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
2013-03-14
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]