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Shadow Configurations: A Network Management Primitive Richard Alimi, Ye Wang, Y. Richard Yang Laboratory of Networked Systems Yale University
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August 19, 2008Yale LANS / SIGCOMM 20082 Configuration is Complex Source: The Yankee Group, 2004 Source: Juniper Networks, 2008 “... human error is blamed for 50-80% of network outages.” “80% of IT budgets is used to maintain the status quo.”
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August 19, 2008Yale LANS / SIGCOMM 20083 Configuration is Complex Source: The Yankee Group, 2004 Source: Juniper Networks, 2008 “... human error is blamed for 50-80% of network outages.” “80% of IT budgets is used to maintain the status quo.” Why is configuration hard today?
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August 19, 2008Yale LANS / SIGCOMM 20084 Simulation & Analysis Depend on simplified models Network structure Hardware and software Limited scalability Hard to access real traffic Configuration Management Today OSPF eBGP VPNs ACLs TE SLAsiBGPTraffic Software Hardware
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August 19, 2008Yale LANS / SIGCOMM 20085 Configuration Management Today Simulation & Analysis Depend on simplified models Network structure Hardware and software Limited scalability Hard to access real traffic Test networks Can be prohibitively expensive OSPF eBGP VPNs ACLs TE SLAsiBGPTraffic Software Hardware
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August 19, 2008Yale LANS / SIGCOMM 20086 Configuration Management Today Simulation & Analysis Depend on simplified models Network structure Hardware and software Limited scalability Hard to access real traffic Test networks Can be prohibitively expensive OSPF eBGP VPNs ACLs TE SLAsiBGPTraffic Software Hardware Why are these not enough?
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August 19, 2008Yale LANS / SIGCOMM 20087 Analogy with Programming Programming Program Target System
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August 19, 2008Yale LANS / SIGCOMM 20088 Analogy with Programming Programming Network Management Program Target System Configs Target Network
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August 19, 2008Yale LANS / SIGCOMM 20089 Analogy with Databases Databases INSERT... DELETE... UPDATE... INSERT... DELETE... UPDATE... STATE A STATE B
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August 19, 2008Yale LANS / SIGCOMM 200810 Analogy with Databases Databases Network Management INSERT... DELETE... UPDATE... INSERT... DELETE... UPDATE... STATE A STATE B ip route... ip addr... STATE A ? router bgp... STATE B STATE C router ospf... STATE D
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August 19, 2008Yale LANS / SIGCOMM 200811 Enter, Shadow Configurations Key ideas Allow additional (shadow) config on each router In-network, interactive shadow environment “Shadow” term from computer graphics OSPF eBGP VPNs ACLs TE SLAsiBGPTraffic Software Hardware
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August 19, 2008Yale LANS / SIGCOMM 200812 Enter, Shadow Configurations OSPF eBGP VPNs ACLs TE SLAsiBGPTraffic Software Hardware Key Benefits Realistic (no model) Scalable Access to real traffic Transactional Key ideas Allow additional (shadow) config on each router In-network, interactive shadow environment “Shadow” term from computer graphics
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August 19, 2008Yale LANS / SIGCOMM 200813 Roadmap Motivation and Overview System Basics and Usage System Components Design and Architecture Performance Testing Transaction Support Implementation and Evaluation
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August 19, 2008Yale LANS / SIGCOMM 200814 What's in the shadow configuration? Routing parameters ACLs Interface parameters VPNs QoS parameters Shadow config Real config System Basics
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August 19, 2008Yale LANS / SIGCOMM 200815 What's in the shadow configuration? Routing parameters ACLs Interface parameters VPNs QoS parameters Shadow config Real config Shadow header marked “1” Real header marked “0” System Basics
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August 19, 2008Yale LANS / SIGCOMM 200816 Example Usage Scenario: Backup Path Verification Primary Backup
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August 19, 2008Yale LANS / SIGCOMM 200817 Example Usage Scenario: Backup Path Verification Send test packets in shadow
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August 19, 2008Yale LANS / SIGCOMM 200818 Example Usage Scenario: Backup Path Verification Disable shadow link XX
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August 19, 2008Yale LANS / SIGCOMM 200819 Example Usage Scenario: Backup Path Verification
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August 19, 2008Yale LANS / SIGCOMM 200820 Example Usage Scenario: Configuration Evaluation Video Server
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August 19, 2008Yale LANS / SIGCOMM 200821 Example Usage Scenario: Configuration Evaluation Video Server
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August 19, 2008Yale LANS / SIGCOMM 200822 Example Usage Scenario: Configuration Evaluation Video Server Duplicate packets to shadow
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August 19, 2008Yale LANS / SIGCOMM 200823 Roadmap Motivation and Overview System Basics and Usage System Components Design and Architecture Performance Testing Transaction Support Implementation and Evaluation
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August 19, 2008Yale LANS / SIGCOMM 200824 Design and Architecture Management Control Plane Forwarding Engine Configuration UI BGP OSPF IS-IS Interface 0 Interface 1 Interface 2 Interface 3 FIB
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August 19, 2008Yale LANS / SIGCOMM 200825 Design and Architecture Management Control Plane Forwarding Engine Configuration UI BGP OSPF IS-IS Shadow-enabled FIB Shadow Bandwidth Control Interface 0 Interface 1 Interface 2 Interface 3
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August 19, 2008Yale LANS / SIGCOMM 200826 Design and Architecture Management Control Plane Forwarding Engine Configuration UI Shadow Management BGP OSPF IS-IS Shadow-enabled FIB Shadow Bandwidth Control Interface 0 Interface 1 Interface 2 Interface 3
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August 19, 2008Yale LANS / SIGCOMM 200827 Design and Architecture Management Control Plane Forwarding Engine Configuration UI Shadow Management Commitment BGP OSPF IS-IS Shadow-enabled FIB Shadow Bandwidth Control Interface 0 Interface 1 Interface 2 Interface 3
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August 19, 2008Yale LANS / SIGCOMM 200828 Design and Architecture Management Control Plane Forwarding Engine Configuration UI Shadow Traffic Control FIB Analysis Debugging Tools Shadow Management Commitment BGP OSPF IS-IS Shadow-enabled FIB Shadow Bandwidth Control Interface 0 Interface 1 Interface 2 Interface 3
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August 19, 2008Yale LANS / SIGCOMM 200829 Design and Architecture Management Control Plane Forwarding Engine Configuration UI Shadow Traffic Control FIB Analysis Debugging Tools Shadow Management Commitment BGP OSPF IS-IS Shadow-enabled FIB Shadow Bandwidth Control Interface 0 Interface 1 Interface 2 Interface 3
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August 19, 2008Yale LANS / SIGCOMM 200830 Shadow Bandwidth Control Requirements Minimal impact on real traffic Accurate performance measurements of shadow configuration
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August 19, 2008Yale LANS / SIGCOMM 200831 Shadow Bandwidth Control Requirements Minimal impact on real traffic Accurate performance measurements of shadow configuration Supported Modes Priority Bandwidth Partitioning Packet Cancellation
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August 19, 2008Yale LANS / SIGCOMM 200832 Observation Content of payload may not important in many network performance testing scenarios Only payload size may matter Packet Cancellation
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August 19, 2008Yale LANS / SIGCOMM 200833 Observation Content of payload may not important in many network performance testing scenarios Only payload size may matter Idea: only need headers for shadow traffic Piggyback shadow headers on real packets Piggybacked shadow header Packet Cancellation
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August 19, 2008Yale LANS / SIGCOMM 200834 Packet Cancellation Details Output interface maintains real and shadow queues Packet cancellation scheduling If real queue non-empty Grab real packet Piggyback shadow header(s) if available Else if shadow queue non-empty Send full shadow packet
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August 19, 2008Yale LANS / SIGCOMM 200835 Commitment Objectives Smoothly swap real and shadow across network Eliminate effects of transient states due to config changes Easy to swap back
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August 19, 2008Yale LANS / SIGCOMM 200836 Commitment Objectives Smoothly swap real and shadow across network Eliminate effects of transient states due to config changes Easy to swap back Issue Packet marked with shadow bit 0 = Real, 1 = Shadow Shadow bit determines which FIB to use Routers swap FIBs asynchronously Inconsistent FIBs applied on the path
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August 19, 2008Yale LANS / SIGCOMM 200837 Commitment Protocol Idea: Use tags to achieve consistency Temporary identifiers Basic algorithm has 4 phases
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August 19, 2008Yale LANS / SIGCOMM 200838 Commitment Protocol Idea: Use tags to achieve consistency Temporary identifiers Basic algorithm has 4 phases Distribute tags for each config C-old for current real config C-new for current shadow config 0 0 0 0 1 1 0: C-old 1: C-new 1 0 1 0 1 0 0
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August 19, 2008Yale LANS / SIGCOMM 200839 Commitment Protocol Idea: Use tags to achieve consistency Temporary identifiers Basic algorithm has 4 phases Distribute tags for each config C-old for current real config C-new for current shadow config Routers mark packets with tags C-old C-new C-old C-new C-old C-new 1 0 1 0 1 0 0
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August 19, 2008Yale LANS / SIGCOMM 200840 C-old C-new C-old C-new C-old C-new 0: C-new 1: C-old 1 0 1 0 1 0 1 Commitment Protocol Idea: Use tags to achieve consistency Temporary identifiers Basic algorithm has 4 phases Distribute tags for each config C-old for current real config C-new for current shadow config Routers mark packets with tags Swap configs (tags still valid)
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August 19, 2008Yale LANS / SIGCOMM 200841 Commitment Protocol Idea: Use tags to achieve consistency Temporary identifiers Basic algorithm has 4 phases Distribute tags for each config C-old for current real config C-new for current shadow config Routers mark packets with tags Swap configs (tags still valid) Remove tags from packets Resume use of shadow bit 0 0 1 0 1 0 1 0 1
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August 19, 2008Yale LANS / SIGCOMM 200842 Commitment Protocol Idea: Use tags to achieve consistency Temporary identifiers Basic algorithm has 4 phases Distribute tags for each config C-old for current real config C-new for current shadow config Routers mark packets with tags Swap configs (tags still valid) Remove tags from packets Resume use of shadow bit For more details, see paper 0 0 1 0 1 0 1 0 1
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August 19, 2008Yale LANS / SIGCOMM 200843 Roadmap Motivation and Overview System Basics and Usage System Components Design and Architecture Performance Testing Transaction Support Implementation and Evaluation
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August 19, 2008Yale LANS / SIGCOMM 200844 Implementation Kernel-level (based on Linux 2.6.22.9) TCP/IP stack support FIB management Commitment hooks Packet cancellation Tools Transparent software router support (Quagga + XORP) Full commitment protocol Configuration UI (command-line based) Evaluated on Emulab (3Ghz HT CPUs)
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August 19, 2008Yale LANS / SIGCOMM 200845 Static FIB 300B pkts No route caching With FIB updates 300B pkts @ 100Mbps 1-100 updates/sec No route caching Static FIB 300B pkts No route caching
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August 19, 2008Yale LANS / SIGCOMM 200846 FIB storage overhead for US Tier-1 ISP Evaluation: Memory Overhead
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August 19, 2008Yale LANS / SIGCOMM 200847 Evaluation: Packet Cancellation Accurate streaming throughput measurement Abilene topology Real transit traffic duplicated to shadow Video streaming traffic in shadow
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August 19, 2008Yale LANS / SIGCOMM 200848 Evaluation: Packet Cancellation Limited interaction of real and shadow Intersecting real and shadow flows CAIDA traces Vary flow utilizations
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August 19, 2008Yale LANS / SIGCOMM 200849 Evaluation: Packet Cancellation Limited interaction of real and shadow Intersecting real and shadow flows CAIDA traces Vary flow utilizations
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August 19, 2008Yale LANS / SIGCOMM 200850 Evaluation: Commitment Applying OSPF link-weight changes Abilene topology with 3 external peers Configs translated to Quagga syntax Abilene BGP dumps
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August 19, 2008Yale LANS / SIGCOMM 200851 Evaluation: Commitment Applying OSPF link-weight changes Abilene topology with 3 external peers Configs translated to Quagga syntax Abilene BGP dumps Reconvergence in shadow
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August 19, 2008Yale LANS / SIGCOMM 200852 Conclusion and Future Work Shadow configurations is new management primitive Realistic in-network evaluation Network-wide transactional support for configuration Future work Evaluate on carrier-grade installations Automated proactive testing Automated reactive debugging
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August 19, 2008Yale LANS / SIGCOMM 200853 Thank you!
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August 19, 2008Yale LANS / SIGCOMM 200854 Backup Slides
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August 19, 2008Yale LANS / SIGCOMM 200855 Evaluation: Router Maintenance Setup Abilene topology with 3 external peers Configs translated to Quagga syntax Abilene BGP dumps
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