Link And Fc Addressing; Domain Id; Port Area; Alpa - Brocade Communications Systems StoreFabric SN6500B Administrator's Manual

1

Link and FC addressing

Link and FC addressing
To understand the addressing mode requirements and restrictions for FICON it is important to
understand the relationship between the link address and the FC address. Understanding this
relationship is also valuable for troubleshooting paths.
Figure 9
FIGURE 9

Domain ID

Although you enter the domain ID in decimal format when configuring a switch, it is represented in
hexadecimal formal in the FC address.
For single-byte addressing the domain area returned from the switch where the channel logs in is
used for the FC address. Therefore the channel and control unit must be in the same logical switch.
With 2-byte link addressing the most significant byte of the link address is used for the domain
area of the FC address. Once 2-byte link addressing is defined for a channel, all link addressing for
that channel must use 2-byte link addressing.

Port area

The port address is the single-byte link address or the least significant byte of a 2-byte link address.
The link address is entered in the HCD in hexadecimal format and is represented in hexadecimal in
the FC address.

ALPA

The Arbitrated Loop Physical Address (ALPA) was originally used in fibre channel for loop devices.
Currently, the ALPA is used for Node Port Identification Virtualization (NPIV), which allows multiple
WWNs to log into the same switch port. The ALPA determines the logical entity to which frames
belong. This is how virtual servers using zLinux or zVM can share the same channel. Since the DCX
and DCX 8510-8 Backbones can have up to 512 ports, the upper two bits of the ALPA are used in
certain addressing modes.
14
represents components of link and FC addresses that are explained in this section.
Link and FC address components
FICON Administrator's Guide
53-1002753-01