IBM Z10 EC manual Link aggregation for z/VM in Layer 2 mode

For latency sensitive applications, the blocking algo- rithm is modifi ed to be “latency sensitive.” For streaming (throughput sensitive) applications, the blocking algorithm is adjusted to maximize throughput. The z/OS TCP/IP stack can dynamically detect the application requirements, making the necessary adjustments to the blocking algo- rithm. The monitoring of the application and the blocking algorithm adjustments are made in real-time, dynamically adjusting the application’s LAN performance.

System administrators can authorize the z/OS TCP/IP stack to enable a dynamic setting, which was previously a static setting. The z/OS TCP/IP stack is able to help determine the best setting for the current running application, based on system confi guration, inbound workload volume, CPU utilization, and traffi c patterns.

Link aggregation for z/VM in Layer 2 mode

z/VM Virtual Switch-controlled (VSWITCH-controlled) link aggregation (IEEE 802.3ad) allows you to dedicate an OSA-Express2 (or OSA-Express3) port to the z/VM operat- ing system when the port is participating in an aggregated group when confi gured in Layer 2 mode. Link aggregation (trunking) is designed to allow you to combine multiple physical OSA-Express3 and OSA-Express2 ports (of the same type for example 1GbE or 10GbE) into a single logi- cal link for increased throughput and for non-disruptive failover in the event that a port becomes unavailable.

•Aggregated link viewed as one logical trunk and con- taining all of the Virtual LANs (VLANs) required by the LAN segment

•Load balance communications across several links in a trunk to prevent a single link from being overrun

•Link aggregation between a VSWITCH and the physical network switch

•Point-to-point connections

•Up to eight OSA-Express3 or OSA-Express2 ports in one aggregated link

•Ability to dynamically add/remove OSA ports for “on demand” bandwidth

•Full-duplex mode (send and receive)

•Target links for aggregation must be of the same type (for example, Gigabit Ethernet to Gigabit Ethernet)

The Open Systems Adapter/Support Facility (OSA/SF) will provide status information on an OSA port – its “shared” or “exclusive use” state. OSA/SF is an integrated component of z/VM.

Link aggregation is exclusive to System z10 and System z9, is applicable to the OSA-Express3 and OSA-Express2 features in Layer 2 mode when confi gured as CHPID type OSD (QDIO), and is supported by z/VM 5.3 and later.

Layer 2 transport mode: When would it be used?

If you have an environment with an abundance of Linux images in a guest LAN environment, or you need to defi ne router guests to provide the connection between these guest LANs and the OSA-Express3 features, then using the Layer 2 transport mode may be the solution. If you have Internet- work Packet Exchange (IPX), NetBIOS, and SNA protocols, in addition to Internet Protocol Version 4 (IPv4) and IPv6, use of Layer 2 could provide “protocol independence.”

The OSA-Express3 features have the capability to perform like Layer 2 type devices, providing the capability of being protocol- or Layer-3-independent (that is, not IP-only).

With the Layer 2 interface, packet forwarding decisions are based upon Link Layer (Layer 2) information, instead of Network Layer (Layer 3) information. Each operating system attached to the Layer 2 interface uses its own MAC address. This means the traffi c can be IPX, NetBIOS, SNA, IPv4, or IPv6.

An OSA-Express3 feature can fi lter inbound datagrams by Virtual Local Area Network identifi cation (VLAN ID, IEEE 802.1q), and/or the Ethernet destination MAC address. Fil- tering can reduce the amount of inbound traffi c being pro- cessed by the operating system, reducing CPU utilization.

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