Spanning FCV CHPIDs
Original Publication Date: 2004-Feb-26
Included in the Prior Art Database: 2004-Feb-26
An extension to the fibre channel protocols (FC-FS and FC-SB-3) used by the FICON bridge channel (FCV) is described to allow it to be shared across logical channel subsystems in a zArchitecture machine with the Multiple Channel Subsystem (MCSS) facility.
Spanning FCV CHPIDs
An extension to the fibre channel protocols (FC-FS and FC-SB-2) used by the FICON bridge channel (FCV) is described to allow it to be shared across logical channel subsystems in a zArchitecture machine with the MCSS facility. Such a capability will: reduce cost by reducing the number of channels, switch ports, and fibers needed to
configure and support ESCON control unit connections for T-Rex simplify the migration to a MCSS and simplifying the I/O configuration definition by
allowing different LCSSes, using the same FCV channel and FICON Bridge to access the same (or different) ESCON switch CU ports provides a generic solution for all ESCON devices
Spanning of FCV channels across logical channel subsystems is achieved by having the FCV-Bridge take advantage of the unused source addresses in the FCV channel protocol. The system allows these unused addresses to be assigned to up to a total of eight logical channel subsystems:
HCD/IOCP/IOP allows definition of spanning FCV CHPIDs. If more than 8 LCSSes are defined, HCD allows user to specify which LCSSes are able to share a specific FCV CHPID. when NOT-spanned only one LSSs can access the FCV channel, it when SPANNED, no-matter how many LCSSs defined, HCD should always allow the user to specify, which LSS can access the spanned FCV channel) Channel finds bridge base port address (source port address, S_ID) during initialization (FLOGI) and that the FCV bridge supports the multiple ESCON logical source port address function IOP assigns an ESCON source port address for each logical CSS that is defined to access CUs over the same spanned FCV CHPID Channel uses different 'CSS' ESCON logical source port address as source for I/O requests from the different logical channel subsystems New field in FICON SB-2 (FCV) header When the bridge builds the ESCON frames, it uses the new ESCON source port address from the FICON SB-2 (FCV) header The 9032-005 will change so that it can receive ESCON frames with different target port addresses and route to the same bridge card:
When connection exists and CU is sending response When connection does not exist, e.g. CU is reconnecting or presenting unsolicited status This invention supports up to 8 LCSSs per spanned FCV channel, the 9032-5 bridge card limit The channel knows when the FCV-bridge card supports this function by adding new bit in the ACCEPT response to the FLOGI. If the FCV channel is defined as spanned but the FCV bridge card does not support the function, the channel does not initialize and enters the protocol error state and cannot be configured on-line.