Chapter 31 Bandwidth Management
UAG Series User’s Guide
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DiffServ and DSCP Marking
QoS is used to prioritize source-to-destination traffic flows. All packets in the same flow are given
the same priority. CoS (class of service) is a way of managing traffic in a network by grouping
similar types of traffic together and treating each type as a class. You can use CoS to give different
priorities to different packet types.
DiffServ (Differentiated Services) is a class of service (CoS) model that marks packets so that they
receive specific per-hop treatment at DiffServ-compliant network devices along the route based on
the application types and traffic flow. Packets are marked with DiffServ Code Points (DSCPs)
indicating the level of service desired. This allows the intermediary DiffServ-compliant network
devices to handle the packets differently depending on the code points without the need to
negotiate paths or remember state information for every flow. In addition, applications do not have
to request a particular service or give advanced notice of where the traffic is going.
Connection and Packet Directions
Bandwidth management looks at the connection direction, that is from which interface the
connection was initiated and to which interface the connection is going.
A connection has outbound and inbound packet flows. The UAG controls the bandwidth of traffic of
each flow as it is going out through an interface.
• The outbound traffic flows from the connection initiator to the connection responder.
• The inbound traffic flows from the connection responder to the connection initiator.
For example, a LAN1 to WAN connection is initiated from LAN1 and goes to the WAN.
• Outbound traffic goes from a LAN1 device to a WAN device. Bandwidth management is applied
before sending the packets out a WAN interface on the UAG.
• Inbound traffic comes back from the WAN device to the LAN1 device. Bandwidth management is
applied before sending the traffic out a LAN1 interface.
