SDN traceroute Tracing SDN Forwarding without Changing Network

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SDN traceroute: Tracing SDN Forwarding without Changing Network Behavior Presenter:Hung-Yen Wang Authors:Kanak Agarwal, Eric

SDN traceroute: Tracing SDN Forwarding without Changing Network Behavior Presenter:Hung-Yen Wang Authors:Kanak Agarwal, Eric Rozner, Colin Dixon, John Carter Published in:Hot. SDN’ 14 Department of Computer Science and Information Engineering National Cheng Kung University, Taiwan R. O. C.

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung University CSIE Computer & Internet Architecture Lab 2

Introduction l Software Defined Networking (SDN) makes it easier to modify the control plane

Introduction l Software Defined Networking (SDN) makes it easier to modify the control plane of networks. But it also potentially makes the network a more complex system. l SDN controller often translates high-level configuration into low-level rules, which can be difficult for network operators to predict the exact low-level rules, and thus expect network behavior. l When troubleshooting a problem, SDN programmer must grapple with many possibilities including bugs in controller logic, switch, individual SDN applications, and their compositions. National Cheng Kung University CSIE Computer & Internet Architecture Lab 3

Introduction l Traceroute can only provide the layer-3(IP) path information, which is limited. l

Introduction l Traceroute can only provide the layer-3(IP) path information, which is limited. l This paper proposed SDN traceroute, which report the path as a list of ports on switches. l SDN traceroute does not modify the existing rules, and only uses a small number of high priority rules to trap probes. National Cheng Kung University CSIE Computer & Internet Architecture Lab 4

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung University CSIE Computer & Internet Architecture Lab 5

Model-driven l Model-driven approaches first gather enough network state to build a model, and

Model-driven l Model-driven approaches first gather enough network state to build a model, and then use that model to answer questions. l Scraping rules from switches directly or controller maintain the correct view of the rules in the network at all time. National Cheng Kung University CSIE Computer & Internet Architecture Lab 6

Active probes and Monitoring l Sending active probes or monitoring production traffic to measure

Active probes and Monitoring l Sending active probes or monitoring production traffic to measure the ground truth behavior of data plane. l Require the network infrastructure to allow for traffic to be trapped or logged as it traverse the network. National Cheng Kung University CSIE Computer & Internet Architecture Lab 7

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung University CSIE Computer & Internet Architecture Lab 8

SDN traceroute –First phase l Using a graph coloring algorithm to color every switch

SDN traceroute –First phase l Using a graph coloring algorithm to color every switch in the networks. l Installing a small numbers of high-priority rules in every switch, which allow them to trap probe packets. National Cheng Kung University CSIE Computer & Internet Architecture Lab 9

SDN traceroute –First phase CONT refers to the send to controller action. National Cheng

SDN traceroute –First phase CONT refers to the send to controller action. National Cheng Kung University CSIE Computer & Internet Architecture Lab 10

SDN traceroute –Second phase l SDN traceroute injects a probe packet into the network

SDN traceroute –Second phase l SDN traceroute injects a probe packet into the network to start tracing the route. National Cheng Kung University CSIE Computer & Internet Architecture Lab 11

SDN traceroute l SDN traceroute uses VLAN priority field(three bits) to carry colors. Default

SDN traceroute l SDN traceroute uses VLAN priority field(three bits) to carry colors. Default tag 000 is reserved for production traffic. l SDN traceroute requires every traffic to carry a color. l TABLE action indicates that the switch should treat the packet as though it had been received on the input port. l Output sequence <switch ID, port> National Cheng Kung University CSIE Computer & Internet Architecture Lab 12

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung University CSIE Computer & Internet Architecture Lab 13

Evaluation l Five IBM Rack-Switch G 8264 Open. Flow-enabled switches connecting several commodity servers

Evaluation l Five IBM Rack-Switch G 8264 Open. Flow-enabled switches connecting several commodity servers running Openvswitch. l Use Floodlight as controller. l Repeatedly installed random routes and verified that SDN traceroute correctly discovered them. l Shows the latency of conducting traces on various network paths. National Cheng Kung University CSIE Computer & Internet Architecture Lab 14

SDN traceroute solution l Undefined switch behavior. l Bugs in the Controller. l SDN

SDN traceroute solution l Undefined switch behavior. l Bugs in the Controller. l SDN traceroute latency. National Cheng Kung University CSIE Computer & Internet Architecture Lab 15

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung University CSIE Computer & Internet Architecture Lab 16

Advantages l Non-invasive l Accurate l Low resource consumption l Arbitrary traffic National Cheng

Advantages l Non-invasive l Accurate l Low resource consumption l Arbitrary traffic National Cheng Kung University CSIE Computer & Internet Architecture Lab 17

Limitations l National Cheng Kung University CSIE Computer & Internet Architecture Lab 18

Limitations l National Cheng Kung University CSIE Computer & Internet Architecture Lab 18

SDN traceroute VS Scraping rules l Switches today have limited TCAM space which prevents

SDN traceroute VS Scraping rules l Switches today have limited TCAM space which prevents upfront static installation of all rules on the switch l Constantly scraping a large number of rules from a large number of switches can be burdensome. National Cheng Kung University CSIE Computer & Internet Architecture Lab 19

Table action support National Cheng Kung University CSIE Computer & Internet Architecture Lab 20

Table action support National Cheng Kung University CSIE Computer & Internet Architecture Lab 20

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung

Outline l l l Introduction Background Proposed Schemes Evaluation Discussion Conclusion National Cheng Kung University CSIE Computer & Internet Architecture Lab 21

Conclusion l By using the actual rules within the switches to debug arbitrary flows

Conclusion l By using the actual rules within the switches to debug arbitrary flows and packets. And need not to change existing rules to trap probes. l Only requires upfront installation of only a small number of rules per switch resulting in a very resource overhead. National Cheng Kung University CSIE Computer & Internet Architecture Lab 22