TRAFFICDRIVEN OPTIMIZATION OF ROUTING FOR METROPOLITAN ETHERNET NETWORKS

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TRAFFIC-DRIVEN OPTIMIZATION OF ROUTING FOR
METROPOLITAN ETHERNET NETWORKS

• András Kern, Tibor Cinkler, István Moldován

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Ethernet in Metro Access Networks

• Ethernet is the most dominating LAN technology
• Cheap equipment high speed (up to 10 Gbps)

• Introduce Ethernet into the Metro network (Metro
  Ethernet Forum)
• consistent network platform

• Ethernet should be Carrier Grade
• Traffic separation
• QoS
• Operation, Administration Management
• Reliability
• Scalability

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Routing in Ethernet Spanning Trees Protocols
(STP)

• Spanning Trees form loop-free logical topologies
• Their shape influenced by Port Costs
• Provide restoration

• MORE VLAN based spanning trees
• Multiple spanning tree instances
• Each tree runs a separate Rapid STP instance
• 1 VLAN ? 1 tree

• By default tree spanning is Topology-Driven
• Port costs based on topology and link capacities
• Costs can be set manually (to obtain desired
  trees)

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Resilience

• MSTP supports restoration
• Does NOT consider either QoS or bandwidth reqs. ?
  may harm them.
• Protection at Ethernet level
• Ethernet Protection Switch (EPS)
• VLAN switching
• 2 VLANs one for working one for backup
• After link failure switch to backup VLAN
• Supports QoS and bandwidth reqs.!!!!

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Quality of Service

• Priority based scheduling
• Lower priority traffic is not served until there
  is higher priority traffic in the queue.
• To ensure low delay for each QoS classamount of
  higher priority traffic should be limited for
  each link
• For each QoS class
• Global
• Static
• Predefined
• limit is given.
• The method of how to determine these limits is
  out of scope.

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Traffic Driven Optimization Method
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Traffic Driven Optimization of Metro Ethernet

• Layer 2 TE
• optimal network utilization, allowing high
  bandwidth but no protection,
• good throughput with dedicated protection
  switching
• To reach it
• Span more tree instances, and
• Assign the VLANs (traffic demands) to these trees
• Optimization aim is to
• Minimize the network usage to maximize the
  throughput while
• Neither QoS nor bandwidth are violated
• We proposed ILP based method to solve this problem

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Resilience in Traffic Driven Metro Ethernet

• Alternatives
• Counting on the repairing capability of RSTP
• Protection based on VLAN switching
• Two link disjoint VLANs for each demands
• same capacity is dedicated at both VLANs
• Only prioritized traffic is protected with VLAN
  switching
• Backup capacity is dedicated for them
• It can be shared with BE traffic!

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Performance of Traffic Driven Optimization
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Assumed Topology

• The traffic flows from the ANs to the ENs
• Root of Tree instances at ENs.

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Traffic model

• 3 QoS 1 best effort traffic class.
• Between every access-edge node pair one
  aggregated demand for each TC
• Throughput estimator parameter (Global traffic
  level)

• Demand sizes are based on
• Traffic Class Ratio
• Global Traffic Level

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Achieved Throughput
The throughput significantly increased! But why?
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Balancing the trees
Topology Driven MSTP
Optimized Tree instance
Bottleneck!!!
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Resilience

• Topology driven
• 100 resilience
• Low throughput
• Optimizing MSTP
• Using redundant links
• Higher throughput but lower resilience
• VLAN protection
• Decreased throughput
• Higher resilience

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Conclusion

• QoS Protection TE
• Can be realized using MSTP
• But tree optimization is required
• We presented an ILP model for
• Optimization
• QoS, capacity and protection constraints are
  fulfilled
• Significantly increased throughput is realized
• RSTP Restoration does not consider
• VLAN switch based protection is proposed
• Halves the throughput but considers QoS!
• Selective protection is proposed
• Tradeoff between throughput and protection

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Thank You