On the Bandwidth Management for HoseModel VPN Service

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On the Bandwidth Management for Hose-Model VPN
Service

• GRADUATE INSTITUTE OF INFORMATION MANAGEMENT
• NATIONAL TAIWAN UNIVERSITY

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Outline

• An Introduction to VPN
• VPN Service Models (Bandwidth management)
• The pipe model
• The hose model
• Implementation Alternatives of the Hose Model VPN
• Hose-Model VPN Service Provisioning
• Future Works

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Private Network

• A Private Network (PN) is established by
  dedicated leased lines connecting several
  geographically dispersed sites (endpoints).
• Each site is a campus or a branch office of an
  enterprise.
• Since the lines are dedicated, security and
  Quality of Service (QoS) are ensured.
• But connecting a large number PN sites with
  dedicated lines is expensive.

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Virtual Private Network

• Virtual Private Network (VPN) is a replacement
  for Private Network.
• A VPN establishes connectivity between a set of
  endpoints over a shared network infrastructure
  (eg MPLS network backbone).
• The goal of VPN is to provide endpoints with a
  service comparable to Private Network.
• Thus providers of VPN services need to address
  QoS and security issues.

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VPN Three Types

• In terms of commercial applications, VPN can be
  classified into three types
• Access VPN (a.k.a Remote Access VPN)
• Intranet VPN (a.k.a Enterprise VPN)
• Extranet VPN (a.k.a E-commerce VPN)

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VPN Three Types (cont)
Nomadic user
Enterprise B
Shard Network or
Enterprise A
Enterprise A
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Outline

• An Introduction to VPN
• VPN Service Models (Bandwidth management)
• The pipe model
• The hose model
• Implementation Alternatives of the Hose Model VPN
• Hose-Model VPN Service Provisioning
• Future Works

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VPN Service Models

• VPN customers need a flexible ways to specify
  their bandwidth requirement.
• Two common VPN service Models are
• The Customer-pipe model
• The Hose model

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The Customer-Pipe Model

• In this model, VPN customers buy a customer-pipe
  for each endpoints pair.
• VPN customers need to specify bandwidth
  requirement of each customer-pipe in advance.
• VPN service provider uses a path between
  endpoints pair to implement a customer-pipe.
• VPN service provider also need to allocate
  adequate bandwidth along the path.

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The Customer-Pipe Model (cont)
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The Pro and Cons of the Customer Pipe Model

• Pro
• The task of bandwidth allocation becomes more
  simple.
• Con
• It requires the customer to have precise
  knowledge of the bandwidth requirement of each
  endpoints pair in advance.
• Bandwidth made available to a customer pipe
  cannot be allocated to other traffic.

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Motivation for the Hose-Model

• VPN customers may unwilling to unable to know the
  bandwidth requirement between each endpoints pair
  in advance.
• This is especially true when the number of
  endpoints per VPN is large.

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The Hose Model

• In this model, VPN customers only need to specify
  two parameters for each endpoint
• Egress bandwidth requirement the bandwidth for
  aggregate outgoing traffic from the endpoint to
  all the other endpoints.
• Ingress bandwidth requirement the bandwidth for
  aggregate incoming traffic out of all the other
  endpoints to this endpoint.

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Advantages of the Hose Model

• Ease of specification
• Flexibility

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Challenge of Provision the Hose Model VPN

• From a VPN service providers perspective, it is
  more challenging to support the hose model VPN
• The need to meet the bandwidth requirement with a
  very weak specification.
• This complicate the VPNs bandwidth management
  issue.

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Outline

• An Introduction to VPN
• VPN Service Models
• The pipe model
• The hose model
• Implementation Alternatives of the Hose Model
• Hose-Model VPN Service Provisioning
• Future Works

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Implementation Alternatives of the Hose Model

• The most important implementation alternatives
  for the hose model VPNs are
• Provider-pipe algorithm
• Hose-specific state algorithm
• VPN-specific state algorithm
• Tree routing algorithm

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Provider-Pipe scheme
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Hose-specific state scheme
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VPN-specific state scheme
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Tree RoutingScheme
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Is the Hose Model a Viable Alternative

• The main question to introduce the hose model in
  ISP networks is how does it relate to the
  customer pipe solution in terms of bandwidth
  efficiency.
• The flexibility of the hose model will never pay
  off if it requires significant overprovisioing
  compared to customer-pipe models.

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Generate Comparable Hose Model Parameters
Customer-Pipe Model parameters
Hose-Model parameters
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Overprovisioning Factor

• The ratio between the bandwidth reservation of
  the hose and the customer-pipe model is called
  overporvisioning factor. It is a good indicator
  of the required extra capacity.

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Experimental Results
Provider-pipe
VPN-specific state
Hose-specific state
Tree routing
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Experimental Results
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Outline

• An Introduction to VPN
• VPN Service Models (Bandwidth management)
• The pipe model
• The hose model
• Implementation Alternatives of the Hose Model VPN
• Hose-Model VPN Service Provisioning
• Future Works

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Hose-Model VPN Service Provisioning

• In terms of VPN service provisioning, service
  provider must establish multiple VPNs on the
  network backbone in an on-line manner.
• The available bandwidth for VPN service on links
  of the network backbone is finite.
• VPN setup request arrive one by one
  independently.
• Each VPN setup request corresponds to a
  Hose-Model VPN to be established.
• Information about future VPN setup request is
  unknown.

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Hose-Model VPN Service Provisioning

• If there is not enough residual bandwidth on the
  link when the bandwidth is being allocated, vri
  will be rejected.
• In this scenario, the performance metric for
  comparing different VPN provisioning algorithm is
  rejection ratio.

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Example

• In this scenario, even tree routing algorithm
  cannot achieve rejection ratio.
• Service provider received two VPN setup requests
  vr1(2,3,3) and vr2(3,3,3).
• The available bandwidth on all links is 5 units.

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Rejection Ratio of Tree Routing Scheme
vr2 will be rejected, the rejection ratio
achieved is 50.
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Optimal Arrangement
Both VPN setup requests will be accepted, the
rejection ratio achieved is 0.
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Modified Tree Routing Algorithm

• The design philosophy of MTRA is to look after
  both bandwidth allocation efficiency and load
  balance.
• It can reduce rejection ratio effectively.

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Parameters Configuration
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Experimental Results
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Future Works

• In order to ensure service quality and
  availability of VPN services, seamless recovery
  from failures is essential.
• Failure restoration algorithm for Hose-Model VPN.

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Recovery from Link Failure
Tree Link (1,4) fail and the corresponding backup
path is activated
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