RAD Data comm IPmux-11 - Manual (Page 27)

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) Ч 8] Ч
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
e bytes/fram TDM
The maximum Ethernet throughput mode is calculated by:
Unframed
bits 8 *
n * 47
data
TS * 8000
* )
size frame
(
⎪
⎪
⎭
⎪⎪
⎬
⎫
⎪
⎪
⎩
⎪⎪
⎨
⎧
+ +
48 47 6
4 4 4 4 4 4 4 3 4 4 4 4 4 4 4 2 1
payload overhead frame VLAN
Framed
bits 8 *
n * 47
2
* 500
pointer
1 - 8) * (47
* 8000
data
TS * 8000
* )
size frame
(
⎪
⎪
⎪
⎭
⎪
⎪
⎪
⎬
⎫
⎪
⎪
⎪
⎩
⎪
⎪
⎪
⎨
⎧
⎥⎥
⎤
⎢⎢
⎡
+ +
+ +
48 47 6 48 47 6
48 47 6
4 4 4 4 4 4 4 3 4 4 4 4 4 4 4 2 1
CAS
TS TS
payload overhead frame VLAN
Note