Specifications

IPmux-4 Installation and Operation Manual Chapter 1 Introduction
Functional Description 1-13
Ethernet Throughput
Configuring the TDM bytes per frame (TDM bytes/frame) parameter can reduce
Ethernet throughput (bandwidth or traffic traveling through the Ethernet). This
parameter controls the number of TDM bytes encapsulated in one frame. The
TDM bytes/frame parameter can be configured to nX48 bytes where n is an
integer between 1 and 8. Configuring TDM bytes/frame to a higher value reduces
the IP/Ethernet overhead segment of the total packet and thus can significantly
reduce the total Ethernet throughput.
On the other hand, packetization delay and intrinsic packet delay variation (PDVT)
are increased and this contributes to a higher end-to-end delay. This effect can be
small and negligible when a full E1 (or many timeslots) are transferred but can be
very significant when few E1/T1 timeslots are transferred. In this case, the
packetization delay and the intrinsic PDV when configuring a large value of TDM
bytes / frame can be very large and may exceed the maximum PDVT (jitter) buffer
on the receiving end. The tables below show the throughput as a function of the
TDM bytes/frame configuration for a full E1 and a full T1.
Due to a limitation of IPmux-4, when configuring it to operate at TDM bytes/frame
values which are >288, a single packet loss (in the IP network) will cause the jitter
buffer to be flushed, so that he whole buffer contents will be lost. Thus, it is
recommended to use values that are
≤
288.
Table 1-4. Ethernet Throughput – Unframed E1
TDM
bytes/frame
Frame
Length
(bytes)
Overhead
(bytes)
Overhead*
(%)
Packets
per
Second
Throughput
(Mbps)
48 94 46 96 5447 4.1
96 142 46 48 2724 3.1
144 190 46 32 1816 2.76
192 238 46 24 1362 2.6
240 286 46 19 1089 2.5
288 334 46 16 908 2.43
336 382 46 14 778 2.38
384 430 46 12 681 2.34
*
100x
)Frame/Bytes(TDM
)bytes(Overhead
(%)Overhead =
Note
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