IBM PowerPRS Q-64G
Packet Routing Switch
Preliminary
Table 3-5. Ingress Data Packet and Control Packet, Byte H0 Field Descriptions
Bit(s)
Field Name
Extended Bitmap
Parity
Description
Designates the range of output ports addressed by the destination bitmap in the data packet
header:
256-Gbps Configuration
512-Gbps Configuration
0
1
Ports 0 to 7
Ports 7 and 15
0
1
Ports 0to 15
Ports 15 to 31
Output port mapping for the 256-Gbps configuration is detailed in Table 3-6, and output port map-
ping for the 512-Gbps configuration is detailed in Table 3-7.
Note that each ingress packet header addresses only half the output ports. This reduces the desti-
nation bitmap field length and increases the packet payload size. Because only half the ports are
addressed in a single packet cycle, broadcast operation requires two packet cycles. A multicast
packet requires either one or two packet cycles, depending on whether the active bits are distrib-
uted over half the ports or all the ports.
0
1
Header parity.
Specifies the traffic type (red data packet, blue data packet, or idle packet) and the application
method of the bitmap filter to the ingress packet destination bitmap. The bitmap filter is specified
with the Bitmap Filter Register (page 125). The PowerPRS Q-64G uses the resulting masked desti-
nation bitmap to route the packet. If the resulting bitmap is all zeros, the PowerPRS Q-64G ignores
the packet. Note that control packets are detected before the bitmap filter is applied.
Protection Field Color
Bitmap Filter
00
01
Not applicable
Red (backup)
Not applicable (packet is an idle packet or a service packet).
Packet destination bitmap is bitwise ANDed with bitwise
complement of bitmap filter.
2:3
Protection
10
11
Red (active)
Packet destination bitmap is bitwise ANDed with bitmap
filter.
Blue (unfiltered) Packet destination bitmap is used as is (unfiltered).
This filtering function supports switchover and load balancing (see Section 3.11 Switchover Support
on page 57).
Flags traffic as best-effort bandwidth traffic when the best-effort discard function is enabled.
1
The packet is flagged as best-effort bandwidth traffic, and the PowerPRS Q-64G can dis-
card it, if necessary.
0
The packet is flagged as guaranteed bandwidth traffic, and the PowerPRS Q-64G cannot
discard it.
4
Best Effort
When the best-effort discard function is enabled, excess output port congestion triggers a mecha-
nism that discards best-effort bandwidth traffic to provide output port access to guaranteed band-
width traffic. The best-effort discard function is enabled with the best-effort discard enable bit in the
Configuration 0 Register (page 110). See Section 3.4.6 Best-Effort Discard on page 49 for more
information.
Send Grant
Reports the status of the send grant for the priority specified by the grant priority flywheel.
5
Reports the status of the subport grant of the type specified by the subport grant type/subport
flywheel and the priority specified by the grant priority flywheel.
Subport Grant
Specifies the packet priority for data packets:
00
01
10
11
Priority 0 (highest priority)
Priority 1
Priority 2
6:7
Packet Priority
Priority 3 (lowest priority)
This field is ignored for control packets because control packets do not have a specific priority (see
Section 3.1.2 on page 26).
For data packets, the protection field, best-effort bit, and packet priority field of the packet qualifier byte (H0)
are processed without modification. The best-effort bit is ignored unless the best-effort discard function is
enabled (see Section 3.4.6 Best-Effort Discard on page 49). The protection field and packet priority field are
always processed by the PowerPRS Q-64G, and the user must set them to the appropriate values.
Functional Description
Page 34 of 199
prsq-64g.01.fm
December 20, 2001
IBM [ IBM ]
