
DS34S132 DATA SHEET
19-4750; Rev 1; 07/11
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but is generally not important to consider since its impact is only during the “start-up” of a TDM Line.
Table 9-7. Maximum S132 Ethernet Media PDV
Maximum Number
of Bundles
Packet Size for 100 Mb/s Interface
Packet Size for 1000 Mb/s Interface
64 Bytes
193 Bytes
1500 Bytes
64 Bytes
193 Bytes
1500 Bytes
32 Bundles
0.215 ms
0.663 ms
3.89 ms
0.0215 ms
0.0663 ms
0.389 ms
256 Bundles
1.73 ms
5.30 ms
31.1 ms
0.172 ms
0.530 ms
3.11 ms
As depicted in
Table 9-7, the S132 Ethernet media interface (MII/GMII) can introduce a high PDV level with
systems that have a high number of Bundles when using the 100 Mb/s interface and a large packet size. Most
applications will want to minimize delay. The S132 Ethernet Media PDV parameter can be minimized by using
smaller packet sizes and the 1000 Mb/s Interface. A TXP Bundle that is used for Clock Recovery at the far PW End
Point should be programmed for S132 high priority TXP processing (B.BCDR3.TXBPS). If only one TXP Bundle
from each receive TDM port is programmed for high priority, then each high priority TXP Bundle will not be delayed
by more than 31 other Bundles (no more than one Bundle for each of the other enabled TDM Ports).
The following provides an example set of assumptions for a T1-SAT PW:
Ethernet Media PDV
Packet Payload size = 193 bytes (PCT = 1 ms)
MPLS Header size with 2 MPLS Labels, Control Word, RTP Headers and 4-byte Ethernet FCS = 46 bytes
Ethernet Media Type = 100 Mb/s
Maximum PW Bundles (not including OAM Bundles) = 32
Ethernet Media PDV = [# Bundles * (# bytes per pkt + 20 byte IPG) * 8 bits/byte] ÷ line rate
Ethernet Media PDV = [32 * (193 + 46 + 20) * 8b] ÷ 100 Mb/s = [32 * (259 * 8b)] ÷ 100 Mb/s = 660 us
Scheduling PDV
The scheduling PDV is assumed to be “hidden” by the Ethernet Media PDV and can be ignored.
BFD PDV
RXP & TXP BFD settings = 125 us (in each direction)
MTIE PDV
The startup MTIE is assumed to be insignificant except at startup.
Total PDV
Total PDV = Network PDV + Ethernet Media PDV + Scheduling PDV + TXP & RXP BFD PDV + MTIE PDV
Total PDV = Network PDV + 660 us + (125 us * 2) = Network PDV + 910 us
The S132 can support up to 500 ms of packet Jitter (PDV) for up to 256 Bundles (one Jitter Buffer is provided for
each Bundle). In most cases, however, the PDV of a network will be limited to a much smaller value like 10 ms. The
Jitter Buffers for all Bundles are located in a single block of memory that begins at the SDRAM address specified by
G.BMCR2.JBSO. The Jitter Buffer memory block is divided into equal sized Jitter Buffer FIFOs according to the
G.GCR.JBMD setting (one FIFO per Bundle; JBMD sets the depth for all Jitter Buffer FIFOs to 32 Kbyte, 64 Kbyte,
128 Kbyte or 256 Kbyte).
The Maximum PDV that each Jitter Buffer can support can be determined according to the equation below. The
“Register Guide”, “SDRAM” subsection includes a table (based on this equation) that describes the “Maximum
PDV” each Jitter Buffer can store for various combinations of PCT, JBMD and “maximum Timeslots in a Bundle”.
Max PDV in ms = Integer(([Roundup((JBMD in bytes) – 2048) ÷ ((PCT in ms / 0.125) + 4)) + 1] * PCT in ms) ÷ 2)
where the “Roundup” function provides the next higher integer value for non-integer numbers
In addition to the global Jitter Buffer settings (JBSO and JBMD) there are two Jitter Buffer settings for each Bundle
to program the Bundle’s Jitter Buffer Playout Watermark (B.BCDR5.PDVT) and Jitter Buffer Overrun Watermark
(B.BCDR5.MJBS).