<s>
PME	B-Protocol
Aggregation	I-Protocol
Function	I-Protocol
(	O
PAF	O
)	O
is	O
a	O
computer	B-Architecture
networking	I-Architecture
mechanism	O
defined	O
in	O
Clause	O
61	O
of	O
the	O
IEEE	O
802.3	O
standard	O
,	O
which	O
allows	O
one	O
or	O
more	O
Physical	O
Medium	O
Entities	O
(	O
PMEs	O
)	O
to	O
be	O
combined	O
to	O
form	O
a	O
single	O
logical	O
Ethernet	O
link	O
.	O
</s>
<s>
The	O
PAF	O
is	O
located	O
in	O
the	O
Physical	B-Protocol
Coding	I-Protocol
Sublayer	I-Protocol
(	O
PCS	O
)	O
,	O
between	O
the	O
Media	B-Protocol
Access	I-Protocol
Control	I-Protocol
(	O
MAC	O
)	O
-PHY	O
Rate	O
Matching	O
function	O
and	O
the	O
Transmission	O
Convergence	O
(	O
TC	O
)	O
sublayer	O
.	O
</s>
<s>
PAF	O
is	O
an	O
optional	O
function	O
which	O
was	O
defined	O
before	O
2007	O
for	O
two	O
IEEE	O
802.3	O
interfaces	O
:	O
2BASE-TL	B-Protocol
and	O
10PASS-TS	O
,	O
both	O
of	O
which	O
were	O
Ethernet	B-Protocol
in	I-Protocol
the	I-Protocol
First	I-Protocol
Mile	I-Protocol
(	O
EFM	O
)	O
copper	O
physical	O
layers	O
.	O
</s>
<s>
PME	B-Protocol
Aggregation	I-Protocol
function	I-Protocol
has	O
the	O
following	O
characteristics	O
:	O
</s>
<s>
A	O
frame	B-Protocol
check	I-Protocol
sequence	I-Protocol
(	O
FCS	O
)	O
is	O
appended	O
to	O
each	O
fragment	O
,	O
which	O
is	O
then	O
transmitted	O
by	O
the	O
next	O
available	O
active	O
PME	O
in	O
the	O
aggregated	O
group	O
.	O
</s>
<s>
The	O
PME	B-Protocol
Aggregation	I-Protocol
function	I-Protocol
was	O
first	O
defined	O
in	O
IEEE	B-Protocol
802.3ah	I-Protocol
in	O
2004	O
.	O
</s>
<s>
While	O
allowing	O
great	O
flexibility	O
in	O
Transmitter	O
and	O
Receiver	O
implementations	O
it	O
requires	O
an	O
overhead	O
consuming	O
about	O
5%	O
of	O
the	O
bandwidth	O
(	O
estimation	O
for	O
2BASE-TL	B-Protocol
protocol	O
,	O
including	O
64B/65B	O
encapsulation	O
)	O
.	O
</s>
<s>
Inverse	B-Protocol
Multiplexing	I-Protocol
for	I-Protocol
ATM	I-Protocol
(	O
IMA	O
)	O
is	O
another	O
aggregation	O
protocol	O
,	O
which	O
unlike	O
PAF	O
uses	O
fixed-size	O
cells	O
,	O
sending	O
them	O
across	O
multiple	O
links	O
in	O
a	O
Round-Robin	B-Algorithm
fashion	O
.	O
</s>
<s>
IMA	O
is	O
optimized	O
for	O
ATM	O
and	O
in	O
the	O
extreme	O
cases	O
(	O
short	O
Ethernet	O
frames	O
)	O
may	O
add	O
as	O
much	O
as	O
40%	O
overhead	O
due	O
to	O
the	O
AAL5	B-Protocol
encapsulation	O
.	O
</s>
<s>
ITU-T	O
G.998.3	O
(	O
Multi-pair	O
bonding	O
using	O
time-division	B-Protocol
inverse	O
multiplexing	O
)	O
specification	O
,	O
a.k.a.	O
</s>
<s>
G.Bond/TDIM	O
,	O
defines	O
a	O
symmetric	O
aggregation	O
protocol	O
,	O
in	O
which	O
both	O
sides	O
of	O
a	O
point-to-point	B-Architecture
link	I-Architecture
exchange	O
information	O
about	O
the	O
aggregation	O
,	O
so	O
there	O
's	O
no	O
need	O
for	O
a	O
separate	O
header	O
.	O
</s>
<s>
G.Bond/TDIM	O
is	O
optimized	O
for	O
both	O
Time-Division	B-Protocol
Multiplexing	I-Protocol
and	O
packet	O
traffic	O
with	O
less	O
than	O
3%	O
overhead	O
(	O
estimation	O
for	O
Ethernet	O
traffic	O
,	O
including	O
Generic	B-Protocol
Framing	I-Protocol
Procedure	I-Protocol
(	O
GFP	O
)	O
encapsulation	O
)	O
.	O
</s>
