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Overview of IBM Networking
CMCC Adapter Features for TCP/IP Environments
BC-245
Cisco IOS Bridging and IBM Networking Configuration Guide
78-11737-02
Supported Environments
The Cisco IOS software supports the following environments and features on the CMCC adapters:
• TCP/IP Environments—CLAW, TCP/IP offload, IP host backup, CMPC+, and TN3270 server
features
• SNA and APPN Environments—CSNA, CMPC, and TN3270 server features
CMCC Adapter Features for TCP/IP Environments
The Cisco IOS software supports the following features for CMCC adapters in TCP/IP environments:
• Common Link Access to Workstation, page 245
• TCP/IP Offload, page 245
• IP Host Backup, page 246
• Cisco Multipath Channel+, page 246
• TN3270 Server, page 248
Common Link Access to Workstation
To transport data between the mainframe and a CMCC adapter in TCP/IP environments, Cisco IOS
software implements the CLAW channel protocol. Each CLAW connection requires two devices out of
a maximum of 256. Although this allows for a maximum of 128 CLAW connections per interface, a
maximum of 32 CLAW connections per interface is recommended.
The CLAW packing feature enables the transport of multiple IP packets in a single channel operation
and significantly increases throughput performance between a mainframe and a CMCC adapter.
Currently, IBM’s TCP/IP stack does not support the CLAW packing feature.
The CLAW packing feature requires changes to the mainframe CLAW driver support. In partnership with
Cisco, Interlink Computer Science (now Sterling Software) has made the corresponding CLAW driver
change to Cisco IOS for S/390 Release 2 and Interlink TCPaccess 5.2. Customers must make the
necessary changes to their host configurations to enable the CLAW packing feature.
For details about configuring a CMCC adapter for CLAW, see the “Configuring CLAW and TCP/IP
Offload Support” chapter in this publication.
TCP/IP Offload
The Cisco TCP/IP offload feature supports IBM’s MVS, VM, and Transaction Processing Facility (TPF)
operating systems. The TCP/IP offload feature for CMCC adapters delivers the same function as the
TCP/IP offload function on the 3172 Interconnect Controller (Model 3), but with increased performance.
For details about configuring a CMCC adapter for TCP/IP offload, see the “Configuring CLAW and
TCP/IP Offload Support” chapter in this publication.