How Can You Have QoS When…
Jennifer Rexford
AT&T Labs--Research
How Can You Have QoS When…
• A typographical error by a network
operator can bring down your service?
• Routing anomalies and slow convergence
might (temporarily) discard your traffic?
• You don’t know how to set the QoS
parameters and estimate your bill?
• You can’t tell who is to blame for the
QoS violation you have experienced?
A single typo can bring down your network?
• Router configuration problems
– Non-standard “assembly language” programming
– Configuring individual routers not a network
– Complexity in network protocols and mechanisms
• … lead to performance problems
– Human error responsible for half of outages
– Security holes, resource inefficiency
– Delay and cost in configuring and troubleshooting
• … and some research challenges
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Models of protocol configuration state
Codifying of best common practices
Tools for error checking and data mining
Systems for automated configuration
The routing system discards your packets?
• Routing problems
– Transient instability during routing convergence
– Blackholes, route hijacking, policy oscillation,…
– Congestion due to sub-optimal routing configuration
• … lead to performance problems
– Packets dropped, discarded, or out-of-order
– Forwarding loops consuming extra bandwidth
• … and some research challenges
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Faster data-plane convergence
Detection and diagnosis of anomalies
Checking of configuration errors and policy conflicts
Better traffic engineering and capacity planning
Customers don’t know what QoS params to select?
• QoS specification problems
– Don’t know the traffic mix by 5-tuple
– Can’t accurately map the 5-tuple to applications
– Can’t predict how much their bill will be
• … leads to slow QoS adoption
– Customers want QoS but can’t specify it
– Customers want QoS but are wary of their bill
• … and some research challenges
– Traffic measurement and characterization
– Digging below the 5-tuple in the IP/TCP header
– Mapping traffic classes into QoS classes
Customers don’t know who is to blame?
• Finger-pointing problem
– Hard to detect QoS violations
– Even harder to diagnose them
– Even harder to ascribe blame
• … leads to low end-to-end QoS adoption
– SLAs based just on basic availability
– SLAs only for “on net” traffic in one domain
• … and some research challenges
– Measurements for the finger-pointing problem
– Techniques for outsourcing the finger-pointing
to a third-party or the provider
Conclusion
• We need to solve these problems!