doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

More R

eliab

le Gro

up

Cast P

rop

osa

l Presen

tatio

n

Date: 2

009-0

3-0

1 A

uth

ors:

Ad

ditio

nal a

uth

ors o

n n

ext slid

e

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

Au

thor L

ist (Con

t.)

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 3

Ab

stract

Th

is pro

posa

l specifies th

e enh

an

cemen

ts to th

e 802.1

1

MA

C th

at en

ab

les imp

roved

link

reliab

ility fo

r gro

up

cast

au

dio

vid

eo strea

m tra

nsm

ission

.

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 4

Fea

tures

•T

hree A

ck p

olices to

sup

port th

e vario

us ty

pes o

f the ta

rget

ap

plica

tion

s an

d p

rovid

e the flex

ibility

to m

eet the n

eeds o

f d

ifferent sca

lab

ility a

nd

imp

lemen

tatio

n co

mp

lexity

–D

irected

–U

nso

licited retries

–B

lock

Ack

•C

om

patib

le to n

on

-802.1

1aa sta

tion

s –

Co

ncealm

ent o

f retried g

rou

p ad

dressed

frames

•E

xten

sion

of R

TS

/CT

S fo

r gro

up

ad

dressed

fram

e tran

smissio

n

pro

tection

–

Allev

iate the h

idd

en n

od

e and

OB

SS

pro

blem

by

reservin

g th

e med

ium

an

d p

rotectin

g th

e follo

win

g g

rou

p ad

dressed

frame tran

smissio

ns

•M

RG

-SP

Pow

er Man

agem

ent m

od

e to red

uce M

AC

deliv

ery

laten

cy fo

r gro

up

ad

dressed

stream

s –

Tran

smits th

e gro

up

add

ressed fram

es via E

DC

A w

ithin

Sch

edu

led

Serv

ice Perio

ds

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 5

MR

G S

ervice C

ap

ab

ility

•M

ore R

eliab

le Gro

up

cast (M

RG

) Serv

ice allo

ws a

non

-AP

ST

A to

req

uest g

reater relia

bility

for o

ne o

r more g

rou

p a

dd

ressed

stream

s

•T

wo lev

els of M

RG

cap

ab

ilities

–R

obust A

V S

treamin

g

•D

irected

•U

nso

licited retries

•R

etry co

ncealm

ent

•M

RG

-SP

pow

er man

agem

ent

–A

dvan

ced M

RG

•T

he ab

ov

e

•B

lock

Ack

–A

dv

ertised in

Ex

tend

ed C

apab

ilities info

rmatio

n elem

ent

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 6

MR

G S

ervice S

etup

MR

G R

equest

MR

G R

esponse

Exten

ded

AD

DB

A R

equest

Exten

ded

AD

DB

A R

esponse

Wh

en th

e ST

A

sup

port

Ad

van

ced M

RG

Unso

licited M

RG

Resp

onse (o

ptio

nal)

Non-A

P S

TA

A

P

Ack

Ack

Ack

Ack

Ack

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 7

Rob

ust A

V S

tream

ing A

ction

Fra

mes

•R

ob

ust A

V S

tream

ing A

ction

Fra

mes

•M

RG

Req

uest F

ram

e

•M

RG

Resp

on

se Fra

me

Actio

n field

valu

e M

ean

ing

0

MR

G R

equest

1 M

RG

Resp

onse

2 –

255

Reserv

ed

Categ

ory

Actio

n D

ialo

g T

ok

en M

RG

Req

uest

Elem

ents

Octets

1 1

1 varia

ble

Categ

ory

Actio

n D

ialo

g T

ok

en M

RG

Resp

on

se

Elem

ents

Octets

1 1

1 varia

ble

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 8

MR

G R

equ

est Elem

ent

•M

RG

Ack

Policy

Elem

ent

ID

Len

gth

G

rou

p

Ad

dress

MR

G

Ack

Policy

MR

G P

ow

er

Man

agem

ent

Mod

e

TS

PE

C

Elem

ent

Sch

edu

le

elemen

t

(op

tion

al)

Octets

1

1

6

1

1

57

0 o

r 14

Valu

e M

RG

Ack

Policy

No

tes

0 M

RG

-Serv

ice-Can

cel

1 M

RG

-Directed

2 M

RG

-Unso

licited-R

etry

3 M

RG

-Blo

ck-A

ck

4-2

55

Reserv

ed

•M

RG

Pow

er Man

agem

ent M

ode

Valu

e M

RG

Pow

er Man

agem

ent M

ode

No

tes

0 R

eserved

1 A

ll-Activ

e/Any-P

S o

r FM

S

2 M

RG

-SP

3-2

55

Reserv

ed

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 9

MR

G R

espon

se elemen

t

Elem

ent ID

L

ength

G

roup

Address

MR

G A

ck

Policy

MR

G P

ow

er

Man

agem

ent

Mode (o

ptio

nal)

Sch

edu

le

Elem

ent

(optio

nal)

Octets

1

1

6

1

1

0 o

r 14

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

0

Blo

ck A

ck A

ction

Fra

mes

Actio

n field

valu

es M

ean

ing

0

AD

DB

A R

equest

1

AD

DB

A R

esponse

2

DE

LB

A (E

xtend

ed)

3

Exten

ded

AD

DB

A R

equ

est

4

Exten

ded

AD

DB

A R

espon

se

5–255

Reserv

ed

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

1

Exten

ded

AD

DB

A R

equ

est Fra

me

•E

xten

ded

Blo

ck A

ck P

ara

meter S

et field

Ord

er In

form

atio

n

1

Categ

ory

2

Actio

n

3

Dialo

g T

oken

4

Blo

ck A

ck P

arameter S

et

5

Blo

ck A

ck T

imeo

ut V

alue

6

Blo

ck A

ck S

tarting

Seq

uen

ce Co

ntro

l

7

Exten

ded

Blo

ck A

ck P

ara

meter S

et

8

AD

DB

A M

RG

Gro

up

Ad

dress

Bits

B0

B1 B

15

AD

DB

A M

RG

Gro

up A

ddress

Presen

t

Reserv

ed

Octets

----------------------------2 --------------------------

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

2

Exten

ded

AD

DB

A R

espon

se Fra

me

Ord

er In

form

atio

n

1

Categ

ory

2

Actio

n

3

Dialo

g T

oken

4

Statu

s Code

5

Blo

ck A

ck P

arameter S

et

6

Blo

ck A

ck T

imeo

ut V

alue

7

Exten

ded

Blo

ck A

ck P

ara

meter S

et

8

AD

DB

A M

RG

Gro

up

Ad

dress

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

3

DE

LB

A F

ram

e Form

at

•D

EL

BA

MR

G G

rou

p A

dd

ress is inclu

ded

if DE

LB

A M

RG

Gro

up

A

dd

ress Presen

t field is set

•D

EL

BA

Para

meter S

et

Ord

er In

form

atio

n

1

Categ

ory

2

Actio

n

3

DE

LB

A P

ara

meter S

et

4

Reaso

n C

ode

5

DE

LB

A M

RG

Gro

up

Ad

dress

Bits

B0 B

9

B10

B11

B12 B

15

Reserv

ed

DE

LB

A M

RG

Gro

up A

ddress

Presen

t

Initiato

r T

ID

Octets

----------------------------2 --------------------------

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

4

MR

G A

ck P

olicy

an

d P

ow

er Man

agem

ent

Mod

e Mod

ificatio

n

•T

he M

RG

AP

may u

pd

ate th

e ack

policy

an

d p

ow

er

man

agem

ent m

od

e by eith

er:

–T

ransm

itting

un

solicited

MR

G R

espo

nse fram

es ind

ivid

ually

addressed

to each

MR

G g

roup m

ember w

ith n

ew M

RG

ack p

olicy

and

po

wer m

anag

emen

t setting

,

or

–T

ransm

itting

an u

nso

licited M

RG

Resp

on

se frame in

gro

up

cast

addressed

to th

e MR

G g

roup ad

dress w

ith n

ew M

RG

ack p

olicy

and

po

wer m

anag

emen

t setting

.

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

5

MR

G S

ervice T

eard

ow

n

•T

o ca

ncel a

MR

G a

greem

ent b

etween

a n

on

-AP

ST

A a

nd

an

AP

, eith

er –

Non-A

P S

TA

sends an

MR

G R

equest fram

e with

the A

ck P

olicy

set to

MR

G-S

ervice-C

ancel

or

–A

P tran

smits an

indiv

idually

addressed

MR

G R

esponse fram

e with

the

Ack

Po

licy set to

MR

G-S

ervice-C

ancel.

•A

P m

ay

can

cel the M

RG

service fo

r an

MR

G strea

m b

y eith

er –

transm

itting a series o

f indiv

idually

addressed

MR

G R

esponse fram

es w

ith th

e Ack

Policy

set to M

RG

-Serv

ice-Can

cel to each

non-A

P S

TA

g

rou

p m

emb

er

or

–tran

smittin

g a g

roup ad

dressed

MR

G R

esponse fram

e with

the A

ck P

olicy

set to

MR

G-S

ervice-C

ancel.

•S

uch

can

cellatio

n sh

all a

lso ca

use th

e Blo

ck A

ck a

greem

ent to

be

can

celled.

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

6

MR

G-D

irected A

ck

•S

imila

r to D

MS

, bu

t

–W

ork

with

MR

G-S

P p

ow

er man

agem

ent

–E

nab

le AP

to sw

itch to

oth

er Ack

po

licies

•T

ran

smit g

rou

p a

dd

ressed M

SD

Us a

s ind

ivid

ually

ad

dressed

fram

es to a

MR

G g

rou

p m

emb

er in a

n A

-

MS

DU

fram

e form

at

•L

ow

efficiency

, not a

scala

ble so

lutio

n, h

igh

dela

y, b

ut

pro

vid

es best relia

bility

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

7

MR

G-U

nso

licited-R

etry •

Tra

nsm

it each

MS

DU

mu

ltiple tim

es, sub

ject to th

e

lifetime lim

it.

–R

etransm

itted fram

es sent w

ith th

e RA

set to th

e MR

G

Co

ncealm

ent ad

dress (n

ext slid

e) to av

oid

du

plicated

frames at

non-8

02.1

1aa S

TA

s

–W

hen

retransm

itting an

MP

DU

, for all retran

smissio

ns, th

e AP

shall in

vo

ke its b

acko

ff pro

cedu

re.

•L

ow

efficiency

, scala

ble so

lutio

n, d

elay d

epen

ds o

n

imp

lemen

tatio

n, p

rovid

es limited

reliab

ility

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

8

Con

cealm

ent o

f MR

G T

ran

smissio

ns

•P

reven

ts du

plica

te gro

up

ad

dressed

fram

es from

bein

g

passed

up

the M

AC

-SA

P o

f MR

G-in

cap

ab

le ST

As

•M

SD

Us retra

nsm

itted v

ia th

e MR

G-U

nso

licited-R

etry

or M

RG

-Blo

ck-A

ck A

ck p

olicies sh

all b

e sent in

an

A-

MS

DU

fram

e form

at w

ith th

e RA

set to th

e MR

G

Con

cealm

en

t address

–T

o-b

e-assigned

-by-A

NA

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 1

9

MR

G-B

lock

-Ack

•E

xten

d th

e Blo

ck A

ck m

echan

ism to

gro

up

cast.

•O

nly

sup

port im

med

iate b

lock

ack

policy

•T

he ex

tent o

f efficiency

, dela

y a

nd

reliab

ility p

rovid

ed

are flex

ible a

nd

dep

end

ent o

n im

plem

enta

tion

, scala

ble.

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

0

MR

G B

lock

Ack

Req

with

Imm

edia

te Blo

ck A

ck P

olicy

•M

RG

BA

R In

form

atio

n field

in M

RG

Blo

ckA

ckR

eq co

nta

ins a

list of

MR

G g

rou

p m

emb

ers from

wh

ich th

is Blo

ckA

ckR

eq is req

uestin

g a

B

lock

Ack

respon

se.

•T

he M

RG

gro

up

mem

bers in

the list sh

all sen

d th

eir Blo

ckA

ck in

the

ord

er that th

ey a

re specified

in th

e MR

G B

AR

Info

rmatio

n field

.

MR

G A

P

Blo

ck

AckR

eq

MR

G g

rou

p m

em

ber 1

MR

G g

rou

p m

em

ber 2

MR

G g

rou

p m

em

ber 3

Data

D

ata

Blo

ck

Ack

Not in

clu

ded in

the M

RG

BA

R

Info

rmatio

n fie

ld

Blo

ck

Ack

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

1

MR

G B

lock

Ack

Req

Fra

me

•S

end

to M

RG

gro

up

ad

dress

•In

clud

e MR

G B

AR

Info

rmatio

n

Fra

me

Contro

l D

ura

tion

/ID

RA

TA

F

CS

B

AR

C

ontro

l B

AR

In

form

atio

n

MR

G B

AR

In

form

atio

n

MR

G B

AR

Bitm

ap

Contro

l M

RG

BA

R P

artia

l B

itmap

Octets: 2

2

6

6

2

V

ariable

Variab

le 4

MR

G B

AR

Info

rmatio

n

Length

Octets: 1

1

V

ariable

MA

C H

eader

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

2

MR

G B

lock

Ack

Fra

me

Fram

e

Contro

l D

uratio

n/ID

R

A

TA

FC

S

BA

Contro

l

BA

Info

rmatio

n

MR

G G

roup

Address

BA

Ack

Policy

M

ulti-

TID

Com

pressed

Bitm

ap

MR

G

Reserv

ed

TID

_IN

FO

B0

B1

B2

B3

B4

B11

B12

B15

Octets: 2

2

6

6

2

V

ariable

6

4

MA

C H

eader

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

3

Collisio

n A

void

ing P

roced

ure

•M

RG

AP

ma

y select

on

e MR

G g

rou

p

mem

ber a

nd

use o

ne

RT

S/C

TS

or o

ther

pro

tection

meth

od

to

set NA

V to

pro

tect the

follo

win

g g

rou

p

ad

dressed

fram

e tra

nsm

ission

.

AP

1

ST

A1

ST

A2

ST

A3

AP

3

ST

A7

ST

A8

ST

A9

Back

off

AP

1

ST

A1

ST

A2

ST

A3

Pro

tected M

RG

TX

OP

Pro

tection

Stag

eM

RG

Tx S

tage

MR

G D

ata Fram

es

CTS

RTS

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

4

MR

G-S

P

•A

n A

P a

dvertises th

e MR

G serv

ice perio

ds in

MR

G

Resp

on

se elemen

t

–C

on

tain S

ched

ule elem

ent (sch

edu

le info

, service start tim

e,

service in

terval, sp

ecification

interv

al)

–N

on-A

P S

TA

gro

up m

ember sh

all wak

es up at th

e service start

time

–T

he S

ervice P

eriod en

ds w

hen

the A

P tran

smits th

e QoS

gro

up

add

ressed fram

e with

the E

OS

P b

it set to 1

.

•S

hall n

ot b

e tran

smitted

simu

ltan

eou

sly v

ia th

e MR

G-

SP

an

d eith

er the A

ll-Activ

e/An

y-P

S o

r FM

S P

ow

er

Man

agem

ent m

od

es.

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

5

Back

up

Slid

es

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

6

Com

plex

ities of S

equ

ence C

ou

nter

•M

echan

ism 1

(mech

1): o

ne seq

uen

ce cou

nter fo

r all

gro

up

cast tra

ffic, non

-QoS

fram

es, an

d m

an

agem

ent

fram

es

–A

s per to

day

•M

echan

ism 2

(mech

2): o

ne seq

uen

ce cou

nter p

er gro

up

ad

dressed

stream

•In

the n

ext 4

slides w

e show

the p

ros a

nd

con

s of ea

ch

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

7

Mech

1 - C

on

s

•If th

ere is 1 seq

# co

un

ter for a

ll GA

fram

es yet o

ne B

A a

greem

ent p

er GA

, an

d th

e AP

tra

nsm

its mu

ltiple G

A strea

ms (o

r mgm

t fram

es or n

on

-QoS

fram

es), then

the R

X d

oes n

ot

kn

ow

wh

ether th

e holes it h

as in

its BA

bitm

ap

are d

ue to

missin

g fra

mes in

the 1

1aa G

A

stream

or o

ther fra

mes. T

he R

X m

ust h

old

on

to th

e pack

ets un

til: –

Wo

rkaro

un

d 1

: New

frames cau

se its BA

win

do

w to

adv

ance, so

that th

e old

est frames can

be released

up

the

MA

C-S

AP

. Pro

blem

: guaran

teed larg

e delay

s; delay

s are unbounded

if new

pack

ets arrive slo

wly

[U

naccep

table]

–W

ork

around 2

: AP

sends u

nicast B

AR

frames reg

ularly

to ad

van

ce the B

A w

indow

in clien

ts. The A

P h

as ad

ditio

nal p

rocessin

g to

match

ho

les again

st each 1

1aa G

A stream

as on

ly it k

no

ws w

hich

are gen

uin

e ho

les and

wh

ich are n

ot. U

p to

a lifetime lim

it, the A

P retries th

e missin

g p

ackets, sen

din

g a u

nicast B

AR

and

gettin

g a

BA

. If there are h

oles fro

m o

ther p

ackets o

r the lifetim

e limit is ex

ceeded

, the A

P h

as to p

erform

an ad

ditio

nal

BA

R/B

A ex

chan

ge to

get th

e client to

release bu

ffered p

ackets u

p th

e MA

C-S

AP

. An

d th

is add

ition

al BA

R/B

A

need

s to h

appen

with

each g

roup m

ember, ev

en fo

r gro

ups w

ith 1

0-2

0-1

00 m

embers (e.g

. the b

road

cast gro

up)

and so

this scales p

oorly

.

–W

ork

arou

nd

3: S

ame as 2

excep

t that th

e BA

Rs are sen

t GA

, and

the B

AR

sched

ules th

e BA

s imm

ediately

afterw

ards. T

he A

P can

transm

it a GA

BA

R w

ith an

empty

BA

sched

ule if th

e AP

only

wish

es to ad

van

ce the

BA

win

dow

of th

e gro

up. T

his is a n

ew B

AR

form

at, and req

uires n

ew A

DD

BA

.request/resp

onse fo

rmats also

.

•In

pro

cessing B

As, th

e AP

mu

st keep

track

of th

e holes p

er GA

stream

•In

ord

er to red

uce th

e need

for a

n a

dd

ition

al B

AR

to a

dvan

ce the B

A w

ind

ow

in clien

ts, the A

P

shou

ld seq

uen

ce fram

es for o

ne G

A a

nd

its exch

an

ges o

f BA

R a

nd

BA

s befo

re send

ing fra

mes

for a

noth

er GA

•R

epair req

uests (N

AC

Ks) a

re challen

gin

g/im

possib

le, since a

client d

etecting a

missin

g

sequ

ence n

um

ber ca

nn

ot a

scribe th

at to

a m

issing M

SD

U fo

r a G

A o

f interest.

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

8

Mech

1 - P

ros

•N

o a

dd

ition

al seq

# co

un

ter requ

ired w

ithin

the A

P

•N

o p

ossib

ility o

f du

plica

te removal in

legacy

clients ca

usin

g sid

e-effects (e.g

. an

imp

lemen

tatio

n th

at d

oes d

up

licate rem

oval b

efore

gro

up

ad

dress filterin

g still d

oes n

ot o

ver-rem

ove fra

mes)

•A

llow

s fram

es sent v

ia th

e legacy

No-A

ck/N

o-R

etry A

ck p

olicy

to

be reu

sed a

s initia

l tran

smissio

ns (m

uch

less overh

ead

in m

ixed

cells)

•T

he req

uirem

ent fo

r regu

lar B

AR

s an

d B

As to

all S

TA

s seems lik

e a h

ack

, an

d a

hack

that w

ou

ld sta

y w

ith 8

02.1

1 ev

er afterw

ard

s, ev

en in

an

all-8

02.1

1aa w

orld

. Yet th

e overh

ead

of th

e hack

is still lik

ely less th

an

the o

verh

ead

of tra

nsm

itting th

e gro

up

ad

dress

stream

twice, so

the lo

ng term

pain

is mod

est bu

t the sh

ort term

b

enefits a

re hig

h.

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 2

9

Mech

2 - P

ros

•S

imp

le BA

beh

avio

r: holes a

re imm

edia

tely v

isible to

AP

an

d

client a

s missin

g p

ack

ets –

no

extra laten

cy

–n

o ex

tra BA

Rs n

eeded

to u

pd

ate the B

A b

itmap

win

do

w

•S

hou

ld b

e com

patib

le with

legacy

du

plica

te removal if g

rou

p

ad

dress filterin

g o

ccurs b

efore d

up

licate rem

oval.

–F

rom

802.1

1:2

007, th

ere is near silen

ce as to w

hich

hap

pen

s first. Only

in

the u

nm

aintain

ed A

nn

ex C

, for u

nicast, is th

ere is add

ress filtering

on

p

90

6 th

en d

up

remo

val later o

n p

90

8. F

or m

ulticast, th

ere is filtering

on

p

90

6 y

et no

du

p rem

ov

al at all on

p9

08

. Bu

t that w

ou

ld b

e the p

lace for it,

so it lo

ok

s mu

ch lik

e du

p rem

ov

al after add

ress filtering

is the n

om

inal

imp

lemen

tation

.

•In

the lo

ng term

, wh

en a

ll dev

ices in a

gro

up

are 1

1aa-en

ab

led,

there is n

o a

dd

ition

al o

verh

ead

from

du

plica

te stream

s or ex

tra

BA

Rs

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 3

0

Mech

2 - C

on

s

•S

epara

te seq# co

un

ter for leg

acy

(No A

ck/N

o R

etry) G

A fra

mes

an

d fo

r each

GA

stream

are d

ifferent, so

correla

tion

betw

een th

e tw

o strea

ms is im

possib

le.

–If a B

SS

has b

oth

kin

ds o

f clients fo

r a GA

stream, th

e stream n

eeds to

be

sent tw

ice: via N

o A

ck/N

o R

etry an

d v

ia 11

aa, and

the N

o A

ck/N

o R

etry

frames d

on

't assist the reliab

ility o

f the 1

1aa stream

(yet th

is is still better

than

MC

2U

C fo

r 2 clien

ts)

•S

hou

ld b

e com

patib

le with

legacy

du

plica

te removal (if g

rou

p

ad

dress filterin

g o

ccurs b

efore d

up

licate rem

oval, a

s per th

e n

om

inal im

plem

enta

tion

describ

ed u

nd

er "P

ros"

), yet n

ot

gu

ara

nteed

.

•E

xtra

seq# co

un

ters need

ed w

ithin

AP

s

•D

up

licate d

etection

requ

ires the R

X to

main

tain

a ca

che o

f <

Ad

dress1

, TID

, seq#>

for G

A strea

ms o

f interest

doc.: IE

EE

802.11

-09/0

340r0

Subm

ission

Mar 2

009

Brian

Hart, C

isco S

ystem

s S

lide 3

1

Seq

uen

ce Cou

nter S

um

mary

•M

ech1 (o

ne seq

uen

ce cou

nter fo

r all g

rou

pca

st traffic,

non

-QoS

fram

es, an

d m

an

agem

ent fra

mes) u

sing

Work

aro

un

d 3

seems to

have th

e low

est nea

r-term

overh

ead