Visara CNA-8000 Planning Guide - Manual (Page 17)

CNA-8000 Migration and Planning Guide
707156-002 2-3
XCA Gateway Operation
Setting up an XCA (External Communication Adapter) gateway is quite easy and is more
advantageous for LAN attached PUs than previous gateway types. Introduced with the
IBM 3172, a single subchannel is associated with a network adapter on the CNA-8000. If
multiple network adapters are to be used for the XCA function, then a minimum of one
subchannel for each network adapter is required. Up to 255 downstream PUs can connect
through each XCA gateway. If you need more than 255 downstream PUs to connect
through an adapter, you can define an additional XCA gateway. Up to eight XCA
gateways may be assigned to a single network adapter. Note that for performance
reasons, you would likely want to limit the number of downstream PUs through a single
adapter to a smaller number.
Downstream PUs are typically set up to dynamically connect through the XCA to request
connection to their Switched Major Node definition in VTAM. Each downstream PU is
expected to provide a unique ID to VTAM (XID) which VTAM uses to match to the
appropriate Switched definition (matched to the IDBLK and IDNUM parameters). If no
such match is found, then the attempted connection will be rejected. Successful matches
IBM S390 IBM z990
Director
Appears to the host as if the channel where
directly attached to a LAN (Token Ring or
Ethernet)