A survey of multipath routing for traffic engineering

1
A survey of multipath routing for traffic
engineering

• Gyu Myoung Lee
• Broadband Network Laboratory
• Tel) [phone]

2
Contents

• Introduction
• Multipath routing fundamentals
• Multipath routing algorithms
• Multipath routing in traditional IP network
• Multipath routing in MPLS networks
• Multipath routing in optical Internet
• Summary and conclusions
• Future work

3
Introduction

• A survey of multipath routing for traffic
  engineering
• Traffic Engineering
• Optimization of the operational performance of a
  network
• Including load-balancing, constraint-based
  routing, multi-path routing, fast re-routing,
  protection switching
• Multipath routing
• Various multipath routing mechanisms for traffic
  engineering
• solutions for effectively calculating the
  multipaths
• ways to minimize delay and increase throughput
• Apply multipath routing MPLS/GMPLS network

4
Multipath routing fundamentals

• Multipath routing
• Aggregating the resources of multiple paths and
  reducing the blocking probabilities in QoS
  oriented network
• Used for providing Quality of Service (QoS)
• Focus
• Optimal network utilization and route stability
  taking into consideration link and node failure
• Objective
• To dynamically multiplex the incoming traffic
  onto an optimal route ? guaranteeing the required
  level of service
• Two of the characteristics that can be used for
  determining a path set
• Path quantity the number of available paths
  between nodes
• Path independence

5
The benefits of multipath routing

• Load balancing
• To make more use of available network resources
  in order to minimize the risk of traffic
  congestion.
• Quality of Service
• Several architectures for implementing QoS
• IntServ per-flow based, not scalable
• Router require large amount of memory to store
  routing and reservation state and maintain
  consistency
• DiffServ
• Not an efficient and scalable solution when link
  failures occur
• Allow for aggregation of flows and provide a
  scalable solution
• Quality is guaranteed for individual flows within
  this aggregate

6
Multipath routing algorithms
7
Multipath routing algorithms - 1

• Equal Cost Multi-path (ECMP)
• Routing technique for routing packets along
  multiple paths of equal cost using simple round
  robin distribution
• OSPF-Optimized Multi Path (OMP) use ECMP
• Multiple Path Algorithm (MPA)
• Finds a subset of paths that satisfy a condition
  for loop-freeness
• Can be implemented as an extension to OSPF

8
Multipath routing algorithms - 2
9
Multipath routing algorithms - 3
10
Multipath routing in traditional IP network
11
Multipath routing in traditional IP network
12
Minimum Delay Routing Using Distributed
Computation - 1
A Minimum Delay Routing Algorithm Using
Distributed Computation (1977) multi-path routing
that guarantees minimum average delays
Extensions of the minimum delay algorithm to
handle topological changes
Using A failsafe distributed routing protocol
(1979) Second derivative algorithms for minimum
delay distributed routing in networks
(1984) second derivatives to increase the
convergence rate of the original minimum delay
algorithm Distributed routing with on-line
marginal delay estimation (1990) An improved
technique for measuring the marginal delays
13
Minimum Delay Routing Using Distributed
Computation - 2
Improve the minimum delay algorithm
The modeling of adaptive routing in
data-communication networks (1977) A failsafe
distributed protocol for minimum delay routing
(1981)
A Simple Approximation to Minimum-Delay Routing
(1999) A simpler algorithm can achieve
near-optimal routing On the impact of aggregation
on the performance of traffic aware routing
(2000) The impact of granularity on network and
routing behavior ? A constrained multipath
traffic engineering scheme for MPLS networks
(2002)
14
Linear-programming (LP) problem

• A linear or piece-wise linear penalty function
• To minimize the penalty for all links in the
  network
• Solving the linear-programming (LP) problem ?
  split ratio

Explicit routing algorithms for Internet traffic
engineering (1999) Minimize the maximum of link
utilization
Internet Traffic Engineering by Optimizing OSPF
Weights (2000) Optimal general routing
Internet Traffic Engineering without Full Mesh
Overlaying (2001) Optimal traffic split using LP
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Packet splitting methods

• How packets are split on multiple paths
• Three main approaches RFC2991 (2000)
• modulo-N hash
• hash-threshold (most commonly used)
• highest random weight
• Performance of hash-threshold RFC2992 (2000)
• A Traffic Engineering Approach based on
  Minimum-Delay Routing (2000)
• treat UDP and TCP packets in a different fashion
• propose a modified version of hash-threshold
  scheme
• to generate and insert in the packet a random key
  based on the source-destination IP addresses and
  port numbers (at ingress router)

16
Dynamic multipath routing schemes
Dynamic multi-path routing and how it compares
with other dynamic routing algorithms for high
speed wire area networks (1992) The shortest path
is used under light traffic conditions and
multiple paths are utilized as the shortest path
become congested
Load-sensitive routing for long-lived IP flows
(1999) An adaptive flow-level load control scheme
for multipath forwarding (2001) The enhance
routing scheme separating long-lived and
short-lived flows
Dynamic multipath routing (DMPR) an approach to
improve resource utilization in networks for
real-time traffic (2001) DMRP in networks and
switches carrying connection-oriented traffic
(2001) Improve resource utilization of a network
carrying real-time traffic by re-routing on
going calls through shorter routes
17
An adaptive flow-level load control scheme for
multipath forwarding

• Adaptive multipath load control method
• Flow classifier
• Detect long-lived flows through the flow
  characteristics of the duration and the size
• Dividing flows into long-lived and short-lived
• Avoid the congestion from the burst transient
  flows
• The minimal per-flow states at router
• Maintained by aggregating flows with the
  destination network prefix

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QoS routing using multipath
QoS routing via multiple paths using bandwidth
reservation (1998) QoS routing via multiple paths
for time constraint (buffer adjustment at the
receiver)
Performance of fast bandwidth reservation with
multipath routing (1998) Analysis of multi-path
routing (1999) The connection establishment time
for multipath reservation is significantly lowered
Impact of resource reservation on the distributed
multi-path quality of service routing scheme
(2001) combines resource reservation with the
ticket-based distributed multi-path QoS routing
Multipath QoS routing with bandwidth guarantee
(2001) The concept of forwarding with routing
marks ? reduce forwarding complexity
19
Multipath routing in MPLS networks
20
Traffic engineering with MPLS

• The emergence of MPLS
• Provides basic mechanisms for facilitating
  traffic engineering
• Explicit routing allows a particular packet
  stream to follow a pre-determined path
• Constraint-based routing
• Avoids placing too many LSPs on any link
• Multiple LSP setup ? traffic split (using
  multipath routing)
• Administrative policies in online path
  computation
• Resource color ? to achieve a degree of desired
  LSP placement
• Network planning
• The ability to gather per-LSP statistics ?
  reflect the changing traffic distribution
• The priority feature
• Offer different grades of service
• The ability to re-optimize the path of an LSP
• Rerouting of a LSP (survivability)

21
Multipath routing in MPLS networks
22
Finding traffic split ratio
23
MATE Multipath AIMD
24
MATE mechanism

• MATE functions in an ingress node

25
Multipath AIMD

• Distributed Rate Allocation Multipath AIMD
• Additive-Increase Multiplicative-Decrease (AIMD)
  feedback algorithms
• both efficient and fair in allocating traffic to
  network paths
• Binary feedback from LSPs
• Each LSP j periodically sends messages to all
  sources containing a binary signal fj 0, 1
  indicating its congestion rate
• Utilization Bj ? fj 1
• Utilization lt Bj ? fj 0
• Source adapt rate using AIMD
• fj 1 ? multiplicative decrease (0 lt kr 1)
• fj 0 ? additive increase (ka gt 0)

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Failure recovery (fault tolerant)

• Traffic engineering using multiple
  multipoint-to-point LSPs (2000)
• Traffic engineering method using multiple
  multipoint-to-point LSPs
• Backup routes are used against failures
• Fault tolerance and load balancing in QoS
  provisioning with multipath MPLS paths (2001)
• Approaches for fault tolerance and load balancing
  in QoS provisioning using multiple alternative
  paths
• Searches for maximally disjoint (i.e., minimally
  overlapped) multiple paths
• The impact of link/node failures becomes
  significantly reduced
• The use of multiple paths renders QoS services
  more robust in unreliable network conditions
• All the computed paths must satisfy given
  multiple QoS constraints

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Multipath routing in optical Internet
28
Multipath routing in optical Internet

• Wavelength resource management
• In the data-driven approach to provisioning, the
  boundary routers use traffic measurements to
  autonomously control the number of lightpaths
• Adaptive Bandwidth Management (UCL, Nortel)
• Availability of multiple diverse paths provides
  opportunity to improve QoS for streams by dynamic
  load balancing across those paths according to
  the value of the traffic and path
  characteristics.
• This would improve the utilisation of the network
• Adaptive multipath load balancing

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Abstract architecture for IP over Photonic network
IP Layer
Priority
Photonic/IP adapter
IP Border Router
IP Service Controller
IP Service Controller
IP Border Router
Q
Offered rate meter per path per O/P port
Rate control per path per O/P port
IP/Photonic traffic adapter
Provisioning Request
Provisioning Request
R
Bandwidth allocation
O-UNI
Photonic Layer
Photonic N/w Controller
Photonic N/w Controller
Resource availability
Wavelength allocator
IP/ Photonic adapter
Resource Controller
fPolicies, Request
Number of wavelengths
Q
R
Photonic switch
Photonic switch
O/P port wavelength path un/bind/modify
Wavelengths used per O/P port
Notes 1. The IP service and Photonic Network
controller functions are embedded in the
distributable resource Broker 2.
Message passing and Method invocations are local/
remote accordingly
Q Query R Response
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Adaptive Multipath Load Balancing proposal for
bandwidth management
Port Allocation mapping Function fstatics, dynam
ics, CoS, policy..etc
Flow ID Hash Function f6-tuple.. etc
O/P 1
Path A
I/P 1
Optical Cloud
Path B
Destination
I/P i
O/P n
Diverse and Disjoint paths
IP/Optical border router-switch with multiple
wavelength channels (or MPLS switches with
multiple LSPs)
31
Summary and conclusions

• Multipath Routing
• Effectively used for maximum utilization of
  network resources
• Aggregating the resources of multiple paths
• Reducing the blocking probabilities
• Allowing data transfer at higher rate when
  compared to single path
• Increase the reliability of delivery
• Various algorithms
• Effectively calculating the multipaths
• Minimize delay and increase throughput

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Future work

• Traffic Engineering objectives
• QoS routing, multi-path routing/traffic
  splitting, load balancing, path protection and
  fast re-route
• TE can be directly addressed by a
  connection-oriented MPLS/GMPLS based approach.
• Traffic engineering using multipath in
  GMPLS-based optical network
• Objective
• Optical resource optimization (load balancing)
• Reduce blocking probability
• Fault tolerance
• Control plane (Routing Signaling)
• Traffic aggregation and classification
  (flow-level control)
• Constrained-based multipath explicit route setup

33
References - 1

• Multipath routing fundamentals
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References - 2

• Multipath routing in traditional IP network
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References - 3

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• Multipath routing in MPLS networks
• 38 E. C. Rosen, A. Viswanathan, and R. Callon,
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• 39 D. Awduche et al, Requirements for Traffic
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37
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Any Questions?

• Thank you for listening!!!