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configure diffserv dscp-mapping ports
ExtremeWare Software 7.3.0 Command Reference Guide 1637
configure diffserv dscp-mapping ports
configure diffserv dscp-mapping <input_codepoint>/<output_codepoint> ports
<portlist> {egress {no-congestion | congestion} | ingress}
Description
Configures a mapping between an input DiffServ code point (DSCP) and an associated output DSCP for
the specified PoS or ATM ports.
Syntax Description
Default
By default, all the tables are initialized such that DSCPs are not altered by the mapping operations; for
example, an input DSCP value of n is always mapped to an output DSCP value of n. Additionally,
dscp-mapping
is performed without regard to whether
diffserv examination
is enabled on the port.
Usage Guidelines
Three DSCP mapping tables are supported per SONET port. One of the tables is used in the ingress
direction and two are used for egress flows (onto the SONET link). The two egress tables are for the
congested and non-congested states, as determined by the RED algorithm (in other words, the
congested state is when the average queue length is greater than the minimum RED threshold). If RED
is not enabled on the SONET port, then the egress congested-state mapping table is not used.
The tables are very simple. In the ingress direction, the input DSCP of a packet received from the
SONET link is replaced with an output DSCP before the packet is forwarded. The replacement is
straightforward; the input DSCP is used as an index into a 64-entry table that contains the output
DSCPs associated with each of the input DSCP values. The operation is similar in the egress direction,
with the DSCP mapping occurring before the packet is transmitted onto the SONET link(s). The
mapping operation is performed after the packet has been assigned to a QoS profile. One potential use
of the DSCP mapping capability is reconciliation of varying DiffServ policies at the boundary between
autonomous systems (for example, at the boundary between two ISPs). The availability of different
tables for the congested/non-congested states is useful for marking operations that increase the drop
probability of packets during times of congestion, as discussed in the DiffServ assured forwarding (AF)
RFC.
input_codepoint Specifies one of the 64 possible DiffServ code point values as the input code
point.
output_codepoint Specifies one of the 64 possible DiffServ code point values as the output code
point.
portlist Specifies the port number(s).
egress Applies the DSCP mapping to the egress direction.
no-congestion Applies the DSCP mapping to the egress mapping table for the non-congested
state.
congestion Applies the DSCP mapping to the egress mapping table for the congested
state.
ingress Applies the DSCP mapping to the ingress direction.