Introduction
In response to a reported performance problem between SSRL and ANL reported by Brian Kobilka's group, Phil Reese of Stanford campus looked at the perfSONAR Bwctl (iperf) plots shown below.
Stanford to ESnet at Sunnyvale | Denver/ESnet to Stanford | Chicago/Esnet to Stanford | ANL/ESnet to Stanford |
|---|---|---|---|
| | | |
It is seen that as the distance from source to Destination increases, the asymmetry between the two directions also increases. This could be due to loss in one of the paths (the one to Stanford). Any loss can dramatically degrade performance. See for example:
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...
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- The
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- following
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- graph
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- might
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- be
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- useful:
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- it
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- shows
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- the
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- random
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- loss
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- rate
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- affect
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- on
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- tcp
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- flavors
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- across
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- a
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- dummynet
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- on
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- a
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- 250mbps
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- link
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- (this
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- was
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- before
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- gig-e
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- was
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- common
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- place).
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- 162ms.
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- Single
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- tcp
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- flow.
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- The
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- full
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- analysis
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- available
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- at
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- (~pp152).
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- warning:
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- long
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- and
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- arduous
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- content
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- !
- Also see the ESnet presentation at TERENA 2013 , in particular slides 22 onwards
Seen from ANL
From Phil Reese:
Poking at the other end, I found another perfsonar at ANL collecting throughput traffic back toward the west cost. See anlborder-ps.it.anl.gov
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and
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look
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at
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the
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throughput
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graphs
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available
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there.
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From
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those,
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it
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seems
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like
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there
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is
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symmetry
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to
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Kansas
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at
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least
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but
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then
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it
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degrades
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as
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the
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route
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moves
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further
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west.
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From
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Stanford,
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we
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are
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primarily
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an
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I2
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site
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but
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it
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looks
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like
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once
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we
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get
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into
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the
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CENIC
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world,
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there
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is
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a
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blending
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of
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routes
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between
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I2
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and
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ESnet.
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Not
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sure
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if
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that
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is
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a
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problem
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or
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not.
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