a distributed approach for virtual network...

A Distributed Approach for Virtual Network Discovery

João Nogueira, Márcio Melo, Jorge CarapinhaPortugal Telecom InovaçãoSusana Sargento ([email protected])Instituto de Telecomunicações, Aveiro, Portugal

FutureNet III - Workshop on Network of the Future

mailto:[email protected]

Outline

• Introduction & Motivation

• Virtual Network Platform

• Related Work on Discovery Algorithms

• Distributed Topology Discovery

• Performance Results

– Simulation and Experimental Results

• Conclusions

2A Distributed Approach for Virtual Network Discovery10th December 2010, IEEE GLOBECOM 2010 - Workshop on Network of the Future

Introduction & Motivation

Virtualization• Sharing the same Infrastructure

– Better utilization of network resources ;– Reduction of CAPEX and OPEX;– Utilization of the same infrastructure for different organizations,

network providers and service providers;

• Development and deployment of new Architectures and Protocols in production networks

• Security and Isolation– Fault tolerance and performance guarantees;

• Reduction of costs for creating, running and combining multiple networks, applications and network services


Internetor LAN

Agent

Virtual Network Platform

Control Centre

Manager

User

Substrate Network


Virtual Network Control Centre


Functionalities

• Physical and Virtual Resource and Topology Discovery– Automatic discovery of both node resources and link resources.

• Substrate and Virtual Network Monitoring– Monitoring functions which periodically update resource usage

(CPU, RAM, HDD, Interfaces).

• Virtual Network Mapping– Embedding algorithm for Virtual Networks taking into account

virtual nodes and links specifications

• Virtual Network Management– Changing virtual resource state (i.e. rebooting , pausing),

assigned RAM amount in run-time, deleting the resource or even the entire Virtual Network.


Related Work on Topology Discovery

• Physical topology discovery

– Commercial applications exist that rely on Layer 3 information;

• Virtual Network Discovery

– The current scientific studies are usually focused on overlay networks (mostly Gossip-based algorithms)• None specially targeted at network virtualization

• However their principles (the sharing of information, propagation and topology building) can be applied.


Distributed Topology Discovery Algorithm

• Neighborhood concept

• Agents register themselves in a predefined multicast group at layer 2– Exchange messages with each other

• Spanning Tree concept– In a given network segment, one of the Agents has a special function

• Designated Root (DR) – Election of the node with the lowest of the Agents’ ID

– Reduce the information exchange of the distributed approach

– Transmit all the information about its network segment to a new Agent arriving at the network

• BGP concept– Advertisements with information from the several hops they traverse



• Physical Topology Discovery

– The Agent sends link-local multicast Hello messages through its active interfaces;

– The Hello exchange messages allows each Agent to know its physical neighborhood.

• Virtual Topology Discovery

– Agents exchange two types of messages:• Local Resources – Local Virtual Resources Information

• Remote Resources - Remote Resource Information Propagation



• Bootstrapping

– Agents must have a unique ID (given by the Manager at startup)

• Resource Update Mechanism (two possible situations):

– When a new local resource created.

– Or as a consequence of a received resource advertisement (i.e. forwarding advertisement);

• Resource Removal Mechanism

– In order to maintain the consistency in the existing databases;

– The forwarding mechanisms are similar to the ones of new virtual resource advertisement.


Simulation Results

• Performed in Matlab®• The Physical and Virtual Topologies were generated using

the Waxman Model– Virtual Networks were generated selecting randomly half of

physical nodes

• Three discovery algorithms were compared– The proposed one– Uncontrolled Flooding– Gossip –based: with flooding probability of 50%

• Simulation Parameters– Simulations repeated 10 times– Plotted the mean and the 95% confidence interval


Discovery Algorithm Scalability Tests – Number of Physical Nodes

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Proposed Algorithm



A Distributed Approach for Virtual Network Discovery10th December 2010, IEEE GLOBECOM 2010 - Workshop on Network of the Future

Discovery Algorithm Scalability Tests – Number of Virtual Networks

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0 5 10 15 20 2510

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Number of Virtual Networks

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100 Physical Nodes

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Experimental Results

• Real scenario of 0 to 40 running virtual networks

– They were equal and their topology was an exact replica of the underlying physical network

• Two discovery approaches were considered:

– Centralized: The Manager has full knowledge of the existing nodes (physical and virtual) and performs computations in order to acquire the topologies

– Distributed: The agents communicate with each other, in order to determine existing virtual links, and report back to the manager


Experimental Results –Distributed vs. Centralized Discovery

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0 5 10 15 20 25 30 35 400

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Virtual Networks

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Manager Physical & Virtual Network Topology Discovery Time vs Virtual Networks

Centralized

Distributed


Conclusions and Future Work

• Developed distributed discovery algorithm:– Provides a simple, fast and low overhead mechanism for virtual

and physical topology discovery

• Simulation results and experimental tests conducted:– Simulation results show improvements in the order of three

magnitudes over other algorithms– Experimental results provide evidence of the advantages of

using a distributed technique for topology discovery.

• Use the distributed discovery algorithm for fault-management

• Mobility of virtual resources • Investigate Multi-provider environments.


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