PM7311 pmc-sierra, PM7311 Datasheet - Page 64

• Manufacturer Part Number: PM7311
• Description: Freedm 84a1024l Assp Telecom Standard Datasheet
• Manufacturer: pmc-sierra

Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2021832, Issue 2
10.3.2
Fragments are defined as per FRF.12 and RFC 1990. The chunk is stored in external SDRAM in a
data structure that is indexed on a per datagram basis. The fragment builder can simultaneously
reconstruct 1024 datagrams (one per HDLC channel).
Completed datagrams are forwarded to the lookup and re-sequencing stage. This stage performs a
header lookup that is used to determine the connection identifier. A connection record associated
with the CI contains a number of state variables used in the re-sequencing operation and to guide
the remaining ingress operations for the datagram. Re-sequencing is required when ML-FR or
ML-PPP is active on a given set of HDLC channels. Given the variable length of data transfers
and skew between the physical links in the multi-link bundle, re-sequencing is essential to
enabling multi-link protocols. Both 12 and 24 bit sequence numbers are supported for PPP while
the 12 bit FRF.12 format is supported for FR.
The incoming sequence number is compared with the expected sequence number. If the two are
equal, the datagram does not need to be re-sequenced and is logically passed to the ingress queue
or the packet/frame builder depending on the style of data transfer (packet or fragment) requested
for the Any-PHY channel.
If the sequence numbers do not align, a re-sequencing operation is triggered and the datagram is
logically placed in the re-sequencing buffers. The datagram is removed from the re-sequencing
buffers when the re-sequencing operation has correctly re-sequenced the datagrams. These
datagrams are passed to the frame builder or the ingress queue manager depending on the mode
of transfer. In addition to re-sequencing, a loss detection algorithm detects lost datagrams.
When the Any-PHY transfer is frame/packet based, the frame builder constructs complete frames
or packets from the datagrams that have been constructed by the fragmentation builder. These
complete frames/packets are transferred to the ingress queue manager.
The ingress queue manager retrieves the frame/packet from the external chunk buffer memory
and transfers it to the upstream system device via the Any-PHY interface.
Egress Path
Figure 15 shows the elements and data transformations that occur as data traverses the FREEDM
84A1024L from the Any-PHY to the SBI interface.
FREEDM 84A1024L ASSP Telecom Standard Product Data Sheet
Released
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