Understanding QoS Configuration on the Matrix N-Series
February 22, 2008
Page 9 of 29
discarding
traffic
imposed
by
rate
limiting,
delays
are
induced
into
its
transmission
by
retaining
the
data
for
future
transmission.
However,
the
delays
must
also
be
bounded
to
the
degree
that
the
traffic
is
sensitive
to
delays.
Understanding QoS Configuration on the Matrix N-Series
This
section
discusses
the
six
components
for
configuring
QoS
and
displaying
QoS
status
on
an
N
‐
Series
switch
router:
CoS
Port
‐
Type
:
Determines
the
transmit
queue
(TxQ)
and
Inbound
Rate
Limiting
(IRL)
resource
capabilities
of
the
ports
in
your
system.
Knowledge
of
these
capabilities
is
important
when
configuring
queue
behaviors.
Port
group
membership
and
the
port
resources
available
are
determined
by
port
type.
CoS
Port
Groups
:
Provide
for
the
grouping
of
ports
by
the
same
class
of
service
features
and
port
type.
CoS
Port
Resource
Table
:
Enables
the
association
of
rate
limiter
and
rate
shaper
values
to
a
port.
CoS
Reference
Mapping
Table
:
Maps
your
defined
TxQ
and
IRL
index
references,
used
by
the
CoS
settings
table,
to
the
physical
queue
and
rate
limiter
settings
created
in
the
port
‐
resource
table.
CoS
Settings
Table
:
Used
for
CoS
parameter
assignment
and
contains
the
current
settings
for
each
class
of
service
feature.
Each
class
of
service
entry
consists
of
an
entry
index,
an
802.1p
priority,
an
optional
ToS
value,
a
transmit
queue
reference,
and
an
optional
IRL
reference.
CoS
State
:
A
global
setting
that
must
be
enabled
for
a
configured
CoS
to
affect
port
behavior.
When
enabled,
CoS
state
associated
with
a
port
supersedes
current
default
or
modified
port
‐
level
controls
for
priority
queue
mapping,
port
rate
limiting,
and
transmit
queue.
When
disabled
the
port
settings
apply.
Numerous
QoS
values
are
associated
with
each
other
through
reference.
With
the
exception
of
802.1p
priority
and
ToS,
CoS
values
are
first
mapped
to
a
port
group,
which
associates
a
CoS
configuration
with
a
port
type.
A
port
group
has
the
following
CoS
parameters
associated
with
it:
•
Physical
port(s)
•
Strict
or
weighted
fair
queuing
behavior
•
Rate
‐
limit
setting(s)
•
Rate
‐
shaping
setting(s)
•
A
port
queue
•
A
port
reference
Understanding
how
these
parameters
are
first
mapped
to
the
port
group
and
then
to
a
TxQ
or
IRL
reference
is
the
key
to
understanding
QoS
configuration.
Where
appropriate,
the
task
column
in
Procedure 1
on
page 21
identifies
these
mapping
relationships.
See
“
Determining
CoS
Port
‐
Type”
on
page 10
and
“
Configuring
CoS
Port
Groups”
on
page 11
for
a
port
group
discussion.
Note:
It is recommended that you use Enterasys NetSight Policy Manager as an alternative to CLI
for configuring policy-based CoS on the Enterasys Matrix Series devices.
A policy discussion is outside the scope of this document and will be limited to the relevant
configuration example commands.
