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Newsletter: Delay Emulation for Packet over SONET and ATM

Welcome to another February 2013 issue of GL Communications' Newsletter providing information into our new Packet Delay Network Emulator application for our LightSpeed1000™ product. This hardware/software provides full duplex delay emulation for PoS and ATM based traffic from 1 ms to 500 ms. Data rates for OC-3/12 and STM-1/4 are supported.

LightSpeed1000™ Packet/Cell Delay


Voice, data, and video traffic is exploding as smartphones, IP TV, video streaming, and "cloud" based services takeoff. A majority of the backbone transport for these applications continues to be SONET and SDH optical transmission. A dominant protocol for IP transport is PoS (Packet over SONET) and another is ATM (Asynchronous Transfer Mode). Both schemes are packet based, with ATM using fixed size packets of 53 bytes called "cells", and PoS using variable packet sizes closely matching to Ethernet frames. See PoS frame format. See ATM frame format.

Both technologies can and often do coexist in a network. ATM switches often aggregate cell traffic in the access area (from DSL lines) and PoS is used more frequently in the core network for high speed transport, due to better efficiency. Core Routers, DSLAMs, Edge Routers, and User applications over such hybrid networks will benefit from lab testing and verification before deployment.

GL's LightSpeed1000™ hardware platform (PCIe Card) is capable of OC-3/12 and STM-1/4 Wire-Speed Processing on Dual Optical Ports for such functions as wire-speed recording and wire-speed playback. Normally, the LightSpeed1000™ is used for protocol analysis of ATM, PoS, Raw unchannelized and unframed data, and Ethernet traffic at IP, UDP, and higher layers. The hardware can be easily configured / programmed for delaying of ATM cells or PPP packets. In this mode, the user can:

  • test the impact of delay and congestion under various real world conditions,
  • assess impact of delay on SLA (Service Level Agreements),
  • simulate satellite delay and long Fiber Loops
  • test WAN application performance under deteriorated but repeatable conditions
  • packet / cell out of sequence, duplication, errors, and drop are features that will be added in future releases

Other Key Features

Packet Delay Network Emulator feature combines hardware and software based functions to achieve precision and flexibility. Delays are programmable from 1 ms to 500 ms with incremental delays of 1 ms. SONET/SDH overhead, scrambling, HDLC processing are terminated on the receive side and regenerated on the transmit side. PPP frames are removed from the payload, time stamped and store and forwarded based on user delay settings. ATM cells are similarly store and forwarded. Flags and idle cells are inserted as appropriate in the output stream. The Packet Delay Network Emulator is transparent to higher layer protocols above ATM and PoS. A simple GUI allows user modification of delay and port settings.

For comprehensive information on the Packet Delay Network Emulator application, please visit OC3/12 STM1/4 Delay Emulation web page.

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