1. (bandwidth control) Jeff Boote Internet2
BWCTL
(bandwidth control)
Jeff Boote
Internet2
9 November 2018

2. What is it?
A resource allocation and scheduling daemon for arbitration of iperf tests
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3. Problem Statement
Users want to verify available bandwidth from their site to another.
Methodology
Verify available bandwidth from each endpoint to points in the middle to determine problem area.
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4. Typical Solution
Run “iperf” or similar tool on two endpoints and hosts on intermediate paths
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5. Typical road blocks Need software on all test systems
Need permissions on all systems involved (usually full accounts*)
Need to coordinate testing with others *
Need to run software on both sides with specified test parameters *
(* bwctl was designed to help with these)
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6. Functionality (bwctl)
Bwctl client application makes requests to both endpoints of a test
Communication can be “open”, “authenticated”, or “encrypted” (encrypted is reserved for future)
Requests include a request for a time slot as well as a full parameterization of the test
Current client is limited in that one of the endpoints must be the localhost, but the protocol is designed to support 3 parties
Same “basic” command line options as iperf (some options limited or not implemented.)
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7. Functionality (bwctld)
bwctld on each test host
Accepts requests for “iperf” tests including time slot and parameters for test
Responds with a tentative reservation or a denied message
Reservations by a client must be confirmed with a “start session” message
Resource “Broker”
Runs tests
Both “sides” of test get results
Can add a timeout so that “start session” message must be received within a given timeout to thwart DOS
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8. Scheduling
A time slot is simply a time-dependent resource that needs to be allocated just like any other resource.
Scheduling is therefore just an extension of the resource allocation model.
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9. Resource Allocation Model
Growing Spheres of control
Is the basic parameterization of the requested test allowed?
Does the bwctld have enough resources to allow test?
Does this host (possibly running other tools) have enough resources?
Does this <higher level…> have enough resources?
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10. Resource Allocation (bwctld)
At the bwctld level:
Each connection is “classified” (authentication)
Each classification is associated with a set of hierarchical limits
bwctld.limits
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11. Architecture
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12. Demo “mostly” same command-line as Iperf
-s and –c options take the remote host as an argument
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13. Abilene test points available
Policy is “in flux”
Unclear what resources to allocate to each group
Unclear how “limited” resources will be
Basic Steps:
Locally tested bwctl (key based authentication)
Registration of key with Abilene
“For now”
Run tests and collect data!
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14. Specific difficulties
UDP
Iperf doesn’t always send at requested rate
Iperf sender hangs (likely Linux/iperf interaction – could be due to signal handling of the bwctl level)
End of session is difficult to detect, which is problematic for a “scheduled” timeslot
Iperf sometimes takes large amounts of time to finish
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15. Specific difficulties
TCP
Large pipe to small pipe
Launch a large window
Test waits until completion
Terminate test to remain within schedule
Þ Sets of incomplete tests to interpret
Multiple test points with very different delays presents difficulties for window size selection (and other path specific characteristics)
bwctl uses the peer to peer server connection to deduce a “reasonable” window
If at all possible path specific parameters need to be dynamically configured
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16. Future Steps Server-less client side for end hosts
Integrated tester (based upon Thrulay)
3-party tests (client not on one of the endpoints)
Integration with “standard” authentication services
Open source development
Thrulay is a tool being developed by Stanislav Shalunov that combines achievable bandwidth and rtt delay.
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17. Availability http://e2epi.internet2.edu/bwctl/
Beta version currently available
Mail lists:
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18. 11/9/2018