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University of Kansas

Telecommunications & Information Sciences Laboratory

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AAI Maximum Throughput Experiments

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Abstract

These experiements illustrate that with the proper cell-level flow control, close to full utilization of the 45 Mb/s DS3 WAN links of the AAI can be attained.

KU/GSFC Throughput Results

In these experiments, DEC Alpha workstations at the University of Kansas (KU) and at NASA Goddard Space Flight Center (GSFC) were configured with DEC ATM interfaces, with virtual circuits routed from GSFC over ATDnet, the AAI, and MAGIC to KU. These experiments used a TCP window size of 208 kB, an IP MTU size of 9180 bytes, and an application write buffer size of 64 kB. The round-trip time between KU and UT-ARL was 36.3 ms. LLC encapsulation of AAL5 PDUs was used for these experiments. We were able to get extremely close to the application throughput limit for ATM over DS3 (34 Mb/s), as shown below.

Experiments

Source Destination Pacing Throughput Cell Losses
mauchly.ukans.aai.net cobra.nasa.atd.net 45 Mb/s 33.77 Mb/s 0% (1)
cobra.nasa.atd.net mauchly.ukans.aai.net - 27.29 Mb/s 0% (2)

Comments

  1. numerous packet errors observed with pacing above this level
  2. occasional packet errors observed (10 per 30 seconds), no pacing

Workstation Information

Host Type OS Interface
mauchly.ukans.aai.net DEC AXP 3000/400 OSF/1 v3.0 DEC OTTO OC-3c ATM interface
cobra.nasa.atd.net DEC AXP 3000/400 OSF/1 v3.2 DEC OTTO OC-3c ATM interface

Acknowledgements

We appreciate the efforts of Javad Boroumand, Suresh Bhogavilli, and Gary Veum at NASA Goddard Space Flight Center in helping to configure and execute these tests.

KU/UT AAI Throughput Results

In these experiments, a DEC Alpha workstation at the University of Kansas (KU) and an SGI workstation at the University of Texas Applied Research Lab (UT-ARL) were configured with OC-3c ATM interfaces, with virtual circuits over the AAI and MAGIC to KU. These experiments used a TCP window size of 256 kB, an IP MTU size of 9180 bytes, and an application write buffer size of 64 kB. The round-trip time between KU and UT-ARL was 35 ms. Null encapsulation of AAL5 PDUs was used for these experiments. We were able to get extremely close to the application throughput limit for ATM over DS3 (34 Mb/s) in this case as well, as shown below.

Experiments

Source Destination Pacing Throughput Cell Losses
mauchly.ukans.aai.net psicorp.utexas.aai.net 45 Mb/s 33.34 Mb/s 0% (1)
psicorp.utexas.aai.net mauchly.ukans.aai.net - 33.80 Mb/s 0% (2)

Comments

  1. numerous packet errors observed with pacing above this level
  2. no packet errors were observed due to packet pacing from processing limitations (speculation)

Workstation Information

Host Type OS Interface
mauchly.ukans.aai.net DEC AXP 3000/400 OSF/1 v3.0 DEC OTTO OC-3c ATM interface
psicorp.utexas.aai.net SGI Indigo2 (200Mhz) IRIX 5.3 Fore ESA-200 OC-3c ATM interface
ForeThought_3.0.1b driver

Acknowledgements

We appreciate the efforts of Lenny Tropiano at the Applied Research Lab at the University of Texas in helping to configure and execute these tests.