NetworkScheduling.pdf

Network Scheduling in

Software-defined Environments

Tal Mizrahi*

◊

, Yoram Moses*

*Technion – Israel Institute of Technology

◊

Marvell

SDN Research Group, IRTF IETF 96, Berlin, Germany

Outline

•

Background

•

Use cases

•

Accurate scheduling

•

Conclusion

Outline

•

Background

•

Use cases

•

Accurate scheduling

•

Conclusion

Software Defined & Programmable Networks

The TimedSDN Project 4

switch

switch

switch

switch

Controller / NMS

switch

switch

switch

switch

vSwitch

•

Centralized

•

Flexible

at a Glance

Controller

The TimedSDN Project 5

Switches

Synchronized

clocks

A protocol allowing the controller to

Outline

•

Background

•

Use cases

•

Accurate scheduling

•

Conclusion

Using Time in Network-managed Environments

The TimedSDN Project 7

Client

Server 1

Server 2

...

Server n

T

T

T

Client

Server 1

Server 2

...

Server n

T

T

T

Coordinated

Using

Time

to Coordinate

Updates

The TimedSDN Project 8

Timed sequence

Switches invoke update according

to a scheduled sequence

OpenFlow

I2RS

…

Simultaneous

Time

is Optimal for Flow Swaps

[INFOCOM ‘16]

The TimedSDN Project 9

A key benefit of SDN:

Dynamic path allocation based on network load

controller

...

o

2

o

controller

...

o

2

o

Time

is Optimal for Flow Swaps

[INFOCOM ‘16]

The TimedSDN Project 10

A key benefit of SDN:

Dynamic path allocation based on network load

old

new

Temporary congestion.

If O

, O

are

not

updated

at the

same time

…

controller

...

o

2

o

Time

is Optimal for Flow Swaps

[INFOCOM ‘16]

The TimedSDN Project 11

A key benefit of SDN:

Dynamic path allocation based on network load

old

new

If O

, O

are updated

Consistent Path Update

0

The TimedSDN Project 12

S

S

S

S

S2 S1

S3 S4

S2 S1

S3 S4

S2 S1

S3 S4

S2 S1

S3 S4

1

2

3

0. The ‘before’ configuration.

1. Controller updates S

.

2. Controller updates S

.

3. Controller updates S

.

S

S

S

S

after

before

wait…

wait…

Simultaneous Updates?

The TimedSDN Project 13

En-route packets run into a ‘black hole’.

Not consistent!

S2 S1

S3 S4

S2 S1

S3 S4

S2 S1

S3 S4

S2 S1

S3 S4

Timed

Multi-phase Consistent Updates

[SOSR ‘15]

The TimedSDN Project 14

-

The controller sends timed update messages to S

1

, S

2

, S

3

.

-

Scheduled updates occur at times T

1

, T

2

, T

3

.

T

1

T

2

T

3

Controller does not need to wait between steps!

S2 S1

S3 S4

S2 S1

S3 S4

S2 S1

S3 S4

S2 S1

ingress

switch

vSwitch

Timestamped Domain

External

Network

VNF

egress

switch

Using

Timestamps

instead of

[SWFAN ‘16]

The TimedSDN Project 15

Timestamp is

•

Pushed by ingress switch.

•

Removed by egress switch.

X

Timestamp can be used in processing of

intermediate devices.

•

Delay measurement.

•

Passive performance monitoring.

https://tools.ietf.org/html/draft-ietf-ippm-alt-mark

Timestamp-based marking.

Outline

•

Background

•

Use cases

•

Accurate scheduling

•

Conclusion

Accurate Synchronization: It’s Already Here

The TimedSDN Project 17

Precision Time Protocol (PTP)

[

IEEE 1588 2008

]

~

1

μ

sec

accuracy

Mobile backhaul

Power substations

Industrial automation Financial applications

China Mobile: over 1,000,000 PTP-enabled base stations

T

IME

F

LIP

: Timestamp-based TCAM Lookup

conventional

The TimedSDN Project 18

packet’s search

key

action

s

, …, s

TCAM

Network Device

action

s

, …, s

TCAM

Network Device

T

s

, …, s

T

³

T

TCAM

Network Device

action

The timestamp is used in the TCAM key –

time range

.

COTS switches can synchronize clocks very accurately ~ 1 μsec.

[Using IEEE 1588 Precision Time Protocol (PTP) or GPS]

TimeFlip

The TimedSDN Project

The Cost of T

IME

F

LIP

: 1 Bit / 1 Entry

•

Theorem: if

𝑇𝑂𝐿 ≥ 2

𝑙𝑜𝑔

2

(∆)

, then the every

timestamp range requires as little as:

–

1 bit in the timestamp field.

–

1 TCAM entry.

T

s

, …, s

T

³

T

TCAM

Network Device

search

key

action

Large # of bits in timestamp field?

T

IME

F

LIP

: Would it Work on a Real Switch?

Yes !!

The TimedSDN Project 20

Microbenchmark: TimeFlip was tested on a

Outline

•

Background

•

Use cases

•

Accurate scheduling

•

Conclusion

The

Project

The TimedSDN Project 22

Why do we need

time

in SDN?

Scheduling

protocols

Accurate scheduling

methods

SDN Clock

synchronization

R

EVERSE

PTP

[HotSDN ‘14, ISPCS ‘14]

T

IME

F

LIP

[INFOCOM ‘15]

O

NE

C

LOCK

[NOMS ‘16]

OpenFlow

Scheduled Bundles

[INFOCOM ’16]

NETCONF

Time Capability

[NOMS ’16]

Multi-phase

updates

[SOSR, ‘15]

Network-managed

coordination

[NOMS, ‘16]

Flow Swaps

T

IME

4

[INFOCOM, ‘16]

Data Plane

Timestamping

The

Project – Practical Aspects

The TimedSDN Project 23

Scheduling

protocols

OpenFlow

Scheduled Bundles

[INFOCOM ’16]

NETCONF

Time Capability

[NOMS ’16]

OpenFlow 1.5

RFC 7758

The

Project – Practical Aspects

OpenFlow

Scheduled

Bundles

The TimedSDN Project 24

https://github.com/TimedSDN

Open Source Prototypes

NETCONF

Time

Capability

ReversePTP

OpenFlow

Scheduled

at a Glance

Controller

The TimedSDN Project 25

Switches

Synchronized

clocks

A protocol allowing the controller to

The

Project – Future Directions

Data plane

timestamping

Timed Updates

SFC

NETCONF

RFC 7758 ++

I2RS

NVO3

Time

as a network

programming

abstraction

P4

Implementation and

wide-scale

experiments

We would be happy to collaborate with

vendors / operators who are interested!

…

…

Thanks!

The

Timed

Project

http://tx.technion.ac.il/~dew/TimedSDN.html

A Closer Look at T

IME

F

LIP

The TimedSDN Project

Further details can be found in:

•

TimeFlip paper (

http://tx.technion.ac.il/~dew/TimeFlipINFOCOM.pdf

)

•

TimeFlip presentation (

http://tx.technion.ac.il/~dew/TimeFlipInfocomPres.pdf

)

SDN Switches

The TimedSDN Project 29

switch

switch

switch

switch

controller

switch

switch

switch

switch

TCAM1 TCAM2 ... TCAMn

incoming packet

TCAM: Ternary Content Addressable Memory

•

Memory for quick searching

•

Top-down search: first match “wins”

•

Ternary: 0 / 1 / *

•

* = don’t care

The TimedSDN Project 30

action

s

, …, s

TCAM

Network Device

packet’s search

T

IME

F

LIP

: Timestamp-based TCAM Lookup

conventional

The TimedSDN Project 31

packet’s search

key

action

s

, …, s

TCAM

Network Device

action

s

, …, s

TCAM

Network Device

T

s

, …, s

T

³

T

TCAM

Network Device

action

The timestamp is used in the TCAM key –

time range

.

COTS switches can synchronize clocks very accurately ~ 1 μsec.

[Using IEEE 1588 Precision Time Protocol (PTP) or GPS]

TimeFlip

Time-based Updates using T

IME

F

LIP

The TimedSDN Project 32

controller

...

o

2

o

old

new

TimeFlip:

switch accurately

starts using ‘new’ at T

₀

.

T

s

, …, s

T

³

T

TCAM

Network Device

search

key

‘new’

Example: Timestamp Format

The TimedSDN Project 33

Second Fraction

Seconds

Time.Sec

Time.Frac

Example: T

IME

F

LIP in Practice

The TimedSDN Project 34

Time.Sec

1

Time.Frac

*

…

*

*

*

Periodic range

0

... timestamp

value

1 second

action

timestamp field2 field3 field4 …

Flow Table

Network Device

packet header

Goal: schedule an update to be performed at

2016-07-22 11:41:11

(at the beginning of the second)

Procedure: (steps also appear in the figure)

Step : install a TimeFlip with ‘1’ in the

lsbit of the seconds field, and ‘don’t care’ in

the rest.

Step : the update becomes effective

exactly at the turn of the second.

Step : make the TCAM rule permanent by

writing ‘don’t care’ to the lsbit of the

timestamp field.

1

2

3

References

The TimedSDN Project 35

[1] T. Mizrahi, Y. Moses, "Software Defined Networks: It's About Time", IEEE INFOCOM, 2016.

[2] T. Mizrahi, Y. Moses, "OneClock to Rule Them All: Using Time in Networked Applications", IEEE/IFIP Network Operations and Management Symposium (NOMS), 2016. [3] T. Mizrahi, E. Saat, Y. Moses, "Timed Consistent Network Updates", ACM SIGCOMM Symposium on SDN Research (SOSR), 2015.

[4] T. Mizrahi, E. Saat, Y. Moses, "Timed Consistent Network Updates in Software Defined Networks", IEEE/ACM Transactions on Networking (ToN), 2016. [5] T. Mizrahi, O. Rottenstreich, Y. Moses, "TimeFlip: Scheduling Network Updates with Timestamp-based TCAM Ranges", IEEE INFOCOM, 2015.

[6] T. Mizrahi, Y. Moses, "Time-based Updates in Software Defined Networks", workshop on hot topics in software defined networks (HotSDN), 2013. [7] T. Mizrahi, Y. Moses, "On the Necessity of Time-based Updates in SDN", Open Networking Summit (ONS), 2014.

[8] 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), 2014.

[9] T. Mizrahi, Y. Moses, "ReversePTP: A Software Defined Networking Approach to Clock Synchronization", workshop on hot topics in software defined networks (HotSDN), 2014. [10] T. Mizrahi and Y. Moses, "ReversePTP: A clock synchronization scheme for software defined networks", International Journal of Network Management (IJNM), 2016.

[11] T. Mizrahi, Y. Moses, "Time4: Time for SDN", arXiv preprint arXiv:1505.03421, 2016.

[12] T. Mizrahi, Y. Moses, "The Case for Data Plane Timestamping in SDN", IEEE INFOCOM Workshop on Software-Driven Flexible and Agile Networking (SWFAN), 2016. [13] T. Mizrahi, Y. Moses, "Time Capability in NETCONF", RFC 7758, 2016.