CONFIDENTIAL
CY7C9538
Document #: 38-02095 Rev. *B
Page 7 of 46
Programmable Frame Tagging Engine
The Programmable Frame Tagging Engine provides preclas-
sification of the packets/frames at the wire rate. This helps in
utilizing the link layer device more efficiently.
The Programmable Frame Tagging Engine enables the user
to perform preclassification of all the incoming packets into
one of the 16 possible categories. Since each channel can
have up to 16 different categories, and up to 16 virtual concat-
enated channels are possible, this engine supports up to 256
different categories. For classification, two-pass comparison
can be specified. For each comparison a field of up to six bytes
can be selected within the first 64 bytes of the packet and
compared with up to 16 programmed values. The comparison
is on a bit by bit basis and any bit comparison can be masked
with a user programmable mask register. A four-bit tag is
attached to the cell/packet, based on the match. Host CPU can
program these parameters through register programming.
The following drawing demonstrates one possible combi-
nation of classification with the help of the Programmable
Frame Tagging Engine.
The following functions can be achieved with the help of the
Programmable Frame Tagging Engine:
Incoming packet analysis to parse packets/frames/cells at wire
speed.
User-programmable routing of control packets to CPU for
processing.
Incoming frames tagged based on bits (such as congestion) in
incoming packets.
User-programmable offset to locate Ethernet and other frames
within DOS and other proprietary MAN networking protocols
to allow MPLS processing.
SONET/SDH
Control Packets
Data
Packets
Packets not
belonging to this
Node
TTL-expired and
other discard
packets
Tagging enables sorting of packets by
Host System
Errored packets
(CRC and Parity)
Node-sourced
packets to be
sinked
POSIC2GVC-R
Host System
Data
Tag #0
Tag #1
Tag #2
Tag #13
Data
Data
Data
Tag #14
Data
Data
Tag #15
Tag #n
Data
........
System Memory at
Figure 4. Frame Tagging Engine Data Sorting Diagram
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