Designing a New Routing Simulator for DiffServ MPLS Networks

1
Designing a New Routing Simulator for DiffServ
MPLS Networks
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• Peng Zhang
• Zhansong Ma
• Raimo Kantola
• pgzhang, zhansong, kantola_at_tct.hut.fi
• http//www.tct.hut.fi/u/pgzhang/QRS/index.html

SCSC 2001 International Symposium on Performance
Evaluationof Computer and Telecommunication
Systems Orlando, Florida, July
2
Contents
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• DiffServ MPLS network functions
• QoS Routing Performance and Cost
• Enhanced QoS Routing Simulator
• Link State Update Algorithms
• Simulation Study of LSU Algorithms

3
DiffServ Architecture
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY
Customer Services
Operation, management and provision
QoS signaling
DS Domain
Ingress node
Egress node
Interior node
Classifying, marking
shaping
Forwarding PHB
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DS Traffic Engineering Functions
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY
Ingress node
meter
classifier
marker
queuer
dropper
Interior node
queuer
dropper
marker
queuer
dropper
Egress node
5
Dropping and Queuing
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY
EF queue
AF1 queue
WRED1
AF2 queue
WRED1
AF3 queue
WRED1
AF4 queue
WRED1
BE queue
You can set buffer size, serving rate, wred
parameters etc...
6
Feasibility of QoS Routing
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• QoS Routing
• finds paths that are subject to QoS requirements
  while achieving efficiency in network resource
  utilization
• Benefits of QoS Routing
• enables creation of virtual circuit-like services
  
• improves user satisfaction
• improves network utilization and increases
  network thruput
• Benefits do not come free
• cost of deploying QoS routing protocol
• cost of processing overhead
• cost of storage overhead
• added complexity of routers
• ...
• Whether or not the benefits are worth the cost ?

7
QoS Routing Performance
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• QoS routing performance is usually described in
  terms of the utilization of network resources or
  the throughput achieved by network traffic. It is
  affected by such parameters
• routing algorithm complexity
• link state updating algorithm frequency of
  updating network state
• network topology
• -- a certain routing algorithm may be better
  suitable for certain topologies,
• -- match between the traffic matrix and the
  topology
• high level admission control deciding when to
  accept a request

8
QoS Routing Cost
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• Link state update cost
• cost of generating and receiving LSAs
• traffic cost
• Computation cost
• cost of on-demand path computation
• cost of path pre-computation
• Storage cost
• storing more information than best effort routing
• extra routing table if path pre-computation is
  used
• Other costs
• signaling cost
• software cost
• operation cost
• maintenance cost

9
Link State Update Algorithms
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• Period based (PB)
• timeout T
• an update is sent when timeout T expires, T is
  restarted.
• Threshold based (TB)
• threshold th, last advertised value bwio and
  current value bwic
• updates when (bwio - bwic / bwio )gt th for
  bwio ? 0,
• bwic gt0
  for bwio ? 0
• Equal class based (ECB)
• base class B, classes (0,B),(B,2B),(2B,3B),,et
  c
• updating when available bandwidth changes across
  a class boundary
• Unequal class based (UCB)
• base class B and factor f(fgt1) , classes (0,B),
  (B,(f1)B), ((f1)B, (f2f1)B),
  ((f2f1)B,(f3f2f1)B),, etc
• updating when available bandwidth changes across
  a class boundary

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Multi-path QoS Routing
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• Motivation
• The development of MPLS and DiffServ
• The development of QoS routing (e.g., QOSPF)
• The development of multi-path (QoS) routing in
  legacy networks
• E.g., ATM networks
• Content
• Find multiple disjoint paths between a pair of
  nodes that satisfy QoS requirements (e.g.,
  bandwidth, delay)
• Link disjoint paths or node disjoint paths
• For example, two link disjoint paths have no
  common links
• Fully disjoint paths and partly disjoint paths
• Fully disjoint paths have no common links/nodes
• Partly disjoint paths have common links/nodes but
  not all
• On-line or off-line path computation
• On-line computation uses simple algorithms
• Off-line may use complex algorithms
• Combination Once link failures happen, the
  on-line computation is used first for fast
  restoration and the off-line computation is used
  later for path optimization

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Multi-path QoS Routing (contd)
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• Benefits
• Enhance network reliability and survivability
• If one or more paths fail, other paths are
  available
• If one or more paths fail, users traffic are not
  interrupted
• Minimize network delay
• Improve network resource utilization
• Satisfy users traffic requirements
• Metrics
• Simplicity
• There lack simple and efficient multi-path
  routing algorithms
• There are few multi-path QoS routing algorithms
• Stability
• Routing algorithms should efficiently work in
  various network environment, e.g., various
  network topologies, various traffic.

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Multi-path QoS Routing (contd)
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• Considerations in QRS
• Implement simple multi-path (QoS) routing
  algorithms
• Inherit single path (QoS) routing algorithms of
  QRS
• I.e., lowest cost (LC) and widest bandwidth (WB)
• Based on link state schema (e.g., OSPF)
• Algorithms in QRS
• Two-step-link-disjoint-lowest-cost
• The first step find a lowest cost path that
  satisfies the bandwidth requirement
• The second step prune the links used in the
  first path and then calculate the lowest cost
  path in the residue topology
• Two-step-node-disjoint-lowest-cost
• Two-step-link-disjoint-widest-bandwidth
• Two-step-node-disjoint-widest-bandwidth
• Current work
• Implement more multi-path QoS routing algorithms
• Evaluate the performance of these algorithms and
  their impact on the network traffic

13
Enhanced QoS Routing Simulator
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY
RM
Realtime Traffic Source/Sink
QOSPF
ERSVP
NODE(Classifier, marker)
LINK(dropper, queuer)
http//www.tct.hut.fi/pgzhang/QRS/index.htm This
version supports DiffServ and MPLS
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ISP Topology
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY
Minimum cut is 56Mb/s 30 Mb/s Shortest path
algorithm is able to use 3 of 5 alternative
links.
Link Bandwidth 6Mb/s
15
Simulations with UCB
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY
16
Summary
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• We have implemented a QoS Routing Simulator that
  supports IntServ, DiffServ and MPLS.
• It can be used to study dynamics, stability, cost
  and performance and scalability of QoS routing.
• We demonstrated the use of the Simulator for
  Unequal Class Based (UCB) link state updates. In
  UCB, the performance and cost are affected by two
  variables, by setting suitable values, this
  algorithm can produce a good combination of
  performance and cost.
• Most recently two multi-path QoS routing
  algorithms have been added to the Simulator.
• The Simulator is available for download on our
  www-site.

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QoS Routing Protocol(QOSPF)
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY
18
QoS Routing Algorithms
TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF
TECHNOLOGY

• Lowest cost algorithm
• finds a path p between source
• node and destination node such
• that the path bandwidth b(p)?B
• (required bandwidth) and the
• path has the least cost
• first eliminates all links that do
• not meet the bandwidth
• requirement
• then uses Dijkastra's algorithm
• to find the least cost path.

• Widest bandwidth algorithm
• finds a path p between source
• node and destination node such
• that the path bandwidth b(p)?B
• (required bandwidth) and the
• path has the widest bandwidth
• first eliminates all links that
• do not meet the bandwidth
• requirement
• then uses the variation of
• Dijkastra's algorithm to find
• the the widest path.