<s>
A	O
metropolitan-area	O
Ethernet	O
,	O
Ethernet	O
MAN	O
,	O
or	O
metro	B-Protocol
Ethernet	I-Protocol
network	O
is	O
a	O
metropolitan	O
area	O
network	O
(	O
MAN	O
)	O
that	O
is	O
based	O
on	O
Ethernet	O
standards	O
.	O
</s>
<s>
An	O
Ethernet	O
interface	O
is	O
typically	O
more	O
economical	O
than	O
a	O
synchronous	B-Protocol
digital	I-Protocol
hierarchy	I-Protocol
(	O
SONET/SDH	B-Protocol
)	O
or	O
plesiochronous	B-Protocol
digital	I-Protocol
hierarchy	I-Protocol
(	O
PDH	O
)	O
interface	O
of	O
the	O
same	O
bandwidth	O
.	O
</s>
<s>
A	O
typical	O
service	O
provider	O
's	O
network	O
is	O
a	O
collection	O
of	O
switches	B-Protocol
and	O
routers	B-Protocol
connected	O
through	O
optical	B-Architecture
fiber	I-Architecture
.	O
</s>
<s>
The	O
topology	B-Architecture
could	O
be	O
a	O
ring	B-Architecture
,	O
hub-and-spoke	O
(	O
star	O
)	O
,	O
or	O
full	O
or	O
partial	O
mesh	B-Architecture
.	O
</s>
<s>
The	O
core	O
in	O
most	O
cases	O
is	O
an	O
existing	O
IP/MPLS	B-Protocol
backbone	O
but	O
may	O
migrate	O
to	O
newer	O
forms	O
of	O
Ethernet	O
transport	O
in	O
the	O
form	O
of	O
10Gbit/s	O
,	O
40	O
Gbit/s	O
,	O
or	O
100	O
Gbit/s	O
speeds	O
or	O
even	O
possibly	O
400Gbit/s	O
to	O
Terabit	B-Protocol
Ethernet	I-Protocol
network	O
in	O
the	O
future	O
.	O
</s>
<s>
Ethernet	O
on	O
the	O
MAN	O
can	O
be	O
used	O
as	O
pure	O
Ethernet	O
,	O
Ethernet	B-Protocol
over	I-Protocol
SDH	I-Protocol
,	O
Ethernet	O
over	O
Multiprotocol	B-Protocol
Label	I-Protocol
Switching	I-Protocol
(	O
MPLS	B-Protocol
)	O
,	O
or	O
Ethernet	O
over	O
DWDM	O
.	O
</s>
<s>
MPLS-based	O
deployments	O
are	O
costly	O
but	O
highly	O
reliable	O
and	O
scalable	O
and	O
are	O
typically	O
used	O
by	O
large	O
service	O
providers	O
.	O
</s>
<s>
This	O
is	O
the	O
network	O
that	O
connects	O
customer	O
equipment	O
,	O
and	O
may	O
include	O
optical	O
network	O
terminal	O
(	O
ONT	O
)	O
,	O
a	O
residential	O
gateway	O
,	O
or	O
office	O
router	B-Protocol
.	O
</s>
<s>
Often	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
,	O
microwave	O
or	O
digital	O
subscriber	O
line	O
technologies	O
are	O
employed	O
,	O
but	O
some	O
of	O
them	O
using	O
point-to-point	O
Ethernet	O
over	O
"	O
home-run	O
"	O
direct	O
fibre	O
.	O
</s>
<s>
This	O
part	O
of	O
the	O
network	O
includes	O
nodes	O
such	O
as	O
Multi	O
Tenanted	O
Unit	O
switches	B-Protocol
,	O
optical	B-Protocol
line	I-Protocol
terminals	I-Protocol
in	O
an	O
outside	O
plant	O
or	O
central	O
office	O
cabinet	O
,	O
Ethernet	B-Protocol
in	I-Protocol
the	I-Protocol
first	I-Protocol
mile	I-Protocol
equipment	O
,	O
or	O
provider	O
bridges	O
.	O
</s>
<s>
A	O
MAN	O
may	O
include	O
the	O
transport	O
technologies	O
MPLS	B-Protocol
,	O
PBB-TE	B-Protocol
and	O
T-MPLS	O
,	O
each	O
with	O
its	O
own	O
resiliency	O
and	O
management	O
techniques	O
.	O
</s>
<s>
A	O
core	O
network	O
often	O
uses	O
IP-MPLS	O
to	O
connect	O
different	O
MANs	O
together	O
.	O
</s>
<s>
Much	O
of	O
the	O
functionality	O
of	O
Ethernet	O
MANs	O
such	O
as	O
virtual	O
private	O
lines	O
or	O
virtual	B-Application
private	I-Application
networks	I-Application
is	O
implemented	O
by	O
the	O
use	O
of	O
Ethernet	O
VLAN	B-General_Concept
tags	O
that	O
allow	O
differentiation	O
of	O
each	O
part	O
of	O
the	O
network	O
.	O
</s>
<s>
A	O
Multiprotocol	B-Protocol
Label	I-Protocol
Switching	I-Protocol
(	O
MPLS	B-Protocol
)	O
metro	B-Protocol
Ethernet	I-Protocol
network	O
uses	O
MPLS	B-Protocol
in	O
the	O
service	O
provider	O
's	O
network	O
.	O
</s>
<s>
The	O
subscriber	O
will	O
get	O
an	O
Ethernet	O
interface	O
on	O
copper	O
(	O
for	O
example	O
,	O
100BASE-TX	B-Protocol
)	O
or	O
fiber	O
(	O
such	O
as	O
100BASE-FX	O
)	O
.	O
</s>
<s>
The	O
customer	O
's	O
Ethernet	O
packet	O
is	O
transported	O
over	O
MPLS	B-Protocol
and	O
the	O
service	O
provider	O
network	O
uses	O
Ethernet	O
again	O
as	O
the	O
underlying	O
technology	O
to	O
transport	O
MPLS	B-Protocol
.	O
</s>
<s>
So	O
,	O
it	O
is	O
Ethernet	O
over	O
MPLS	B-Protocol
over	O
Ethernet	O
.	O
</s>
<s>
Label	B-Protocol
Distribution	I-Protocol
Protocol	I-Protocol
(	O
LDP	O
)	O
signaling	O
can	O
be	O
used	O
as	O
site	O
to	O
site	O
signaling	O
for	O
the	O
inner	O
label	O
(	O
VC	O
label	O
)	O
and	O
Resource	O
reSerVation	O
Protocol-Traffic	O
Engineering	O
(	O
RSVP-TE	B-Protocol
)	O
or	O
LDP	O
may	O
be	O
used	O
as	O
Network	O
signaling	O
for	O
the	O
outer	O
label	O
.	O
</s>
<s>
One	O
restoration	O
mechanism	O
used	O
in	O
an	O
MPLS	B-Protocol
based	O
Metro	B-Protocol
Ethernet	I-Protocol
Networks	O
is	O
Fast	O
ReRoute	O
(	O
FRR	O
)	O
to	O
achieve	O
sub-50ms	O
convergence	O
of	O
MPLS	B-General_Concept
local	I-General_Concept
protection	I-General_Concept
.	O
</s>
<s>
For	O
each	O
deployment	O
situation	O
the	O
benefit	O
versus	O
cost	O
of	O
MPLS	B-Protocol
must	O
be	O
weighed	O
carefully	O
,	O
so	O
if	O
not	O
implemented	O
on	O
a	O
carrier	O
's	O
distribution	O
network	O
there	O
might	O
be	O
more	O
benefit	O
for	O
MPLS	B-Protocol
the	O
core	O
network	O
.	O
</s>
<s>
A	O
comparison	O
of	O
MPLS-based	O
Metro	B-Protocol
Ethernet	I-Protocol
against	O
a	O
pure	O
Ethernet	O
MAN	O
:	O
</s>
<s>
Scalability	O
In	O
a	O
properly	O
designed	O
Ethernet	O
VLAN	B-General_Concept
network	O
,	O
each	O
switched	O
path	O
can	O
have	O
4094	O
single	O
tag	O
VLANs	B-General_Concept
.	O
</s>
<s>
Some	O
aggregation	O
and	O
core	O
switches	B-Protocol
can	O
classify	O
traffic	O
by	O
two	O
VLANs	B-General_Concept
using	O
IEEE	O
802.1ad	O
VLAN	B-General_Concept
stacking	O
,	O
so	O
with	O
such	O
aggregation	O
devices	O
properly	O
placed	O
in	O
the	O
center	O
of	O
a	O
network	O
,	O
end	O
segments	O
and	O
rings	O
of	O
single	O
tag	O
devices	O
can	O
receive	O
only	O
the	O
traffic	O
that	O
they	O
need	O
.	O
</s>
<s>
When	O
using	O
MPLS	B-Protocol
,	O
Ethernet	O
VLANs	B-General_Concept
have	O
local	O
meaning	O
only	O
(	O
like	O
Frame	O
Relay	O
PVC	O
)	O
.	O
</s>
<s>
Same	O
scalability	O
considerations	O
apply	O
to	O
the	O
MAC	O
addresses	O
where	O
in	O
a	O
pure	O
Layer	O
2	O
Ethernet	O
MAN	O
all	O
MAC	O
addresses	O
are	O
being	O
shared	O
across	O
the	O
network	O
,	O
although	O
this	O
issue	O
can	O
be	O
managed	O
by	O
smart	O
network	O
design	O
and	O
choosing	O
switches	B-Protocol
with	O
MAC	O
tables	O
sufficient	O
for	O
the	O
size	O
of	O
network	O
segments	O
.	O
</s>
<s>
Resiliency	O
pure	O
Ethernet	O
network	O
resiliency	O
relies	O
on	O
a	O
Spanning	B-Protocol
Tree	I-Protocol
Protocol	I-Protocol
,	O
IEEE	O
802.1w	O
RSTP	O
or	O
IEEE	O
802.1s	O
MSTP	O
(	O
30	O
to	O
sub	O
50ms	O
convergence	O
depending	O
on	O
network	O
design	O
)	O
while	O
MPLS-based	O
MANs	O
use	O
mechanisms	O
such	O
as	O
MPLS	B-General_Concept
Fast	I-General_Concept
Reroute	I-General_Concept
to	O
achieve	O
SDH-like	O
(	O
50ms	O
)	O
convergence	O
times	O
.	O
</s>
<s>
Metro	B-Protocol
Ethernet	I-Protocol
can	O
also	O
use	O
Link	B-Architecture
aggregation	I-Architecture
or	O
Resilient	O
Packet	O
Ring	B-Architecture
where	O
appropriate	O
to	O
add	O
link	O
redundancy	O
and	O
recovery	O
in	O
distribution	O
networks	O
.	O
</s>
<s>
Multiprotocol	O
convergence	O
with	O
the	O
maturity	O
on	O
pseudowires	O
standards	O
(	O
ATM	O
virtual	B-Protocol
leased	I-Protocol
line	I-Protocol
VLL	O
,	O
FR	O
VLL	O
,	O
etc	O
.	O
)	O
</s>
<s>
an	O
MPLS-based	O
Metro	B-Protocol
Ethernet	I-Protocol
can	O
backhaul	O
IP/Ethernet	O
traffic	O
together	O
with	O
virtually	O
any	O
type	O
of	O
traffic	O
coming	O
from	O
customer	O
or	O
other	O
access	O
networks	O
(	O
i.e.	O
</s>
<s>
End	O
to	O
End	O
OAM	O
MPLS-based	O
MAN	O
offers	O
a	O
wide	O
set	O
of	O
troubleshooting	O
and	O
OAM	O
MPLS-based	O
tools	O
which	O
enrich	O
Service	O
Providers	O
ability	O
to	O
effectively	O
troubleshoot	O
and	O
diagnose	O
network	O
problems	O
.	O
</s>
<s>
However	O
,	O
there	O
are	O
now	O
Ethernet	O
OAM	O
tools	O
defined	O
in	O
IEEE	B-Protocol
802.1AB	I-Protocol
,	O
IEEE	O
802.1ag	O
and	O
Ethernet	B-Protocol
in	I-Protocol
the	I-Protocol
First	I-Protocol
Mile	I-Protocol
(	O
IEEE	B-Protocol
802.3ah	I-Protocol
)	O
for	O
monitoring	O
and	O
troubleshooting	O
Ethernet	O
networks	O
.	O
</s>
<s>
EOAM	B-Architecture
(	O
Ethernet	B-Architecture
Operations	I-Architecture
,	I-Architecture
Administration	I-Architecture
,	I-Architecture
and	I-Architecture
Maintenance	I-Architecture
)	O
is	O
a	O
protocol	O
for	O
installing	O
,	O
monitoring	O
,	O
and	O
troubleshooting	O
MANs	O
and	O
WANs	O
.	O
</s>
<s>
Some	O
service	O
providers	O
deployed	O
metro	B-Protocol
Ethernet	I-Protocol
networks	O
using	O
fixed	B-General_Concept
wireless	I-General_Concept
technology	O
.	O
</s>
<s>
These	O
networks	O
commonly	O
are	O
engineered	O
with	O
a	O
majority	O
of	O
the	O
network	O
traffic	O
using	O
a	O
mesh	B-Architecture
of	O
multi-point	O
and	O
point-to-point	O
microwave	B-Application
links	I-Application
.	O
</s>
<s>
Carriers	O
have	O
more	O
recently	O
been	O
referred	O
to	O
as	O
metro	B-Architecture
wireless	I-Architecture
in	O
many	O
cases	O
.	O
</s>
<s>
Metro	B-Architecture
Wireless	I-Architecture
providers	O
in	O
many	O
cases	O
are	O
able	O
to	O
produce	O
shorter	O
installation	O
times	O
due	O
to	O
less	O
permitting	O
and	O
procedure	O
necessary	O
.	O
</s>
<s>
In	O
late	O
September	O
2007	O
Verizon	O
Business	O
announced	O
metro	B-Protocol
Ethernet	I-Protocol
across	O
Asia-Pacific	O
including	O
Australia	O
,	O
Singapore	O
,	O
Japan	O
and	O
Hong	O
Kong	O
using	O
Nortel	O
equipment	O
.	O
</s>
<s>
In	O
late	O
January	O
2009	O
,	O
Windstream	O
announced	O
it	O
would	O
begin	O
offering	O
metro	B-Protocol
Ethernet	I-Protocol
service	O
to	O
small	O
and	O
medium	O
business	O
customers	O
.	O
</s>
<s>
In	O
May	O
2011	O
,	O
Comcast	O
announced	O
its	O
own	O
metro	B-Protocol
Ethernet	I-Protocol
services	O
to	O
business	O
customers	O
in	O
the	O
United	O
States	O
.	O
</s>
