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Emulab Documentation

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From: Jay Lepreau <lepreau>
To: planetlab-announce, emulab-users
Subject: [Planetlab-announce] Emulab interface to Planetlab, now in production
Date: Mon, 22 Sep 2003 12:02:30 MDT

Hello frantic NSDIers and PlanetLab users,

Thanks to those listed at the end of the message, PlanetLab vserver
VMs are now available as another device type in Emulab/Netbed.  We've
also added load-driven allocation with admission control.  Optionally
combined with Emulab's queuing facilities, that is useful for sharing
PlanetLab resources when they are scarce.  You might use the Emulab
interface to get the N least-loaded nodes that satisfy your optional
node type criteria, perhaps queuing your request until enough become
available, or simply to provide a richer and more friendly interface
to the nodes and your experiment.

[LATER NOTE: In contrast to our cluster support, our PlanetLab
support is not about topology: instead we provide you a bunch of
(v)nodes fully interconnected through the normal Internet.  We
don't provide tunnels or link emulation or topology emulation.]

Most of the normal Emulab facilities are now available to Planetlab
users.  Many of these features derive from creating more or less
first-class virtual nodes in each vserver, from having a first-class
notion of a dynamic slice (an Emulab "experiment"), the database, and
the Web interface.  The new backend includes a combination dslice
service manager and resource broker that are integrated with the
Emulab experiment lifecycle control flow, by extending Emulab's
existing support for wide-area and virtual nodes.


FEATURES of note include:
  -Request nodes by last-mile type, by specific physical node, or mixed.
  -For each vnode you get:
      Real Unix user accounts & pubkeys for everyone in your project
      Transparent ssh setup (on a per-vnode port)
      Optional loading of initial tarballs or RPMs
      Optional automatic startup of a command at vnode boot
      Liveness monitoring
      Your symbolic node name inserted into the global DNS
      Per-vnode port range allocation (by convention; not enforced)
      Automatic account update when project members join or leave
  -Reboot by vnode, or by entire experiment
  -Modification of existing experiments, including more or fewer nodes
  -Find new nodes to replace failed ones: 3 clicks
  -Optional max-duration after which resources are released (swapout)
  -Combine Emulab cluster nodes with PlanetLab nodes in same expt
  -Handy frills include 1 click ssh-in-xterm popup window to vnode.

It takes about 8 minutes to set up an 80 node experiment in a dynamic
slice if all nodes work; about 13 minutes if a few fail.  Despite a
fair amount of monitoring-- which we will improve-- many PlanetLab
nodes fail in unpredictable ways; we do a few retries, but you control
whether experiment creation proceeds despite some failures.

We classify Planetlab nodes into types according to their effective
"last-mile" link; you can request any Plab node or specific subtypes.
The subtypes currently are: Internet2 end hosts, North American
commodity Internet nodes, nodes outside North America, and DSL nodes.
Current counts:
 127  Any Planetlab node
   3 	Plab nodes on DSL lines
  12 	Plab nodes on the commodity Internet, in North America
  24 	Plab nodes outside North America
  88    Plab end-hosts on Internet2

Emulab currently finds the approximately least-loaded nodes with free
disk space that satisfy your type and usage specifications.  You
optionally specify your CPU and memory usage from 1 (very low) to 5
(very high), and Emulab uses that in selecting nodes, from load data
Ganglia provides every 5 minutes.  Overloaded nodes are not eligible,
thus providing admission control, but if you queue your experiment
allocation request Emulab will keep trying until nodes become
available, and then notify you by email.


HOW TO USE
1. Use the following heavily commented 'ns' file as a template; it's easy.
     http://www.emulab.net/tutorial/planetlab.ns
2. You need an Emulab account and be a legal PlanetLab user.  We
currently verify the latter manually via PlanetLab's list of PIs; you
don't need a Planetlab account.  Therefore, your Emulab project head
must be a PlanetLab PI or associated with them at the PI's
institution, and we must turn on that project's Plab-ok bit.  So
either have your PI or advisor start a new Emulab project or request
testbed-ops@emulab.net to set the bit for an existing project.  Like
any PlanetLab user, you of course must abide by the PlanetLab AUP.


CAVEATS
As nodes show up in planet-lab.org's dslice system, they are
automatically added to our DB, with their type heuristically intuited.
Many nodes do not successfully run (the deprecated) dslice or its
supporting programs, which is why we have only 127 right now.  Some of
of those are very flaky or down; at any time you will likely find a
useful set of 110-120.  When Tammo's new dynamic slice mechanism
becomes stable and replaces the partially deployed dslice, all useful
Planetlab nodes should become available through Emulab.
 
What we haven't (yet?) provided for these nodes that we do for our
other wide area nodes are SFS, tunneled overlays, and node selection
by best-matching paths.

Formal documentation is lacking.  Improvements in all areas will be
forthcoming; the load and type support, including the interface, is
crude and preliminary, but the system is working reasonably.  We
welcome any kind of comments, either to me or to testbed-ops@emulab.net.


THANKS
Many thanks to Brent Chun, especially, who is extremely prompt about
corresponding and fixing things-- he's a one man rapid-response team.
Thanks to Mic Bowman for his experienced advice about which PlanetLab
resources get scarce.  Thanks to Larry Peterson for getting the dslice
mechanism turned back on for awhile so we can provide this, to Tammo
for doing that, and to Larry and Dave Culler for encouraging us to
provide a place for PlanetLab users to queue their requests--
unfortunately I doubt we're in time for even the most desperate
NSDIers, but things will get tight again.

In the Emulab crew, the bulk of the thanks go to Austin Clements who
implemented most of the code last summer, and to Kirk Webb, Leigh
Stoller, Rob Ricci, and Mike Hibler, who did a whole lot more to
make this real and put it into production.


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