MT92210 Datasheet, PDF (41/175 Pages) Zarlink Semiconductor Inc – 1023 Channel Voice Over IP Processor

Data Sheet
MT92210
“Type of Service”
Treatment
TOSv4_X - IPv4
TOS field
TOSv6_X - IPv6
TOS field
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
6.5
Post-search Confirmation
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:
b31 b30 b29 b28 b27 b26 b25 b24 b23 b22 b21 b20 b19 b18 b17 b16 b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
+0 I0 I1 I2
I31
+4
+8
+C
+10
+14
+18
+1C I224
I253 I254 I255
Figure 21 - Flow Table
Zarlink Semiconductor Inc.
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