Time and Timestamping in Softwarized Environments

Transcription

1 Time and Timestamping in Softwarized Environments Tal Mizrahi, Yoram Moses Technion Israel Institute of Technology April 2016

2 The First Synchronized Clocks Railway switch 2

3 Networks: Communications vs. Trains SDN Controller Train Control Center Network switch Railway switch 3

4 Timed at a Glance Controller A protocol allowing the controller to schedule network updates Synchronized clocks Switches 4

5 Accurate Synchronization: It s Already Here Precision Time Protocol (PTP) [IEEE ] ~1μsec accuracy But what about Software Defined Networks? Mobile backhaul Power substations Open Networking Foundation (ONF) SDN product directory Industrial automation Financial applications China Mobile: over 1,000,000 PTP-enabled base stations ~70% ~70% of the SDNenabled silicons have native PTP support. 5

6 Timed at a Glance Challenge: A protocol allowing the controller to schedule network updates Controller Synchronized clocks Switches 6

7 The Project Why do we need time in SDN? Flow Swaps TIME4 [INFOCOM, 16] Multi-phase updates [SOSR, 15] Data Plane Timestamping [SWFAN, 16] ONECLOCK to Rule Them All [NOMS, 16] Scheduling protocols Accurate scheduling methods SDN Clock synchronization OpenFlow Scheduled Bundles [INFOCOM 16, OpenFlow 1.5] TIMEFLIP [INFOCOM 15] REVERSEPTP [HotSDN 14, ISPCS 14] NETCONF Time Capability [NOMS 16, RFC7758] ONECLOCK [NOMS 16] 7

8 The Project Why do we need time in SDN? Flow Swaps TIME4 [INFOCOM, 16] Multi-phase updates [SOSR, 15] Data Plane Timestamping [SWFAN, 16] ONECLOCK to Rule Them All [NOMS, 16] Scheduling protocols Accurate scheduling methods SDN Clock synchronization OpenFlow Scheduled Bundles [INFOCOM 16, OpenFlow 1.5] TIMEFLIP [INFOCOM 15] REVERSEPTP [HotSDN 14, ISPCS 14] NETCONF Time Capability [NOMS 16, RFC7758] ONECLOCK [NOMS 16] 8

9 Time is Optimal for Flow Swaps [INFOCOM 16] A key benefit of SDN: Dynamic path allocation based on network load old new o 1... o 2 controller 9

10 Time is Optimal for Flow Swaps [INFOCOM 16] A key benefit of SDN: Dynamic path allocation based on network load If O 1, O 2 are not updated at the same time Temporary congestion. old new o 1... o 2 controller O 2 is updated first. 10

11 Time is Optimal for Flow Swaps [INFOCOM 16] TIME4 If O 1, O 2 are updated at the same time: No congestion! A key benefit of SDN: Dynamic path allocation based on network load old new o 1... o 2 controller 11

12 The Project Why do we need time in SDN? Flow Swaps TIME4 [INFOCOM, 16] Multi-phase updates [SOSR, 15] Data Plane Timestamping [SWFAN, 16] ONECLOCK to Rule Them All [NOMS, 16] Scheduling protocols Accurate scheduling methods SDN Clock synchronization OpenFlow Scheduled Bundles [INFOCOM 16, OpenFlow 1.5] TIMEFLIP [INFOCOM 15] REVERSEPTP [HotSDN 14, ISPCS 14] NETCONF Time Capability [NOMS 16, RFC7758] ONECLOCK [NOMS 16] 12

13 Example: Consistent Path Update Sequential update approaches: [Dionysus 14] [zupdate 13] [Vanbever et al. 11] [Francois et al. 07] 0. The before configuration. 1. Controller updates S Controller updates S Controller updates S 3. X before after S 3 S 4 S 2 S 1 S 3 S 4 S 3 S 4 wait S 3 S 4 wait S 3 S 4 S 2 S 1 S 2 S 1 S 2 S 1 S 2 S

14 Simultaneous Updates? En-route packets run into a black hole. Not consistent! S 3 S 4 S 3 S 4 S 3 S 4 S 3 S 4 S 2 S 1 S 2 S 1 S 2 S 1 S 2 S

15 Timed Multi-phase Consistent Updates [SOSR 16] - The controller sends timed update messages to S 1, S 2, S 3. - Scheduled updates occur at times T 1, T 2, T 3. Controller does not need to wait between steps! S 3 S 4 S 3 S 4 S 3 S 4 S 3 S 4 S 2 S 1 S 2 S 1 S 2 S 1 S 2 S 1 T 1 T 2 T 3 15

16 The Project Why do we need time in SDN? Flow Swaps TIME4 [INFOCOM, 16] Multi-phase updates [SOSR, 15] Data Plane Timestamping [SWFAN, 16] ONECLOCK to Rule Them All [NOMS, 16] Scheduling protocols Accurate scheduling methods SDN Clock synchronization OpenFlow Scheduled Bundles [INFOCOM 16, OpenFlow 1.5] TIMEFLIP [INFOCOM 15] REVERSEPTP [HotSDN 14, ISPCS 14] NETCONF Time Capability [NOMS 16, RFC7758] ONECLOCK [NOMS 16] 16

17 Using Timestamps instead of The advantages of timestamping are well-known, e.g., [Lamport 78]. Current work: Data Plane Timestamping (DPT) in SDN. ingress egress Timestamp is switch switch External Pushed by ingress switch. Network Removed by egress switch. VNF X vswitch Timestamp can be used in processing of intermediate devices. Timestamped Domain 17

18 DPT Header Example: NSH Encapsulation All traffic is encapsulated with an NSH. NSH may include a timestamp [NSH-Timestamp]. ingress switch VNF egress switch External Network [NSH-Timestamp] is under discussion in the SFC working group of the IETF. NSH is used for Service Function Chaining (SFC). Defined by the SFC working group of the IETF. vswitch Timestamped Domain Network Service Header (NSH) encapsulation [NSH-Timestamp] R. Browne, A. Chilikin, B. Ryan, T. Mizrahi, and Y. Moses, Network service header timestamping, draft-browne-sfc-nsh-timestamp, work in progress, IETF,

19 Timestamps Ranges SDN switch (OpenFlow / P4) match action procedure SDN Switch SDN Switch DPT Processing Flow Table Flow Table packet header field1 field2 field3 action packet header timestamp field2 field3 field4 action Each bit has a ternary value: 0 // 1 // * Timestamp-based ranges [TimeFlip, INFOCOM 15] Extremal range (T T 0 ) Periodic range T timestamp value 0... timestamp value 19

20 Timestamp Format Network Time Protocol (NTP) timestamp format: Time.Sec Seconds Time.Frac Second Fraction 32 bits 32 bits 20

21 Timestamps Ranges: Examples SDN Switch DPT Processing SDN Switch DPT Processing packet header Flow Table timestamp field1 field2 field3 timestamp field1 field2 field3 action packet header Flow Table timestamp field2 field3 field4 action 0 1 * * * * 1 * * * * Time.Sec Time.Frac 2 31 >T 2 30 T 2 31 * * Time.Sec 1 * Time.Frac * Extremal range: T timestamp value Periodic range 0... timestamp value 1 second 21

22 DPT Use Case 1: Network Telemetry Delay measurement Loss measurement S 1 S 2 T 1 T 2 Time One-way delay: T 2 -T 1 Obviously DPT can be used for delay measurement. How can DPT be used for loss measurement? 22

23 Color-based Loss Measurement [Coloring]: All data packets from S 1 to S 2 include a 1-bit color. Measurement is performed separately for each block. S 1 inserts 1-bit color into packet header. S 1 toggles color. S 1 and S 2 maintain per-color counters. S 1 and S 2 periodically export counters to central point, e.g., SDN controller. S 1 S 2 CS1 1 CR1 1 CS0 1 CR0 1 CS1 2 CR1 2 Controller can compute: Packet loss = (CS1 2 -CS1 1 )-(CR1 2 -CR1 1 ) Time [Coloring] M. Chen, L. Zheng, G. Mirsky, G. Fioccola, and T. Mizrahi, IP Flow Performance Measurement Framework, draft-chen-ippm-coloringbased-ipfpm-framework, work in progress,

24 Color-based Delay Measurement Delay measurement: T 1 S 1 S 2 T 2 Time T 3 Controller can compute: Two-way delay = (T 4 -T 1 )-(T 3 -T 2 ) T 4 24

25 Color-based Measurement Q: How does an SDN switch toggle the color? A: Controller periodically updates S 1 coloring policy... Overhead on the controller S 1 S 2 CS1 1 CR1 1 CS0 1 CR0 1 CS1 2 CR1 2 Time 25

26 DPT-based Coloring Choose 1 bit from the timestamp. Use this bit as the color. Time.Sec Seconds Time.Frac Second Fraction Each switch has two match-action rules: Timestamp bit=0 Timestamp bit=1 Each block: a constant time interval. The controller is not involved in the color toggling. color timestamp value 26

27 DPT-based Coloring DPT allows for both delay and loss measurement. No other fields are necessary! A 1-bit timestamp is sufficient! Time.Sec Time.Frac Seconds Second Fraction color timestamp... value DPT-based coloring reduces the load on controller. 27

28 DPT Use Case 2: Consistent Updates Multicast tree update Two-phase update [Reitblatt et al. 12]. S 2 attaches version tags to packets. before / after. Indicate distribution tree. Guarantees per-packet consistency. before S 3 S 4 after S 2 S 1 28

29 Two-Phase Consistent Updates 1. Controller sends after configuration to S 1,S 2 (subject to after version tag). 2. Controller updates S 2 to start sending after version tag. S 3 S 4 S 3 S 4 S 3 S 4 S 2 S 1 S 2 S 1 S 2 S

30 DPT-based One-Phase Consistent Updates 1. Controller sends after configuration to S 1,S 2 (subject to Timestamp T threshold ). 2. Controller updates S 2 to start sending after version tag. Switches automatically start using the after path when Timestamp T threshold The DPT is the version tag. S 3 S 4 S 3 S 4 DPT S 3 S 4 S 2 S 1 S 2 S 1 S 2 S

31 DPT-based One-Phase Consistent Updates DPT reduces the load on controller. DPT reduces the management overhead of per-flow version tags. 31

32 DPT Use Case 3: Elephant Flow Load Balancing 20 Gbps elephant flow A src S 1 S 2 S 20 5 dst B S 3 S 4 Stateless load balancing: - Equal Cost Multiple Paths (ECMP) 50% utilization. - Random Packet Spraying (RPS) [Dixit et al. 13]. Stateful methods, e.g., Round Robin. 32

33 DPT-based Load Balancing Push DPT to all packets. 20 Gbps elephant flow A src S 1 S 2 S 20 5 dst B S 3 S 4 DPT-based load balancing:... A B A B toggle interval... timestamp value 33

34 DPT-based Load Balancing A src S 1 S 2 S 20 5 dst B S 3 S 4 How does the controller compute the toggle interval? L = maximal packet length. BW = total bandwidth of the two links.... Toggle interval = L / BW Independent of the flow rate! Toggle interval A B A B... timestamp value 34

35 Goodput of DPT-based Load Balancing Load balancing using 1-bit from the DPT. DPT: higher goodput than RPS / ECMP. Toggle interval = L / BW 1 msec Time.Sec Seconds Time.Frac Second Fraction A B A B... timestamp value A B 35

36 The Project Why do we need time in SDN? Flow Swaps TIME4 [INFOCOM, 16] Multi-phase updates [SOSR, 15] Data Plane Timestamping [SWFAN, 16] ONECLOCK to Rule Them All [NOMS, 16] Scheduling protocols Accurate scheduling methods SDN Clock synchronization OpenFlow Scheduled Bundles [INFOCOM 16, OpenFlow 1.5] TIMEFLIP [INFOCOM 15] REVERSEPTP [HotSDN 14, ISPCS 14] NETCONF Time Capability [NOMS 16, RFC7758] ONECLOCK [NOMS 16] 36

37 OneClock to Rule Them All [NOMS 16] Many networked applications require time - Sensors - Actuators - IoT devices - Switches - Routers - Toasters Client Client T T T Server 1 Server 2... Server n T T T Server 1 Server 2... Server n Coordinated operation Coordinated snapshot 37

38 Summary

39 Summary Controller A protocol allowing the controller to schedule network updates Synchronized clocks Switches The Timed Project 39

40 Thanks!

41 References [1] T. Mizrahi, Y. Moses, Software Defined Networks: It s About Time", IEEE INFOCOM, [2] T. Mizrahi, Y. Moses, OneClock to Rule Them All: Using Time in Networked Applications, IEEE/IFIP Network Operations and Management Symposium (NOMS), [3] T. Mizrahi, E. Saat, Y. Moses, "Timed Consistent Network Updates", ACM SIGCOMM Symposium on SDN Research (SOSR), ( [4] T. Mizrahi, O. Rottenstreich, Y. Moses, "TimeFlip: Scheduling Network Updates with Timestamp-based TCAM Ranges", IEEE INFOCOM, ( [5] T. Mizrahi, Y. Moses, "Time-based Updates in Software Defined Networks", the second workshop on hot topics in software defined networks (HotSDN), ( [6] T. Mizrahi, Y. Moses, Using ReversePTP to Distribute Time in Software Defined Networks, International IEEE Symposium on Precision Clock Synchronization for Measurement, Control and Communication, (ISPCS), ( [7] T. Mizrahi, Y. Moses, "ReversePTP: A Software Defined Networking Approach to Clock Synchronization", in the third workshop on hot topics in software defined networks (HotSDN), ( [8] T. Mizrahi, Y. Moses, "Time4: Time for SDN", arxiv preprint arxiv: , ( [9] Open Networking Foundation, OpenFlow switch specification, Version 1.5.0, ( [10] Open Networking Foundation, OpenFlow extensions 1.3.x package 2, ( 41