Towards the Standardization of Transparency and Isolation Metrics for Virtual Network Elements in SDN

Transcription

1 Towards the Standardization of Transparency and Isolation Metrics for Virtual Network Elements in SDN K. Tutschku In collaboration with D. Stezenbach O. Nawaz M. Fiedler

2 Virtual Networks for Convergent Services Stellt X zur Verfügung Peer Diversity Exploit diversity of resources Locate optimal resources Stellt X zur Verfügung Transfer von Segment B Index server Stellt X zur Verfügung Transfer von Segment A Sucht X Overlays Overlays: application-oriented topology, addressing, and routing Multi-Network Services Self-operation of functions OS virtualization Consolidation and efficient operation Strong isolation of resources Network Virtualization Software Defined Networking Integration of technologies and administrative domains by smart programming Push application-layer mechanisms safely down the stack Re-use of generic infrastructure on small time scale Key requirements: sharing, aggregation, isolation, transparency

3 What are the performance requirements of virtual network elements in SDN?

4 Difficulties of Resource Sharing in Virtualized Environments Share Virtual CPU Virtual Memory Virtual I/O Virtual Machine Virtual Machine Monitor Virtual Machin e CPU Memory I/O (Performance) Requirements: Isolation: Fault Tolerance, Privacy, Security, Fairness, Safety, no impacts to other slices Transparency: performance for traffic as expected Scalability: Performance shall not depend on number of active slices Link Virtual Router Unfair sharing on short time scale Fair sharing on long time scale Disturbance of other slices in theory inevitable due to crosstalk because of sharing.

5 Difficulties of Resource Sharing in Virtualized Environments: Larger Scope V-net 1 var(delay) VN networks topology & requirements Interaction a) space-division b) time-division Network configuration a) physical entity selection V-net n max(delay) Timing Sharing: deferred sending of packets leads to delays Aggregation: re-ordering of packet might lead to delay Timing alignment of data packets becomes important for performance

6 What is Isolation and Transparency? Share Virtual CPU Virtual Memory Virtual I/O Virtual Machine Monitor Virtual Machine Virtu al Mach ine Language terms: Isolation: is the feature that no virtual entity may impact the behavior of any other similar virtual entity on the same CPU Memory I/O physical element. Transparency: is the feature of a virtual system that a user is not able to recognize that the system, he or she is using, runs in a virtual environment. Transparency is related to fidelity. Fidelity: is the feature that a software running in virtualized environment should provide identical results as running on the real machine, barring from timing effects [Adam et al. 2006]. These feature can either be fulfilled or not fulfilled! Is there a quantitative evaluation available? For example, for judging the quality of a (virtual) network element?

7 Evaluation Concept: Comparative Analysis General concept for the numerical analysis of the impacts of networks/network elements on traffic streams (developed by Fiedler und Tutschku since 2003) Compares the statistical characteristics of traffic stream at the In and Out of a (network) element. May applied on time scales Overview: source Ingress (in, before) Monitoring Point (ingress) Statistic on W (typically exchanged after W) Data Flow sampling every T System Under Test (SUT) egress (out,after) Disturbance by SUT Monitoring Point (egress) sampling every T destination Comparison

8 Basic Metric for Isolation and Transparency Share Virtual Machine Aim on the influence of virtualization on single packets: Virtual CPU Virtual Memory Virtual I/O Virtual Machine Monitor Virtu al Mach ine CPU Memory I/O

9 Advanced Metrics for Isolation and Transparency Share Virtual CPU Virtual Memory Virtual I/O Virtual Machine Monitor Virtual Machine Virtu al Mach ine CPU Memory I/O Multi-timescale metrics: a second class of metrics evaluates the performance based on multiple timescales. Considers timing alignment between packet on multiple timescales. Throughput statistic (for given T) Mean value and variance (for given T) T = time interval on which statistical value is computed = time scale

10 Evaluation of the Elements by the Metrics Measurement set-up:

11 First Results CDF of Inter-Packet Times: Significant Difference between Input and Output

12 First Results Throughput Coefficient of Variation on Multiple Timescales: Ratio of deviation between ingress/egress on a given time scale defines quality of isolation and transparency Time scale depends on application

13 Summary and Outlook SDN and Network Virtualization will have specific performance requirements resulting from the needs of Sharing, Isolation and Transparency The understanding of the changes in the inter-packet timing alignment is the key towards metrics for the quality of virtualization technology Future research will involve the improvements of the metrics (incl. their accuracy) how to implement control of virtual network based on the deviation of the performance

14 Thank you! Questions?