<s>
A	O
network	B-General_Concept
processor	I-General_Concept
is	O
an	O
integrated	O
circuit	O
which	O
has	O
a	O
feature	O
set	O
specifically	O
targeted	O
at	O
the	O
networking	B-Architecture
application	O
domain	O
.	O
</s>
<s>
Network	B-General_Concept
processors	I-General_Concept
are	O
typically	O
software	O
programmable	O
devices	O
and	O
would	O
have	O
generic	O
characteristics	O
similar	O
to	O
general	O
purpose	O
central	B-General_Concept
processing	I-General_Concept
units	I-General_Concept
that	O
are	O
commonly	O
used	O
in	O
many	O
different	O
types	O
of	O
equipment	O
and	O
products	O
.	O
</s>
<s>
In	O
modern	O
telecommunications	O
networks	O
,	O
information	O
(	O
voice	O
,	O
video	O
,	O
data	O
)	O
is	O
transferred	O
as	O
packet	B-Protocol
data	I-Protocol
(	O
termed	O
packet	B-Protocol
switching	I-Protocol
)	O
which	O
is	O
in	O
contrast	O
to	O
older	O
telecommunications	O
networks	O
that	O
carried	O
information	O
as	O
analog	O
signals	O
such	O
as	O
in	O
the	O
public	O
switched	O
telephone	O
network	O
(	O
PSTN	O
)	O
or	O
analog	O
TV/Radio	O
networks	O
.	O
</s>
<s>
The	O
processing	O
of	O
these	O
packets	B-Protocol
has	O
resulted	O
in	O
the	O
creation	O
of	O
integrated	O
circuits	O
(	O
IC	O
)	O
that	O
are	O
optimised	O
to	O
deal	O
with	O
this	O
form	O
of	O
packet	B-Protocol
data	I-Protocol
.	O
</s>
<s>
Network	B-General_Concept
processors	I-General_Concept
have	O
specific	O
features	O
or	O
architectures	O
that	O
are	O
provided	O
to	O
enhance	O
and	O
optimise	O
packet	B-Protocol
processing	O
within	O
these	O
networks	O
.	O
</s>
<s>
Network	B-General_Concept
processors	I-General_Concept
have	O
evolved	O
into	O
ICs	O
with	O
specific	O
functions	O
.	O
</s>
<s>
The	O
newer	O
circuits	O
are	O
programmable	O
and	O
thus	O
allow	O
a	O
single	O
hardware	B-Architecture
IC	O
design	O
to	O
undertake	O
a	O
number	O
of	O
different	O
functions	O
,	O
where	O
the	O
appropriate	O
software	O
is	O
installed	O
.	O
</s>
<s>
Network	B-General_Concept
processors	I-General_Concept
are	O
used	O
in	O
the	O
manufacture	O
of	O
many	O
different	O
types	O
of	O
network	B-Device
equipment	I-Device
such	O
as	O
:	O
</s>
<s>
Reconfigurable	O
Match-Tables	O
were	O
introduced	O
in	O
2013	O
to	O
allow	O
switches	B-Protocol
to	O
operate	O
at	O
high	O
speeds	O
while	O
maintaining	O
flexibility	O
when	O
it	O
comes	O
to	O
the	O
network	O
protocols	O
running	O
on	O
them	O
,	O
or	O
the	O
processing	O
to	O
does	O
to	O
them	O
.	O
</s>
<s>
P4	B-Language
is	O
used	O
to	O
program	O
the	O
chips	O
.	O
</s>
<s>
An	O
RMT	O
pipeline	B-General_Concept
relies	O
on	O
three	O
main	O
stages	O
;	O
the	O
programmable	O
parser	O
,	O
the	O
Match-Action	O
tables	O
and	O
the	O
programmable	O
deparser	O
.	O
</s>
<s>
The	O
parser	O
reads	O
the	O
packet	B-Protocol
in	O
chunks	O
and	O
processes	O
these	O
chunks	O
to	O
find	O
out	O
which	O
protocols	O
are	O
used	O
in	O
the	O
packet	B-Protocol
(	O
Ethernet	B-Protocol
,	O
VLAN	O
,	O
IPv4	B-Protocol
...	O
)	O
and	O
extracts	O
certain	O
fields	O
from	O
the	O
packet	B-Protocol
into	O
the	O
Packet	B-Protocol
Header	O
Vector	O
(	O
PHV	O
)	O
.	O
</s>
<s>
Certain	O
fields	O
in	O
the	O
PHV	O
may	O
be	O
reserved	O
for	O
special	O
uses	O
such	O
as	O
present	O
headers	O
or	O
total	O
packet	B-Protocol
length	O
.	O
</s>
<s>
The	O
Match-Action	O
tables	O
are	O
a	O
series	O
of	O
units	O
that	O
read	O
an	O
input	O
PHV	O
,	O
match	O
certain	O
fields	O
in	O
it	O
using	O
a	O
crossbar	O
and	O
CAM	B-Data_Structure
memory	I-Data_Structure
,	O
the	O
result	O
is	O
a	O
wide	O
instruction	O
that	O
operates	O
on	O
one	O
or	O
more	O
fields	O
of	O
the	O
PHV	O
and	O
data	O
to	O
support	O
this	O
instruction	O
.	O
</s>
<s>
The	O
deparser	O
takes	O
in	O
the	O
PHV	O
as	O
well	O
as	O
the	O
original	O
packet	B-Protocol
and	O
it	O
's	O
metadata	O
(	O
to	O
fill	O
in	O
missing	O
bits	O
that	O
were	O
n't	O
extracted	O
into	O
the	O
PHV	O
)	O
and	O
then	O
outputs	O
the	O
modified	O
packet	B-Protocol
as	O
chunks	O
.	O
</s>
<s>
FlexNIC	O
attempts	O
to	O
apply	O
this	O
model	O
to	O
Network	B-Protocol
Interface	I-Protocol
Controllers	I-Protocol
allowing	O
servers	O
to	O
send	O
and	O
receive	O
packets	B-Protocol
at	O
high	O
speeds	O
while	O
maintaining	O
protocol	O
flexibility	O
and	O
without	O
increasing	O
the	O
CPU	O
overhead	O
.	O
</s>
<s>
In	O
the	O
generic	O
role	O
as	O
a	O
packet	B-Protocol
processor	O
,	O
a	O
number	O
of	O
optimised	O
features	O
or	O
functions	O
are	O
typically	O
present	O
in	O
a	O
network	B-General_Concept
processor	I-General_Concept
,	O
which	O
include	O
:	O
</s>
<s>
Pattern	O
matching	O
–	O
the	O
ability	O
to	O
find	O
specific	O
patterns	O
of	O
bits	O
or	O
bytes	O
within	O
packets	B-Protocol
in	O
a	O
packet	B-Protocol
stream	O
.	O
</s>
<s>
Key	O
lookup	O
–	O
the	O
ability	O
to	O
quickly	O
undertake	O
a	O
database	O
lookup	O
using	O
a	O
key	O
(	O
typically	O
an	O
address	O
in	O
a	O
packet	B-Protocol
)	O
to	O
find	O
a	O
result	O
,	O
typically	O
routing	B-Protocol
information	I-Protocol
.	O
</s>
<s>
Data	O
bitfield	O
manipulation	O
–	O
the	O
ability	O
to	O
change	O
certain	O
data	O
fields	O
contained	O
in	O
the	O
packet	B-Protocol
as	O
it	O
is	O
being	O
processed	O
.	O
</s>
<s>
Queue	B-Application
management	O
–	O
as	O
packets	B-Protocol
are	O
received	O
,	O
processed	O
and	O
scheduled	O
to	O
be	O
sent	O
onwards	O
,	O
they	O
are	O
stored	O
in	O
queues	B-Application
.	O
</s>
<s>
Control	O
processing	O
–	O
the	O
micro	O
operations	O
of	O
processing	O
a	O
packet	B-Protocol
are	O
controlled	O
at	O
a	O
macro	O
level	O
which	O
involves	O
communication	O
and	O
orchestration	O
with	O
other	O
nodes	O
in	O
a	O
system	O
.	O
</s>
<s>
Quick	O
allocation	O
and	O
re-circulation	O
of	O
packet	B-Protocol
buffers	O
.	O
</s>
<s>
Pipeline	B-General_Concept
of	O
processors	O
-	O
each	O
stage	O
of	O
the	O
pipeline	B-General_Concept
consisting	O
of	O
a	O
processor	O
performing	O
one	O
of	O
the	O
functions	O
listed	O
above	O
.	O
</s>
<s>
Parallel	B-Operating_System
processing	I-Operating_System
with	O
multiple	O
processors	O
,	O
often	O
including	O
multithreading	B-General_Concept
.	O
</s>
<s>
Specialized	O
microcoded	B-Device
engines	O
to	O
more	O
efficiently	O
accomplish	O
the	O
tasks	O
at	O
hand	O
.	O
</s>
<s>
With	O
the	O
advent	O
of	O
multicore	B-Architecture
architectures	O
,	O
network	B-General_Concept
processors	I-General_Concept
can	O
be	O
used	O
for	O
higher	O
layer	O
(	O
L4-L7	O
)	O
processing	O
.	O
</s>
<s>
Additionally	O
,	O
traffic	O
management	O
,	O
which	O
is	O
a	O
critical	O
element	O
in	O
L2-L3	O
network	B-General_Concept
processing	I-General_Concept
and	O
used	O
to	O
be	O
executed	O
by	O
a	O
variety	O
of	O
co-processors	O
,	O
has	O
become	O
an	O
integral	O
part	O
of	O
the	O
network	B-General_Concept
processor	I-General_Concept
architecture	O
,	O
and	O
a	O
substantial	O
part	O
of	O
its	O
silicon	O
area	O
(	O
"	O
real	O
estate	O
"	O
)	O
is	O
devoted	O
to	O
the	O
integrated	O
traffic	O
manager	O
.	O
</s>
<s>
Modern	O
network	B-General_Concept
processors	I-General_Concept
are	O
also	O
equipped	O
with	O
low-latency	O
high-throughput	O
on-chip	O
interconnection	O
networks	O
optimized	O
for	O
the	O
exchange	O
of	O
small	O
messages	O
among	O
cores	O
(	O
few	O
data	O
words	O
)	O
.	O
</s>
<s>
Using	O
the	O
generic	O
function	O
of	O
the	O
network	B-General_Concept
processor	I-General_Concept
,	O
a	O
software	O
program	O
implements	O
an	O
application	O
that	O
the	O
network	B-General_Concept
processor	I-General_Concept
executes	O
,	O
resulting	O
in	O
the	O
piece	O
of	O
physical	O
equipment	O
performing	O
a	O
task	O
or	O
providing	O
a	O
service	O
.	O
</s>
<s>
Some	O
of	O
the	O
applications	O
types	O
typically	O
implemented	O
as	O
software	O
running	O
on	O
network	B-General_Concept
processors	I-General_Concept
are	O
:	O
</s>
<s>
Packet	B-Protocol
or	O
frame	O
discrimination	O
and	O
forwarding	O
,	O
that	O
is	O
,	O
the	O
basic	O
operation	O
of	O
a	O
router	B-Protocol
or	O
switch	B-Protocol
.	O
</s>
<s>
Quality	O
of	O
service	O
(	O
QoS	O
)	O
enforcement	O
–	O
identifying	O
different	O
types	O
or	O
classes	O
of	O
packets	B-Protocol
and	O
providing	O
preferential	O
treatment	O
for	O
some	O
types	O
or	O
classes	O
of	O
packet	B-Protocol
at	O
the	O
expense	O
of	O
other	O
types	O
or	O
classes	O
of	O
packet	B-Protocol
.	O
</s>
<s>
Access	O
Control	O
functions	O
–	O
determining	O
whether	O
a	O
specific	O
packet	B-Protocol
or	O
stream	O
of	O
packets	B-Protocol
should	O
be	O
allowed	O
to	O
traverse	O
the	O
piece	O
of	O
network	B-Device
equipment	I-Device
.	O
</s>
<s>
Encryption	O
of	O
data	O
streams	O
–	O
built	O
in	O
hardware-based	O
encryption	O
engines	O
allow	O
individual	O
data	O
flows	O
to	O
be	O
encrypted	O
by	O
the	O
processor	O
.	O
</s>
