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(1)

802.1 AVB Support for

Coordinated Shared Network

IEEE 802.1 AV WG

Nov 07 Atlanta, Georgia

Philippe Klein ([email protected])

(2)

Coordinated Shared Network

•

Time domain multiple access (TDMA) network

•

Coordinated contention free media access controlled by a single

elected or designated network controller (NC)

•

Interface for priority (& parameterized) QoS

•

CSN is the trend of the more recent (OFDM based) home

networks :

–

Moca (coax)

–

Homeplug (powerline)

–

UWB, 802.15 (wireless)

–

HCCA 802.11

(3)

Shared Network Support

in Current Draft IEEE 802.1 AVB

•

IEEE 802.1as includes the current 802.11 AP/STA topology

•

”similar *” to the shared network topology if a single node only is

connected to a bridge…

[*] SN supports node-to-node connections while 802.1 does not support STA-STA connections (if

Direct Link Protocol is not supported)

Bridge

STA

STA

AP

Bridge

Endpoint

SN node

Endpoint

SN node

SN node

802.11

(4)

Shared Network Backbone Support

in IEEE 802.1 AVB

•

Current draft model does not support SN

backbone

connecting

multiple bridges

–

No support in the current IEEE 802.1 AVB standard for AVB to AVB SN link

–

However, an 801.11 STA / Bridge discussion has being initiated in the joint AVB

and Video Transport TG.

Bridge

STA

AP

Bridge

SN node

SN node

SN node

Bridge

STA/Bridge

Bridge

802.11

(5)

AVB Support for Coordinated Shared Network

•

Proposal

: AVB Standard layer interface for any Coordinated

Shared Network (CSN)

–

MoCA

–

HomePlug

–

Future 802.11 with STA-Bridge support

–

…

AVB

Coordinated

Shared Network

AVB

NC

AVB

NC = Network Controller

(6)

MoCA Network Characteristics

•

802.3 Link emulation over coax

–

Bridge 802.3 packets over coax

medium

•

Synchronized access network

–

Network access is controlled by an

single (self-selected or preferred)

Network Coordinator (NC)

•

Clock Services

–

NC periodically broadcasts clock

references to all the nodes

–

Nodes maintain a local timer,

resynchronized by the NC clock

references

–

Max permissible jitter defined by

the specs

802.3

802.3

802.3

802.3

MoCA

node

MoCA

node

MoCA

NC node

MoCA

node

coax

(7)

Topology Option #1

•

CSN Adapter (CSNA) is a 802.3 / CSN bridge

Implementing a full bridge HW/SW functionality might be too expensive for low

end adapters

CONS

Natural decomposition – Cascaded bridges

Bridge 2 Bridge interface is well defined

PRO

E

E

E

E

CSNA

BRIDGE

Bridge #1

E

Bridge #2

B2B Interface

E

E

E

E

CSNA

BRIDGE

Bridge #4

E

Bridge #3

B2B Interface

E

E

E

E

CSNA

BRIDGE

Bridge #6

E

Bridge #5

B2B Interface

(8)

Topology Option #2

•

CSN Adapter emulates links (CSNA is seen as a PHY)

Transparent to AVB (LLDP & RSP messages should be spoofed & modified)

SNA inner queue latencies

SN link latencies might change over time

No Bridge interface to export / import CSN characteristics / policies for 802.1Qav

CONS

Cheaper implementation

Transparent to AVB

PRO

E

E

E

E

CSNA

BRIDGE

Bridge #1

802.3 Link

Emulation

E

E

E

E

CSNA

BRIDGE

Bridge #2

E

E

E

E

CSNA

BRIDGE

Bridge #3

(9)

Ingress / Egress Queue Latencies

•

IBQ-EBQ latencies and policies are covered by IEEE 802.1Qav

•

CSNA’s S&F inner queues cannot be transparent to AVB:

–

IAQ-EAQ max latencies should be queried and accounted for by the AVB

–

IAQ-EAQ policies should be exported by the AVB

•

Could be done thru a AVB standardized sub-layer interface

Sub-layer interface

CSN Adapter

IBQ

EBQ

IAQ

EAQs

802.3 AVB

EBQ

IBQ

EAQ

IAQ

(10)

AVB Messages CSN Handling

•

SN Native Sync handling

Boundary Clock or

Transparent Clock

802.1 as

Clock Synchronization

Msgs

•

Similar to non AVB intermediate bridge…

–

Request are transparently forwarded from

SN edge to edge

–

Responses are intercepted and eventually

modified (if i.e. the SN capabilities are lower

than the 802.3 capability for this link)

Spoofed &

intercepted by CSN

802.1 at

Stream Reservation

Protocol Msgs

•

LLDP queries messages broadcasted to

every CSNAs

•

LLDP responses forwarded over the CSN

Spoofed and

broadcasted by CSN

802.1 ab

Link Layer Discovery

Protocol Msgs

CSN Handling

Messages

(11)

AVB LLDP Messages Broadcasting

CSN

CSNA2

LLDP

CSNA3

broadc

asted

802.3

AVB2

802.3

AVB3

LLDP

CSNA1

LLDP

802.3

AVB1

802.3

port

LLDP

broadcasted

LLDP

LLDP

•

LLDP messages are encapsulated in CSN containers and broadcasted over the

CSN network

–

802.3 AVB port supposedly connected to a (P2P FD) 802.3 link now could receive

LLDP message from multiple links….

802.3

port

802.3

port

(12)

AVB SRP Messages Interception

CSNA1

CSN

CSNA2

AVB1

AVB2

SRP Req

SRP Req

NC

forwarding

modified

CSN Rsv Req

•

Available bandwidth of the SN link might be lower that the bandwidth

reservation acknowledged by AVB2

–

AVB reservation responses should be demoted by the SN

–

do we need feedback msg to AVB2 to update AVB2 ?

SRP Rsp

SRP Rsp

intercepted

Upd

SRP Rsp

SRP Req

CSN Rsv Rsp

(13)

SN 802.1as Clock Model

OC = Ordinary Clock

S-BC = Simple Boundary Clock

TC = Transparent Clock

CSN

CSN

Model #1

Model #2

TC

CSNA

AVB

OC

CSNA

SBC

CSNA

AVB

OC

CSNA

AVB

TC

CSNA

AVB

S-BC

CSNA

(14)

SN AVB Timing Services

•

AVB Timing Services

–

If the CSN clock is accurate enough, the 802.1as CSN media

dependant part could be provided by the CSN time services:

•

NC’s master clock periodically broadcasted to all CSNAs

•

CSNAs local timer synchronized on NC’s master clock references

•

Time-stamped Txm frames

•

AVB CSN Timing SAP:

–

Sync, Follow_Up,

(15)

Link Delay SAP

AVB

Pdelay_Req

Pdelay_

Resp

Pdelay_F

U (t

1

,t

2

)

CSNA

T

1

t

1

t

2

T

2

LinkDelay* = ( (T

2

-T

1

) - (t

2

- t

1

) ) / 2

(16)

CSN Propagation Delay Measurement

between 2 CSNAs

CSNA

a

CSN

CSNA

b

[t] Tx Packet Header ‘s Timestamp

(t) API Parameters

CSN_PropagationDelay = ( (ta

2

-ta

1

) - (tb

2

-tb

1

) ) / 2

tb

2

ta

2

CSN Pd

_Resp(

tb

1

) [tb

2

]

ta

1

CSN Pd_Req

uest() [ta

1

]

tb

1

CSNA

a

CSN

CSNA

b

tb

2

ta

2

CSN Pd

_Resp(

tb

1

)

ta

1

CSN Pd_Req

uest()

tb

1

CSN Pd

_Resp_

FU(tb

2

)

(17)

Transparent Clock Sync SAP

Sync ()

GT = AVB Grand Time FRC = free running clock

ld = AVB - SNA link delay tx

i

= free running clock time

pd = SN propagation delay

CSNA

a

CSN

CSNA

b

AVB

a

AVB

b

T

1

ta

1

ta

2

tb

1

Sync ()

tb

2

GT

ta1

= T

1

+ ld

a

Sync_FU (T

1

)

CSN Sync ()

Sync_FU (GT

tb2

)

GT

tb1

= GT

ta2

+ pd

a-b

ld

a

pd

a-b

ld

b

CSN Sync_FU (GT

ta2

)

GT

ta2

= GT

ta1

+∆T(ta

2

-ta

1

)

GT

tb2

= GT

tb1

+∆T(tb

2

-tb

1

)

(18)

Boundary Clock Sync SAP

Sync ()

GT = AVB Grand Time CSN-LC = CSN Local Clock

ld = AVB - CSNA link delay tx

i

= CSN Local Clock time

pd = CSN propagation delay

CSNA

a

CSN

CSNA

b

AVB

a

AVB

b

T

1

ta

1

Sync ()

tb

1

GT

ta1

= T

1

+ ld

a

∆t = GT

ta1

– ta

1

Sync_FU (T

1

)

CSN GT Sync (

∆

t )

Sync_FU (GT

tb1

)

GT

tb1

= tb

1

+ ∆t

ld

a

pd

a-b

ld

b

CSN-LC ta

¥

CSNC Sync

¥

CSNC Sync

CSN-LC tb

¥

CSN Master Clock

~

~

~

~

(19)
(20)

References

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