Rapid Spanning Tree Protocol and Ethernet applications development€¦ · · 2013-07-29Rapid Spanning Tree Protocol and Ethernet applications development Embedded switches, specific

Rapid Spanning Tree Protocoland Ethernet applications development

Embedded switches, specific protocols, SW support

T3LAB Consortium, Via S. Bassanelli 9/11, Bologna Italy

Simone Cilli ([email protected])

mailto:[email protected]?subject=Industrial Ethernet Seminar 2012: Comment

Outline

13/12/2011Standard Ethernet for Industrial

Applications - T3LAB Bologna - Italy2

• Network topologies

• Spanning Tree Protocol (STP, RSTP, MSTP)

• Embedded switch

• TCP/IP protocol improvement

• Software package for embedded Ethernet switch

• Demo

Network Topologies

Standard Ethernet for Industrial


• Layout of computer cables and network devices

Physical Topology

• The way in which the devices see the network

Logical Topology

Network Topology

=

Physical Topology + Logical Topology

13/12/2011

Network Topologies



• Cheap and easy to implement

• Require less cable then other topologies

Advantages

• Disruption when device are added or removed

• Single break point

• Difficult to troubleshoot

Disadvantages

BUS LINE/CHAIN RING

• Easy to implement and to install

Advantages

• High delay for an high number of nodes

• Single point failure

Disadvantages

• Cable faults are easily located

• Easy to install

• Robustness

Advantages

• Loop


Disadvantages

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Network Topologies



MESH TREE

• Easily expanded without disruption

• Easy to troubleshoot and isolate problem

Advantages

• Require more cable then other topologies

• Central node is a point of failure

• Difficult to implement

Disadvantages

• Redundant paths

• Easy to expand

Advantages

• High cable cost

• Complicated implementation and management

Disadvantages

• Easy to expand

• Allow an high number of nodes

• Fully connected but no loops

Advantages

• A node failure affects all the leaf nodes

• Difficult to manage

Disadvantages

STAR

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Network Topologies



NODE

NODE NODE

NODE• Easy to expand



Advantages



Disadvantages NODE NODE

NODE

Robustness?High

performace

TREE

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Network Topologies



NODE

NODE

NODE

NODE

NODE

NODE




Advantages




Disadvantages

Robustness?High

performace

CHAIN

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Network Topologies



NODE

NODE

NODE

NODE

NODE

NODE




• Cable faults are easily located

• Easy to install

• Robustness

Advantages




Disadvantages

Robustness!High

performace

RING

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NODE

NODE

NODE

NODE

Network Topologies



Physical

Topology

Logical

Topology

NODE

NODE NODETREERING

AVOID LOOP RSTP

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“The Spanning Tree Protocol (STP)

is a network protocol that ensures

a loop-free topology for any

bridged Ethernet local area network”

Spanning tree protocol

•Standard IEEE 802.1D, IEEE 802.1W, IEEE 802.1D-2004

•Create spanning tree of connected layer 2 bridges

•Prevent loops and broadcast radiation

•Reconfiguration after a network fault

• Include spare (redundant) links to provide automatic backup paths if an active link fails

Rapid Spanning Tree Protocol

(RSTP) for a faster convergence

13/12/2011



Port States

STP (802.1D) RSTP (802.1W) Is port included in active topology?

Is port learning MAC addresses?

Disabled Discarding No No

Blocking Discarding No No

Listening Discarding Yes No

Learning Learning Yes Yes

Forwarding Forwarding Yes Yes

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Port Roles

Root

BA

RR

• This is the port closest tothe root bridgeRoot port

A

• It is designated if it can send the best BPDU on its segment

Designated port

DD

D • Alternate path to a designated port. It isblocked

Alternate port

• Alternative port to a bridge that is alreadyconnected

Backup portA R

D

B

The protocol electsa root node

(Root of logical tree)

D

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• Blocked portDisabled port

• Port not included in the topologyEdge port



STP BDPUProtocol Identifier [1:2]

Protocol Version

Identifier

[3]

BPDU Type [4]

Flags [5]

Root Identifier [6:13]

Path Cost [14:17]

Bridge Identifier [18:25]

Port Identifier [26:27]

Message Age [28:29]

Max Age [30:31]

Hello Time [32:33]

Forward Delay [34:35]

Message sent to the MAC01:80:C2:00:00:00

It is a multicast ethernet address

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Protocol Version

Identifier

[3]

BPDU Type [4]

Flags [5]


Path Cost [14:17]



Message Age [28:29]

Max Age [30:31]

Hello Time [32:33]


0 1 2 3 4 5 6 7

Topologychange ACK

Agreement

Forwarding

Learning

Port role

Proposal

Topologychange

FLAGS

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Protocol Version

Identifier

[3]

BPDU Type [4]

Flags [5]


Path Cost [14:17]



Message Age [28:29]

Max Age [30:31]

Hello Time [32:33]


•Current node identifier

Bridge Identifier

• Identifier of the port that generate the message

Port Identifier

•Network’s root identifier

Root Identifier

•Cost from the current node to the root

•Based on port’s speed

Path Cost

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RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3

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RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3

0. Disable all ports

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BPDU Handling

Bridge 1

Bridge 4Bridge 2

Bridge 3

0. Disable all ports 1. Root election

1. PROPOSAL (2)

Priority:B1 > B2B2 > B3B3 > B4

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1. PROPOSAL (1)



RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3



STP send aproposal and wait

2 x FORWARD DELAY TIME for a

silence agreement

RSTP IMPROVEPERFORMANCE

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1. PROPOSAL (1)

2. AGREEMENT (1)



RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3


2. AGREEMENT (1)

1. PROPOSAL (1)


13/12/2011

2. AGREEMENT (3)

1. PROPOSAL (3)STP send aproposal and wait

2 x FORWARD DELAY TIME for a

silence agreement


Only one root nodeis admitted

• Bridge 1 and 2:“Bridge 1 is root”• Bridge 3 and 4:“Bridge 3 is root”



RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3



Only one root nodeis admitted

• Bridge 1 and 2:“Bridge 1 is root”• Bridge 3 and 4:“Bridge 3 is root”

13/12/2011

Proposal (3)

Proposal (1)

Proposal (1)Proposal (3)



RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3



Bridge 1 is nowthe root bridge

of all the network

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Agreement (1)

Proposal (1)

Proposal (1)Agreement (1)



RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3


BPDU 1

BPDU 1

2. Determineleast cost path(set RP and DP)

R R

DD

BPDU 1

BPDU 1D D

R

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RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3


BPDU 1

BPDU 1


R R

DD

BPDU 1

D D

R A

3. Disable other ports

13/12/2011




RSTP Protocol

Bridge 1

Bridge 4Bridge 2

Bridge 3


BPDU 1

BPDU 1


R R

DD

BPDU 1

D D

R A

3. Disable other ports

Root continues BPDU 1 generation

Bridge generate BPDU 1every HELLO TIME

13/12/2011


RSTPimprovment

BPDU 1



RSTP Reconfiguration

Bridge 1

Bridge 4Bridge 2

Bridge 3

BPDU 1

R R

DD

BPDU 1

D D

R A

13/12/2011




Bridge 1

Bridge 4Bridge 2

Bridge 3

BPDU 1

R

D

BPDU 1

D D

R A

LINK

FAILURE

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Bridge 1

Bridge 4Bridge 2

Bridge 3

BPDU 1

R

D

D

R A

Bridge 2B1 is disconnected…

I’m thenew ROOT bridge!

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1. Proposal (2)




Bridge 1

Bridge 4Bridge 2

Bridge 3

BPDU 1

R

D

D

R A



Bridge 3I have a secondarypath to the current

root Bridge.Try to re-open it…

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1. Proposal (2)




Bridge 1

Bridge 4Bridge 2

Bridge 3

BPDU 1

R

D

D





13/12/2011

2. Proposal (1)

RD2. TCN

3. TCACK

2. TCN

3. TCACK

1. Proposal (2)

Topology change notification (TCN) and Topology Change ACK

(TCACK) clear infosabout how to reach

B3. They are sent every time a port

switch to forwarding state




Bridge 1

Bridge 4Bridge 2

Bridge 3

BPDU 1

R

D

D3. Agreement (1)

R

STP use timer and slow transition between portstates and takes more

than 30 seconds.RSTP may take less than

a second…




13/12/2011

R

D

Topology change notification (TCN) and Topology Change ACK

(TCACK) clear infosabout how to reach

B3. They are sent every time a port

switch to forwarding state

2. Proposal (1)

BPDU 1

Where

N - Number of switches

TL - Time required by a switch to detect a link failure (Net. pkts, hw detection,…)

TPA - Time required by a pair of switches to perform RST Proposal-Agreement

handshaking



RSTP results

Protocol IEEE Standard

Max Bridge

Diameter

Topology Single ring link failover time(for different number of switches)

10 – 15 -20

STP 802.1D 40 Any > 30 seconds

RSTP 802.1W 40 Any Several seconds

RSTP 802.1D-2004 40 Any < 50 ms - < 75 ms - < 100ms

TL + (N – 3)*TPA, if N is even

TL + (N – 2)*TPA, if N is odd

Worst case ring network failover time (single link failure):

13/12/2011

T3LAB Software support



• Ethernet

• VLAN

• PTP

• RSTP

• …

What else?

13/12/2011

µSwitch

Embedded switch



NODE

Switch• Intelligence on the device• Protocol runs on the switch• High cost

µSwitch• Intelligence moved to controller• Support of protocols• Low cost

Switch

13/12/2011

Abstract node

Eth

Eth

Eth Eth

Host

Eth

Eth

Eth Eth

Host

Mngmnt

SPI

SPI

RSTP

RSTP

HOST PORT

Mngmnt

Embedded switch: Host port



Host communicates with the otherhosts via ethernet using a µswitch’s special port (Host Port) µSwitch has N other ports Host uses SPI to check/set switch registers.The distinction between host port and other ports allow to:• RSTP traffic management: TAIL TAG,

static MAC table…• PTP traffic management (If it’s

supported): check message, packetstimestamping…

13/12/2011

EthHost SPI SPI

HOST PORT

Eth

µSwitch

MAC MII Phy Phy MII MAC

SPI

SPI

EthµSwitch

MAC

MII

MII

MAC

Host

Eth

Embedded node

Embedded switch: Tail Tag



Host

µSwitch

Host

µSwitch

Start

VLAN Filtering

Tail Tagging

Static Table Search

Dynamic TableSearch

End

13/12/2011

RSTP BPDU

EXCHANGE

Host

µSwitch

Host

µSwitch

DATA

TRANSFER

Host to host communicastion

Switch to switch communicastion

The RSTP BPDU exchange is a point to point communicationHow host select the switch’s destination port? How hostknows the switch’s source

port?TAIL TAG

µSwitch



Embedded switch: TX Tail tag

EthernetNIC module

RSTP protocol

Host

RSTPBPDU

TAIL

RSTPBPDU

RSTP send its BPDUthrough specific switch’s ports

How controller routes the packetsinto the µswitch?

TAIL TAG

Tail Tag enabled

13/12/2011




EthernetNIC module

Applications

µSwitch

OtherPKT

Where is theTAIL TAG?

Tail Tag enabled

13/12/2011

Host

OtherPKT

T3LABEthernet

NIC moduleµSwitch




ApplicationsOtherPKT

OtherPKT

TAIL

OtherPKT

T3LAB Ethernet NIC module:

1. Forward RSTP BPDU packets2. Add Tail Tag byte to other packets

Tail Tag enabled

13/12/2011

Host

µSwitch



Embedded switch: RX Tail tag

Applications

EthernetNIC module

OtherPKT

Tail Tag disabled

13/12/2011

Host

OtherPKT

µSwitch




RSTP Protocol

Where is theTAIL TAG?

orWhich is

the source port?

EthernetNIC module

RSTPBPDU

Tail Tag disabled

13/12/2011

Host

RSTPBPDU

T3LABEthernet

NIC module

RSTP Protocol

µSwitch

RSTP BPDU




T3LAB Ethernet NIC module

3. Forward RSTP BPDU packets tothe controller

4. Remove Tail Tag byte to otherpackets received

Tail Tag enabled

13/12/2011

Host

RSTPBPDU

TAIL

RSTPBPDU

TAIL

µSwitchT3LAB

EthernetNIC module




Applications

OtherPKT

OtherPKT

TAIL

OtherPKT

T3LAB Ethernet NIC module

3. Forward RSTP BPDU packets tothe controller

4. Remove Tail Tag byte to otherpackets received

Tail Tag enabled

13/12/2011

Host

TCP/IP Improvements



• VLAN• Priority Management

• VLAN priority mapping• Differentiated services (DS)

• Routing Rules (Static and dynamicMAC table management)

• PTP timestamp(ApplicationLayer Driver / HW)

• Tail Tagging• Ethernet port monitoring

Stack:• Linux• Texas NDK BIOS• NucleusChallenge:• Socket structures modification (Texas NDK BIOS, Nucleus)• Missing operation (recvmsg in Texas NDK BIOS, …)• Priority management (Nucleus)

• Association between VLAN and priority

Switch configurationProtocol challenge

Stack challenge

13/12/2011




µSwitch

Hardware

PTP RSTPNET

CONTROLLER

Ethernet

IP

UDP TCP

Host Net Controlleris the demo

network monitor

13/12/2011




µSwitch

13/12/2011

SPIETH CABLE

PTP RSTP

Host

What about an HW change?

Custom protocols foreach platform...

High porting cost!




µSwitch

13/12/2011

PTP RSTP

Host

NETCONTROLLER

SPI

+ T3LAB Porting KIT

SPIETH CABLE

High costreduction!

TASK MEM NET TIME SWITCH




• Clock synchronization via PTP

• Network management via RSTP

• VLAN support

• HW and OS isolation

• Fast porting to a new architecture

13/12/2011

Demo T3LAB

• BeagleBoard xM

• Texas InstrumentsDaVinci

Board


Applications - T3LAB Bologna - Italy4913/12/2011

Other T3LAB boards:• Microcontroller STR9 Dongle• FPGA Spartan 6 (Micro Blaze

Softcore)• Zynq 7000

• Cisco 300 Series

• Marvell 88E7251Switch

• Micrel KS8895

• Micrel KSZ8463µSwitch

Demo T3LAB



Switch Cisco300 Series

Switch Marvell88E7251

13/12/2011

µSwitch MicrelKSZ8463

BeagleBoard xM


Texas DaVinci


PC Windows+

Browser connected to

Webserver+

VLC

PC Linux+

Webserver+

PTP Master

BeagleBoard xM

Demo T3LAB



Net Controllerretrieve infos fromall the monitorednodes and show

them in a web page

Demo T3LAB



ROOT nodePath cost is 0

Alternate portThe network break is

here becausethis BBxM has a lower

ID then the Cisco

Bridge50

Bridge100

Bridge32768

Bridge4096

Bridge32769

The monitorshows you the

current network topology and the

ports status

Demo T3LAB



The browser executes HTTP request to the webserver

for video and time(PHP service).

If there isn’t an answerstop the video and show a

message

A video is showed using VLCThe buffering is setted to 1

second but the video flow iscontinuos

Demo T3LAB



Bridge50

Bridge100

Bridge32768

Bridge4096

Bridge32769

Bridge 32769Port 1 from root to

designatedPort 2 from alternate

to root

After a network breakRSTP reconfigures the

network

Demo T3LAB



PTP chartsAll the monitorednodes send ptp

information to the net controller

A special page shows a single chart and

compute statistics on PTP data

Standard Ethernet for Industrial Applications - T3LAB Bologna - Italy56

Simone Cilli

• +39 051 [email protected]

Claudio Salati

• +39 051 [email protected]

Thank you!Questions?

Contacts

13/12/2011

mailto:[email protected]

mailto:[email protected]

Bibliography• “Understanding Rapid Spanning Tree Protocol (802.1W)”, Cisco,

Document ID: 24062;

• “Rapid Spanning Tree Protocol: A new solution from an old technology”, Wald Wojdak, TELECOM, Reprinted from CompactPCI System / March 2003;

• “Performance of the Rapid Spanning Tree Protocol in Ring Network Topology”, Michael Pustylnik, Mira Zafirovic-Vukotic, Roger Moore, RuggedCom, Inc.

• IEEE 802.1D-2004

Standard Ethernet for Industrial Applications - T3LAB Bologna - Italy5713/12/2011

Documents

Rapid Spanning Tree Protocol and Ethernet applications development€¦ · · 2013-07-29Rapid Spanning Tree Protocol and Ethernet applications development Embedded switches, specific