User`s manual

RNAS-1200 Series Modify Network Settings
6-3
There are seven modes for IP bonding / port trunking. Below you will find summaries of their weak points and
strong points. In most cases, mode five—IEEE 802.3ad, or LACP—will probably be the preferred mode.
1. Balance-rr (Round-Robin)
Round robin mode transmits network packets in sequential order from the first available network interface
(NIC slave) through the last. This mode provides rudimentary load balancing and high fault tolerance. If a
switch is being used, an appropriate switch configuration will be required. Be warned: some switches do
not support balance-rr. If the bandwidth of one of the NICs deteriorates, then the total bandwidth of the
interface drop an equal amount.
2. Active Backup (Failover)
In failover mode, only one NIC in the bond is used to actively transmit packets. The alternate NIC becomes
active if, and only if, the default fails. The single, logical interface's MAC address is externally visible on
only one NIC (port) at a time, to avoid distortion in network switches. This mode provides strong
redundancy and high fault tolerance.
3. Balance-xor
Balance-xor balances outgoing traffic across the active ports using hashed protocol headers. This lets it
accept incoming traffic from either port. The hash used to transmit network packets is [(source MAC
address XOR'd with destination MAC address) modulo NIC slave count]. This mode provides high
load balancing and high fault tolerance.
4. Broadcast
This mode does not provide load balancing: both network interfaces are used to transmit identical packets.
This provides high fault tolerance.
5. IEEE 802.3ad (Dynamic Link Aggregation, or LACP)
This is the most reliable and effective interface bonding mode; it uses hashed protocol headers that enable
it balance outgoing traffic across all active ports while allowing it to accept incoming traffic from any active
port. LACP automatically creates aggregation groups that share the same speed and duplex settings.
According to the standard, frames must be delivered in order and connections may not receive packets out
of order. Minimal switch configuration is required.
6. Balance-tlb (Adaptive Transmit Load Balancing)
This mode balances the outgoing traffic according to peer. Outgoing network traffic is distributed according
to the current load (computed relative to the speed) on each network interface. Incoming traffic is not
balanced: all incoming traffic is received by one designated network interface. If this receiving interface
fails, the other will take over the MAC address of the failed receiver.
7. Balance-alb (Adaptive Load Balancing)
This mode is essentially the same as balance-tlb but it also balances incoming traffic, as well. Balance-alb
is balance-tlb plus receive load balancing (rlb). The bonding driver intercepts ARP replies sent by the local
system (on their way out) and overwrites the source hardware address with the unique hardware address
of an NIC in the logical interface so that different network-peers will use different MAC addresses for their
network traffic. It does not require any special network switch support.