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  • Packets routed if possible, no guarantee. Collisions, congestion, etc. No real effort to guarantee QoS to network flows Isochronous = time sensitive VOIP – minimum round trip latency for two way conversation. In order and min jitter for smooth audio Video – Min Jitter to reduce buffering. Guaranteed throughput.
  • Per flow QoS, vs per QoS Class. Engineer QoS traffic to traverse underused routes (less interference) RSVP can reserve network resources required for flow, can be used with admission control, but flow could use more resources than it guaranteed. Over provisioning typically used to guarantee QoS (expensive, inflexible) WFQ, search for next queue to transmit. Admittedly MSci project is more complex, but virtualisation could simplify QoS decisions (to a schedular) Could introduce smart per flow queuing techniques depending upon flow type (e.g. MPEG, VOIP)
  • Prototype to test this approach Software router on commodity hardware Allocation of resources
  • Green = QoS Red = Best Effort
  • MPEG
  • VMWare, VirtualPC Linux
  • VM’s Running Linux
  • Briefly describe click
  • Number of different responsibilitys Only involved modification to open source RSVP daemon to support routelets PPE modify – e.g. dst MPLS label / MAC address, etc
  • Checks if it is MPLS Hashtable Click hooks straight into drivers
  • No soft real time scheduler available for Xen at time of projec Depend upon previous routers well behaved flows for input usage
  • Linux is much more complex than necessary - Scalability problems TLB misses, storing all of the CPU registers. Not necessary with trusted domains. MPLS has very simple processing requirements, most of the processing involves classification Atropos not supported in recent versions of Xen, SEDF not stable.
  • Specific Virtualisation optimisations could reduce some major bottlenecks
  • (presentation)

    1. 1. Resource Virtualisation of Network Routers Ross McIlroy, Joe Sventek (ross@dcs.gla.ac.uk, joe@dcs.gla.ac.uk) Department of Computing Science University of Glasgow
    2. 2. <ul><li>QoS in the Internet </li></ul><ul><li>Proposed Approach </li></ul><ul><li>Implementation of QuaSAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Experience Gained </li></ul><ul><li>Conclusions </li></ul>
    3. 3. The Problem <ul><li>The Internet provides an inherently best effort service </li></ul><ul><li>However, many recent Internet applications require Quality of Service guarantees </li></ul><ul><ul><li>Isochronous network flows </li></ul></ul><ul><ul><ul><li>Voice over IP </li></ul></ul></ul><ul><ul><ul><li>Streaming Video </li></ul></ul></ul><ul><ul><li>High Throughput applications </li></ul></ul><ul><ul><ul><li>Grid Utilities </li></ul></ul></ul><ul><ul><ul><li>Streaming Video </li></ul></ul></ul><ul><ul><ul><li>Peer to Peer </li></ul></ul></ul>
    4. 4. Previous Research into Network QoS <ul><li>Integrated / Differentiated Services </li></ul><ul><li>Traffic Engineering (e.g. MPLS) </li></ul><ul><li>Resource Reservation Protocols (e.g. RSVP) </li></ul><ul><li>However, less research into how router resources (e.g. processing time) should be provisioned to guarantee QoS to network flows </li></ul><ul><ul><li>Over provisioning typically used </li></ul></ul><ul><ul><ul><li>Expensive </li></ul></ul></ul><ul><ul><ul><li>Inflexible </li></ul></ul></ul><ul><ul><li>Weighted Fair Queuing </li></ul></ul><ul><ul><ul><li>Complex calculation for each packet </li></ul></ul></ul><ul><ul><ul><li>Simple queuing of packets within flows </li></ul></ul></ul>
    5. 5. <ul><li>QoS in the Internet </li></ul><ul><li>Proposed Approach </li></ul><ul><li>Implementation of QuaSAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Experience Gained </li></ul><ul><li>Conclusions </li></ul>
    6. 6. Overall Approach <ul><li>Each QoS network flow is assigned its own virtual router - routelet </li></ul><ul><li>Each routelet runs on its own virtual machine </li></ul><ul><li>Routelets are assigned a proportion of the router’s resources required to support the flow’s QoS requirements </li></ul><ul><li>This provides resource usage partitioning between network flows </li></ul>
    7. 7. QuaSAR Components <ul><li>Main Router </li></ul><ul><ul><li>Controls creation of routelets and their assignment to QoS flows </li></ul></ul><ul><ul><li>Routes best effort traffic </li></ul></ul><ul><li>Routelets </li></ul><ul><ul><li>Process and route packets from a QoS MPLS flow </li></ul></ul><ul><li>Packet Demultiplexing </li></ul><ul><ul><li>Identifies packets from QoS flows </li></ul></ul><ul><ul><li>Directs QoS packets to the correct Routelet for processing </li></ul></ul>
    8. 8. QuaSAR Architecture Overview Packet Demultiplexer Main Best-Effort Router Idle Routelet Pool QoS Routelets Input NIC Channels Output NIC Channels
    9. 9. Possible Applications <ul><li>Per QoS flow partitioning on access networks </li></ul><ul><li>Virtual trunking of traffic on access / medium area networks </li></ul><ul><li>Application specific traffic processing for different traffic flows </li></ul><ul><li>Packet scheduling within traffic flows </li></ul>
    10. 10. <ul><li>QoS in the Internet </li></ul><ul><li>Proposed Approach </li></ul><ul><li>Implementation of QuaSAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Experience Gained </li></ul><ul><li>Conclusions </li></ul>
    11. 11. Virtualisation in QuaSAR <ul><li>Virtualisation divides the resources of a computing system into multiple execution environments </li></ul><ul><li>A virtualisation layer provides the illusion of a real machine to multiple virtual machines </li></ul><ul><li>QuaSAR uses the Xen Virtual Machine Monitor to isolate QoS Routelets within virtual machines </li></ul><ul><ul><li>Xen chosen due to increase in performance and scalability caused by paravirtualisation approach </li></ul></ul><ul><ul><li>Paravirtualisation presents an idealised virtual machine interface, rather than attempting to fully emulate the real hardware </li></ul></ul>
    12. 12. QuaSAR Hierarchically Main Best-Effort Router Input NIC Channels Output NIC Channels Packet Demultiplexer Packet Demultiplexer Idle Routelet Pool QoS Routelets Real Hardware Virtualisation Layer Virtual Machines Virtual Machine Virtual NIC
    13. 13. Routelets <ul><li>Routelets perform simple packet processing using Click Modular Router </li></ul><ul><ul><li>Each Routelet only processes one MPLS LSP, therefore only simple processing needed </li></ul></ul><ul><ul><li>Routelets could be specialised for certain types of traffic </li></ul></ul>
    14. 14. Main Router <ul><li>Routes any best effort traffic using standard Linux Routing Software </li></ul><ul><li>Creates a Pool of Routelet VMs (initially all idle) </li></ul><ul><li>Assigns QoS flows to routelets when new flow creation is signalled using RSVP messages </li></ul><ul><ul><li>Chooses a routelet for this new flow </li></ul></ul><ul><ul><li>Modifies Routelet’s packet forwarding engine for this flow </li></ul></ul><ul><ul><li>Assigns a proportion of the machine’s resources (CPU, NIC bandwidth, etc) to routelet based upon flow’s flowspec </li></ul></ul><ul><ul><li>Updates Demultiplexer to pass packets from this flow to the chosen routelet </li></ul></ul>
    15. 15. Demultiplexing Framework <ul><li>Click Modular Router used to create a switch which passes packets to the routelet processing their flow </li></ul><ul><ul><li>Peeks at MPLS label and compares this with a table of Label / Virtual Network Device pairs </li></ul></ul><ul><ul><li>Passes packet to the Virtual Network Device corresponding to the packet’s label </li></ul></ul><ul><ul><li>Any packets which don’t match are passed to the best effort router </li></ul></ul><ul><li>Routelets are linked to the demultiplexer through Virtual Network Devices </li></ul><ul><li>Bypasses the Linux Network Stack </li></ul>
    16. 16. Restricting Resource Usage <ul><li>CPU Usage </li></ul><ul><ul><li>Xen’s Virtual Machine Scheduler decides when routelets can make progress in processing packets </li></ul></ul><ul><ul><li>Soft Real-time Scheduler could provide guarantees about times to process packets associated with a certain routelet </li></ul></ul><ul><li>Network Bandwidth Usage </li></ul><ul><ul><li>Credit based system to limit each routelet’s maximum outgoing network usage </li></ul></ul><ul><li>Memory Usage </li></ul><ul><ul><li>Not significantly important with QuaSAR (Linux uses most of each routelet’s assigned memory) </li></ul></ul><ul><ul><li>Statically assigned at routelet startup </li></ul></ul>
    17. 17. <ul><li>QoS in the Internet </li></ul><ul><li>Proposed Approach </li></ul><ul><li>Implementation of QuaSAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Experience Gained </li></ul><ul><li>Conclusions </li></ul>
    18. 18. Results - Latency
    19. 19. Results - Partitioning
    20. 20. <ul><li>QoS in the Internet </li></ul><ul><li>Proposed Approach </li></ul><ul><li>Implementation of QuaSAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Experience Gained </li></ul><ul><li>Conclusions </li></ul>
    21. 21. Problems with QuaSAR <ul><li>Linux OS running for each routelet </li></ul><ul><li>Context switch overhead between routelets </li></ul><ul><li>Memory protection between domains </li></ul><ul><li>Much of the work per packet occurs during classification </li></ul><ul><ul><li>This is assigned to the best effort router, therefore much of the flow’s work does not occur in its routelet </li></ul></ul><ul><li>Routelets have no direct access to physical network devices </li></ul><ul><li>No soft real-time scheduler for Xen available during this project </li></ul>
    22. 22. <ul><li>QoS in the Internet </li></ul><ul><li>Proposed Approach </li></ul><ul><li>Implementation of QuaSAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Experience Gained </li></ul><ul><li>Conclusions </li></ul>
    23. 23. Conclusions <ul><li>Virtualisation can be used to partition a router into several distinct routelets </li></ul><ul><ul><li>QoS flow partitioning opportunities </li></ul></ul><ul><ul><li>Virtual segregation of network for management purposes </li></ul></ul><ul><li>Application specific routelets can be built for different classes of network traffic </li></ul><ul><li>It is possible to build a router which uses virtualisation without a huge loss in performance </li></ul>
    24. 24. QuaSAR Hierarchically (Actual) Packet Demultiplexer Domain 0 Domain 0 Real Hardware Virtualisation Layer Virtual Machines
    25. 25. Demultiplexer - Click Architecture best effort router best effort router best effort router best effort router
    26. 26. Results - Jitter
    27. 27. Results - Throughput