Intel IXP1200 manual Dram Data Buffer Format, 2 3 4 5 6 7 8 Bytes, Enet SrcAdr

IXP1200 Network Processor Family ATM OC-3/12/Ethernet IP Router Example Design

Figure 29. Buffer Descriptor Format for Ethernet Transmit Destination Port

0

1

2

3

3	3	2	2	2	2	2	2	2	2	2	2	1	1	1	1	1	1	1	1	1	1	9	8	7	6	5	4	3	2	1	0
1	0	9	8	7	6	5	4	3	2	1	0	9	8	7	6	5	4	3	2	1	0
RCV_PORT					FL_ID					START_BYTE								END_BYTE								ELE_COUNT
																-1

Entry	Description
RCV_PORT	Receive Port
FL_ID	Free list ID
START_BYTE	Frame start location in the buffer (zero-based)
END_BYTE	Number of bytes in the last MPKT - minus 1 (e.g. 0 means 1 byte)

ELE_COUNT

Number of 64-byte MPKTs in packet

4.4.2DRAM Data Buffer Format

Packet payloads are stored in DRAM data buffers. Depending on if the data was received on an ATM or Ethernet port, the payload will land in a different place within the data buffer..

Figure 30. DRAM Data Buffer Format - 12 Byte Offset (Received by ATM)

0 1 2 3 4 5 6 7 8 9	1	1	1	1	1	1	1	1	1	1	2	... Bytes ->
	0	1	2	3	4	5	6	7	8	9	0

ATM

Header

LLC/SNAP

IP ... IP Pad

AAL5 Trailer

Figure 31. DRAM Data Buffer Format - 6 Byte Offset (Received by ATM, Transmitted by Ethernet)

0 1 2 3 4 5 6 7 8 9	1	1	1	1	1	1	1	1	1	1	2	... Bytes ->
	0	1	2	3	4	5	6	7	8	9	0

Enet Dest Addr

Enet Src Addr

Typ

IP ... IP

Figure 32. DRAM Data Buffer Format - 6 Byte Offset (Received by Ethernet, Transmitted by ATM)

0	1	2	3	4	5	6	7	8	9	1	1	1	1	1	1
										0	1	2	3	4	5
								LLC/SNAP						IP

... Bytes ->

... IP Pad AAL5 Trailer

Figure 33. DRAM Data Buffer Received by Ethernet

0 1 2 3 4 5	6 7 8 9	1	1	1	1	1	...	Bytes ->
		0	1	2	3	4
Enet DstAdr	Enet SrcAdr			TYP		IP ...		IP

40 Application Note

Modified on: 3/20/02,