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Center for Applied Internet Data Analysis
FIX-West at Ames Research Center (ARC)

NLANR web caching hierarchy

FIX-West, at Ames Research Center (ARC), houses and helps support what has since project inception been NLANR's most popular root web cache, had a description of NLANR's caching hierarchy.

performance measurements

CAIDA intends to place an end-to-end performance testing box at Ames in late 1998.

flow stats collection

Back in 1995, we established the NLANR/Fix-West real time flow data web site ( - No longer available), which supported customized graphs through interactive CGI scripts. Unfortunately for the measurement availability, the exchange infrastructure at FIX-west has changed dramatically over the last two years, such that this monitoring machine is no longer on a facet of the FIX topology that carries any `interesting' traffic.

The wide-area traffic transiting the FIX now crosses an OC3 link and requires a special Coral OC3 monitoring device. Coral/OC3mon can collect summary traffic flow statistics in real-time, or collect short packet header traces for later in-depth analysis.

We have placed an OC3mon at FIX-west, which sits on one of the 4 OC-3 links between AIX (ARC) and MAE-west. Our Oc3mon is just on one of these four links, which all share traffic via the Digitial gigaswitch's load balancing techniques, which forestalls tight integrity of flow-based analysis/statistics.

In particular, when a packet arrives destined for a hunt group, it picks a hunt group member on which to attempt to transmit. If that member is busy (i.e., the crossbar is in use), it tries the next hunt group member, etc. The choice of initial hunt group member is essentially random, but not neccesarily evenly distributed. (so far as we could tell from the engineers we asked.) Definitely not round-robin or per flow or anything predictable. ...

6 may 98,
  Last Modified: Tue Oct-8-2019 11:21:11 PDT
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