Log for
電訊台
VPWS with Smart SFP
The TDM circuits flows through the VPWS with smart SFP packetizing the incoming TDM frames. Packetizing happens with the following process:
All frames from the TDM lines are channelized until E1 and then packetized.
The packetization is done by adding:
RTP header – For DCR clocking support
VLAN header – For uniquely identifying the E1 channel
ENET header – The Ethernet DMAC and SMAC
CW – control word for communicating the sequence number, faults in the access side
Payload – the incoming TDM frames are chopped into 193Bytes frames and added into the payload.
The packets mentioned previously sent to the NPU.
The E1 channel is mapped into a sub-interface (with specific VLAN).
The packets received into the NPU with that specific VLAN number go through the VPWS logic and gets pseudowired (xconnected) with the configuration in a specific sub-interface.
QOS configured under the sub-interface gets applied to this PW.
宜家可以做到直接用 Smart SFP 黎將舊 circuit 當 Ethernet 咁 send……
Adaptive Clock Recovery (ACR)
Adaptive Clock Recovery (ACR) is an averaging process that negates the effect of random packet delay variation and captures the average rate of transmission of the original bit stream. ACR recovers the original clock for a synchronous data stream from the actual payload of the data stream. In other words, a synchronous clock is derived from an asynchronous packet stream. ACR is a technique where the clock from the TDM domain is mapped through the packet domain. ACR is supported on only framed Smart SFP.
Differential Clock Recovery (DCR)
Differential Clock Recovery (DCR) is another technique used for Circuit Emulation (CEM) to recover clocks based on the difference between PE clocks. TDM clock frequency are tuned to receive differential timing messages from the sending end to the receiving end. A traceable clock is used at each end, which ensures the recovered clock is not affected by packet transfer. DCR is supported on only framed Smart SFP.
Data city is Singapore, Family office is HK 😁
Changi Business Park好似都滿了