Freescale Semiconductor MPC8313E Family Reference Manual page 790

Enhanced Three-Speed Ethernet Controllers
1
PID Bit Name
0101 0–7 — Reserved, should be written with zero.
8–31 SAH Source MAC address, most significant 24 bits. Defaults to 0x000000.
0110 0–7 — Reserved, should be written with zero.
8–31 SAL Source MAC address, least significant 24 bits. Defaults to 0x000000.
0111 0–15 — Reserved, should be written with zero.
16–31 ETY Ethertype of next layer protocol, that is, last ethertype if layer 2 headers nest. Defaults to 0xFFFF.
Using the filer to match ETY does not work in the case of PPPoE packets, because the PPPoE ethertype
in the original packet, 0x8864, is always overwritten with the PPP protocol field. Thus, matches on
ETY == 0x8864 always fail.
Instead, software should use PID=1 fields IP4 (ETY = 0x0021) and IP6 (ETY = 0x0057) to distinguish
PPPoE session packets carrying IPv4 and IPv6 datagrams. Other PPP protocols are encoded in the
ETY field, but many of them overlap with real ethertype definitions. Consult IANA and IEEE for
possible ambiguities.
A value in the length/type field greater than 1500 and less than 1536 is treated as a type encoding by
the parser. Since no recognized types exist in this range, the controller will not parse beyond the
length/type field of any such frame.
Note that the eTSEC filer gets multiple packet attributes as a result of parsing the packet. The behavior
of the eTSEC is that it pulls the innermost ethertype found in the packet; this means that in many
supported protocols that have inner ethertypes, in order to file based on the outer ethertype, arbitrary
extraction should be used instead of the ETY PID. There are four cases that need to be highlighted.
1. The jumbo ethertype (0x8870)—In this case, the eTSEC assumes that the following header is
2. The PPPoE ethertype described above.
3. The VLAN tag ethertype (0x8100)—In this case, one can use the PID=1 VLN bit to indicate that the
4. The MPLS tagged packets. In this case, one can use arbitrary extraction bytes to compare to the
Users of the eTSEC parser/filer should be aware of a difference in behavior between rev 1 and rev 2
silicon in cases where the Ethernet type/length field contains a value between 1500 and 1536.
In rev 2 silicon, values between 1500 and 1536 are interpreted as a type. Since there are currently no
valid types in this range publicly defined by IANA, the controller will not parse beyond the length/type
field of any such frame.
If the same packet is encountered with rev 1 silicon, parser/filer behavior is different. With rev 1 silicon,
such packets are treated as payload length. S/W must confirm the parser and filer results by checking
the type/length field after the packet has been written to memory to see if it falls in this range.
1000 0–19 — Reserved, should be written with zero.
20–31 VID VLAN network identifier (as per IEEE Std 802.1Q). This value defaults to 0x000 if no VLAN tag was
found, or the VLAN tag contained only priority information.
1001 0–28 — Reserved, should be written with zero.
29–31 PRI VLAN user priority (as per IEEE Std 802.1p). This value defaults to 000 (best effort priority) if no VLAN
tag was found.
MPC8313E PowerQUICC II Pro Integrated Processor Family Reference Manual, Rev. 3
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Table 15-35. RQFPR Field Descriptions (continued)
LLC/SNAP. LLC/SNAP has an associated Ethertype, and the ETY field is populated with that
ethertype. This makes it impossible to file on jumbo frames.
In this case, one can use arbitrary extracted bytes to pull the outermost Ethertype.
packet had a VLAN tag.
actual ethertype if a filer rule is intending to file based on an MPLS label existence.
Description
NOTE
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