X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=FAQ;h=91f400700db1988d8cc5741c443c905504ed4cb6;hb=refs%2Fheads%2Fof1.1;hp=61bbb69cfc97d26db0448feb9d16a864cb470944;hpb=629a6b48e923b1015cfdfe81f9accf99371310fa;p=openvswitch diff --git a/FAQ b/FAQ index 61bbb69c..91f40070 100644 --- a/FAQ +++ b/FAQ @@ -3,6 +3,171 @@ Frequently Asked Questions ========================== +General +------- + +Q: What is Open vSwitch? + +A: Open vSwitch is a production quality open source software switch + designed to be used as a vswitch in virtualized server environments. A + vswitch forwards traffic between different VMs on the same physical host + and also forwards traffic between VMs and the physical network. Open + vSwitch supports standard management interfaces (e.g. sFlow, NetFlow, + RSPAN, CLI), and is open to programmatic extension and control using + OpenFlow and the OVSDB management protocol. + + Open vSwitch as designed to be compatible with modern switching + chipsets. This means that it can be ported to existing high-fanout + switches allowing the same flexible control of the physical + infrastructure as the virtual infrastructure. It also means that + Open vSwitch will be able to take advantage of on-NIC switching + chipsets as their functionality matures. + +Q: What virtualization platforms can use Open vSwitch? + +A: Open vSwitch can currently run on any Linux-based virtualization + platform (kernel 2.6.18 and newer), including: KVM, VirtualBox, Xen, + Xen Cloud Platform, XenServer. As of Linux 3.3 it is part of the + mainline kernel. The bulk of the code is written in platform- + independent C and is easily ported to other environments. We welcome + inquires about integrating Open vSwitch with other virtualization + platforms. + +Q: How can I try Open vSwitch? + +A: The Open vSwitch source code can be built on a Linux system. You can + build and experiment with Open vSwitch on any Linux machine. + Packages for various Linux distributions are available on many + platforms, including: Debian, Ubuntu, Fedora. + + You may also download and run a virtualization platform that already + has Open vSwitch integrated. For example, download a recent ISO for + XenServer or Xen Cloud Platform. Be aware that the version + integrated with a particular platform may not be the most recent Open + vSwitch release. + +Q: Does Open vSwitch only work on Linux? + +A: No, Open vSwitch has been ported to a number of different operating + systems and hardware platforms. Most of the development work occurs + on Linux, but the code should be portable to any POSIX system. We've + seen Open vSwitch ported to a number of different platforms, + including FreeBSD, Windows, and even non-POSIX embedded systems. + + By definition, the Open vSwitch Linux kernel module only works on + Linux and will provide the highest performance. However, a userspace + datapath is available that should be very portable. + +Q: What's involved with porting Open vSwitch to a new platform or + switching ASIC? + +A: The PORTING document describes how one would go about porting Open + vSwitch to a new operating system or hardware platform. + +Q: Why would I use Open vSwitch instead of the Linux bridge? + +A: Open vSwitch is specially designed to make it easier to manage VM + network configuration and monitor state spread across many physical + hosts in dynamic virtualized environments. Please see WHY-OVS for a + more detailed description of how Open vSwitch relates to the Linux + Bridge. + +Q: How is Open vSwitch related to distributed virtual switches like the + VMware vNetwork distributed switch or the Cisco Nexus 1000V? + +A: Distributed vswitch applications (e.g., VMware vNetwork distributed + switch, Cisco Nexus 1000V) provide a centralized way to configure and + monitor the network state of VMs that are spread across many physical + hosts. Open vSwitch is not a distributed vswitch itself, rather it + runs on each physical host and supports remote management in a way + that makes it easier for developers of virtualization/cloud + management platforms to offer distributed vswitch capabilities. + + To aid in distribution, Open vSwitch provides two open protocols that + are specially designed for remote management in virtualized network + environments: OpenFlow, which exposes flow-based forwarding state, + and the OVSDB management protocol, which exposes switch port state. + In addition to the switch implementation itself, Open vSwitch + includes tools (ovs-controller, ovs-ofctl, ovs-vsctl) that developers + can script and extend to provide distributed vswitch capabilities + that are closely integrated with their virtualization management + platform. + +Q: Why doesn't Open vSwitch support distribution? + +A: Open vSwitch is intended to be a useful component for building + flexible network infrastructure. There are many different approaches + to distribution which balance trade-offs between simplicity, + scalability, hardware compatibility, convergence times, logical + forwarding model, etc. The goal of Open vSwitch is to be able to + support all as a primitive building block rather than choose a + particular point in the distributed design space. + +Q: How can I contribute to the Open vSwitch Community? + +A: You can start by joining the mailing lists and helping to answer + questions. You can also suggest improvements to documentation. If + you have a feature or bug you would like to work on, send a mail to + one of the mailing lists: + + http://openvswitch.org/mlists/ + + + +Releases +-------- + +Q: What does it mean for an Open vSwitch release to be LTS (long-term + support)? + +A: All official releases have been through a comprehensive testing + process and are suitable for production use. Planned releases will + occur several times a year. If a significant bug is identified in an + LTS release, we will provide an updated release that includes the + fix. Releases that are not LTS may not be fixed and may just be + supplanted by the next major release. The current LTS release is + 1.4.x. + +Q: What features are not available in the Open vSwitch kernel datapath + that ships as part of the upstream Linux kernel? + +A: The kernel module in upstream Linux 3.3 and later does not include + the following features: + + - Bridge compatibility, that is, support for the ovs-brcompatd + daemon that (if you enable it) lets "brctl" and other Linux + bridge tools transparently work with Open vSwitch instead. + + We do not expect bridge compatibility to ever be available in + upstream Linux. If you need bridge compatibility, use the + kernel module from the Open vSwitch distribution instead of the + upstream Linux kernel module. + + - Tunnel virtual ports, that is, interfaces with type "gre", + "ipsec_gre", "capwap". It is possible to create tunnels in + Linux and attach them to Open vSwitch as system devices. + However, they cannot be dynamically created through the OVSDB + protocol or set the tunnel ids as a flow action. + + Work is in progress in adding these features to the upstream + Linux version of the Open vSwitch kernel module. For now, if + you need these features, use the kernel module from the Open + vSwitch distribution instead of the upstream Linux kernel + module. + + - Patch virtual ports, that is, interfaces with type "patch". + You can use Linux "veth" devices as a substitute. + + We don't have any plans to add patch ports upstream. + +Q: What features are not available when using the userspace datapath? + +A: Tunnel and patch virtual ports are not supported, as described in the + previous answer. It is also not possible to use queue-related + actions. On Linux kernels before 2.6.39, maximum-sized VLAN packets + may not be transmitted. + + Configuration Problems ---------------------- @@ -129,6 +294,10 @@ A: Wireless base stations generally only allow packets with the source point, so the same problems will show up with the Linux bridge or any other way to do bridging. +Q: Is there any documentation on the database tables and fields? + +A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. + VLANs ----- @@ -150,7 +319,7 @@ A: Many drivers in Linux kernels before version 3.3 had VLAN-related that works around bugs in kernel drivers. To enable VLAN splinters on interface eth0, use the command: - ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true + ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true For VLAN splinters to be effective, Open vSwitch must know which VLANs are in use. See the "VLAN splinters" section in @@ -243,6 +412,15 @@ A: The configuration for VLANs in the Open vSwitch database (e.g. via Controllers ----------- +Q: What versions of OpenFlow does Open vSwitch support? + +A: Open vSwitch supports OpenFlow 1.0. It also includes a number of + extensions that bring many of the features from later versions of + OpenFlow. Work is underway to provide support for later versions and + can be tracked here: + + http://openvswitch.org/development/openflow-1-x-plan/ + Q: I'm getting "error type 45250 code 0". What's that? A: This is a Open vSwitch extension to OpenFlow error codes. Open @@ -315,6 +493,65 @@ Q: My OpenFlow controller doesn't see the VLANs that I expect. A: See answer under "VLANs", above. +Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop" + but I got a funny message like this: + + ofp_util|INFO|normalization changed ofp_match, details: + ofp_util|INFO| pre: nw_dst=192.168.0.1 + ofp_util|INFO|post: + + and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst + match had disappeared, so that the flow ends up matching every + packet. + +A: The term "normalization" in the log message means that a flow + cannot match on an L3 field without saying what L3 protocol is in + use. The "ovs-ofctl" command above didn't specify an L3 protocol, + so the L3 field match was dropped. + + In this case, the L3 protocol could be IP or ARP. A correct + command for each possibility is, respectively: + + ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop + + and + + ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop + + Similarly, a flow cannot match on an L4 field without saying what + L4 protocol is in use. For example, the flow match "tp_src=1234" + is, by itself, meaningless and will be ignored. Instead, to match + TCP source port 1234, write "tcp,tp_src=1234", or to match UDP + source port 1234, write "udp,tp_src=1234". + +Q: How can I figure out the OpenFlow port number for a given port? + +A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to + respond with an OFPT_FEATURES_REPLY that, among other information, + includes a mapping between OpenFlow port names and numbers. From a + command prompt, "ovs-ofctl show br0" makes such a request and + prints the response for switch br0. + + The Interface table in the Open vSwitch database also maps OpenFlow + port names to numbers. To print the OpenFlow port number + associated with interface eth0, run: + + ovs-vsctl get Interface eth0 ofport + + You can print the entire mapping with: + + ovs-vsctl -- --columns=name,ofport list Interface + + but the output mixes together interfaces from all bridges in the + database, so it may be confusing if more than one bridge exists. + + In the Open vSwitch database, ofport value -1 means that the + interface could not be created due to an error. (The Open vSwitch + log should indicate the reason.) ofport value [] (the empty set) + means that the interface hasn't been created yet. The latter is + normally an intermittent condition (unless ovs-vswitchd is not + running). + Contact -------