Internet Info 1997 December/Internet_Info_CD-ROM_Walnut_Creek_December_1997.iso/ietf/93mar/mbone-minutes-93mar.txt

Text File | 1993-05-13 | 12KB | 303 lines

CURRENT_MEETING_REPORT_


Reported by Matt Mathis/PSC

Minutes of the MBONE Engineering and Operations BOF (mbone)

IETF Organizational Discussion

We debated the need for a formal MBONE Working Group.  This requires
someone to volunteer to be the Chair and to draft a Charter.  After some
inconclusive discussion it was observed that no one was willing to
volunteer.  The people present were mostly network operators who are
participating in the mbone.  Unfortunately a number of network operators
who feel victimized by the mbone were not present.

General Issues


   o We must balance the risk:  The Mbone is dangerous, but the
     applications are very useful, and may drive the next generation
     Internet technology.

   o Critical problems are largely due to the lack of tools to manage
     the mbone.

   o There are at least three constituents in the Mbone/multicast
     community:  Network operators, who are providing the mbone core (at
     least in the NSFnet context), network subscribers, who are
     typically mbone stubs and finally, mbone end users.  There was
     considerable discussion about these groups, and their identity.
     These three groups have substantially different cultures,
     approaches to problems and worries.

      -  The network operators have a service oriented perspective and
         an intimate understanding of the underlying topology.  Almost
         all of the people present were network operators.

      -  The subscribers are typically researchers who want mbone
         connectivity but are not really interested in the details.
         They usually operate stub tunnels to connect campuses into the
         mbone.

      -  The mbone end users are most likely applications developers or
         true users, and use local area multicasting to reach a
         subscriber tunnel.  This community is likely to have no
         knowledge about operational details of the mbone.

      -  [I have since realized that there are a number of core mbone
         hubs which are managed by multicast researchers on the premises
         of a network operator, with only minor supervision by the

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         operator.  This straddles the operator/subscriber distinction
         above.]


   o We discussed the mbone mailing list.  Some people wanted to split
     the mailing list such that operators could have candid discussions
     about debugging without kibitzing from overzealous users.  The
     consensus was not to make any changes and use the mbone list as it
     stands.

   o The hypothetical problem came up about a subscriber who was not
     getting satisfactory service from his network operator.  Would
     operators support tunnels into other regionals?  The Group was
     unanimous that this is a bad practice, and shouldn't be allowed.
     Furthermore, subscriber to subscriber tunnels are even worse, and
     the operators should not to provide such poor service that their
     subscribers resort to such tactics.  There was some discussion of
     the business implications to network operators.

   o We discussed the new encapsulated tunneling code.  The original
     code is a seriously bastardized use of LSRR. The new mrouted
     supports both, defaulting to encapsulation.  Use the ``srcrt''
     directive in mrouted.conf to get LSRR. Matt pointed out that those
     who most endanger the rest of the Internet were also those who
     didn't require the new encapsulation code for performance.  A long
     discussion of capabilities ensued.  One salient point was that the
     LSRR code seriously violates the IP specifications.  There was talk
     of adding clean source routing options to the encapsulating code
     such that network operators could prevent tunnels from moving to
     fall back infrastructure during network failures.  This would cause
     multicasting load to be shed during failures of primary IP
     connectivity.


Most of the rest of the meeting was spent drafting a wish list.  Some of
the items are appropriate for a future meeting of this BOF or Working
Group.  Other items are appropriate for specific groups or projects
involved in multicast research.  The items are ordered by priority
within each section, but the sections are independent of each other.
Throughout the discussion it was understood that resources are tight,
and in many cases we were asking people to contribute effort without
additional support.

Items for Network Operators or Some Future Mbone Working Group


   o Put more pressure on router vendors to provide implementations that
     perform well with LSRR.

   o Generate an mbone operational guidelines document.  This could be
     started by splitting the existing FAQ document into separate user
     and operator documents.

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   o Explicitly engineer the mbone topology, metrics, and thresholds.
     This is a daunting task with insufficient tools or poor knowledge
     of the actual Internet topology.

   o There needs to be a global policy on bandwidth budgeting and
     allocation.  The mbone is currently a single global resource, and
     must be allocated as such.  Sometimes there will be two groups with
     legitimate reasons to do multichannel world-wide multicasts, and
     there must be some mechanism to arbitrate between their needs.


Infrastructure Tools, to Help Engineer and Operate the Mbone Itself


   o Three different Mapping tools:

      -  A configuration map which shows all configured tunnels, even if
         they are not ``up'' - to discover configuration anomalies.
      -  A tunnel map (done:  Pavel Curtis's tool)
      -  A flow map, showing the distribution tree for an arbitrary
         transmitter.

   o Alarms that can be triggered by excessive mbone traffic, such that
     sites with large pipes can protect the rest of the Internet.

   o A ``tunnel trap'' to detect unauthorized (e.g., client-to-client)
     tunnels passing through a regional.  Several algorithms were
     discussed.

   o Snmp/opstats style tools for logging load (traffic) levels.

   o Map Tracing - proxy IP traceroute along tunnels to detect when they
     share the common infrastructure.

   o Traceroute (follow the path from the transmitter to a receiver) -
     deemed to be almost the same as the flow map but not as useful.  (A
     Flow map gives the entire flow topology.)


Transport tools, to Verify, Monitor and Diagnose Signal Quality

These should use the Audio Video Transport protocol (AVT) directly
without specific knowledge of the applications, except to mimic
aggregate traffic statistics.  All should be supported on all platforms
supporting mrouted.  (Not just the platform supporting some particular
application).


   o Signal quality meters - To display packet loss and delay statistics
     throughout the distribution tree.  It is critical that this tool

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     run on every mrouted platform.

   o (Talk) Spurt correlated signal quality - Display packet loss and
     delay statistics correlated with the start of talk spurts - to
     detect interactions due to competition between the mbone and other
     Internet traffic.  (TCP congestion avoidance takes one round trip
     time to back off, so congested links are often late/lossy during
     the initial second of a talk spurt).

   o Basic test generator - generate traffic streams to mimic the 1st
     order statistics of the more popular applications (Correct average
     packet rate and size).  Again it is important that this tool not
     require the actual transmitting platform, because the lead time to
     acquire the transmitters has historically prevented the IETF
     multicasts from being tested in advance.

   o Modulation test generator:  Transmit 5 second bursts (``spurts'')
     of the above generator separated by 5 seconds of silence,
     synchronized with GMT. This can be used to detect many different
     problems using clock based monitors.  It is important that the
     generators be (roughly) synchronized so this technique can be used
     with an entire suite of sources.  A typical use might be to emulate
     up to two video and two audio sources for an IETF, and correlating
     network events, such as device errors and ethernet collision rates,
     against the clock to determine if the mbone is causing a particular
     problem.


Applications which do not use AVT should have their own set of the above
tools.

It is imperative that the majority of these tools run on all mrouted
capable platforms.  It is currently very difficult to sectionalize
distribution problems on paths through multiple mrouted tunnels that are
incapable of running the specific applications.

Mrouted/tunnel Implementation Features


   o Encapsulated tunnels (already done)

   o Support for ``on demand'' host tunnels, such that mrouted can be
     used as a reflector for hosts that don't support multicast, such as
     Mac's.  (This isn't really high priority, but it is relatively easy
     to implement).

   o Implement pruning.  Currently all multicast traffic goes to all
     tunnel connected nodes within the TTL limit, even if there are no
     listeners.  Note that TTL mechanism is still needed because pruning
     is not fast enough to protect slow links.

   o Implement aggregate packet rate and bandwidth limits, to protect

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     the underlying IP infrastructure from being flooded.

   o The routing protocol, DVMRP, should use the same tunnels as the
     data to prevent the situations we see today where the unicast
     routing can follow some path, but the data can not.  DVMRP sees the
     tunnel as up but all of the data is discarded.

   o Support LSRR on encapsulated tunnels, so tunnels can be anchored to
     specific IP infrastructure.

   o Correct/work around the BSD bug which prevents DVMRP from asserting
     the source address of a tunnel on a multi-interfaced host.  This
     causes IP routing to break tunnels when they move to other
     interfaces because the other end does not recognize the source IP
     address.  [A possible solution, which also partially addresses the
     tunnel anchors, would be to specify the first hop address and have
     mrouted install static host routes for tunnels.]

   o Mrouted support for traceroute and mapping infrastructure tools.

   o There needs to be a logging facility/level for monitoring DVMRP
     routing problems.  Such a facility would report tunnel up/down
     events and routing table changes.


Steve Deering was present and both contributed and noted our comments.

The wish lists were presented to both the AVT Working Group and to the
Operational Requirements Area Directorate (ORAD). There was general
agreement that the items on the wish list are desirable and appropriate,
but nobody agreed to implement anything.

There were some network operators present at the ORAD meeting who were
upset that the MBONE BOF did not become a working group or take stronger
positions regarding operational practices.  However most of these people
were operators who had chosen not to participate in the mbone, and were
therefore not in control of its impact on their own facilities.

Thanks to Jamshid Mahdavi for taking the Minutes.  It should be noted
that the attendee list below was reconstructed after the fact and may
not contain the names of all participants.

Attendees

Erik-Jan Bos             [e-mail]
Douglas Carson           [e-mail]
Henry Clark              [e-mail]
Steve Deering            [e-mail]
Dale Finkelson           [e-mail]
Eugene Hastings          [e-mail]
Daniel Long              [e-mail]
Bill Manning             [e-mail]

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Matt Mathis              [e-mail]
David O'Leary            [e-mail]
Curtis Villamizar        [e-mail]
Linda Winkler            [e-mail]
Paul Zawada              [e-mail]



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