and NSX port groups on the distributed vSwitch.

Transport Zone

The final step is to create a transport zone. This defines a “data center” or a “site” where NSX runs. This limits the broadcast domain. Per transport zone you are able to select wether the NSX Controller should handle multicast replication (Unicast mode) or that the network should handle this (Multicast or Hybrid mode). The recommended choice is Unicast mode so you won’t require multicast routing protocols or IGMP from the network. VMware eliminates the need for smart network hardware even further with this, but the solutions runs best with optimized hardware of course running as IP CLOS Fabric offering “Layer 2 as a service” using network virtualization.

Logical Switches

Now the deployment is ready to have the first VXLAN segments created, which are called Logical Switches. These networks are created as distributed port groups, so you can use the standard tools to connect VM’s to these virtual networks and suddenly you are using VXLAN transport!

 

I hope this article gave you some insight in how NSX is configured and what components it consists of.

 

Happy Labbing!

 

Rick Mur

Using the Junos Space REST API


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