Broadcom BCM5722 - Figure 73: File Transfer Scenario: File Transfer Complete; Figure 74: Pause Control Frame

BCM5722 Programmer’s Guide
10/15/07
Broadcom Corporation
Page 517 Pause Control Frame Document 5722-PG101-R
FILE TRANSFER COMPLETE
The Client has caught up with the transmission flow of the Server (see Figure 73). The Client’s RX buffers/memory is below
the flow control threshold. The file is transfer is complete. This scenario was a worst-case cascade, where the pause delay
propagated through the LAN. The Switch could absorb the Client’s pause delay, without having to flow control the Server.
Figure 73: File Transfer Scenario: File Transfer Complete
PAUSE CONTROL FRAME
The minimum size frame is 512 bits or 64 bytes (see Figure 74). MAC control frames must pad zeros into the unused portion
of the payload. A flow control frame contains the following fields:
• Destination address field, set to 01-80-C2-00-00-01
• Source address field set to unique MAC address of sender
• LL/Type field set to the 802_3_MAC_CONTROL value, set to 88–08
• MAC control pause opcode (00-01), pause_time, and reserved field (zeros)
Figure 74: Pause Control Frame
Gigabit Server
Switch
Gigabit Client
File
Destination address
Source address
LL/Type
MAC control opcode
MAC control parameters
Reserved field
6 bytes
6 bytes
2 bytes
2 bytes
64 bytes - 20 bytes -
mac_ctrl_parm_len
2 bytes
42 bytes
01 80 C2 00 00 01
XX XX XX XX XX XX
88 08
00 01
00 10
00 00 00 ...
Delay 10 Quanta (Slot times)
Pause frame opcode
Pause frame opcode
Source address
Multicast address
Pause Frame