Huawei Quidway S3500 Series Operation Manual page 341

Operation Manual - QoS/ACL
Quidway S3500 Series Ethernet Switches
Table 1-15 Letters and their meanings
Letter
A
B
C
D
E
F
G
H
I
J
K
L
M
N
The offsets listed in the above table are the field offsets in the SNAP+tag 802.3 data
frame. In the user-defined ACL, you can use the rule mask and offset parameters to
select any bytes from the first 64 bytes of the data frame and compare them with the
user-defined rule to filter the matched data frames and process accordingly. The rules
defined by the user can be some fixed properties of the data. For example, to filter all
the TCP packets, you can define the rule as "06", the rule mask as "FF" and the offset
as 35. In this case, the rule mask coordinates with the offset and picks up the TCP
protocol number field from the data frame and compares it with the user-defined rule
string to get all the TCP packets.
Meaning
Destination MAC
address
Source MAC
address
Data frame length
field
VLAN tag field
DSAP (Destination
Service Access
Point) field
SSAP (Source
Service Access
Point) field
Ctrl field
org code field
Encapsulated Data
type
IP version
TOS field
IP packet length
ID number
Flags field
Huawei Technologies Proprietary
Offset Letter
0 O TTL field
Protocol number (6
6 P is TCP and 17 is
UDP).
12 Q IP checksum
14 R Source IP address
Destination
18 S
address
19 T TCP source port
20 U TCP destination port
21 V Sequence number
Acknowledgement
24 W
field
IP
26 XY and
unused bit
Currently
27 Z
bits and flags bit
28 a Window Size field
30 b Others
32
1-15
Chapter 1 ACL Configuration
Meaning Offset
34
35
36
38
IP
42
46
48
50
54
header length
currently 58
unused
59
60
62