Etherchannel

Etherchannel and Fast EtherChannel are registered trademarks of Cisco and derive from Ethernet and Channel (English Channel ). Etherchannel is the word for art was invented by Kalpana (now Cisco) and refers to a method for combining multiple physical Ethernet interfaces into one logical channel, at Fast Etherchannel multiple Fast Ethernet interfaces can be bundled. Etherchannel has partially established as everyday expression for the Ethernet channel bundling and is colloquially not only for Cisco products used ( generic term similar pace and paper towels ). The technique was originally used solely to increase the data throughput between two Ethernet switches ( also invented by Kalpana ). Soon after the introduction of Etherchannel there were also implementations for connecting servers and other systems.

Other names

Although there are incompatibilities and technical differences (depending on the manufacturer or context) used for the bundling of Ethernet interfaces, the following terms as synonyms:

• Bonding, in the Linux environment.
• Etherchannel, Cisco.
• Link aggregation, IEEE
• Port aggregation, at Hewlett -Packard.
• Trunking, Sun Microsystems, as well as other manufacturers.

Operation

Generally a plurality of physical Ethernet interfaces to connect two devices are connected together, that is, two interfaces can be bundled to transport the double amount of data, 4 therefore, the four -fold amount. It makes sense to combine fast as possible interfaces, 2 x Ethernet (half duplex ) correspond to 20 Mbit / s, 3 times Fast Ethernet (full-duplex ) and Fast Etherchannel is already 600 Mbit / s A maximum increase in performance is achieved for many bundling method, when the number of bundled ports is a power of two. Thus, for example, be achieved by aggregation of eight Fast Ethernet interfaces almost the bandwidth of a Gigabit Ethernet interface. Another advantage is increased resiliency. As can vary one or more interfaces, without the logical channel is interrupted in some processes. Only the data throughput decreases according to the missing links.

Bundling process

• Round Robin: Here all available lines are alternately sequentially used.
• DA trunking: Here you select the basic interface based on the modulo of the destination MAC address.
• SA trunking: Here you select the basic interface based on the modulo of the source MAC address.
• SA -DA - trunking: Here you select the basic interface based on the modulo of the source MAC address and destination MAC address.
• Adaptive Trunking: Here is another only switched on at 100 % utilization of the first elementary interface.
• Dynamic Trunking: With the help of proprietary Arif 's, or the IEEE -compliant LACP EtherChannels can be defined dynamically.

Basic implementation

The basic implementation of a channel bundling between two Ethernet switches come with surprisingly small changes (compared to a normal switch). Of course, the management interface must be extended to define the trunks. Then the way, like a switch gets its SAT ( Source-Address -Table - table with the MAC addresses of the sender) learned, affected, and finally broadcasts and packets that are addressed to unknown destination MAC addresses treated separately from the trunk.

• Management Interface: that the menu structures are concerned, certainly needs no great explanation.
• Address learning phase: Receives a switch on a trunk port, an unknown sender address, so these are not automatically the address stack ( SAT) is assigned to this port, but the switch tries to match all the members of the trunk a same network load and therefore new distribute sender addresses evenly on all companies in the trunk ports. Consequently, so received by the port that the fewest entries leads currently in its satellite, the new address.
• Broadcasts and unknown addresses: These are not sent in a trunk on all ports, but only one per trunk line, generally the port is selected with the lowest port number.

There are no other actions necessary to carry out a simple implementation. The implementation of the transport mechanisms (cut through, store and forward, etc. ) do not change. However, this implementation is far from optimal and is really only for the coupling of two nets. A disadvantage is that each MAC address only one port of the trunk is used - for a single station, it means that she has no benefits - benefits only the network as a whole. Further, it may happen that the most active stations are randomly assigned to all the same port, hence the load is not evenly distributed within the trunk. There are also bundling method, which can bind powerful servers. All these facts have resulted in many manufacturers offer different, but also more sophisticated implementations, but these are not generally compatible with each other.

• Ethernet