Specifications

IPmux-11 Installation and Operation Manual Chapter 1 Introduction

Functional Description 1-11

Ethernet Throughput

Increasing payload size reduces the ratio of the TDMoIP header segment in the

packet, thus significantly reducing the total Ethernet throughput

Increased payload 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; 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 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.

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 N x 48 bytes where n is an

integer between 1 and 30.

 To calculate Ethernet throughput and intrinsic PDV as a function of

TDM bytes/frame:

Ethernet load (bps) =

[(frame overhead (bytes) + TDM bytes/frame) x 8] x frames/second

Frame overhead = Ethernet overhead + IP overhead = 46 bytes

The frame overhead does not include:

• Preamble field: 7 bytes

• SFD field: 1 byte

• Interframe gap: 12 bytes

• VLAN field (when used): 4 bytes.

Frame/second =

Unframed: 5447/n for a full E1

4107/n for a full T1

Framed: 8000 x k/(46.875 x n)

Where k = number of assigned timeslots

Where n =

ebytes/framTDM

Note