MT92220BG Zarlink Semiconductor, MT92220BG Datasheet - Page 55

• Manufacturer Part Number: MT92220BG
• Description: Description = 1023 Channel Voice Over IP/AAL2 Processor ;; Package Type = Epbga ;; No. Of Pins = 608
• Manufacturer: Zarlink Semiconductor

Data Sheet
6.5
Once the mask has been applied, the CRC calculated, and the profile number added, the resulting 60-bit
identification key is then used to navigate through the binary tree until the node containing that key is found. When
this node is found, it is associated to a post-search confirmation structure that tells the look-up system if the node
actually corresponds to the headers of the given packet (because a CRC is performed, collisions between various
CRC can occur).
The post-search confirmation structure contains a copy of the headers used to form the identification key. When a
packet hits a post-search confirmation structure, its headers are compared to the headers contained in the
structure: if they match, the packet belongs to that structure. One last verification is done before the packet is
completely validated: its IP address index is looked up in the Flow Table pointed to by the packet’s Flow Table
Pointer. The Flow Table is used to verify if the destination IP address of the packet is a legal address to be received
on this logical subnet. If the match is ‘1’, then the packet is valid and is sent to the Routing Destination indicated by
the post-search confirmation structure. If the match is ‘0’, then the packet has failed the post-search verification and
continues to be searched. The Flow Table look-up is optional, and should not be performed when trying to match
structures that don’t have a destination IP address, for instance if an MPLS label is being searched, or a packet
containing RTP over AAL5.
The format of the Flow Table is as follows:
+1C
+10
+14
+18
+C
+0
+4
+8
Post-search Confirmation
I224
b31
I0 I1 I2
b30
“Type of Service”
Treatment
TOSv4_X - IPv4
TOS field
TOSv6_X - IPv6
TOS field
b29
b28
b27
b26
b25
b24
b23
b22
Indicates what to do when the hardware encounters these
TOS values.
“00” = don’t change priority;
“01” = reserved;
“10” = change packet priority to low priority;
“11” = change packet priority to high priority.
Each profile entry contains the treatment values for TOS
N*16 to N*16+15, where N is the profile entry number. In
this way, all 256 values for the TOS are treated. These
values are not in any way linked to the profile; they just
reside in the same memory.
Table 15 - Fields and Description
b21
b20
b19
Zarlink Semiconductor Inc.
Figure 29 - Flow Table
b18
b17
b16
b15
b14
b13
b12
b11
b10
b9
b8
b7
b6
b5
b4
b3
I253
b2
MT92220
I254
b1
I255
b0
I31
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