Renesas - 汽车以太网中冗余设计的时间同步与通信

TIME SYNCHRONIZATION AND COMMUNICATION IN REDUNDANT NETWORKS IEEE ETHERNET & IP @ AUTOMOTIVE TECHNOLOGY DAY DETROIT, SEPTEMBER 2019

THORSTEN HOFFLEIT

AUTOMOTIVE NETWORKING COMPETENCE CENTER AUTOMOTIVE SOLUTION BUSINESS UNIT

RENESAS ELECTRONICS CORPORATION

AGENDA

▪Need for redundancy & time synchronization

▪Operation of IEEE 802.1CB (Frame replication and elimination for redundancy) and effects in case of package loss/ link loss

▪Alternative approach to IEEE 802.1CB

▪Improvements coming up in IEEE 802.1AS

(Timing and Synchronization for Time sensitive Applications)

▪Summary and conclusion

IN VEHICLE CONNECTIVITY

MOVE TOWARDS ZONE-BASED ARCHITECTURE WITH ETHERNET BACKBONE

IN VEHICLE CONNECTIVITY

MOVE TOWARDS ZONE-BASED ARCHITECTURE WITH ETHERNET BACKBONE

▪New E/E architectures will use Ethernet as backbone ▪Limited bandwidth and latency are constraints

▪Reliable service oriented communication is key ▪Mechanisms are required to guarantee data delivery ▪IEEE 802.1CB

▪IEEE802.1AS-rev

IEEE 802.1CB

EXAMPLE CRITICAL STREAMS

Talker

Listener

Listener

Sequence generation function

Individual recovery function/ stream splitting Sequence recovery function

Stream identification

Every stream from a talker

undergoes identification function

Examines sequence numbers and discards duplicates from single ingress port. Duplicate frames if needed to all configured outputs.

Examines sequence numbers and discards duplicates from different ingress ports.

Finally only one package is received by listener system and removes sequence number

At talker side two “identical” packages are created (member streams). “R -Tag” with sequence number is added.

IEEE 802.1CB

SYSTEM CONTEXT

▪Failure models in IEEE 802.1CB

▪Frame loss

▪Link loss

▪Stuck transmitter

▪Ring architecture also supports component failure

▪Redundant path keeps communication

ongoing

▪Additional system countermeasures required ▪Redundancy does not come for free

▪Architectural considerations

▪Additional cables

▪Additional ports

▪Increased communication traffic

SEQUENCE ORDERING

CHALLENGE FOR APPLICATION

Challenges:

▪Package disordering (depends on traffic type )▪History list depth

T1

T2T3T4T5T6T1’T2’T4’T5’T6’T A T1’’

T2’’

T3’’

T4’’

T5’’

T6’’

B C

C T7T7’T7’’

D T1’’’T2’’’T3’’’T4’’T5’’T6’’

C L

T1’

T2’

T4’

T5’

T6’

T3’’’

T7’

T

L

A

B

D

C

Countermeasures:

▪Avoid bursts by using shapers/ use preemption

▪Reorder sequence with help of sequence numbers in transport layer ▪Accept disordered packages and solve in application layer

T3’CB bridge