IBM z/OS - page 23

Queued Direct Input/Output (QDIO)

The OSA-Express Gigabit Ethernet, 1000BASE-T Ethernet

and Token-Ring features support QDIO (CHPID type OSD),

which is unique to IBM. QDIO was ﬁ rst introduced to the

world on the z900, in Communication Server for OS/390 2.7.

Queued Direct Input/Output (QDIO), a highly efﬁ cient data

transfer architecture, breaks the barriers associated with

the Channel Control Word (CCW) architecture increasing

data rates and reducing CPU cycle consumption. QDIO

allows an OSA-Express feature to directly communicate

with the server’s communications program through the use

of data queues in memory. QDIO helps eliminate the use

of channel program and channel control words (CCWs),

helping to reduce host interrupts and accelerate TCP/IP

packet transmission.

TCP/IP connectivity is increased with the capability to

allow up to a maximum of 160 IP stacks per OSA-Express

port and 480 devices. This support is applicable to all the

OSA-Express features available on the z990 and is pro-

vided through the Licensed Code (LIC).

Full Virtual Local Area Network (VLAN) support is available

on z990 in z/OS V1.5 Communications Server (CS) for the

OSA-Express 1000BASE-T Ethernet, Fast Ethernet and

Gigabit Ethernet features when conﬁ gured in QDIO mode.

Full VLAN is also available with z/OS V1.2 on z900 and

z800 using appropriate LIC upgrade on Fast Ethernet and

Gigabit Ethernet features. Full VLAN support in a Linux on

zSeries environment was delivered for QDIO mode in April

2002 for z800 and z900. z/VM V4.4, and later, also exploits

the VLAN technology offering one global VLAN ID for IPv4.

z/VM V5.1 provides the support for one global VLAN ID for

IPv6.

z990 OSA-Express Gigabit Ethernet

The new z990 OSA-Express Gigabit Ethernet LX and Giga-

bit Ethernet SX features replace the z900 Gigabit Ethernet

features for new build z990. The new OSA-Express GbE

features have a new connector type, LC Duplex, replacing

the current SC Duplex connectors used on the prior z900

Gigabit Ethernet features. The new Checksum ofﬂ oad sup-

port on these z990 features is designed to ofﬂ oad z/OS

V1.5 and Linux on zSeries TCP/IP stack processing of

Checksum packet headers for TCP/IP and UDP.

Switch /

Router

Server

TCP/IP applications

TN3270 browser

access to SNA appls.

Enterprise Extender

for SNA end points

QDIO Mode - TCP/IP

pSeries, RS/6000

xSeries, Netfinity

Gigabit

Ethernet

Server

Router

IP Router

Remote Office

4/16/100 Mbps

Token-Ring

10/100 Mbps

Ethernet

4/16 Mbps

Token-Ring

IP WAN

Intranet

Internet or

extranet

Gigabit Ethernet

(fiber or copper)

Gigabit Ethernet

(fiber or copper)

10/100 Mbps

Ethernet