Comtech EF Data CDM-570A Installation And Operation Manual page 626

L.1.3 DiffServ QoS Mode
The IP Packet Processor QoS can be set to DiffServ Mode to make it fully compliant to the
Differential Services QoS RFC standards. When the QoS mode is set to DiffServ, the system
automatically configures the rules with DSCP code points, priority values, and WRED. You can
only configure the service rate and drop precedence levels for Assured Forwarding (ASFD)
classes.
Class Selector DiffServ Code Points (DSCP) – Some implementations of DiffServ will prioritize
traffic by Class Selector assignment. This is defined in the DSCP within the IP header. The first
three bits of the DSCP define the Class Selector Precedence (or Priority):
Class Selector
Precedence 1
Precedence 2
Precedence 3
Precedence 4
The IP Packet Processor will prioritize the traffic based upon the DSCP Class Selector
Precedence.
All traffic that does not have the DSCP Class Selector Precedence defined
(000 000) will be placed in the Default Queue and have a Precedence of 9.
Expedited Forwarding and Assured Forwarding DSCP – Another implementation of DiffServ
uses all six bits of the DSCP to define Expedited and Assured Forwarding:
DiffServ Type
Expedited Forwarding
Assured Forwarding – Class 1
Assured Forwarding – Class 2
Assured Forwarding – Class 3
Assured Forwarding – Class 4
Expedited Forwarding (EF) DSCP – This defines premium service and is recommended for real
time traffic applications such as VoIP and video conferencing.
Assured Forwarding (AF) DSCP – This defines four service levels and also uses the last three
bits of the DSCP to define the Drop Precedence (Low, Medium, or High). The Drop Precedence
determines which packets will most likely be dropped during periods of over congestion, similar to
WRED. As a result, each of the four AF service levels also have three Drop Precedence levels for
which the IP Packet Processor provides 12 separate queues.
Minimum Bandwidth (AF only) – Minimum specification that allows a committed information
rate (CIR) to be applied to user-defined classes of traffic, or the default of no minimum bandwidth
can be selected.
Maximum Bandwidth (AF only) – This can be assigned to a flow to restrict the maximum
bandwidth that any particular flow will utilize, or the default of no bandwidth restriction can be
selected.
Advanced Quality of Service (QoS) Option
CDM-570A/570AL Satellite Modem with Optional Packet Processor
IP Packet
DSCP Processor
Priority
001 000 7
010 000 6
011 000 5
100 000 4
Class Selector
Precedence 1
Precedence 8
Precedence 8
Precedence 8
Precedence 8
L–8
Class Selector DSCP
Precedence 5 101 000
Precedence 6 110 000
Precedence 7 111 000
Default 000 000
DSCP IP Packet Processor Priority
101 110
001 xx0
010 xx0
011 xx0
100 xx0
Revision 5
IP Packet
Processor
Priority
3
2
1
9
3
7
7
7
7
MN-CDM570A