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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
Server
Server
IP
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