as-kiessling-Improvements-4-gPTP-Gen-1-v3.ppt
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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
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
Page 2
-
Usage of the “syncReceiptTimeout”
-
Identification of the GM in the Sync
2013-03-14
IEEE 802.1 Plenary Session – Orlando
Type of Frames
Sync- 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
Page 3
2013-03-14
IEEE 802.1 Plenary Session – Orlando
Announce frame
Every device starts with periodically sending
Announce Messages every announce interval
Established Sync Tree
B4
GM
Announce Messages include the timesynchronization spanning tree vectors
M
S
B0
S
M
M
M
S
B1
Best Master Clock Algorithm (BMCA) uses
these vectors to set up the loop-free Sync Tree
(like BPDUs for the RSTP Tree)
M
M
B3
S
P
M
S
B5
M
B2
M
MasterPort (RSTP Designated-Port)
S
SlavePort (RSTP-Root Port)
D
DisabledPort
P
PassivePort (other States)
Time Aware System
(Bridge /End-Station)
Page 4
2013-03-14
IEEE 802.1 Plenary Session – Orlando
Sync frame
Sync Frame is send more frequently than
Announce Frames and includes
information for synchronization
B4
GM1
Follow the given sync tree established
through announce frames
Loop prevention by using loop-free sync
tree
Sync
Messages
B0
B1
B3
B5
B2
Page 5
2013-03-14
IEEE 802.1 Plenary Session – Orlando
Problem with the 802.1 as Sync Tree
Stations with a Passive Port should not answer with old,
previously stored information
Ring-Topology with stored GM Information's
Wished Behaviour
new Information should renew
the old stored information
B4
GM
M
S
0
1
2
3
B0
S
M
M
B1
M
Real behaviour
stored information dominates
0
2
1
S
P
3
P
S
S
B3
S
P
M
B2
Answer with
stored Information
0
1
2
3
GM + GM-failed
GM
Old GM
Stack-Time
Deletion of the old stored
information
Page 6
2013-03-14
Sharing of „wrong“ GM
Information
IEEE 802.1 Plenary Session – Orlando
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
Page 7
-
Usage of the “syncReceiptTimeout”
-
Identification of the GM in the Sync
2013-03-14
IEEE 802.1 Plenary Session – Orlando
previous presented possible solutions
802.1 as Announce Frame
TLV Type
+ Length
Path Sequence
4 Byte
N * 8 Byte
Optimized path trace TLV
Avoid long Announce Messages
1
GM
2
GM
Hop-Count
B0
16 Byte
How to get a useful maximum Number
Deletion of stored information
What should cause the deletion
„Guard“-Timer to remind
the deletion of the GM
0
1
2
S
P
3
P
S
Industrial Ring
Using a special frame information
GM
Like proprietary solutions
1
Using an timeout
Sync Messages are send out more often
2
2013-03-14
B49
B2
49
B48
3
B3
Page 8
B1
50
B0
48
50 devices in the Ring
B47
IEEE 802.1 Plenary Session – Orlando
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
Page 9
-
Usage of the “syncReceiptTimeout”
-
Identification of the GM in the Sync
2013-03-14
IEEE 802.1 Plenary Session – Orlando
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)
Page 10
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IEEE 802.1 Plenary Session – Orlando
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
Sync Path Diode
Sync Message
Established Sync-Path
M
GM1
GM2
S
Port Roles block wrong frames
B4
GM
B
B0
B1
B3
B2
Page 11
2013-03-14
B5
GM2
P
IEEE 802.1 Plenary Session – Orlando
Open Problem for Gen 2! – Identification of the GM
B4
GM1
High Available Synchronization
&
B5
B4
GM2
GM1
B0
Sync Path Diode
Sync Message
Established Sync-Path
M
B5
GM2
GM2
S
GM
B3
GM1
=
B4
B1
B2
Only
B4
B5
Sync-Path
for GM 1
GM
GM
Only
B4
Sync-Path
for GM 2
B0
B0
B3
B1
B5
B3
B1
B5
GM
P
B2
Page 12
P
2013-03-14
Sync from
GM1 or GM2 ?
B2
IEEE 802.1 Plenary Session – Orlando
Thank you for your attention!
Marcel Kießling
Innovation Manager
I IA SC IC TI
Phone: +49(911)-895 3888
E-Mail: [email protected]