C
LASS
OF
S
ERVICE
C
ONFIGURATION
2-59
Mapping Layer 3/4 Priorit ies to CoS Values
This switch supports several common methods of prioritizing layer 3/4
traffic to meet application requirements. Traffic priorities can be specified
in the IP header of a frame, using the priority bits in the Type of Service
(ToS) octet or the number of the TCP/UDP port. If priority bits are used,
the ToS octet may contain three bits for IP Precedence or six bits for
Differentiated Services Code Point (DSCP) service. When these services
are enabled, the priorities are mapped to a Class of Service value by the
switch, and the traffic then sent to the corresponding output queue.
Because different priority information may be contained in the traffic, this
switch maps priority values to the output queues in the following manner:
• The precedence for priority mapping is IP Port Priority, IP Precedence
or DSCP Priority, and then Default Port Priority.
• IP Precedence and DSCP Priority cannot both be enabled. Enabling
one of these priority types will automatically disable the other.
• IP Precedence/DSCP and IP Port Priority settings are global and apply
to all ports on the switch.
Selecting IP Precedence/DSCP Priority
The switch allows you to choose between using IP Precedence or DSCP
priority. Select one of the methods or disable this feature .
Command Attributes
•IP Precedence/DSCP Priority Status – Selects IP Precedence,
DSCP, or disables both priority services.
Web – Click Priority/IP Precedence Priority. Select “IP Precedence” or
“IP DSCP” from the IP Precedence/DSCP Priority Status menu.