Quality of Service Guide QoS and QoS Policies
Edition: 01 3HE 11014 AAAC TQZZA 143
As an example, in a scenario where the uplink bandwidth is limited to a fractional E1
link with 2 x DS0 channel groups, downloading software for a new release can
disrupt TDM pseudowire traffic, especially if SGT traffic is always serviced first over
all other traffic flows. Having the option to map a subset of SGT to data queues will
ensure that the mission-critical traffic flows effectively. For example, if FTP traffic is
redirected to the best-effort forwarding queue, FTP traffic is then serviced only after
all higher-priority traffic is serviced, including network control traffic and TDM
pseudowire traffic. This redirection ensures the proper treatment of all traffic types
matching the requirements of the network.
Redirection of SGT applications is done using the config>router>sgt-qos>
application>fc-queue or config>service>vprn>sgt-qos>application>fc-queue
command.
Redirection of the global ping application is not done through the sgt-qos menu
hierarchy; this is configured using the fc-queue option in the ping command. Refer
to the 7705 SAR OAM and Diagnostics Guide, “OAM and SAA Command
Reference”, for details.
SGT redirection is supported on the base router and the virtual routers on ports with
Ethernet or PPP/MLPPP encapsulation.
3.7.5.2 Network Queue QoS Policies
Network queue policies define the queue characteristics that are used in determining
the scheduling and queuing behavior for a given forwarding class or forwarding
classes. Network queue policies are applied on ingress and egress network ports, as
well as on the ring ports and the add/drop port on the 2-port 10GigE (Ethernet)
Adapter card and 2-port 10GigE (Ethernet) module.
Caution:
• Timeouts for signaling and/or routing protocols can initiate a session teardown. The
teardown will not only have local impacts as severe as losing the sole uplink of a node
but could also be network-wide if loss of a node is propagated throughout the network.
In this scenario, routing protocols, as an example, will rerun on all the nodes within the
same area, generating a CPU load and extra control-plane traffic. Such a scenario
could cause potential instability across the network or an area of the network. To avoid
this scenario, the user must ensure that uplink capacity is enough to transmit all crucial
SGT plus the mission-critical user traffic, and SGT redirection should only be used for
the non-mission-critical traffic that can tolerate delay and jitter.
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