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diff --git a/README.bonding b/README.bonding new file mode 100644 index 0000000..e81b7c9 --- /dev/null +++ b/README.bonding @@ -0,0 +1,179 @@ +Bonding (link aggrigation) +========================== + +Features +-------- +* Full support of features offered by the bonding kernel module. +* Selectable bonding mode using a single parameter in rc.inet1.conf. +* Easy addition of interfaces to the bond using a parameter in rc.inet1.conf. +* Custom bonding module options can be proided using the generic parameter + IFOPTS[x] in the configuration file. + + +Implementation +-------------- +[This section can be removed from the final README.bonding as it relates to + implimentation by Pat rather than user level configuration] + +Pat should add a /lib/modprobe.d/bonding.conf (preferred) or +/etc/modprobe.d/bonding.conf file to a package (probably network-scripts), with +content: + options bonding max_bonds=0 + options rtnl-link-bond max_bonds=0 +in order to disable the automatic creation of a bond0 interface when the kernel +module is loaded. + +Rationale: Even though the bond0 interface may be scheduled for creation +because it's configured in rc.inet1.conf, having the interface in an up state +before configuration will prevent it from being configured due to rc.inet1's +checking of interface state before going through the process of setting up the +interface. + +This check is necessary in rc.inet1 because rc.inet1 has no way of knowing +whether the interface has been brought up by itself or by some other means - +there is no state information stored by rc.inet1, which prevents it from +knowing. It is also not possible to rely on the interface being configured +with an IP address to determine if it has been configured or not - a bond +interface may be used as part of a bridge, and would thus not have an IP +configured to validate against. + +Effects: Previous versions of Slackware followed the default behaviour when +loading the bonding module, and would automatically create a bond0 interface +for the user to configure. This behaviour would now change to prevent a bond0 +interface being created at load time in order for rc.inet1 to be able to +configure a user defined bond0 interface in rc.inet1.conf at a later time. + +Since Slackware has never had support for bond interfaces in previous versions, +the automatic creation of a bond interface has never been a defined behaviour - +users should not have relied on that behaviour. + +Effects if not used: In its present form, rc.inet1 checks whether an interface +is up before it tries to configure it based on the interfaces present in +rc.inet1.conf - rc.inet1 will not try to reconfigure an interface which is up +and running, instead issuing an debug message that the interface is already up +when being run with any of the 'start' options. + +Without the inclusing of the bonding.conf options file, rc.inet1 would be +unable to work with a bond0 interface in it's present form. It is also highly +unlikely that rc.inet1 could be coded to *not* check whether an interface is up +before trying to configure it - this check is fundamental to the way it works. + + +Configuration +------------- +Bonding interfaces can be configured via two new bond specific parameters in +rc.inet1.conf, plus use of the generic IFOPTS[x] parameter. New parameters +are: + BONDNICS[x]="" The space delimited list of interfaces to add to this + bond. The interfaces will be brought up and configured + while bringing up the interface, so do not need to be + previously defined in rc.inet1.conf. A bond can be + created with only 1 interface, but does not become + useful until at least 2 interfaces are configured. + + BONDMODE[x]="" This parameter sets the bonding mode for this + interface. If not specified when BONDNICS[x] has been + used, the default is 'balance-rr'. See below for a + list of all bonding modes available. + +The following bond modes are available: + balance-rr This mode is also known as round-robin mode. Packets + are sequentially transmitted and received through each + interface one by one. This mode provides load + balancing functionality along with fault tolerance. + active-backup When in this mode only one interface set to active, + while all other interfaces are in the backup state. If + the active interface fails, a backup interface replaces + it as the only active interface in the bond. This mode + only provides fault tolerance, no load balancing. + This mode requires that the 'primary <interface>' + option be configured with the IFOPTS[x] parameter. + balance-xor The source MAC address uses exclusive or (XOR) logic + with the destination MAC address. This calculation + ensures that the same slave interface is selected for + each destination MAC address. This mode provides fault + tolerance and load balancing. + broadcast All packets are sent to all the slaved interfaces. This + mode provides fault tolerance, but may result in + duplicate packets arriving at the destination. + 802.3ad Also known as LACP. This mode creates aggregation + groups that share the same speed and duplex settings, + and it requires a switch that supports an IEEE 802.3ad. + This mode uses all interfaces to form the aggregation + group and provides fault tolerance and load balancing. + balance-tlb This mode ensures that the outgoing traffic + distribution is set according to the load on each + interface and that the current interface receives all + the incoming traffic. If the assigned interface fails + to receive traffic, another interface is assigned to + the receiving role. This provides fault tolerance and + load balancing. + balance-alb The receiving packets are load balanced through Address + Resolution Protocol (ARP) negotiation. This mode + provides fault tolerance and load balancing. + +Module specific interface options can be set using the the IFOPTS[x] paramter, +which takes a pipe (|) delimited list of options for the interface. The +following are the most useful options which can be set with IFOPTS[x]: + miimon Specifies the MII link monitoring frequency in milliseconds. + This determines how often the link state of each slaved + interface is checked for link failures. A value of zero + disables MII link monitoring, but this is NOT advised. A value + of 100 is a good starting point. The default value is 0, so be + sure to set this option with ALL modes. + lacp_rate This option specifies the rate at which the host will ask the + link partner to transmit LACPDU packets in 802.3ad mode. + Possible values are: + slow Transmit LACPDUs every 30 seconds. + fast Transmit LACPDUs every 1 second. + The default is slow, but fast is recommended. + primary The interface (eth0, eth2, ...) selecting which slave is the + primary device. The specified interface will always be the + active slave while it is available. Only when the primary is + off-line will alternate interfaces be used. This is useful + when one interface is preferred over another (eg, when one + interface has higher throughput than another). This option + is only valid for active-backup, balance-tlb and balance-alb + modes. + xmit_hash_policy + Selects the transmit hash policy to use for interface selection + in balance-xor, 802.3ad, and balance-tlb modes. Possible + values are: + layer2 Use XOR of source/dest hardware MAC addresses + and packet type ID fields to generate the hash. + This algorithm will place all traffic to a + particular network peer on the same slave. + layer2+3 Use a combination of layer2 and layer3 protocol + information (hardware MAC addresses and IP + addresses) to generate the hash. + This algorithm will place all traffic to a + particular network peer on the same slave. + This policy is intended to provide a more + balanced distribution of traffic than layer2 + alone, especially in environments where a + layer3 gateway device is required to reach most + destinations. + layer3+4 This policy uses upper layer protocol + information, when available, to generate the + hash. This allows for traffic to a particular + network peer to span multiple slave interfaces, + although a single connection will not span + multiple slaves. + The default value is layer2. Additional (lesser used) policies + are available, and documented in kernel source documentation: + /usr/src/linux/Documentation/networking/bonding.txt + +The IFOPTS[x] option should always include the 'miimon' option - not using this +option will result in network degradation. +In 'active-backup' mode, the 'primary' option should also be supplied. +When using '802.3ad mode', set "lacp_rate fast" for faster recovery from an +interface failure. +In other modes, the 'xmit_hash_policy' should be set. + +Full documentation of the bonding layer is available in the kernel source +documentation: /usr/src/linux/Documentation/networking/bonding.txt. + + +-- +Darren 'Tadgy' Austin. +<darren (at) afterdark.org.uk> |