MNS-BB
Software User Guide
-57-
more expeditiously.
11.7
QoS on Ethernet
The LE2425A and LEV2525A Switches have the capability to provide QoS at Layer 2. At Layer 2,
the frame uses type of service (ToS) as specified in IEEE 802.1p . ToS uses 3 bits, just like IP
precedence, and maps well from Layer 2 to layer 3, and vice versa.
The switches have the capability to differentiate frames based on ToS settings. When two queues are
present (high or low), frames can be placed in either and serviced via the weight set on all ports. This
placement of queues, added to the weight set plus the particular tag setting on a packet allows each
queue to have different service levels.
The QoS implementations provided mapping of ToS (or IP precedence) to CoS (class of service). In
this instance, an Ethernet frame CoS setting can be mapped to the ToS byte of the IP packet, and vice
versa. A ToS level of 1 equals a CoS level of 1. This provides end-to-end priority for the traffic flow.
11.8 CLI
LE2425A and LEV2525A Switches support three types of QoS; Port based, Tag based and ToS based
(Layer 3).
11.8.1
To set the QoS type on the switch.
LE2425A#
qos
<enter>
LE2425A(qos)##
Note:
QoS is disabled by default on the switch.
Set QoS
<
type
> [
ports
] [
priority
] [
tos
] [
tag
] : Sets the QOS for a particular port. The following types
of QOS are supported:
a.
Port QOS
b.
Tag QOS
c.
Tos QOS (Layer 3)
d.
None.
Note
: Not all packets received on a port have high priority. IGMP and BPDU packets have high
priority by default.
11.8.2 Functions of QoS settings:
Port QOS
: If we set a port to high priority then all the packets received on that port will be assigned
to high priority regardless of the type of the packet.
TAG QOS
: If a packet contains a tag, the port (if tag QoS is enabled) on which the packet was
received then looks to see at which level that tag value is set. Regardless of the tag value, if there is a
tag, that packet is automatically assigned high priority.
TOS QOS
: (Layer 3) When a port is set to TOS QOS, the most significant 6-bits of the IPv4 packet
(which has 64 bits) are used. If the 6 bits are set to TOS QOS for the specific port number the packet
went to, that packet is assigned high priority by that port.
Syntax
:
setqos type=<port|tag|tos|none> [port=<port|list|range>]
[priority=<high|low>] [tos=<0-63|list|range>][tag=<0-7|list|range>]
Depending on the type of QOS, the corresponding field has to be set. For example, for QOS type tag,
the tag levels have to be set, and for QOS type ToS, the ToS levels have to be set. If the priority field
is not set, it then defaults to low priority. ToS has 64 levels and the valid values are 0-63 and a tagged
packet has 8 levels and the valid values are 0-7.
Note
: Setting type to none will clear the QOS (
Disable
) for all the ports.
Set port weight:
Sets the port priority weight for
All
the ports. Once the weight is set, all the ports
