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 Internetwork Packet Exchange (IPX), NetBIOS, and SNA pro- tocols, 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.

Layer 2 transport mode is supported by z/VM and Linux on System z.

OSA Layer 3 Virtual MAC for z/OS

To simplify the infrastructure and to facilitate load balanc- ing when an LPAR is sharing the same OSA Media Access Control (MAC) address with another LPAR, each operating system instance can now have its own unique “logical” or “virtual” MAC (VMAC) address. All IP addresses associ- ated with a TCP/IP stack are accessible using their own VMAC address, instead of sharing the MAC address of an OSA port. This applies to Layer 3 mode and to an OSA port shared among Logical Channel Subsystems.

This support is designed to:

Improve IP workload balancing

Dedicate a Layer 3 VMAC to a single TCP/IP stack

Remove the dependency on Generic Routing Encapsu- lation (GRE) tunnels

Improve outbound routing

Simplify confi guration setup

Allow WebSphere Application Server content-based routing to work with z/OS in an IPv6 network

Allow z/OS to use a “standard” interface ID for IPv6 addresses

Remove the need for PRIROUTER/SECROUTER function in z/OS

OSA Layer 3 VMAC for z/OS is exclusive to System z, and is applicable to OSA-Express3 and OSA-Express2 features when confi gured as CHPID type OSD (QDIO).

31

Page 31
Image 31
IBM Z10 BC manual Layer 2 transport mode When would it be used?, OSA Layer 3 Virtual MAC for z/OS