Specifications

Chapter 1 Introduction Installation and Operation Manual
1-18 Functional Description IPmux-24 Ver. 1.5
SAToP
PCT (ms) =
TS
0.125N ×
N – Number of TDM bytes in packet
TS – Number of timeslots in one frame (32 for E1 or 24 for T1)
Round Trip Delay
The voice path round-trip delay is a function of all connections and network
parameters.
(±2 msec) RT Delay
(msec)
= 2 × (PCT + Jitter Buffer Level) + network round trip delay
Ethernet Throughput
Increasing payload size reduces the ratio between the TDMoIP/IP/Ethernet header
segment in the packet and the payload, thus reducing the total Ethernet
throughput.
On the other hand, packetization delay is 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.
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.
³ 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 (IP) = Ethernet overhead + IP overhead = 46 bytes
Frame overhead (MPLS) = Control Word + MPLS overhead + Ethernet overhead =
22 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 × n)
Note