Specifications

Installation and Operation Manual Chapter 1 Introduction
MiTOP-E1/T1 Ver. 1.0 Functional Description 1-7
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
For CESoPSN encapsulation the number of TDM bytes equals to 31 (E1) or 24 (T1).
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: 8000 × k/n
Framed: 8000/ TDM frame
Where k = 32 (E1) or 24 (T1)
Where n = TDM bytes
The maximum Ethernet throughput is calculated by:
PCT
1
bits 8)
bytes) (in size frame
( ××++
444444344444421
payloadoverhead frameVLAN
Where:
• VLAN is an optional field: if enabled it adds 4 bytes to the frame overhead
• payload = number of TDM bytes in frame
• frame overhead = size of 46 bytes, include MAC, LLC, IP and UDP layer
The result is in bits per second (bps).
Timing Modes
Synchronization between TDM devices is maintained by deploying advanced clock
distribution mechanisms. The clocking options are:
• Loopback timing – the E1/T1 Tx clock is derived from the E1/T1 receive (Rx) clock
• Adaptive timing – the E1/T1 Tx clock is regenerated from the network packet
flow. Jitter and wander of the recovered clock are maintained at levels that
conform to G.823/G.824 traffic or synchronization interfaces.
• Internal timing – the Tx clock is derived from an internal oscillator.
In adaptive timing, the regenerated clock is subject to network packet delay
variation. That is why the quality of the adaptive clock depends on the quality of
the network.
Note
Note