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ATM vs frame relay

Short answer

ATM uses fixed 53-byte cells with VPI/VCI identifiers, offering high speeds (155 Mbps+), predictable delay, and QoS classes. Frame relay uses variable-length frames, DLCI, lower speed. ATM advantages: integrated voice/video/data, guaranteed QoS, scalable. Disadvantages: 9.4% cell tax, segmentation overhead, complexity, higher cost.

How does ATM differ from frame relay? What are the advantages and disadvantages of ATM compared to frame relay?

ATM (Asynchronous Transfer Mode) is a cell-switching technology that uses fixed-size 53-byte cells (5-byte header + 48-byte payload) over virtual circuits identified by VPI/VCI. Frame relay uses variable-length frames and DLCI.

Differences

PointATMFrame relay
Data unitFixed 53-byte cellVariable frame (up to ~1600 B)
Speed155 Mbps, 622 Mbps and more56 kbps to 45 Mbps
IdentifierVPI/VCIDLCI (10 bits)
QoSClasses CBR, VBR, ABR, UBROnly CIR and DE bit
TrafficVoice, video and dataMainly data
DelaySmall and predictableVariable
LayerOwn layers (AAL, ATM)Data link layer
CostHighLower

Advantages of ATM

  • Very high speed, easy hardware switching due to fixed cells.
  • Small, predictable delay and jitter, good for real-time voice and video.
  • Guaranteed quality of service.
  • One network for voice, video and data; scalable.

Disadvantages of ATM

  • Cell tax: 5 of 53 bytes (about 9.4 %) are header overhead, and padding of partly filled cells.
  • Segmentation and reassembly of packets (AAL) adds complexity and delay.
  • Expensive equipment and complex management.
  • Less suited to bursty LAN data than frame relay or Ethernet.

✓ Answer checked by Claude Sonnet 5.5

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