Joint ITU-T/IEEE Workshop
on The Future of Ethernet Transport
(Geneva, 28 May 2010)
Time Awareness for Bridged
LANs: IEEE 802.1 Audio Video
Bridging
Michael Johas Teener
Sr. Technical Director,
Broadcom
Geneva, 28 May 2010
Agenda
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802.1 AV Bridging Task Group
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What we do
Why is it needed?
! " What is AV Bridging?
! " Where will it be used?
! " Possible interactions with ITU efforts
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Geneva, 28 May 2010
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IEEE 802.1 Audio Video
Bridging Task Group
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Formed in late 2005 to provide the
specifications that will allow timesynchronized low latency streaming
services through 802 networks
Four projects:
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P802.1AS: Time Synchronization (in sponsor ballot)
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Discussed in the next presentation
P802.1Qat: Stream Reservation (in sponsor ballot)
IEEE Std 802.1Qav-2009: Forwarding and Queuing for
Time-Sensitive Streams
P802.1BA: AVB Systems (in development)
Geneva, 28 May 2010
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Why is it needed?
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Common IT-oriented networks have
inadequate QoS controls
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all use 802.1 “priority” (actually, “traffic class”)
no time-based services, no standardized queuing or
traffic shaping
no guarantees, timing synchronization difficult
Adding QoS to layer 2 networks is not
enough
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E.g., adding streaming QoS to G.hn only provides better
services on a particular G.hn subnet … QoS lost going to
WiFi or Ethernet
QoS is a NETWORK problem, not just a link problem
Geneva, 28 May 2010
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Audio Video Bridging
AVB
end
point
Streaming
QoS only
guaranteed in
AVB cloud
end
point
legacy
bridge
peer device not
AVB capable
AVB
end
point
devices outside of AVB
cloud still communicate with
all other devices using
legacy "best effort" QoS
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AVB
bridge
half duplex
link can't
do AVB
Enet
hub
end
point
AVB
end
point
AVB
switch
AVB
switch
end
point
AVB "cloud"
(defended network)
AVB
end
point
AVB
end
point
AVB
end
point
filtering/retagging active
best effort link
streaming QoS link
AVB is based on 802.1Q bridges
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The bridges connect together LANs that use different layer 2
technologies: Ethernet, WiFi, MoCA, G.hn
Geneva, 28 May 2010
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AVB provides …
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Bounded latency …
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For 100Mbit/sec it’s about 250 usec per link,
for 1Gbit/sec it’s about 25 usec link
… with no dropped packets due to
congestion …
! " … for streams that do not exceed
their maximum bandwidth
established using the end-to-end
“Stream Reservation Protocol”
! " PLUS a high-quality time reference
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Geneva, 28 May 2010
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AVB Will Be Used …
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… in professional audio/video
environments
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… in automotive applications
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Infotainment, sensor systems
… in consumer electronics
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Audio and video studios, stadiums, hospitals,
airports, live performances
Home A/V networking and interconnects
… in industrial systems
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Sensors, actuators, motion control
Geneva, 28 May 2010
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AVB Provides Carrier
Networks …
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Precise synchronization services
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Connection-oriented services
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802.1AS - IEEE 1588v2 as applied to 802.1 bridged networks.
Much better MTIE than needed for SONET
802.1Qat - Stream Reservation Protocol to manage streams
802.1Qav - Guaranteed latency and bandwidth for established
streams
Removes the need for external PHY-level
synchronization
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Any 802.3 PHY will work, nothing special needed, full
configuration flexibility
Support for other full-duplex point-to-point PHYs trivial
Support for shared media MACs allowed (EPON, 802.11,
MoCA) via sublayer definition
Geneva, 28 May 2010
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Putting it All
Together
CE
CE
TDM
IWF
IWF
TDM
Differential Timing
Messages
Packet
Switched
Network
IWF
IWF
Recovered
TDM timing
based on the
differential
timing
messages
TDM
CE
CE
TDM
802.1at/av
Synchronization
Network
TDM Service Clocks
PRC
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802.1AS
Time Sync
Synchronization
Network
PRC
AVB supports multiple independently
clocked streams/domains
Geneva, 28 May 2010
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Thank you!
Geneva, 28 May 2010