介紹何謂 Link Aggregation 及如何在 ASUSTOR NAS 設定。

1. Link Aggregation 簡介

1.1 什麼是 Link Aggregation?
Link aggregation (又名 trunking, bonding 或 teaming) 可將兩個或多個網路介面結合為一。欲使用Link Aggregation，你的多個網路介面需接到同一個網路交換器 (switch) 上，此外，該網路交換器也必須支援設定 Link Aggregation。 在本篇文章中，我們將以兩個網路介面為範例進行說明。
Link Aggregation 主要可提供以下兩種優點：
a. 負載平衡 (Load Balancing)
網路流量將會被分配至兩個網路介面，而對於用戶端而言，將只會視為單一連線。此種模式主要在於能夠藉由多重管道以提昇傳輸可靠度。
b. 網路容錯 (Fault tolerance /Failover)
網路容錯優點主要在於當其中一個網路介面失效或斷線時，另一個網路介面仍能夠負擔起傳輸的責任，讓資料傳輸不致於中斷，提昇 NAS 系統的可得性 (availability)。

Link aggregation網路聚合只會提升總流量throughput，不會提升單一裝置PC的速度。

1.2 Link aggregation 模式
ASUSTOR NAS 提供多種不同的 Link Aggregation 模式，以下將會簡單說明 (英文) 各種模式的傳輸特性：
Round-Robin: Transmits packets in sequential order from the first available connection to the next. This mode provides load balancing and fault tolerance.
Active Backup: Only one connection is active. A different connection becomes active if, and only if, the active connection fails. The aggregated MAC address is externally visible on only one port (network adapter) to avoid confusing the switch. This mode provides fault tolerance.
XOR: Transmits based on the default simple transmit hash policy. This mode provides load balancing and fault tolerance.
This mode supports Static Link Aggregation.
Broadcast: Transmits everything on all connections. This mode provides fault tolerance.
802.3ad (IEEE 802.3ad Dynamic Link Aggregation): Creates aggregation groups that share the same speed and duplex settings. Utilizes all connections in the active aggregator according to the 802.3ad specification. You will need a switch that supports IEEE 802.3ad dynamic link aggregation. This mode provides fault tolerance and load balancing.
Adaptive Transmit Load Balancing: Does not require any special switch support. The outgoing traffic is distributed according to the current load (computed relative to the speed) on each connection. Incoming traffic is received by the current connection. If the receiving connection fails, another connection takes over the MAC address of the failed receiving connection. This mode provides fault tolerance.
Adaptive Load Balancing: Includes transmit load balancing plus receive load balancing for IPV4 traffic and does not require any special switch support. The receive load balancing is achieved by ARP negotiation. This mode provides fault tolerance and load balancing.

Generally speaking, link aggregation modes provide either fault tolerance or load balancing benefits. The benefits provided by each mode are summarized in the chart below.

步驟1

步驟2

步驟3

步驟4

步驟5

步驟 6

套用完成之後，你即可在畫面中看到如下方圖示所示，兩個網路介面已經被綁定成為一個網路介面並已可開始使用。