Changes between Initial Version and Version 1 of Internal/OpenFlow/ofTopology


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Timestamp:
Nov 6, 2011, 9:11:39 PM (13 years ago)
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akoshibe
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  • Internal/OpenFlow/ofTopology

    v1 v1  
     1= Building Network Topologies (with !OpenFlow) =
     2This is a rough overview of the steps one needs to take in order to simulate point-to-point links between nodes sharing a single switch (e.g. within the same broadcast domain), using !OpenFlow-controlled nodes as a means to move traffic from one VLAN to another. The steps described here are incomplete; Things will be updated as methods are refined/improved.
     3
     4== Prerequisites ==
     5VLANs are good for breaking up broadcast domains. If each node is placed on separate VLANs and given a choice of a few "gateways" out of its VLAN, it has no choice but to communicate through the gateway(s). How the gateway nodes moves packets/frames from one VLAN to another depends on which network layer(s) are involved.
     6
     7This page assumes that you have a setup similar to [http://www.orbit-lab.org/wiki/Documentation/OpenFlow SB9], as well as a node with a working install of NetFPGA drivers or !OpenvSwitch, depending on how links are being set up. For the !OpenFlow methods, you also need a !OpenFlow controller that allows you to push flows to your software defined switch. You should have access to the switch that the nodes are sharing as well, since you need to slice it into VLANs. The following links describe setup and use of theses components (internal links):
     8 
     9 * [http://www.orbit-lab.org/wiki/Documentation/OpenFlow/vSwitchImage OpenVswitch] - A software-defined virtual switch with !OpenFlow support, no special hardware required.
     10 * [http://www.orbit-lab.org/wiki/Internal/OpenFlow/HostSetup NetFPGA] - FPGA-based network device with !OpenFlow support
     11 * [http://www.orbit-lab.org/wiki/Internal/OpenFlow/QuantaSetup Quanta LB9A] - The shared medium switch. In this page this switch will be used in !XorPlus (normal) mode. 
     12 * As for the !OpenFlow controller, there is a [http://www.orbit-lab.org/wiki/Internal/OpenFlow/Controllers collection] to choose from.
     13
     14The system used here is Ubuntu10.10 (kernel: 2.6.35-30-generic). Command syntax will change depending on your distro.
     15
     16== Contents ==
     17We first describe some base "sanity-test" setups that do not involve any !OpenFlow elements. These are:
     18 I [#basic Basic Methods]
     19  1.1 [#KernIP Kernel IP routing] (Layer 3) [[BR]]
     20  1.2 [#brctl Linux Bridge] (Layer 2)
     21Then we describe the (ongoing) process of topology setup using !OpenFlow-related elements, such as:
     22 II [#of OpenFlow Methods]
     23  2.1 [#OVS OpenvSwitch] [[BR]]
     24  2.2 [#nfpga NetFPGA OpenFlow switch]
     25!OpenFlow is rather layer-agnostic, defining traffic rules based on a combination of any of the 12 packet header fields that may be used for matching under the !OpenFlow standard. These fields correspond to layers 1~4.   
     26
     27All save the very last method requires that the network node is VLAN aware. Before moving on to Section I we will quickly describe how to add VLAN awareness to the system. 
     28
     29 1. Install and load VLAN module:
     30{{{     
     31 apt-get install vlan
     32 modprobe 8021q
     33}}}
     34 2. Add VLAN interfaces using `vconfig`:
     35{{{
     36 vconfig add eth0 111
     37 vconfig add eth0 222
     38}}}
     39 This creates two virtual LAN interfaces, eth0.111 and eth0.222. The module can be made to load at boot time by appending '8021q' to the list, /etc/modules.
     40
     41== I Basic Methods == #basic
     42These two methods should work on any *nix machine, so they can serve as "sanity checks" for the system you are using as the network node.
     43== 1.1 Kernel IP routing == #KernIP
     44Kernel IP routing is the simplest, in that no extra packages are required if you have multiple Ethernet ports on your node. 
     45=== 1.1.1 Network node setup ===
     46 1. This setup assumes a 1-to-1 mapping of VLANs to subnets. Choose IP blocks, one fore each VLAN. For example, if you have two clients connected across your node, you need two IP blocks, one for each VLAN:
     47  * VLAN 111: 192.168.1.0/24, gateway 192.168.1.13
     48  * VLAN 222: 192.168.2.0/24, gateway 192.168.2.23
     49 The gateway IPs chosen above will be the IP addresses assigned to the VLAN interfaces you have set up earlier on your network node.
     50 
     51 2. Bring up VLAN interfaces with the IP addresses/blocks you have chosen:     
     52{{{
     53 ifconfig eth0 0.0.0.0 up
     54 ifconfig eth0.111 inet 192.168.1.23 broadcast 192.168.1.255 netmask 0xffffff00 up
     55 ifconfig eth0.222 inet 192.168.2.23 broadcast 192.168.2.255 netmask 0xffffff00 up
     56}}}
     57 This configuration can be made permanent by modifying /etc/network/interfaces:
     58{{{
     59auto eth0.111
     60iface eth0.111 inet static
     61    address 192.168.1.13
     62    netmask 255.255.255.0
     63    vlan-raw-device eth0
     64
     65auto eth0.222
     66iface eth0.222 inet static
     67    address 192.168.2.23
     68    netmask 255.255.255.0
     69    vlan-raw-device eth0
     70}}}
     71
     72 3. Enable routing on network node
     73{{{
     74 route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.13
     75 route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.2.23
     76 echo 1 >  /proc/sys/net/ipv4/ip_forward
     77}}}
     78 The last line in the above block is equivalent to running the command:
     79{{{
     80sysctl -w net.ipv4.ip_forward=1
     81}}}
     82 The `ip_forward` flag resets itself after reboot. To make it permanent, add
     83{{{
     84sysctl net.ipv4.ip_forward=1
     85}}}
     86 to /etc/sysctl.conf.
     87=== 1.1.2 End node setup ===
     88Unless you have set up DHCP, you must manually assign an IP address and default gateway to each node. The former should be consistent with the subnet associated with the VLAN to which the end host belongs. For example, the following host is connected to a switch port associated with VLAN 222, so it is assigned an address from the 192.168.2.0/24 block:
     89{{{
     90 ifconfig eth0 inet 192.168.2.4
     91}}}
     92Then you must add reachability information to the node's routing table e.g. the IP addresses that it must send data to in order to have it reach remote subnets. Since there is only one other subnet in this example, a single entry specifying the destination subnet (192.168.1.0/24 - VLAN 111) and the gateway IP in/out of the current node's subnet is added:
     93{{{
     94 route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.2.23
     95}}}   
     96Do this for each remote subnet that the node should be able to communicate with. Once all of the nodes are configured, you should be able to ping end-to-end. 
     97
     98== 1.2 Linux Bridge == #brctl
     99A bridge will ignore VLAN tags, so if you have two VLAN interfaces e.g. eth0.111 and 222 sitting on a trunk, the packets will come in tagged. An intermediate abstraction will strip the tag from the packet (at br0), and the packet will get tagged as appropriate on the outbound. Unlike kernel IP forwrding, bridging works purely at Layer 2, hence you do not need to worry about IP addressing.
     100
     101The first three steps refer to the network node.
     102
     1031. Configure and bring VLANS up as before, sans IP addresses
     104
     1052. Install bridge-utils:
     106{{{
     107 apt-get install bridge-utils
     108}}}
     1093. Create bridge interface, add ports:
     110{{{
     111 brctl addbr br0
     112 brctl addif br0 eth0.111
     113 brctl addif br0 eth0.222
     114}}}
     1154. Set all hosts on the bridged VLANs to the same IP block. 
     116
     117== II !OpenFlow Methods == #of
     118== 2.1 !OpenvSwitch == #OVS
     119== 2.2 NetFPGA !OpenFlow switch == #nfpga
     120The following are the flow configurations applied to the first (trunked) setup.
     121{{{
     122switch 00:00:00:00:00:10:10:10
     123
     124#strip tag from any incoming traffic on port 1
     125  flow-entry port1
     126    active True
     127    ingress-port 1
     128    vlan-id 111
     129    actions strip-vlan,output=4
     130
     131#re-apply VLAN 222 tag to ARP packets bound for port 4, from 1
     132  flow-entry port1-2
     133    active False
     134    ingress-port 1
     135    ether-type 2054
     136    actions set-vlan-id=222,output=4
     137
     138#re-apply tag to IP packets bound for 192.168.1.4
     139  flow-entry port1-3
     140    active False
     141    ether-type 2048
     142    src-ip 192.168.1.1
     143    actions set-vlan-id=222,output=4
     144
     145#re-apply VLAN 111 tag to ARP packets bound for port 1, from 4
     146  flow-entry port2-2
     147    active False
     148    ingress-port 4
     149    ether-type 2054
     150    actions set-vlan-id=111,output=1
     151
     152#re-apply tag to IP packets bound for 192.168.1.1
     153  flow-entry port2-3
     154    active False
     155    ether-type 2048
     156    src-ip 192.168.1.4
     157    actions set-vlan-id=111,output=1
     158
     159#strip tag from any incoming traffic on port 4
     160  flow-entry port4
     161    active True
     162    ingress-port 4
     163    vlan-id 222
     164    actions strip-vlan,output=1
     165!
     166}}}