Extreme Networks BlackDiamond 6800, Installation And User Manual

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3-32 Asynchronous Transfer Mode (ATM) Module Installation and User Guide
Configuring the ATM Module
configured ATM ports. Functions such as access list and destination MAC address QoS
policies are supported, as is the
enable diffserv replacement
command.
Egress frames are always assigned to a QoS profile based on their 802.1p priority. Thus,
when an ATM port receives a frame from the switch fabric with a priority value n, that
frame is assigned to egress QoS profile qpn+1.
The existing
enable diffserv examination ports
and
disable diffserv
examination ports
commands are used on ATM ports to control whether the DiffServ
code point (DSCP) is examined for ingress classification purposes.
When you enable the LLC Encapsulation for Bridged Protocols on an ATM port, non-IP
frames that contain a VLAN tag are assigned to an ingress QoS profile based on their
802.1p priority value. You can configure this assignment using the
config dot1p type
command, which is used to specify the mappings between 802.1p priority values and
QoS profiles. However, if an ATM port receives a frame with a priority value n, for
which there is no mapping to one of the eight profiles (qp1-qp8), that frame is assigned
to ingress QoS profile qpn+1.
If
diffserv examination
is not enabled, then the preceding 802.1p priority
classification rules are applied to tagged IP frames as well.
In both cases, untagged frames are assigned to a single ingress QoS profile (provided
that the port is an untagged member of a VLAN; if that is not the case, then untagged
frames are discarded). This QoS profile defaults to qp1, but you can assign it to another
profile using the
config ports <portlist> qosprofile <qosprofile>
command or
the
config vlan <name> qosprofile <qosprofile>
command (where the port-based
QoS configuration has higher precedence than VLAN-based QoS).
Additionally, if you enable the LLC Encapsulation for Routed Protocols on an ATM port
and do not enable
diffserv examination
on the port, then all ingress frames (received
from the SONET link) are assigned to a single ingress QoS profile. The profile defaults
to qp1, but you can configure it to another profile using the
config ports <portlist>
qosprofile <qosprofile>
command or the
config vlan <name> qosprofile
<qosprofile>
command.
If you enable
diffserv examination
on an ATM port, then ingress IP frames are
assigned to a QoS profile based on the DiffServ code point (regardless of whether you
enabled either LLC Encapsulation for Bridged Protocols or LLC Encapsulation for
Routed Protocols on the port). The existing
config diffserv examination
code-point
command maps DiffServ code points to QoS profiles. This command has
been enhanced for use with ATM ports. The syntax and description of the enhanced
config diffserv examination code-point
command are given below.