Traffic Marking - Watchguard Firebox X15 User Manual

Traffic Marking

If your Firebox X Edge is part of a larger network that uses Quality of Service (QoS) and your upstream device,
LAN equipment, and IPS support it, you can apply marking to each category of network traffic you define on
your Edge. The Edge then marks all traffic that matches the criteria in your Traffic Control rule. When you mark
traffic, you change up to six bits on packet header fields defined for this purpose. The Edge and other marking-
capable external devices use these bits to control how a packet is handled as it is sent over a network.
The use of marking procedures on a network requires that you do extensive planning. You can first identify
theoretical bandwidth available and then determine which network applications are high priority, particularly
sensitive to latency and jitter, or both.
The Firebox X Edge supports two types of Traffic Control marking: IP Precedence marking and DSCP
(Differentiated Service Code Point) marking. IP Precedence marking affects only the first three bits in the IP
type of service (ToS) octet. DSCP marking expands marking to the first six bits in the IP ToS octet. With both
methods, you can choose to:
Preserve the bits in the header, which may have been marked previously by an external device
or
Change the bits to a new value
DSCP values can be expressed in numeric form or by special keyword names that correspond to per-hop
behavior (PHB). Per-hop behavior is the priority applied to a packet when traveling from one point to another
in a network. DSCP marking supports three defined types of per-hop behavior
Best-Effort
Best-Effort is the default type of service and is recommended for traffic that is not critical or real-time.
All traffic falls into this class if you do not use Traffic Control marking.
Assured Forwarding (AF)
Assured Forwarding PHB is recommended for traffic that needs better reliability than the best-effort
service.
Expedited Forwarding (EF)
This type has the highest priority. It is generally reserved for mission-critical and real-time traffic.
Class-Selector (CSx) code points are defined to be backward compatible with Type of Service values. CS1
through CS7 are identical to the last seven options in the Marking drop-down list when IP Precedence is
selected as the marking type.
User Guide
Traffic Management
167