Aggregated Links

To fill the gap between our 1 and 10 Gbit/sec port offerings, AMS-IX also offers aggregated Gigabit Ethernet ports.

To fill the gap between 10 Gbit/sec and the still far away 100 Gbit/sec Ethernet standard, AMS-IX also offers aggregated 10GigabitEthernet ports.

This technique allows for the bundling of two or more Gigabit Ethernet links into one virtual channel towards the shared fabric, negating the need for additional routers.

Link aggregation is also known as EtherChannel, Port Channel, port aggregation (PAgP) or trunking, depending on the vendor involved. The IEEE 802.3ad or LACP specifications are partially applicable (ports are not dynamically added to or removed from the aggregated link, nor can specific flows be moved between individual links, but conversations are kept on one link).

Pricing and Availability

The port prices for aggregated links are identical to the normal port prices. Please make sure to select the option for an aggregated connection in the additional connection form.

AMS-IX currently offers the option of aggregated Gigabit Ethernet and 10Gigabit Ethernet links. No other media types are available for aggregation.

Due to technical limitations of the switches used by AMS-IX it may be necessary to relocate your existing port. If this turns out to be the case, AMS-IX will inform you and advise you of any additional steps necessary for this process.

AMS-IX can deliver aggregated links at all housing locations.

Although a strict reading of the spec forbids it, we can offer aggregated links over different media types of the same speed (1000baseSX and 1000baseLX; or 10GE-LR and 10GE-ER).

Load-Balancing Algorithm for the JetCore platform

AMS-IX's Foundry BigIron 15000 edge switches use a load-balancing algorithm for outgoing traffic that builds a hash based on source and destination IP addresses in the switched Ethernet frames. Multicast and broadcast frames get sent down the first port to have come up. Unicast frames not containing IPv4 packets get distributed based on source MAC address. (For more detailed although already slightly outdated information, see Foundry's website.)

We find that this delivers a very even distribution of traffic over the individual ports, with differences between two ports in general below a few percentage points of load.

The choice of a hash-based algorithm also means that a single flow will not spread itself out over multiple links. This avoids possible packet reordering.

Load-balanced traffic gets divided over 16 hash buckets; this means that for 3-port aggregated links, traffic gets balanced as 6-5-5, leaving the maximum throughput from the switch platform towards your router at 1000/(6/16) = 2,666.67 Mbps. Aggregated links containing 2, 4 or 8 ports do not suffer from this limitation.

For pricing and redundancy reasons, we advise our members to investigate 10GE or to install additional routers over ordering aggregated links containing more than a few Gigabit Ethernet ports.

Load-Balancing Algorithm for the BigIron RX and NetIron MLX platforms

The load-balancing algorithms used in our BigIron RX and NetIron MLX switches uses a modulo operation, leading to the best distribution over links with the entropy available in source and destination IPv4 or IPv6 address, TCP or UDP source and destination port number, as applicable.

Configuration Hints

We have collected information about link aggregation for several router platforms.