Improvement for gPTP Gen 1 (IEEE 802.1 AS)08-01- 2013

IEEE 802.1 Plenary Meeting – Orlando

Marcel Kießling, Siemens AG

Franz-Josef Götz, Siemens AG

IEEE 802.1 Plenary Session – OrlandoPage 2 2013-03-14

Structure of this Presentation

1. Recap of basic mechanisms

- Announce Frame

- Sync Frame

2. Recap of the previous presented possible solutions

- Network with “old” stored information

- Proposed Solutions

3. Preferred Solution

- Usage of the “syncReceiptTimeout”

- Identification of the GM in the Sync

IEEE 802.1 Plenary Session – OrlandoPage 3 2013-03-14

Type of FramesSync- and Announce Frames

All gPTP frames are P2P frames

Announce frames Elect best Grandmaster

Port Role (Slave / Master)

Sync frames Time Sync

Path Delay frames Measure Path/Link Delay

Request

Response

Response Follow Up

IEEE 802.1 Plenary Session – OrlandoPage 4 2013-03-14

Announce frame

Every device starts with periodically sending Announce Messages every announce interval

Announce Messages include the time-synchronization spanning tree vectors

Best Master Clock Algorithm (BMCA) uses these vectors to set up the loop-free Sync Tree (like BPDUs for the RSTP Tree)

B0

B1 B3

B2

B4 GM

M MSS

MMS P

MS

M

S

P

MasterPort (RSTP Designated-Port)

SlavePort (RSTP-Root Port)

PassivePort (other States)

DisabledPortD

Time Aware System (Bridge /End-Station)

B5M SM

M

Established Sync Tree

IEEE 802.1 Plenary Session – OrlandoPage 5 2013-03-14

Sync frame

Sync Frame is send more frequently than Announce Frames and includes information for synchronization

Follow the given sync tree established through announce frames

Loop prevention by using loop-free sync tree

B4 GM1

B0

B1 B3

B2

B5

Sync Messages

IEEE 802.1 Plenary Session – OrlandoPage 6 2013-03-14

Problem with the 802.1 as Sync Tree

Stations with a Passive Port should not answer with old, previously stored informationRing-Topology with stored GM Information's

B0

B1 B3

B2

B4 GM

M MSS

MMS P

MS

GM + GM-failed

Old GM

GM

Stack-Time

31 20S P31 20 SP

31 20

Sharing of „wrong“ GM Information

Answer with stored Information

Wished Behaviournew Information should renew

the old stored information

Real behaviour stored information dominates

Deletion of the old stored information

IEEE 802.1 Plenary Session – OrlandoPage 7 2013-03-14

Structure of this Presentation

1. Recap of basic mechanisms

- Announce Frame

- Sync Frame

2. Recap of the previous presented possible solutions

- Network with “old” stored information

- Proposed Solutions

3. Preferred Solution

- Usage of the “syncReceiptTimeout”

- Identification of the GM in the Sync

IEEE 802.1 Plenary Session – OrlandoPage 8 2013-03-14

previous presented possible solutions

Optimized path trace TLV

Avoid long Announce Messages

Hop-Count How to get a useful maximum Number

Deletion of stored information What should cause the deletion

Using a special frame information Like proprietary solutions

Using an timeout Sync Messages are send out more often

Industrial Ring

B0 B1

B48B2

GM

1

2

3

50

B3

B49

B4750 devices in the Ring

49

48

GM1

2 GM B0

16 Byte

4 Byte

Path SequenceTLV Type+ Length

N * 8 Byte

802.1 as Announce Frame

„Guard“-Timer to remind the deletion of the GM

S PSP

0 1 2 3

IEEE 802.1 Plenary Session – OrlandoPage 9 2013-03-14

Structure of this Presentation

1. Recap of basic mechanisms

- Announce Frame

- Sync Frame

2. Recap of the previous presented possible solutions

- Network with “old” stored information

- Proposed Solutions

3. Preferred Solution

- Usage of the “syncReceiptTimeout”

- Identification of the GM in the Sync

IEEE 802.1 Plenary Session – OrlandoPage 10 2013-03-14

Usage of the “syncReceiptTimeout”

Definition:

Use the “syncReceiptTimeout” to

delete the stored information of the old GM on all ports (Passive Ports)

rerun the BMCA (without old information)

IEEE 802.1 Plenary Session – OrlandoPage 11 2013-03-14

Open Problem in Gen 1? – Identification of the GM

GM identification is not needed up to now because:

Only one GM exists

no Identification

Sync follow the loop free path

Port Roles block wrong frames B4 GM

Established Sync-Path

B0

B1 B3

B2

B5GM2

M

S

Sync Message

GM1

GM2

P

Sync Path Diode

B

IEEE 802.1 Plenary Session – OrlandoPage 12 2013-03-14

Open Problem for Gen 2! – Identification of the GM

High Available Synchronization

B4 GM

Established Sync-Path

B0

B1 B3

B2

B5

M

S

Sync Message

GM1

GM2

P

Sync Path Diode

B4

B0

B1 B3

B2

B5GM

P

Sync-Pathfor GM 1

Sync-Pathfor GM 2

Sync from GM1 or GM2 ?

B4 GM

Only OnlyB5GM

=

B4 GM1

B0

B1 B3

B2

B5GM2

B4 GM1

B5GM2

&

Marcel KießlingInnovation ManagerI IA SC IC TI

Phone: +49(911)-895 3888

E-Mail: kiessling.marcel@siemens.com

Thank you for your attention!

Improvement for gPTP Gen 1 (IEEE 802.1 AS)