<s>
Multi-link	B-Protocol
trunking	I-Protocol
(	O
MLT	O
)	O
is	O
a	O
link	B-Architecture
aggregation	I-Architecture
technology	O
developed	O
at	O
Nortel	O
in	O
1999	O
.	O
</s>
<s>
It	O
allows	O
grouping	O
several	O
physical	O
Ethernet	O
links	O
into	O
one	O
logical	O
Ethernet	O
link	O
to	O
provide	O
fault-tolerance	B-General_Concept
and	O
high-speed	O
links	O
between	O
routers	O
,	O
switches	O
,	O
and	O
servers	O
.	O
</s>
<s>
MLT	O
allows	O
the	O
use	O
of	O
several	O
links	O
(	O
from	O
2	O
up	O
to	O
8	O
)	O
and	O
combines	O
them	O
to	O
create	O
a	O
single	O
fault-tolerant	B-General_Concept
link	O
with	O
increased	O
bandwidth	O
.	O
</s>
<s>
Prior	O
to	O
MLT	O
and	O
other	O
aggregation	O
techniques	O
,	O
parallel	O
links	O
were	O
underutilized	O
due	O
to	O
Spanning	B-Protocol
Tree	I-Protocol
Protocol	I-Protocol
’s	O
loop	O
protection	O
.	O
</s>
<s>
Fault-tolerant	B-General_Concept
design	I-General_Concept
is	O
an	O
important	O
aspect	O
of	O
Multi-Link	B-Protocol
Trunking	I-Protocol
technology	O
.	O
</s>
<s>
Combining	O
MLT	O
technology	O
with	O
Distributed	O
Split	O
Multi-Link	B-Protocol
Trunking	I-Protocol
(	O
DSMLT	B-Protocol
)	O
,	O
Split	O
multi-link	B-Protocol
trunking	I-Protocol
(	O
SMLT	O
)	O
,	O
and	O
R-SMLT	O
technologies	O
create	O
networks	O
that	O
support	O
the	O
most	O
critical	O
applications	O
.	O
</s>
<s>
A	O
general	O
limitation	O
of	O
standard	O
MLT	O
is	O
that	O
all	O
the	O
physical	O
ports	O
in	O
the	O
link	B-Architecture
aggregation	I-Architecture
group	I-Architecture
must	O
reside	O
on	O
the	O
same	O
switch	O
.	O
</s>
<s>
SMLT	O
,	O
DSMLT	B-Protocol
and	O
R-SMLT	O
technologies	O
removes	O
this	O
limitation	O
by	O
allowing	O
the	O
physical	O
ports	O
to	O
be	O
split	O
between	O
two	O
switches	O
.	O
</s>
<s>
Split	O
Multi-Link	O
Trunking450px|centerSMLT	O
mesh	O
with	O
nine	O
1Gig	O
paths	O
(	O
all	O
connections	O
active	O
and	O
load	B-Application
balancing	I-Application
traffic	O
)	O
9Gbit/s	O
full	O
duplex	O
mesh	O
providing	O
18Gbit/s	O
of	O
bandwidth	O
between	O
core	O
switches	O
.	O
</s>
<s>
Split	O
multi-link	B-Protocol
trunking	I-Protocol
(	O
SMLT	O
)	O
is	O
a	O
Layer-2	O
link	B-Architecture
aggregation	I-Architecture
technology	O
in	O
computer	B-Architecture
networking	I-Architecture
originally	O
developed	O
by	O
Nortel	O
as	O
an	O
enhancement	O
to	O
standard	O
multi-link	B-Protocol
trunking	I-Protocol
(	O
MLT	O
)	O
as	O
defined	O
in	O
IEEE	O
802.3ad	O
.	O
</s>
<s>
Link	B-Architecture
aggregation	I-Architecture
or	O
MLT	O
allows	O
multiple	O
physical	O
network	O
links	O
between	O
two	O
network	O
switches	O
and	O
another	O
device	O
(	O
which	O
could	O
be	O
another	O
switch	O
or	O
a	O
network	O
device	O
such	O
as	O
a	O
server	O
)	O
to	O
be	O
treated	O
as	O
a	O
single	O
logical	O
link	O
and	O
load	O
balance	O
the	O
traffic	O
across	O
all	O
available	O
links	O
.	O
</s>
<s>
For	O
each	O
packet	O
that	O
needs	O
to	O
be	O
transmitted	O
,	O
one	O
of	O
the	O
physical	O
links	O
is	O
selected	O
based	O
on	O
a	O
load-balancing	B-Application
algorithm	O
(	O
usually	O
involving	O
a	O
hash	B-Error_Name
function	I-Error_Name
operating	O
on	O
the	O
source	O
and	O
destination	O
Media	B-Protocol
Access	I-Protocol
Control	I-Protocol
(	O
MAC	O
)	O
address	O
information	O
)	O
.	O
</s>
<s>
A	O
general	O
limitation	O
of	O
standard	O
link	B-Architecture
aggregation	I-Architecture
,	O
MLT	O
or	O
EtherChannel	B-Protocol
is	O
that	O
all	O
the	O
physical	O
ports	O
in	O
the	O
link	B-Architecture
aggregation	I-Architecture
group	I-Architecture
must	O
reside	O
on	O
the	O
same	O
switch	O
.	O
</s>
<s>
The	O
SMLT	O
,	O
DSMLT	B-Protocol
and	O
RSMLT	O
protocols	O
remove	O
this	O
limitation	O
by	O
allowing	O
the	O
physical	O
ports	O
to	O
be	O
split	O
between	O
two	O
switches	O
,	O
allowing	O
for	O
the	O
creation	O
of	O
Active	O
load	B-Application
sharing	I-Application
high	O
availability	O
network	O
designs	O
that	O
meet	O
five	O
nines	O
availability	O
requirements	O
.	O
</s>
<s>
The	O
key	O
to	O
the	O
operation	O
of	O
SMLT	O
is	O
the	O
Inter-Switch	B-Protocol
Trunk	I-Protocol
(	O
IST	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
when	O
one	O
switch	O
receives	O
a	O
response	O
to	O
an	O
ARP	O
request	O
from	O
an	O
end	B-Protocol
station	I-Protocol
on	O
a	O
port	O
that	O
is	O
part	O
of	O
an	O
SMLT	O
,	O
it	O
will	O
inform	O
its	O
peer	O
switch	O
across	O
the	O
IST	O
and	O
request	O
the	O
peer	O
to	O
update	O
its	O
own	O
ARP	O
table	O
with	O
a	O
record	O
pointing	O
to	O
its	O
own	O
connection	O
with	O
the	O
corresponding	O
SMLT	O
ID	O
.	O
</s>
<s>
The	O
communication	O
between	O
peer	O
switches	O
across	O
the	O
IST	O
allows	O
both	O
unicast	O
and	O
multicast	O
routing	O
information	O
to	O
be	O
exchanged	O
allowing	O
protocols	O
such	O
as	O
Open	B-Protocol
Shortest	I-Protocol
Path	I-Protocol
First	I-Protocol
(	O
OSPF	B-Protocol
)	O
and	O
Protocol	O
Independent	O
Multicast-Sparse	O
Mode	O
(	O
PIM-SM	O
)	O
to	O
operate	O
correctly	O
.	O
</s>
<s>
The	O
use	O
of	O
SMLT	O
not	O
only	O
allows	O
traffic	O
to	O
be	O
load-balanced	B-Application
across	O
all	O
the	O
links	O
in	O
an	O
aggregation	O
group	O
but	O
also	O
allows	O
traffic	O
to	O
be	O
redistributed	O
very	O
quickly	O
in	O
the	O
event	O
of	O
link	O
or	O
switch	O
failure	O
.	O
</s>
<s>
In	O
a	O
network	O
using	O
SMLT	O
,	O
it	O
is	O
often	O
no	O
longer	O
necessary	O
to	O
run	O
a	O
spanning	B-Protocol
tree	I-Protocol
protocol	I-Protocol
of	O
any	O
kind	O
since	O
there	O
are	O
no	O
logical	O
bridging	O
loops	O
introduced	O
by	O
the	O
presence	O
of	O
the	O
IST	O
.	O
</s>
<s>
Routed-SMLT	O
(	O
R-SMLT	O
)	O
is	O
a	O
computer	B-Architecture
networking	I-Architecture
protocol	O
developed	O
at	O
Nortel	O
as	O
an	O
enhancement	O
to	O
split	O
multi-link	B-Protocol
trunking	I-Protocol
(	O
SMLT	O
)	O
enabling	O
the	O
exchange	O
of	O
Layer	O
3	O
information	O
between	O
peer	O
nodes	O
in	O
a	O
switch	O
cluster	O
for	O
resiliency	O
and	O
simplicity	O
for	O
both	O
L3	O
and	O
L2	O
.	O
</s>
<s>
The	O
R-SMLT	O
protocol	O
works	O
with	O
SMLT	O
and	O
distributed	O
Split	O
Multi-Link	B-Protocol
Trunking	I-Protocol
(	O
DSMLT	B-Protocol
)	O
technologies	O
to	O
provide	O
sub-second	O
failover	O
(	O
normally	O
less	O
than	O
100	O
milliseconds	O
)	O
so	O
no	O
outage	O
is	O
noticed	O
by	O
end	O
users	O
.	O
</s>
<s>
The	O
protocol	O
supports	O
networks	O
designed	O
with	O
SMLT	O
or	O
DSMLT	B-Protocol
triangles	O
,	O
squares	O
,	O
and	O
SMLT	O
or	O
DSMLT	B-Protocol
full	O
mesh	O
topologies	O
,	O
with	O
routing	O
enabled	O
on	O
the	O
core	O
VLANs	O
.	O
</s>
<s>
R-SMLT	O
takes	O
care	O
of	O
packet	O
forwarding	O
in	O
core	O
router	O
failures	O
and	O
works	O
with	O
any	O
of	O
the	O
following	O
protocol	O
types	O
:	O
IP	O
Unicast	O
Static	O
Routes	O
,	O
RIP1	O
,	O
RIP2	O
,	O
OSPF	B-Protocol
,	O
BGP	O
and	O
IPX	O
RIP	O
.	O
</s>
<s>
R-SMLT	O
is	O
supported	O
on	O
Avaya	O
's	O
Ethernet	O
Routing	O
Switch	O
ERS	B-Protocol
8600	I-Protocol
,	O
ERS	B-Protocol
8800	I-Protocol
,	O
VSP9000	O
,	O
ERS	O
8300	O
and	O
MERS	B-Protocol
8600	I-Protocol
products	O
.	O
</s>
<s>
Distributed	O
multi-link	B-Protocol
trunking	I-Protocol
(	O
DMLT	B-Protocol
)	O
or	O
distributed	O
MLT	O
is	O
a	O
proprietary	O
computer	B-Architecture
networking	I-Architecture
protocol	O
designed	O
by	O
Nortel	O
Networks	O
,	O
and	O
now	O
owned	O
by	O
Extreme	O
Networks	O
,	O
used	O
to	O
load	O
balance	O
the	O
network	O
traffic	O
across	O
connections	O
and	O
also	O
across	O
multiple	O
switches	O
or	O
modules	O
in	O
a	O
chassis	O
.	O
</s>
<s>
The	O
protocol	O
is	O
an	O
enhancement	O
to	O
the	O
Multi-Link	B-Protocol
Trunking	I-Protocol
(	O
MLT	O
)	O
protocol	O
.	O
</s>
<s>
DMLT	B-Protocol
allows	O
the	O
ports	O
in	O
a	O
trunk	O
(	O
MLT	O
)	O
to	O
span	O
multiple	O
units	O
of	O
a	O
stack	O
of	O
switches	O
or	O
to	O
span	O
multiple	O
cards	O
in	O
a	O
chassis	O
,	O
preventing	O
network	O
outages	O
when	O
one	O
switch	O
in	O
a	O
stack	O
fails	O
or	O
a	O
card	O
in	O
a	O
chassis	O
fails	O
.	O
</s>
<s>
DMLT	B-Protocol
is	O
described	O
in	O
an	O
expired	O
United	O
States	O
Patent	O
.	O
</s>
<s>
Distributed	O
split	O
multi-link	B-Protocol
trunking	I-Protocol
(	O
DSMLT	B-Protocol
)	O
or	O
Distributed	O
SMLT	O
is	O
a	O
computer	B-Architecture
networking	I-Architecture
technology	O
developed	O
at	O
Nortel	O
to	O
enhance	O
the	O
Split	O
Multi-Link	B-Protocol
Trunking	I-Protocol
(	O
SMLT	O
)	O
protocol	O
.	O
</s>
<s>
DSMLT	B-Protocol
allows	O
the	O
ports	O
in	O
a	O
trunk	O
to	O
span	O
multiple	O
units	O
of	O
a	O
stack	O
of	O
switches	O
or	O
to	O
span	O
multiple	O
cards	O
in	O
a	O
chassis	O
,	O
preventing	O
network	O
outages	O
when	O
one	O
switch	O
in	O
a	O
stack	O
fails	O
or	O
one	O
card	O
in	O
a	O
chassis	O
fails	O
.	O
</s>
<s>
Fault-tolerance	B-General_Concept
is	O
a	O
very	O
important	O
aspect	O
of	O
Distributed	O
Split	O
Multi-Link	B-Protocol
Trunking	I-Protocol
(	O
DSMLT	B-Protocol
)	O
technology	O
.	O
</s>
<s>
Should	O
any	O
one	O
switch	O
,	O
port	O
,	O
or	O
more	O
than	O
one	O
link	O
fail	O
,	O
the	O
DSMLT	B-Protocol
technology	O
will	O
automatically	O
redistribute	O
traffic	O
across	O
the	O
remaining	O
links	O
.	O
</s>
<s>
Combining	O
Multi-Link	B-Protocol
Trunking	I-Protocol
(	O
MLT	O
)	O
,	O
DMLT	B-Protocol
,	O
SMLT	O
,	O
DSMLT	B-Protocol
and	O
R-SMLT	O
technologies	O
create	O
networks	O
that	O
support	O
the	O
most	O
critical	O
networks	O
.	O
</s>
<s>
SMLT	O
is	O
supported	O
on	O
Avaya	O
's	O
Ethernet	O
Routing	O
Switch	O
1600	O
,	O
5500	O
,	O
8300	O
,	O
ERS	B-Protocol
8600	I-Protocol
,	O
MERS	B-Protocol
8600	I-Protocol
,	O
VSP-7000	O
and	O
VSP-9000	O
products	O
.	O
</s>
