Resource Virtualisation of Network Routers

1. Resource Virtualisation of Network Routers Ross McIlroy, Joe Sventek Department of Computing Science University of Glasgow (ross@dcs.gla.ac.uk, joe@dcs.gla.ac.uk)

2. QoS in the Internet Proposed Approach Implementation of QuaSAR Experimental Results Experience Gained Conclusions

3. The Problem • The Internet provides an inherently best effort service • However, many recent Internet applications require Quality of Service guarantees • Isochronous network flows • Voice over IP • Streaming Video • High Throughput applications • Grid Utilities • Streaming Video • Peer to Peer

4. Previous Research into Network QoS • Integrated / Differentiated Services • Traffic Engineering (e.g. MPLS) • Resource Reservation Protocols (e.g. RSVP) • However, less research into how router resources (e.g. processing time) should be provisioned to guarantee QoS to network flows • Over provisioning typically used • Expensive • Inflexible • Weighted Fair Queuing • Complex calculation for each packet • Simple queuing of packets within flows

5. QoS in the Internet • Proposed Approach Implementation of QuaSAR Experimental Results Experience Gained Conclusions

6. Overall Approach • Each QoS network flow is assigned its own virtual router - routelet • Each routelet runs on its own virtual machine • Routelets are assigned a proportion of the router’s resources required to support the flow’s QoS requirements • This provides resource usage partitioning between network flows

7. QuaSAR Components • Main Router • Controls creation of routelets and their assignment to QoS flows • Routes best effort traffic • Routelets • Process and route packets from a QoS MPLS flow • Packet Demultiplexing • Identifies packets from QoS flows • Directs QoS packets to the correct Routelet for processing

8. QuaSAR Architecture Overview Idle Routelet Pool Main Best-Effort Router Packet Demultiplexer Input NIC Channels Output NIC Channels QoS Routelets

9. Possible Applications • Per QoS flow partitioning on access networks • Virtual trunking of traffic on access / medium area networks • Application specific traffic processing for different traffic flows • Packet scheduling within traffic flows

10. QoS in the Internet Proposed Approach • Implementation of QuaSAR Experimental Results Experience Gained Conclusions

11. Virtualisation in QuaSAR • Virtualisation divides the resources of a computing system into multiple execution environments • A virtualisation layer provides the illusion of a real machine to multiple virtual machines • QuaSAR uses the Xen Virtual Machine Monitor to isolate QoS Routelets within virtual machines • Xen chosen due to increase in performance and scalability caused by paravirtualisation approach • Paravirtualisation presents an idealised virtual machine interface, rather than attempting to fully emulate the real hardware

12. Idle Routelet Pool Virtual Machines Virtual Machine Virtual NIC Virtualisation Layer Real Hardware QoS Routelets QuaSAR Hierarchically Main Best-Effort Router Packet Demultiplexer Input NIC Channels Output NIC Channels Packet Demultiplexer

13. Routelets • Routelets perform simple packet processing using Click Modular Router • Each Routelet only processes one MPLS LSP, therefore only simple processing needed • Routelets could be specialised for certain types of traffic

14. Main Router • Routes any best effort traffic using standard Linux Routing Software • Creates a Pool of Routelet VMs (initially all idle) • Assigns QoS flows to routelets when new flow creation is signalled using RSVP messages • Chooses a routelet for this new flow • Modifies Routelet’s packet forwarding engine for this flow • Assigns a proportion of the machine’s resources (CPU, NIC bandwidth, etc) to routelet based upon flow’s flowspec • Updates Demultiplexer to pass packets from this flow to the chosen routelet

15. Demultiplexing Framework • Click Modular Router used to create a switch which passes packets to the routelet processing their flow • Peeks at MPLS label and compares this with a table of Label / Virtual Network Device pairs • Passes packet to the Virtual Network Device corresponding to the packet’s label • Any packets which don’t match are passed to the best effort router • Routelets are linked to the demultiplexer through Virtual Network Devices • Bypasses the Linux Network Stack

16. Restricting Resource Usage • CPU Usage • Xen’s Virtual Machine Scheduler decides when routelets can make progress in processing packets • Soft Real-time Scheduler could provide guarantees about times to process packets associated with a certain routelet • Network Bandwidth Usage • Credit based system to limit each routelet’s maximum outgoing network usage • Memory Usage • Not significantly important with QuaSAR (Linux uses most of each routelet’s assigned memory) • Statically assigned at routelet startup

17. QoS in the Internet Proposed Approach Implementation of QuaSAR • Experimental Results Experience Gained Conclusions

18. Results - Latency

19. Results - Partitioning

20. QoS in the Internet Proposed Approach Implementation of QuaSAR Experimental Results • Experience Gained Conclusions

21. Problems with QuaSAR • Linux OS running for each routelet • Context switch overhead between routelets • Memory protection between domains • Much of the work per packet occurs during classification • This is assigned to the best effort router, therefore much of the flow’s work does not occur in its routelet • Routelets have no direct access to physical network devices • No soft real-time scheduler for Xen available during this project

22. QoS in the Internet Proposed Approach Implementation of QuaSAR Experimental Results Experience Gained • Conclusions

23. Conclusions • Virtualisation can be used to partition a router into several distinct routelets • QoS flow partitioning opportunities • Virtual segregation of network for management purposes • Application specific routelets can be built for different classes of network traffic • It is possible to build a router which uses virtualisation without a huge loss in performance

24. Virtual Machines Virtualisation Layer Real Hardware QuaSAR Hierarchically (Actual) Domain 0 Domain 0 Packet Demultiplexer

25. Demultiplexer - Click Architecture best effort router best effort router best effort router best effort router

26. Results - Jitter

27. Results - Throughput