SMC Networks SMC7724M/VSW manual Mapping Layer 3/4 Priorities to CoS Values

MAPPING LAYER 3/4 PRIORITIES TO COS VALUES

Mapping Layer 3/4 Priorities 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.

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