# Effects of bandwidth management and prioritization

Bandwidth management and traffic prioritization improve the quality of service for important traffic. However, the quality of service for traffic that you define as less important can decrease.

Both features are configured using the same tools. You can use both bandwidth management and traffic prioritization together, or bandwidth management or traffic prioritization individual for any given type of traffic. Bandwidth management and traffic prioritization are not supported on the Modem interfaces of Single Firewalls.

Usually the traffic management process allows all connections to proceed, although some traffic can occasionally slow down when the bandwidth limits are reached. If there is prolonged congestion in the network, lower priority traffic eventually starts to time out. If you set priorities without setting any maximum limits or minimum guarantees for bandwidth, high-priority traffic can even use all available bandwidth, blocking all lower-priority traffic.

In most situations, the guaranteed minimum bandwidths given to important connections allow traffic to proceed. However, even traffic with bandwidth guarantees might not get through, if network links are unable to maintain throughput or if the volume of traffic continuously exceeds the throughput. Make sure that your bandwidth limits and guarantees are granular enough to account for losing bandwidth, for example, due to ISP failure in a Multi-Link environment. Track the total bandwidth use, so that you can increase the throughput before problems appear.

The Firewall can also read and write DiffServ Code Point (DSCP) markers in type of server (ToS) fields. The markers allow you to integrate the Firewall with other network equipment that implements QoS management in your own or your ISP's network.

CAUTION:
Inappropriate bandwidth limits and guarantees only disturb traffic. Make sure the guarantees and limits you set are appropriate for the volume of each type of traffic.