IBM 990 - Manual (Page 23)

Chapter 1. zSeries 990 overview 11
You can choose any combination of OSA features: the OSA-Express Gigabit Ethernet LX
(FC1364), the OSA-Express Gigabit Ethernet SX (FC1365), the OSA-Express 1000BASE-T
Ethernet (FC1366), or OSA-Express Token Ring (FC2367). You can also carry forward your
current z900 OSA-Express features to z990, OSA-Express Gigabit Ethernet LX (FC 2364),
OSA-Express Gigabit Ethernet SX (FC 2365), OSA-Express Fast Ethernet (FC 2366), and
OSA-Express Token Ring (FC 2367).
Gigabit Ethernet
The OSA-Express GbE features (FC1364 and FC1365) have an LC Duplex connector type,
replacing the current SC Duplex connector. This conforms to the fiber optic connectors
currently in use for ISC-3 and the FICON Express features shipped after October 30, 2001.
1000BASE-T Ethernet
The z990 supports a copper Ethernet feature: 1000BASE-T Ethernet. This feature is offered
on new builds and replaces the current OSA-Express Fast Ethernet (FC 2366), which can be
brought forward to z990 on an upgrade from z900.
1000BASE-T Ethernet is capable of operating at 10, 100, or 1000 Mbps (1 Gbps) using the
same Category-5 copper cabling infrastructure that is utilized for Fast Ethernet. The Gigabit
over copper adapter allows a migration to gigabit speeds wherever there is a copper cabling
infrastructure instead of a fiber optic cabling infrastructure.
OSA-Express Integrated Console Controller (OSA-ICC)
An additional function of the OSA-Express 1000BASE-T Ethernet feature is its support as an
OSA-Express 100BASE-T Ethernet Integrated Console Controller. This function supports
TN3270E and non-SNA DFT 3270 emulation and means that 3270 emulation for console
session connections are integrated in the z990 via a port of the 1000BASE-T Ethernet
feature.
Checksum Offload for Linux and z/OS when in QDIO mode
A function introduced for the Linux on zSeries and z/OS environments, called checksum
offload, provides the capability of calculating the Transmission Control Protocol/User
Datagram Protocol (TCP/UDP) and Internet Protocol (IP) header checksums.
Checksum verifies the correctness of files. By moving the checksum calculations to a Gigabit
or 1000BASE-T Ethernet feature, host CPU cycles are reduced.
Improved performance can be realized by taking advantage of the checksum offload function
of the OSA-Express Gigabit Ethernet, and OSA-Express GbE or the 1000BASE-T Ethernet
(when operating at 1000 Mbps (1 Gbps)) features by offloading checksum processing to
OSA-Express (in QDIO mode, CHPID type OSD)) for most IPv4 packets. This support is
available with z/OS V1R5 and later as well as Linux on zSeries.
Token Ring
The OSA-Express Token Ring feature has two independent ports, each supporting
attachment to either a 4 Mbps, 16 Mbps, or 100 Mbps Token Ring Local Area Network (LAN).
The OSA-Express Token Ring feature supports autosensing as well as any of the following
settings: 4 Mbps half- or full-duplex, 16 Mbps half- or full-duplex, or 100 Mbps full-duplex.
Note: The demand for Token Ring on mainframe continues to decline. Migration from
Token Ring to an Ethernet infrastructure is recommended as part of long term planning for
Local Area Network support.