Installation and Operation Manual Chapter 1 Introduction
IPmux-11 Ver. 2.00 Functional Description 1-13
Configuring the TDM bytes per frame (TDM bytes/frame) parameter has impact on
the 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 × 48 bytes where N is an
integer between 1 and 30.
To calculate Ethernet throughput as a function of TDM bytes/frame:
Ethernet load (bps) = [(frame overhead (bytes) + TDM bytes/frame) × 8] ×
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 × k/(46.875 x n)
Where k = number of assigned timeslots
Where n = 48
ebytes/framTDM
The maximum Ethernet throughput mode is calculated by:
Unframed bits 8*
n*47
data
TS*8000
*)
size frame
(
⎪
⎪
⎭
⎪
⎪
⎬
⎫
⎪
⎪
⎩
⎪
⎪
⎨
⎧
++
48476
44444443444444421payloadoverhead frameVLAN
Framed bits 8*
n*47
2
*500
pointer
1- 8)*(47
*8000
data
TS*8000
* )
size frame
(
⎪
⎪
⎪
⎭
⎪
⎪
⎪
⎬
⎫
⎪
⎪
⎪
⎩
⎪
⎪
⎪
⎨
⎧
⎥
⎥
⎤
⎢
⎢
⎡
++
++
48476
48476
48476
44444443444444421
CAS
TSTS
payload overhead frameVLAN
Note