IBM PowerPRS Q-64G
Packet Routing Switch
Preliminary
Table 3-28. Registers and Bits Used for Switchover Support
Register or Register Field
Description
1
0
Transmits all egress idle packets with the color specified by the idle color bit, regardless of the
expected color bit setting. When the color mechanism is not used, this bit must be set to ‘1’.
Enables the switchover mechanism to determine the color of egress idle packets by setting the
expected color bit. The PowerPRS Q-64G sends idle packets of the color specified by the
expected color bit on output port n, if an expected color packet has been received on all active
inputs since the color clear command was last issued and output queue n is empty. Otherwise,
the PowerPRS Q-64G sends idle packets of the opposite color on output port n. The color clear
command is sent through the Color Command Register.
Idle Color Force Bit in the Color
Command Register (page 127)
Specifies the color assigned to all idle packets when the idle color force bit is set to ‘1’:
0
1
Blue idle packets
Red idle packets
Idle Color Bit in the
Color Command Register
In this case, the PowerPRS Q-64G-generated idle packets will not change color during normal
operation.
Specifies the expected color of incoming packets after a color clear command is initiated:
Expected Color Bit in the
Color Command Register
0
1
Blue packets
Red packets
Color Clear Bit in the
Color Command Register
Processed as a command (action is taken on the rising edge) to clear the idle packet color state
machine in preparation for packet color-change detection.
When a bit is active, disables the input port color detection mechanism and sets the corresponding bit
in the Expected Color Received Register. This mask reports if an input port is enabled and active dur-
ing the color-based switchover process.
Color Detection Disable Register
(page 125)
1
0
Either the expected color has been received on the input port since the last color clear command
or the corresponding bit is set in the Color Detection Disable Register.
The opposite color is still being received on the input port.
Expected Color Received Regis-
ter
(page 126)
Specifies the mask applied to the ingress packet destination bitmap for switchover support and load
balancing in redundant switch-plane operation. Application of the bitmap filter depends on the packet
protection field (bits 2:3) of the packet qualifier byte, H0. The incoming packet bitmap is logically
ANDed with either a specified mask (red active packets) or its complement value (red backup pack-
ets), or it is left unfiltered (blue packets; see Table 3-29). For more information about operating this
mask, see Table 3-5 in Section 3.3.4 Ingress Data Packet and Control Packet Format on page 32.
Bitmap Filter Register (page 125)
Table 3-29. Ingress Data Packet Protection Field
Protection Field Value
Packet Color
Red (backup) Packet destination bitmap is bitwise ANDed with the bitwise complement of the bitmap filter.
Red (active) Packet destination bitmap is bitwise ANDed with the bitmap filter.
Blue (unfiltered) Packet destination bitmap is used unfiltered.
Filtering
01
10
11
3.11.1 Scheduled Switchover Process
Redundant switch planes operate under one of two conditions:
• When one switch plane is active and the other is a backup. Data traffic flows only through the active
switch path.
• When both switch planes are operating under load balancing. Data traffic is split between the two switch
planes, which have complementary values in their Bitmap Filter Registers (page 125).
When two switch planes are initially operating under load balancing, the switchover process includes three
phases:
Functional Description
Page 58 of 199
prsq-64g.01.fm
December 20, 2001
IBM [ IBM ]
