QoS and QoS Policies
142
Quality of Service Guide
3HE 11014 AAAC TQZZA Edition: 01
3.7.5.1.2 SGT Redirection
The 7705 SAR can be used in deployments where the uplink bandwidth capacity is
considerably less than if the router is used for fixed or mobile backhaul applications.
However, the 7705 SAR is optimized to operate in environments with megabits per
second of uplink capacity for network operations. Therefore, many of the software
timers are designed to ensure the fastest possible detection of failures, without
considering bandwidth limitations. In deployments with very low bandwidth
constraints, the system must also be optimized for effective operation of the routers
without any interruption to mission-critical customer traffic.
In lower-bandwidth deployments, SGT can impact mission-critical user traffic such
as TDM pseudowire traffic. To minimize the impact on this traffic, SGT can be
redirected to a data queue rather than to the high-priority control queue on egress.
All SGT applications can be redirected to a data queue, but the type of application
must be considered because not all SGT is suitable to be scheduled at a lower
priority. SGT applications such as FTP, TFTP, and syslog can be mapped to a
lower-priority queue.
Traceroute DSCP BE
VRRP DSCP NC1
Table 28 Applications and Support for Configurable DSCP or dot1p Markings (Continued)
Application Supported Marking Default DSCP/dot1p
Note:
• PTP in the context of SGT QoS is defined as Precision Timing Protocol and is an
application in the 7705 SAR. The PTP application name is also used in areas such as
event-control and logging. Precision Timing Protocol is defined in IEEE 1588-2008.
• PTP in the context of IP filters is defined as Performance Transparency Protocol. IP
protocols can be used as IP filter match criteria; the match is made on the 8-bit protocol
field in the IP header.
Caution:
• Care must be taken when determining which SGT applications should be moved to
data queues, as interrupting traffic flow for applications such as routing protocols (for
example, BGP, OSPF, and IS-IS) and MPLS can adversely affect router operation,
services, and the network.
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