MT90883 Zarlink Semiconductor, MT90883 Datasheet - Page 57

• Manufacturer Part Number: MT90883
• Description: (MT90880 - MT90883) TDM to Packet Processors
• Manufacturer: Zarlink Semiconductor

6.8
This is used to determine the destination of incoming traffic on the packet interface from information contained
in the packet header. Up to four separate traffic classes can be identified, and each class can be forwarded
independently. Examples of traffic classes include TDM traffic for forwarding to the WAN interface, CPU control
traffic, and traffic destined for a DSP or other off-chip processing element. Unidentified traffic is sent to the host
processor via the lowest priority queue.
Traffic classes are identified by matching the header against a pre-programmed pattern. If a pattern match is
detected, the traffic can be directed to one of four separate queues to the host interface, or to the WAN
interface. All WAN traffic must contain a two-byte adaptation layer (known as the context descriptor) in a known
position within the first 64 bytes. This contains the context or packet stream to which the packet belongs, and
other information required to synchronize to any changes to the contents of a particular context.
Features include:
•
•
•
•
•
6.8.1
Packet classification in the MT9088x is a three-stage process, as shown in Figure 26. Firstly, the packet header is
masked, to concentrate the classification on the header fields of interest. Four separate masks are applied in paral-
lel across the first 64 bytes of the packet. Next the masked header is compared against up to four possible patterns.
Again, the comparison function is across the first 64 bytes of the packet. This depth of search allows fields from
layer three and four headers to be included in the classification (e.g. IP and UDP headers).
•
•
•
•
Four separate traffic classes
Match on any field of combination of fields within the first 64 bytes
Host traffic can be directed at one of four different queue
Context Descriptor can be placed anywhere in the first 64 bytes (for TDM data packets)
Can interface to devices placing the context descriptor in different places
RFC 1213 MIB II.
RFC 1757Remote Network Monitoring MIB (for SMIv1)
RFC 2819Remote Network Monitoring MIB (for SMIv2)
RFC 2863Interfaces Group MIB
Packet Classification
Pattern Matching
Zarlink Semiconductor Inc.
MT90880/1/2/3
57
Data Sheet