Ethernet Line aggregation on IBM i

Written by Colin DeVilbiss, this blog is an IBM software engineer who works at the Rochester Research and Development Center in Minnesota, mainly for IBM I development communications device drivers. Thank Colin.

On 7.1 Technology Refresh (TR) 3, IBM I increased the ability to aggregate multiple Ethernet ports on an Ethernet line description. A converged line description has two advantages over a single resource's line description: higher reliability and concurrent bandwidth.

As long as there is an aggregated Ethernet port at work, the aggregation line description can be maintained properly. For example, if 4 Ethernet ports are aggregated into one line description, even if three Ethernet ports are disconnected, the line description can remain active so that the workload hosted on it can continue to run.

In addition, applications that use multiple concurrent TCP connections or have multiple remote clients can take advantage of multiple physical connections on the same IP address, leveraging each available resource to increase bandwidth. For example, if you aggregate 4 1gb/s Ethernet ports, you can support up to 4gb/s bandwidth on multiple connections.

New features

Line aggregation enables IBM I administrators to improve their network configuration, make better use of underutilized resources, and adapt to new requirements for future business.

For example, if a partition has a 2-port Ethernet card, but IBM I uses only one of these, in which case we can aggregate two ports to gain additional protection when a network cable, switch port, or NIC is on the wrong port. For some applications, this also multiplies bandwidth and does not add additional hardware overhead.

Similarly, if an IP interface tends to be saturated with bandwidth, line aggregation allows the administrator to progressively increase the bandwidth described by the underlying line without changing the technology used in a particular line. That is, if one GB/s is not enough, line aggregation can provide 2g/b potential bandwidth without upgrading to the 10GB/S architecture.

Create an aggregation line description

The main requirements for creating line aggregations are:

IBM I partition with 7.1 TR 3 and corresponding PTF group installed

This partition has two or more GB/s Ethernet Physical Resources

A switch that supports line aggregation (sometimes called "truking" or "teaming")

On the switch side, the corresponding port must be configured for static aggregation. Depending on the manufacturer, different switches have their own configuration commands and interfaces, please check the appropriate manuals.

Assuming that the target Ethernet resource is CMN02 and CMN03, creating an aggregated line interface is simple:

Crtlineth LIND (Ethagg) rsrcname *agg aggpcy *ethchl *srcdestp (AGGRSCL)

That is, create a new Ethernet line description:

Named Ethagg

Use line aggregation instead of a single hardware resource

Use static allocations for resources (TR3 only supports this option)

Allocate outgoing Ethernet frames to each Ethernet port by source IP address, destination IP address, and TCP port number (this mechanism is most likely to optimally allocate traffic to each port)

Aggregate CMN02 and CMN03

The line description vary on activates all ports, and you can use command Dsplin to view the status of each port. TCP/IP uses the aggregated line description without distinction, just like any other line description.

For more information, refer to Ethernet on System I in IBM Information Center.

In short, Ethernet aggregation allows 7.1 TR3 users to better leverage their Ethernet resources, provide higher reliability and better performance for their network load, and no need to purchase additional hardware.