Quality of Service Guide QoS and QoS Policies
Edition: 01 3HE 11014 AAAC TQZZA 105
3.5.1.1 Network Ingress Tunnel QoS Override
In order to simplify QoS management through the network core, some operators
aggregate multiple forwarding classes of traffic at the ingress LER or PE and use two
or three QoS markings instead of the eight different QoS markings that a customer
device might be using to dictate QoS treatment. However, in order to ensure the
end-to-end QoS enforcement required by the customer, the aggregated markings
must be mapped back to their original forwarding classes at the egress LER (eLER)
or PE.
For IP traffic (including IPSec packets) riding over MPLS or GRE tunnels that will be
routed to the base router, a VPRN interface, or an IES interface at the tunnel
termination point (the eLER), the 7705 SAR can be configured to ignore the
EXP/DSCP bits in the tunnel header when the packets arrive at the eLER. Instead,
classification is based on the inner IP header which is essentially the customer IP
packet header. This configuration is done using the ler-use-dscp command.
When the command is enabled on an ingress network IP interface, the IP interface
will ignore the tunnel’s QoS mapping and will derive the internal forwarding class and
associated profile state based on the DSCP values of the IP header ToS field rather
than on the network QoS policy defined on the IP interface. This function is useful
when the mapping for the tunnel QoS marking does not completely reflect the
required QoS handling for the IP packet. The command applies only on the eLER
where the tunnel or service is terminated and the next header in the packet is IP.
3.5.2 Network Ingress Queuing
Network ingress traffic can be classified in up to eight different forwarding classes,
which are served by 16 queues (eight queues for unicast traffic and eight queues for
multicast (BMU) traffic). Each queue serves at least one of the eight forwarding
classes that are identified by the incoming EXP bits. These queues are automatically
created by the 7705 SAR. Table 11 shows the default network QoS policy for the 16
CoS queues.
The value for CBS and MBS is a percentage of the size of the buffer pool for the
adapter card. MBS can be shared across queues, which allows overbooking to
occur.
Table 11 Default Network Ingress QoS Policy
Queue /FC CIR (%) PIR (%) CBS (%) MBS (%)
Queue-1/BE 0 100 0.1 5
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