Transcript Jon Crowcroft, Cambridge

TAPAS
Cambridge Computer lab
Jon Crowcroft
2nd Feb, 2004
2.2.2004
UCL
TAPAS meeting
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Agenda
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2.2.2004
Background to Networks
Transport SLAs - Transport Options
Monitoring
Multicast
Admin
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TAPAS meeting
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Transport
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IP QoS understood
Residual QoS seen by Transport
Idea of TCP and TCP-Friendly SLA
Driven by Equation (loss/delay)
Relates to typical IP level SLA in “BE”
Can request better or worse!
Ah but what about Multicast…
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TAPAS meeting
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Assurance needs monitoring
• Cost of freedom is eternal vigilance
• Cost of being charged for SLA is…eterna
vigilance:-)
• Need to do more here - but see staff!
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Multicast - protocol and sla
• IP multicast SLAs exist, but rare
• Most talk about service existence, not
performance related
• Agreed with UCL (for now) assume N*M
unicast SLAs ok…(note though failures not
independent)
• Work to proceed on multicast containers
etc
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TAPAS meeting
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D8:container for group
communication
• QoS enabled group communication
– Software deliverable -> Expect to implement M 1-to-N
multicast sessions (I.e. not many to many - note IP
mcast now PIM-SSM favoured anyhow)
• IP Multicast has similar QoS to unicast
• Lack of independence of failurebut even so have
independent failures too => need to monitor as much
about receiver members individually as the receiver group
set
• Cambridge has built a multicast version of TCP
• Seems UCL SLAng framework is fine then!
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Group Trust
• Key Distr for groups a hard problem:
• Forward and backward privacy requires
re-keying when receiver join and leave
• Don’t get much gain over N*M (see Perrig
et al for trees of 1-way function, but needs
“network” support - if implemented in endsystem-only, then this simply makes no
sense • Seems to mitigate against using 1-N even!
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Admin
• Panos->Dresdner Bank :-(
– S/Panos/Michael Dales :-)
– Michael was post-doc at Glasgow…worked on
nemesys (QoS enabled OS
– Arrived in Cambridge today!
• Publications:–
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2.2.2004
Transport options in Comnet journal
contrib to ncl on sla for be
mcast
bologna on m/w
UCL
TAPAS meeting
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